Overpumping emitters.

SWEI

I've said this many times before, but I'll repeat it here for posterity: Most of the magic of a mod/con boiler comes from MODulation. CONdensing can be viewed as a side effect of MODulation. When we reduce (or eliminate) standby losses and overshooot, we see improvements in both comfort and efficiency. What's not to like?

hot_rod

Steve Thompson (Taco) said:

Harvey, here's my take on how a circ "knows" the rate of heat loss. But - before I go into this - my response is not biased (as I previously stated). Really doesn't matter to me which you use (as we have both delta T and delta P - of course Johnny and I would prefer you used a Taco product the much the same way "others" would prefer you use Brand X). Pick the brand and control strategy you are comfortable with.

A delta T circ adjusts it's speed based on what it measures (supply/return temp), delta P adjust it's speed based on what it feels (changes in push back on the impeller or changes in the motor power consumption as zone(s) open and close).

Indirectly (repeat indirectly) a delta T circ can "see" a change in heat load by way of measuring changing return water temps, assuming the supply temp is relatively stable - I'm talking zone circs here. Obviously if the return temp drops (caused by an increased heat load), the software logic will tell the circ to speed up to help move the BTU's to where they need to be replaced (to satisfy the increased heat load) - hence it indirectly "knows" when the load changes. What it can't do is "anticipate" a heat load change (it will not change it's speed until the return water temp changes - again assuming the supply water temp is relatively stable).

I guess you might be able (meaning the following statement is a reach) to say it can react to outdoor air temps when the outdoor reset drops the supply temp. Same deal, the pump reacts to changing return water temps but this time at a lower supply temp caused by higher outside air temps lowering the overall system supply temp.

Bet I just opened up a can or worms :-)... All good. Love The Wall!

Here is where the numbers don't jive with you explanation. One speed boiler, no ODR.

As you stated, assume the supply is relatively stable, ok 180 supply, 160 return. Plug in a flow rate, use the hydronic formula
500 f (∆T) and come up with BTUs delivered, lets use 2 gpm

500 X 2 X 20 ∆= 20,000 btu/hr delivered. Agreed?

Lets say the return drops to 150, same flow rate 2 gpm, same supply 180-150= 30∆
500 X 2 X 30∆ =30,000 but/hr delivered. Agreed?

Why would I want to slow back down to a 20∆ (20,000 btu/hr) to cover an increased, increasing heat load? This is where the "enforced" ∆T concept breaks down, for me.

A fixed speed circ, providing a steady 2 gpm allows that changing ∆ to increase or decrease energy delivered. It will reach thermal equalibrium unless you try and force an operating condition, like a fixed ∆.

An increase in heat output from a distribution system doesn't imply an increase in the load of the building. You assume the heat output of the distribution always equals the heat loss of the building.

So to my way of thinking and using the hydronics formula as the proof neither directly, or indirectly does the pump "see" a change in heat load.


Can you show me, with math where I'm going wrong?

Rich_49

Ican , I can . You would not slow down to a 20* Delta , you would speed up . Obviously the you are now trying to get more output from the same flow . having a circ that SPEEDS UP to stay at the 20* Delta would be better . The Delta T ciorc would readily flow 3 gpm as opposed to 2 gpm .

3gpm = 30,000 / 20x500 . there's the math . Satisfied ?
At below design conditions the boiler is going to cycle no matter what , does circulating 2 gpm make more sense than moving 1.5 gpm and using what's in the boiler ? That's considering the load is 15,000 of course .
Considering your your Delta is increasing from 20* to 30* would suggest that the fluid is cooling down faster than it was , now what could make that happen ? Jeopardy music , the load has changed so we should move more fluid . Remember , you set the parameters , one speed boiler , no odr .

Maybe it was just a bad example Bob

Paul48

The math works, and you're plugging in conditions (impossible to nearly impossible), to win your argument using it. What would cause the return temperature to suddenly drop to 150 degrees? You just argued for stable room air temperature, mind you.

hot_rod

Paul48 said:

The math works, and you're plugging in conditions (impossible to nearly impossible), to win your argument using it. What would cause the return temperature to suddenly drop to 150 degrees? You just argued for stable room air temperature, mind you.

Not trying to win anything Paul48, get over it. I'm presenting numbers to discussed Steves "assumed" conditions.

I'd be glad to use Steves numbers to show then point, if ever he would include them in his discussions. He stated the example of a return temperature drop.

Explain not me what is impossible or nearly impossible in the example?

Harvey Ramer

If you want to do the math, do it right. Every cast boiler has some sort of a high limit differential meaning that waterm temp won't stay consistent and the pump will respond to that. If you break it down that equates to longer off times for the boiler.

hot_rod

Rich said:

Ican , I can . You would not slow down to a 20* Delta , you would speed up . Obviously the you are now trying to get more output from the same flow . having a circ that SPEEDS UP to stay at the 20* Delta would be better . The Delta T ciorc would readily flow 3 gpm as opposed to 2 gpm .

3gpm = 30,000 / 20x500 . there's the math . Satisfied ?
At below design conditions the boiler is going to cycle no matter what , does circulating 2 gpm make more sense than moving 1.5 gpm and using what's in the boiler ? That's considering the load is 15,000 of course .
Considering your your Delta is increasing from 20* to 30* would suggest that the fluid is cooling down faster than it was , now what could make that happen ? Jeopardy music , the load has changed so we should move more fluid . Remember , you set the parameters , one speed boiler , no odr .

Maybe it was just a bad example Bob

My example was a fixed 2 gpm circ, that is clear in the math included.

Now show me the numbers on how the pump, any pump responds changing outdoor temperature. It doesn't, can't directly or indirectly.

This particular discussion is about that statement, nothing more, nothing less. If we can't get by that point, it's fruitless to proceed because you are missing the basics of heat transfer.

Paul48

Assuming a properly sized boiler, and properly sized emitter, running a fixed supply of 180, and a DT circ set at 20.........how does the return get to 150? It is being debated, and you are most certainly trying to win the debate. It doesn't matter to me, either way, I'd just like to see consistent, real-world examples being used. That's not one of them........It's like the judge asking the defendant......Do you still beat your wife?

bob_46

*

Rich_49

hot rod said:

Rich said:

Ican , I can . You would not slow down to a 20* Delta , you would speed up . Obviously the you are now trying to get more output from the same flow . having a circ that SPEEDS UP to stay at the 20* Delta would be better . The Delta T ciorc would readily flow 3 gpm as opposed to 2 gpm .

3gpm = 30,000 / 20x500 . there's the math . Satisfied ?
At below design conditions the boiler is going to cycle no matter what , does circulating 2 gpm make more sense than moving 1.5 gpm and using what's in the boiler ? That's considering the load is 15,000 of course .
Considering your your Delta is increasing from 20* to 30* would suggest that the fluid is cooling down faster than it was , now what could make that happen ? Jeopardy music , the load has changed so we should move more fluid . Remember , you set the parameters , one speed boiler , no odr .

Maybe it was just a bad example Bob

My example was a fixed 2 gpm circ, that is clear in the math included.

Now show me the numbers on how the pump, any pump responds changing outdoor temperature. It doesn't, can't directly or indirectly.

This particular discussion is about that statement, nothing more, nothing less. If we can't get by that point, it's fruitless to proceed because you are missing the basics of heat transfer.

Ok Bob . I'll play . Did you design the system to have a 30* Delta T ? If not and you designed it for a 20* Delta T at design , You really screwed the pooch . How did the Delta T widen from 20 to 30 * .. My explanation is that it got colder out , the load increased , thus why the fluid is cooling more than it was . A Delta T sensing circ can see the widening delta due to the cooler fluid returning and will thus speed up to get the Delta back down to designed for 20* . Now I don't know in what Universe that would not fall under either directly or indirectly but I'd say the pump sensed the changing load somehow
( scratches head) and responded .

Unless you designed for a 30* Delta you chose the wrong circ . Why would one install a fixed 2 gpm circ on a system that could see the need for 3 gpm . Why'd you install the wrong circ .

This is not racing Bob , we are not trying to ,nor should we be trying to see who can heat it faster . Everything we do has a time component .

The only condition that can cause a 30* delta when there was a 20 is that the load has changed and the fluid is losing more heat at the emitter . The reverse is also true , when the load lessens with that same circ the Delta will narrow . If you had a Delta T circ it will see the widening / narrowing between S&R and act accordingly . You really should try it someday and stop asking everyone for evidence . You like experimenting , this one is simple , do the work and quit asking others to do it for you . Should be easy unless there is something we are missing in this oh so politically correct forum .

hot_rod

Rich said:

hot rod said:

Rich said:

Ican , I can . You would not slow down to a 20* Delta , you would speed up . Obviously the you are now trying to get more output from the same flow . having a circ that SPEEDS UP to stay at the 20* Delta would be better . The Delta T ciorc would readily flow 3 gpm as opposed to 2 gpm .

3gpm = 30,000 / 20x500 . there's the math . Satisfied ?
At below design conditions the boiler is going to cycle no matter what , does circulating 2 gpm make more sense than moving 1.5 gpm and using what's in the boiler ? That's considering the load is 15,000 of course .
Considering your your Delta is increasing from 20* to 30* would suggest that the fluid is cooling down faster than it was , now what could make that happen ? Jeopardy music , the load has changed so we should move more fluid . Remember , you set the parameters , one speed boiler , no odr .

Maybe it was just a bad example Bob

My example was a fixed 2 gpm circ, that is clear in the math included.

Now show me the numbers on how the pump, any pump responds changing outdoor temperature. It doesn't, can't directly or indirectly.

This particular discussion is about that statement, nothing more, nothing less. If we can't get by that point, it's fruitless to proceed because you are missing the basics of heat transfer.

Ok Bob . I'll play . Did you design the system to have a 30* Delta T ? If not and you designed it for a 20* Delta T at design , You really screwed the pooch . How did the Delta T widen from 20 to 30 * .. My explanation is that it got colder out , the load increased , thus why the fluid is cooling more than it was . A Delta T sensing circ can see the widening delta due to the cooler fluid returning and will thus speed up to get the Delta back down to designed for 20* . Now I don't know in what Universe that would not fall under either directly or indirectly but I'd say the pump sensed the changing load somehow
( scratches head) and responded .

Unless you designed for a 30* Delta you chose the wrong circ . Why would one install a fixed 2 gpm circ on a system that could see the need for 3 gpm . Why'd you install the wrong circ .

This is not racing Bob , we are not trying to ,nor should we be trying to see who can heat it faster . Everything we do has a time component .

The only condition that can cause a 30* delta when there was a 20 is that the load has changed and the fluid is losing more heat at the emitter . The reverse is also true , when the load lessens with that same circ the Delta will narrow . If you had a Delta T circ it will see the widening / narrowing between S&R and act accordingly . You really should try it someday and stop asking everyone for evidence . You like experimenting , this one is simple , do the work and quit asking others to do it for you . Should be easy unless there is something we are missing in this oh so politically correct forum .

One more time, I'm trying to put some numbers to Steves example, if he has a design in mind ask him , not me.

IF I designed a system for a 20∆, at design condition with a fixed speed zone circ I would expect it to operate at that condition, once up and running. Assuming everything sized and balanced correctly. If the building is at anything other than design, probably most of the heating season I would expect the ∆T to change, up or down a few 5-8 degrees. It will seek and find thermal equilibrium conditions without any imposed conditions. I see no benefit to maintaining a certain ∆ when my system is at 20% or 120% of load.

I have yet to find any product that states it is only at its highest efficiency at a certain tested ∆ condition. To the contrary boilers show a few acceptable ∆ choices in their manuals.

I do have several ∆T circs and I have played with them and believe and understand they can maintain a fixed ∆ across a range. I see several uses for that function, especially if the speed limitations were removed. My point is that it is not needed or required in a properly designed or balanced system zone pump system, cast iron non ODR boiler as Steve suggestedand it may, probably will not amount to a large efficiency gain, other than the ECM function compared to a PSC motor.

Maybe we can convince Dave Sweet to run his new home with 007E zone pumps for a season, document and data log, then a ∆T for a season and compare #

Hatt has spelled out what data needs to be recorded and offered to crunch the numbers, in an above post. That would lay to rest the questions I have. "How much if any efficiency is gained in a properly designed, installed, balanced system, with a forced ∆ condition on the zone pumps"

I think Hatt already has a jump on answering that question from his personal experience.

In direct disagreement with Taco, I state that the VDT pump, once equilibrium has been reached, and utilized on a single zone, will not change speed at anytime during its operation on a CI boiler without OAR and it will absolutely not respond to changes in outdoor temperature as claimed by Taco. It will maintain a fixed DT without, effectively, changing speed whatsoever (see caveat in previous paragraph).

ARsales1

Rich said:

hot rod said:

Rich said:

Ican , I can . You would not slow down to a 20* Delta , you would speed up . Obviously the you are now trying to get more output from the same flow . having a circ that SPEEDS UP to stay at the 20* Delta would be better . The Delta T ciorc would readily flow 3 gpm as opposed to 2 gpm .

3gpm = 30,000 / 20x500 . there's the math . Satisfied ?
At below design conditions the boiler is going to cycle no matter what , does circulating 2 gpm make more sense than moving 1.5 gpm and using what's in the boiler ? That's considering the load is 15,000 of course .
Considering your your Delta is increasing from 20* to 30* would suggest that the fluid is cooling down faster than it was , now what could make that happen ? Jeopardy music , the load has changed so we should move more fluid . Remember , you set the parameters , one speed boiler , no odr .

Maybe it was just a bad example Bob

My example was a fixed 2 gpm circ, that is clear in the math included.

Now show me the numbers on how the pump, any pump responds changing outdoor temperature. It doesn't, can't directly or indirectly.

This particular discussion is about that statement, nothing more, nothing less. If we can't get by that point, it's fruitless to proceed because you are missing the basics of heat transfer.

Ok Bob . I'll play . Did you design the system to have a 30* Delta T ? If not and you designed it for a 20* Delta T at design , You really screwed the pooch . How did the Delta T widen from 20 to 30 * .. My explanation is that it got colder out , the load increased , thus why the fluid is cooling more than it was . A Delta T sensing circ can see the widening delta due to the cooler fluid returning and will thus speed up to get the Delta back down to designed for 20* . Now I don't know in what Universe that would not fall under either directly or indirectly but I'd say the pump sensed the changing load somehow
( scratches head) and responded .

Unless you designed for a 30* Delta you chose the wrong circ . Why would one install a fixed 2 gpm circ on a system that could see the need for 3 gpm . Why'd you install the wrong circ .

This is not racing Bob , we are not trying to ,nor should we be trying to see who can heat it faster . Everything we do has a time component .

The only condition that can cause a 30* delta when there was a 20 is that the load has changed and the fluid is losing more heat at the emitter . The reverse is also true , when the load lessens with that same circ the Delta will narrow . If you had a Delta T circ it will see the widening / narrowing between S&R and act accordingly . You really should try it someday and stop asking everyone for evidence . You like experimenting , this one is simple , do the work and quit asking others to do it for you . Should be easy unless there is something we are missing in this oh so politically correct forum .

Richie,
THANK YOU FOR CLEARNG THIS UP.

I'm having a difficult time trying to understand why others find this hard to comprehend and understand

hot_rod

A Delta T sensing circ can see the widening delta due to the cooler fluid returning and will thus speed up to get the Delta back down to designed for 20* . Now I don't know in what Universe that would not fall under either directly or indirectly but I'd say the pump sensed the changing load somehow
( scratches head) and responded .

If the pump stays at a 2 gpm flow and the ∆ widens 10,° output increases. Assuming as Steve did that input temperature remained the same, boiler has then power to keep up the SWT.

Hydronic formula again.

The heat output increases without any need to change the pump speed. Why force it back to 20 when the 30 is exactly what the system needs to cover the increased load at that exact condition. Hydronic systems have been working like that for years, basic thermodynamics. Why install a $400.00 pump to do exactly what an $80.00 pump can?

Back to Larry Drakes example of how to increase a radiant slab output, open the window! Widen the ∆ from the floor emitter to space and the slab output increases.

∆T circs trying to solve a problem that doesn't exist,

I will concede efficiency gains if the pump is replacing a grossly oversized, over pumped system. No need to flow over 4 fps in todays hydronics.

Paul48

"The heat output increases without any need to change the pump speed. Why force it back to 20 when the 30 is exactly what the system needs to cover the increased load at that exact condition. Hydronic systems have been working like that for years, basic thermodynamics. Why install a $400.00 pump to do exactly what an $80.00 pump can?"

This is what I mean about consistency, or lack there-of.

In another post, you fought tooth and nail about pumping more to deliver more heat. Now, we shouldn't, even though that is exactly what the system needs.

We don't discuss pricing.

hot_rod

Hatterasguy said:

hot rod said:

If the pump stays at a 2 gpm flow and the ∆ widens 10,° output increases. Assuming as Steve did that input temperature remained the same, boiler has then power to keep up the SWT.

I'll ask again.

What is the cause of the change in Δ if the flow remained the same and the SWT remained the same?

In order to get a 10F change in Δ (50% change), you're going to have to find a massive flow rate change or a massive SWT change.

Which is it?

And one more time I'll have you ask Steve Thompson, below is his statement that I merely tried to put some numbers to.

If the extra 10∆ is too large, plug in your own number, the fact remains the increased ∆, however much or little, increases the heat delivered, without the need to change pump speed or gpm delivered.


Indirectly (repeat indirectly) a delta T circ can "see" a change in heat load by way of measuring changing return water temps, assuming the supply temp is relatively stable - I'm talking zone circs here. Obviously if the return temp drops (caused by an increased heat load), the software logic will tell the circ to speed up to help move the BTU's to where they need to be replaced (to satisfy the increased heat load) - hence it indirectly "knows" when the load changes. What it can't do is "anticipate" a heat load change (it will not change it's speed until the return water temp changes - again assuming the supply water temp is relatively stable).

Gordy

time, speed, and distance......

Paul48

Wow....Hat..........I understood that...even with no pictures.

Steve Thompson (Taco)

OK, let me take another shot at this... Example:

- single zone of a multiple zone system
- operating at max heat loss (say 20,000 BTU's)
- assume 180 deg SWT
- assume 160 RWT
- translates to 2 GPM flow from a fixed speed zone circulator.

- same system under minimum load (say 500 BTU's)
- 180 deg SWT (other zones are under load)
- same 2 GPM fixed speed circulator
- translates to 179.5 deg RWT.
Guess you could cycle the zone valve on and off - oops, no zone valve - the zoning is done by a circ in this example.

Assuming we can, what's wrong with slowing the flow under low loads, raising the delta T by a factor of 10 for example to 5 deg F? If the circ speed is cut in half the power is reduced by the cube root (as an example). So, slowing the circ down under low loads (and to compensate for over pumped systems) will produce measurable energy savings. Granted these are low wattage circs - even delta P circs reduce power consumption as they slow down, although unless it sees a zone valve it won't/can't slow down.

Lastly, AS LONG AS THE BOILER MIN FLOW RATE IS SATISFIED (sorry for the caps but this is getting kind of old), it only makes sense (at least to me) to modulate the flow in harmony (in harmony is key) with the modulating firing rate. A 300,000 BTU boiler needs 30 GPM for a 20 deg delta. Assuming 10 to 1 turndown ratio, minimum firing rate is 30,000 BTU so it would be possible to reduce the flow through the boiler to 3 GPM, as long as minimum bla, bla, bla. Rest assured the boiler wouldn't needlessly rapid cycle.

These are the best examples I can come up with - sorry, signing off this one.

Matt_67

If we are talking about a single loop of baseboard the load the pump will 'see' will be virtually identical at all times (after warmup) unless the room is coming out of setback (on a system without outdoor reset). I suppose you could automate the baseboard damper's position using outside temperature ..... probably not a good idea.

On the subject of over pumped emitter - can't we just measure the temp of the pipe with a strap on thermocouple? If we have 180 supply water temp and the pipe at the start of the loop is 180 we're good, right?

If the emitters are connected to a cast iron boiler it would be interesting to see if it is possible to over pump the cast iron block. We would see an increase in stack temp if this were the case. I don't think that is likely.

If there is excess capacity radiation compared to boiler output (again with a cast iron non-modulating boiler) I can only see a couple of percent savings based on RWT. The average water temp will be the same in the system regardless of system flow.

I would not recommend applying a delta t pump as a system pump in a full flow boiler application with a modulating boiler. If you have two controllers looking at the same variable and making changes the system will not be happy.

Matt_67

Is your system a single zone? No zone valves or TRV's?

hot_rod

Hatt said:
A direct pumped system with a VT2218 is the premier solution for a mod-con. It simply has a few growing pains at the moment.

I would suggest a direct pumped system, assuming the boiler has that ability no or very low minimum flow rates, with a VS circulator controlled by the boiler logic, ramping with the burner output, via indoor and outdoor input.,

That would be a premier system in my mind, no need to "box in" a ∆T.

In fact if the control could optimize condensing by at the same time attempting to keep RWT as low as possible, now you could claim increased efficiencies.

I don't see this possible on a fixed temperature cast iron boiler, with ∆T circulation added, either as a single or multiple zone pumped ∆T system. Those are the claims I am trying to substantiate.

hot_rod

Hatterasguy said:

hot rod said:

Hatt said:
A direct pumped system with a VT2218 is the premier solution for a mod-con. It simply has a few growing pains at the moment.

I would suggest a direct pumped system, assuming the boiler has that ability no or very low minimum flow rates, with a VS circulator controlled by the boiler logic, ramping with the burner output, via indoor and outdoor input.,

That would be a premier system in my mind, no need to "box in" a ∆T.

In fact if the control could optimize condensing by at the same time attempting to keep RWT as low as possible, now you could claim increased efficiencies.

I don't see this possible on a fixed temperature cast iron boiler, with ∆T circulation added, either as a single or multiple zone pumped ∆T system. Those are the claims I am trying to substantiate.

Agreed. A VV circulator, controlled by the boiler, is another step up in the advancement of the art. However, the cost for that setup is a bit ridiculous at the moment. You could never achieve a payback on that system.

I'm quite convinced that the VDT and the mod-con can work together effectively with some logic changes on both of them.

Yes but if a contractor or HO is willing to spend in excess of 400 a pop for ∆T zone pumps, that single "expensive" boiler controlled circ pump may not be objectionable.

hot_rod

Hatterasguy said:

hot rod said:

Hatt said:
A direct pumped system with a VT2218 is the premier solution for a mod-con. It simply has a few growing pains at the moment.

I would suggest a direct pumped system, assuming the boiler has that ability no or very low minimum flow rates, with a VS circulator controlled by the boiler logic, ramping with the burner output, via indoor and outdoor input.,

That would be a premier system in my mind, no need to "box in" a ∆T.

In fact if the control could optimize condensing by at the same time attempting to keep RWT as low as possible, now you could claim increased efficiencies.

I don't see this possible on a fixed temperature cast iron boiler, with ∆T circulation added, either as a single or multiple zone pumped ∆T system. Those are the claims I am trying to substantiate.

Agreed. A VV circulator, controlled by the boiler, is another step up in the advancement of the art. However, the cost for that setup is a bit ridiculous at the moment. You could never achieve a payback on that system.

I'm quite convinced that the VDT and the mod-con can work together effectively with some logic changes on both of them.

I'm doubtful that this last sentence would hold true for every type of system, different and mixed emitters and such, various HX designs in the boiler, etc.

And by effectively would that be measured by increased comfort, or reduced fuel cost, or both?
I still stand by the concept of fuel required matches heat load requirements. Certainly staying in condensing mode will use that fuel most efficiently, then it comes down to possible increased comfort. This, combined with 100% turndown would get us us to true constant circulation.

Just switching a fixed speed circ for a VSDT does not change the "amount" of energy required to heat a structure. Electrical consumption would decrease if you go from PSC to ECM, but doubtful to the tune of hundreds of $$ per heating season.

Rich_49

Bob ,
VT2218s do not cost 400.00 . Never have . You should tread lightly , some of your comments and incorrect statements could be viewed as actionable had someone the mind to do so . .

The industry is working very hard to further our cause and usefulness for the long term . Unfortunately in the effort to make hydronics scaleable and saleable some components that have long been necessary to address some issues in systems will become less and less necessary and systems will get less complicated . I for one believe this scares some segments of our manufacture and supply chains to death .

As far as Delta T and Delta P circs are concerned , here is my opinion . A Delta P circ was a step in the process and was the best we had to further energy efficiency in hydronic systems . It's operation was and is based on educated guesses and formulas which have never been completely understood , this is not my opinion but is in fact an unsolved problem of physics under the condensed matter category (turbulence) . A P circ moves matter based on scientific wild **** guesses and will heat a home .

A Delta T circ listens to the system water , uses the hydronics formula , sensible heat rate equation , and designed for Delta Ts as it's information to vary it's speed and increase overall system efficiency .

There is a difference . The difference in your CI boiler scenario is keeping the boiler on and off for longer periods during above design conditions , 90+% of the heating season . Longer on cycles for the boiler are more efficient and it is never more efficient than when off . The Delta T circ moves more energy out of an off boiler lessening standby and stack losses and keeps it on longer throughout the season lessening short cycling .



Hatt ,

I will model a room that is 20,000 BTUh at a 0* design . We can then safely presume that the boiler is a 20,000 BTUh boiler installed in a perfect house with a 2 GPM circ . In the meantime maybe you could tell us how the 40 feet of baseboard will force those same 20,000 BTUh into that same room when it's 50* outside **** . Then we can look at how the Delta T circ benefits that system on all those days over design temps or 90% of the season .

Matt ,

No, 180* water at the beginning of a circuit does not make everything good . Your average water temp through that circuit or zone will vary based on load . At a 20* delta your AWT would be 170* , at an 8 degree delta your AWT is 176 and at a 30* delta your AWT is 165 . How do they vary so much ? a fixed speed circ or a Delta P circ . How can you guarantee an AWT and KNOW what it is for the largest percentage of the season ? A Delta T circ .

Rich_49

hot rod said:

Hatterasguy said:

hot rod said:

Hatt said:
A direct pumped system with a VT2218 is the premier solution for a mod-con. It simply has a few growing pains at the moment.

I would suggest a direct pumped system, assuming the boiler has that ability no or very low minimum flow rates, with a VS circulator controlled by the boiler logic, ramping with the burner output, via indoor and outdoor input.,

That would be a premier system in my mind, no need to "box in" a ∆T.

In fact if the control could optimize condensing by at the same time attempting to keep RWT as low as possible, now you could claim increased efficiencies.

I don't see this possible on a fixed temperature cast iron boiler, with ∆T circulation added, either as a single or multiple zone pumped ∆T system. Those are the claims I am trying to substantiate.

Agreed. A VV circulator, controlled by the boiler, is another step up in the advancement of the art. However, the cost for that setup is a bit ridiculous at the moment. You could never achieve a payback on that system.

I'm quite convinced that the VDT and the mod-con can work together effectively with some logic changes on both of them.

I'm doubtful that this last sentence would hold true for every type of system, different and mixed emitters and such, various HX designs in the boiler, etc.

And by effectively would that be measured by increased comfort, or reduced fuel cost, or both?
I still stand by the concept of fuel required matches heat load requirements. Certainly staying in condensing mode will use that fuel most efficiently, then it comes down to possible increased comfort. This, combined with 100% turndown would get us us to true constant circulation.

Just switching a fixed speed circ for a VSDT does not change the "amount" of energy required to heat a structure. Electrical consumption would decrease if you go from PSC to ECM, but doubtful to the tune of hundreds of $$ per heating season.

You would be wrong Bob . I have switched out PSCs with a VDT on a zoned system . Old oil boiler , 4 zones . took out 4 circs and replaced with 1 circ and 4 zone valves . Boiler ceased to short cycle for much of the season , fuel usage decreased 30% , comfort issues that existed prior went away .

Then we have a report that you should trust from Grundfos , you remember , they presented it on an RPA HydronixTalk that you attended . Matt Baker and Kurt (irk) Vigil both told the story of the Magna they set up as DElta T circ in a campus with 5 buildings that had short cycling and comfort issues . Those issues went away with the addition of that circ (s) . Why would Grundfos do that Bob ? You know because I asked and they answered .
You really should stop peeing in people's ears and telling them it is a warm summer rain and it's refreshing .

Oh , and to avoid any further blind faith Taco references . I learned all this stuff from many dead uncles , father , grandfathers . John Barba's application based training which is unlike other manufacturer's " buy my stuff because" training . Modern Hydronic Heating 3rd and attending and completing Siggy's first ever " Mastering Hydronic System Design " . The main difference between you and I and some others is quite clear .

You and some say what you say and when folks misunderstand it becomes a glitch and fix article and you get to point out the installers mistakes .

I on the other hand must deliver on a consistent basis or disappear , I have nobody to blame . I am accountable , you are not .

Gordy

I'm really not putting a whole lot of stock into Hats observations on his system......Yet. One heating season a 1/3 of which was tweaking, and tuning. I'm still a bit baffled by the goals. Initially it was to prove, or disprove the min.modulation, and flow rate of the selected boiler. The pump selection was the 2218 based on a hunch/theory? Then it seemed there was struggle. Pumps fault, boilers fault. Force emitters, pump, boiler to obtain some result. Results achievable by others.

This system is not a platform........yet to make observations of various system components performance. Whether it be the boiler, circ, or emitters. Give me a system that has a hands off platform design at the beginning of the season. Log performance then make changes.

By logging performance that includes weather, and not just HDD. HDD does not account for wind, and solar influence.

The weather changes that impact a heating system daily is completely thrown out the window by some. If you can not understand the " whole system" that includes the "structure", and the weather that impacts it. How can you possibly pick parts of the system, and comprehend why things are doing what they are doing. ALL variables affecting the system must be considered in the observations.

hot_rod

Rich said:

Bob ,
VT2218s do not cost 400.00 . Never have . You should tread lightly , some of your comments and incorrect statements could be viewed as actionable had someone the mind to do so . .

The industry is working very hard to further our cause and usefulness for the long term . Unfortunately in the effort to make hydronics scaleable and saleable some components that have long been necessary to address some issues in systems will become less and less necessary and systems will get less complicated . I for one believe this scares some segments of our manufacture and supply chains to death .

As far as Delta T and Delta P circs are concerned , here is my opinion . A Delta P circ was a step in the process and was the best we had to further energy efficiency in hydronic systems . It's operation was and is based on educated guesses and formulas which have never been completely understood , this is not my opinion but is in fact an unsolved problem of physics under the condensed matter category (turbulence) . A P circ moves matter based on scientific wild **** guesses and will heat a home .

A Delta T circ listens to the system water , uses the hydronics formula , sensible heat rate equation , and designed for Delta Ts as it's information to vary it's speed and increase overall system efficiency .

There is a difference . The difference in your CI boiler scenario is keeping the boiler on and off for longer periods during above design conditions , 90+% of the heating season . Longer on cycles for the boiler are more efficient and it is never more efficient than when off . The Delta T circ moves more energy out of an off boiler lessening standby and stack losses and keeps it on longer throughout the season lessening short cycling .



Hatt ,

I will model a room that is 20,000 BTUh at a 0* design . We can then safely presume that the boiler is a 20,000 BTUh boiler installed in a perfect house with a 2 GPM circ . In the meantime maybe you could tell us how the 40 feet of baseboard will force those same 20,000 BTUh into that same room when it's 50* outside **** . Then we can look at how the Delta T circ benefits that system on all those days over design temps or 90% of the season .

Matt ,

No, 180* water at the beginning of a circuit does not make everything good . Your average water temp through that circuit or zone will vary based on load . At a 20* delta your AWT would be 170* , at an 8 degree delta your AWT is 176 and at a 30* delta your AWT is 165 . How do they vary so much ? a fixed speed circ or a Delta P circ . How can you guarantee an AWT and KNOW what it is for the largest percentage of the season ? A Delta T circ .

I stand corrected on the cost, I was looking at the VS 0-10 circs, sorry.

Will you supply and install one for 200 bucks? I hope you are making some markup and labor So a homeowner could expect to pay 400 or more for an installed ∆T circ?

hot_rod

Gordy said:

I'm really not putting a whole lot of stock into Hats observations on his system......Yet. One heating season a 1/3 of which was tweaking, and tuning. I'm still a bit baffled by the goals. Initially it was to prove, or disprove the min.modulation, and flow rate of the selected boiler. The pump selection was the 2218 based on a hunch/theory? Then it seemed there was struggle. Pumps fault, boilers fault. Force emitters, pump, boiler to obtain some result. Results achievable by others.

This system is not a platform........yet to make observations of various system components performance. Whether it be the boiler, circ, or emitters. Give me a system that has a hands off platform design at the beginning of the season. Log performance then make changes.

By logging performance that includes weather, and not just HDD. HDD does not account for wind, and solar influence.

The weather changes that impact a heating system daily is completely thrown out the window by some. If you can not understand the " whole system" that includes the "structure", and the weather that impacts it. How can you possibly pick parts of the system, and comprehend why things are doing what they are doing. ALL variables affecting the system must be considered in the observations.

I agree with this 100% Gordy. Which is why it is hard to compare the system before and after across several heating systems. just a change in DHW will throw the numbers off and skew the results.

Hatt is coming to the table with some documented numbers and observations, a step in the right direction when proving or disapproving theories.

hot_rod

Rich said:

hot rod said:

Hatterasguy said:

hot rod said:

Hatt said:
A direct pumped system with a VT2218 is the premier solution for a mod-con. It simply has a few growing pains at the moment.

I would suggest a direct pumped system, assuming the boiler has that ability no or very low minimum flow rates, with a VS circulator controlled by the boiler logic, ramping with the burner output, via indoor and outdoor input.,

That would be a premier system in my mind, no need to "box in" a ∆T.

In fact if the control could optimize condensing by at the same time attempting to keep RWT as low as possible, now you could claim increased efficiencies.

I don't see this possible on a fixed temperature cast iron boiler, with ∆T circulation added, either as a single or multiple zone pumped ∆T system. Those are the claims I am trying to substantiate.

Agreed. A VV circulator, controlled by the boiler, is another step up in the advancement of the art. However, the cost for that setup is a bit ridiculous at the moment. You could never achieve a payback on that system.

I'm quite convinced that the VDT and the mod-con can work together effectively with some logic changes on both of them.

I'm doubtful that this last sentence would hold true for every type of system, different and mixed emitters and such, various HX designs in the boiler, etc.

And by effectively would that be measured by increased comfort, or reduced fuel cost, or both?
I still stand by the concept of fuel required matches heat load requirements. Certainly staying in condensing mode will use that fuel most efficiently, then it comes down to possible increased comfort. This, combined with 100% turndown would get us us to true constant circulation.

Just switching a fixed speed circ for a VSDT does not change the "amount" of energy required to heat a structure. Electrical consumption would decrease if you go from PSC to ECM, but doubtful to the tune of hundreds of $$ per heating season.

You would be wrong Bob . I have switched out PSCs with a VDT on a zoned system . Old oil boiler , 4 zones . took out 4 circs and replaced with 1 circ and 4 zone valves . Boiler ceased to short cycle for much of the season , fuel usage decreased 30% , comfort issues that existed prior went away .

Then we have a report that you should trust from Grundfos , you remember , they presented it on an RPA HydronixTalk that you attended . Matt Baker and Kurt (irk) Vigil both told the story of the Magna they set up as DElta T circ in a campus with 5 buildings that had short cycling and comfort issues . Those issues went away with the addition of that circ (s) . Why would Grundfos do that Bob ? You know because I asked and they answered .
You really should stop peeing in people's ears and telling them it is a warm summer rain and it's refreshing .

Oh , and to avoid any further blind faith Taco references . I learned all this stuff from many dead uncles , father , grandfathers . John Barba's application based training which is unlike other manufacturer's " buy my stuff because" training . Modern Hydronic Heating 3rd and attending and completing Siggy's first ever " Mastering Hydronic System Design " . The main difference between you and I and some others is quite clear .

You and some say what you say and when folks misunderstand it becomes a glitch and fix article and you get to point out the installers mistakes .

I on the other hand must deliver on a consistent basis or disappear , I have nobody to blame . I am accountable , you are not .

Rich, you completely changed the system, replaced 4 pumps with one, this was not a direct swap one pump for another, you obviously corrected other faults in the system. That is a good thing but not the comparison I suggested.

Taking all that training and still misunderstand some of the basics, I do't know what to say?

I think a roundtable discussion with Siggy and Barba on the Merits and Myths of ∆T circulators would be a crowd pleaser. I've heard both sides and know where I sit based on 700 pages worth of heat transfer and thermodynamic, clearly defined and explained. Works for me.

I predict at the end some biased opinions would not be changed, but all the numbers and math manlipulation would be exposed.

Matt_67

Rich- my comment on 180 SWT was simply in regard to emitter over pumping - the OP's original post. If the SWT leaving the boiler is 180 and the pipe temp at the first piece of fin tube is 180 then we don't need to worry about laminar flow. The fins remove the heat from he surface of the pipe - if the pipe is hot the fins will move that energy into the room.

The second part related to a boiler where there is more radiation than boiler capacity - admittedly pretty rare.
For example - if we had the following:
1) 80' baseboard in two loops with capacity at of 610 btu per foot at 180 degree water temp.
AND
2) boiler with 40,000 output capacity.
In this case the boiler would never cycle on high limit and if it were slant fin #30 baseboard the average water temp would be 163 degrees.
Any of the following could be true:
1) 30 degree delta T - 2.67 GPM / 178 SWT / 148 RWT
2) 20 degree delta T - 4 GPM / 173 SWT / 153 RWT
3) 10 degree delta T - 8 GPM / 168 SWT / 158 RWT
4) 5 degree delta T - 16 GPM / 165.5 SWT / 160.5 RWT
The difference in boiler efficiency attributable to the difference in water temp is in the range of 3% with those differences. Nothing to look down at but not enormous savings either.

For what it's worth I have used the taco delta t pumps with good success in several applications with good success - just was saying that in the specific case above I can't see a major savings.

If the boiler is larger than the radiation the numbers get complicated fast - I suspect there may be more opportunity for savings. Maybe you can run the numbers for that.

Gordy

Does anyone here believe it to be possible to hold the same system delta every time at the end of satisfying a heat call with a simple CI boiler, single zone radiant emitter type of system, wet rotar dumb circulator,no outdoor reset. No matter what outdoor temp that imposes a load on the structure?

Rich_49

Bob said ;

I agree with this 100% Gordy. Which is why it is hard to compare the system before and after across several heating systems. just a change in DHW will throw the numbers off and skew the results.

Hatt is coming to the table with some documented numbers and observations, a step in the right direction when proving or disapproving theories.

I state ;
Since Hatt has called me rude for pointing out what should be obvious I will continue , Hatt be damned . Hatt will have No information of value . He simply threw a boiler and circ package into a home with no heat loss performed with no thought toward how the individual zones would perform at various conditions . Many of his observations come on days when the temp was above 40* while putting 150* water through a system that obviously required much lower . This all done while ODR was disabled also . I have the results sent by him to myself , maybe he would post them as I will not share what was sent me in confidentiality for all to see , unless of course Hatt continues to be an insulting know it all . The fact that you would mention Hatts observations as something that could be valuable amazes me . I offer that Hatt's observations and all discussions about that ONE install would only be of value to show people how all important a WHOLE SYSTEM design approach is before trying to succeed in this business .

What Hatt does not understand which he openly states I do not , are Chapters 8 & 9 of MHH 3rd . I have to admit , it really is a shame he does not know what he does not know because he could be much more of an asset to our industry .

I wonder if he figured out how he was gonna push that 20,000 BTUh out of the 40 feet at 50* OAT ?

hot_rod

Rich, Rich, Rich what I clearly stated is that Hatt is at least collecting data and recording his observations. See below

Hatt is coming to the table with some documented numbers and observations, a step in the right direction when proving or disapproving theories.

I have not seen all of the data and I may or may not agree, I may challenge his opinions, you can do the same. He at least is putting numbers to the questions in attempt to formulate an opinions. Don't feel a marketing spin coming from him, as far I know he is not on the payroll of any of the manufacturers products he is installing?

I recently attended a 2 hour pump seminar, presented by a trainer for a major pump manufacturer. I took notes, asked questions, came home analyzed that info.

I formulated questions and asked a friend for his opinion and for help in understanding some confusion I had with info from the seminar.

At this point I'm sticking with the opinions, explanations, math, analogies and history from a trusted P.E. with 40 years of experience and a reputation as a non biased expert in our industry.

If at some point the laws of thermodynamics get updated as you suggest, and the industry accepts the modifications as fact, rewrite or amend all the textbooks we all use and believe, I will revisit my opinion.

I chose not to live a "fact free" life, as seems to be more and more prevalent these days if you watch any news or politics.


Opinions may get taken as fact if they are shouted loud and long enough. I listen to all sides, ask questions and formulate my opinion. Isn't that the basis of how this thread got started in the first place?

As long as reputable sources exist for heat transfer questions, I'll use them.

As I have stated numerous times to you and the wallies, you are entitled to your opinion based on your fact gathering. I don't have a problem not agreeing as I am telling you here and have in private.

If we all agreed all the time HH may turn into a boring hangout.

Rich_49

Matt said:

Rich- my comment on 180 SWT was simply in regard to emitter over pumping - the OP's original post. If the SWT leaving the boiler is 180 and the pipe temp at the first piece of fin tube is 180 then we don't need to worry about laminar flow. The fins remove the heat from he surface of the pipe - if the pipe is hot the fins will move that energy into the room.

The second part related to a boiler where there is more radiation than boiler capacity - admittedly pretty rare.
For example - if we had the following:
1) 80' baseboard in two loops with capacity at of 610 btu per foot at 180 degree water temp.
AND
2) boiler with 40,000 output capacity.
In this case the boiler would never cycle on high limit and if it were slant fin #30 baseboard the average water temp would be 163 degrees.
Any of the following could be true:
1) 30 degree delta T - 2.67 GPM / 178 SWT / 148 RWT
2) 20 degree delta T - 4 GPM / 173 SWT / 153 RWT
3) 10 degree delta T - 8 GPM / 168 SWT / 158 RWT
4) 5 degree delta T - 16 GPM / 165.5 SWT / 160.5 RWT
The difference in boiler efficiency attributable to the difference in water temp is in the range of 3% with those differences. Nothing to look down at but not enormous savings either.

For what it's worth I have used the taco delta t pumps with good success in several applications with good success - just was saying that in the specific case above I can't see a major savings.

If the boiler is larger than the radiation the numbers get complicated fast - I suspect there may be more opportunity for savings. Maybe you can run the numbers for that.

I would state that the scenario being discussed was a steady 180* SWT with a constant flow rate of 2 gpm . Lest we not forget thermal efficiency of the boiler , stack losses and the fact that unless we keep it on we cannot guarantee a constant SWT . It is impossible . There are 2 ways to control the output of a heat emitter ;

1 . Vary supply water temp to the heat emitter while maintaining constant flow rate through it .

This method has been taken off the table by the example used by others .

2. Vary flow rate through the emitter while maintaining constant supply water temperature .

We know we cannot guarantee a constant SWT nor vary the flow because it has been stated that it is constant

4Johnpipe

This is a very dynamic discussion...
My question or 2 cents...In the example of the CI boiler with single zone of fin tube...Why would we not take advantage of a VDT circ that will guarantee 180* at the first section of fin tube and 160* at the last section of fin tube? How many times have some of us been on calls with the complaint that it is sooo hot in this room and then we can hang meat in that room. This condition happens because the rooms / house shed heat equally. However the BTU's delivered are not and cannot be equal due to the water cooling down along the circuit with a fixed speed circ. This is a byproduct of the fixed speed circ. It will heat the "house" nobody will freeze to death but come on!
We are in the comfort business...
The term equilibrium was mentioned...a very elusive state in the heating world. With a VDT circ we can at least deliver the heat with some form of equilibrium...
We have a home 2 floors, 1 zone, constant circulation, ODR, VT2218 and no thermostat...Delivering dam close to equilibrium...

hot_rod

@4Johnpipe
How many times have some of us been on calls with the complaint that it is sooo hot in this room and then we can hang meat in that room. This condition happens because the rooms / house shed heat equally. However the BTU's delivered are not and cannot be equal due to the water cooling down along the circuit with a fixed speed circ. This is a byproduct of the fixed speed circ. It will heat the "house" nobody will freeze to death but come on!
We are in the comfort business...

This sounds like a job that was not designed and or installed and balanced properly.

If the fin tubes are in series, a quick fix may be to adjust the damper, cover or remove fins to dial in the emitter in that room.

If it is piped parallel, add a balancing device to that loop.

That is a classic example where a simulation tool can be used to troubleshoot, not just design. The program shows the temperature drop along the circuit and you add or subtract fin tube length to get it to match the requirement defined by the load calc. Of course it is easier to fix over radiated rooms.

Do a room by room load calc, measure the emitter in the room and see how it matches the required emitter.

With this SIM program you can define the exact piping circuit, select various circulators, add a balance valve and fine tune the system to the exact requirement. It should be used on every job, maybe 10% of installers and designers ever bother.

I say the rooms do not "shed" heat equally, due to exposure, window size, doors, insulation detail, etc. The room by room load calc will narrow that down, granted an exisiting building will involve some guess work regarding insulation detail, and infiltration number.

I doubt the meat locker room will be corrected just by enforced ∆T, if the emitter is mismatched mid circuit.

All systems strive for and will reach thermal equilibrium IF you, we, don't throw something in the way to prevent that, a temperature limiting device for example.
Now equilibrium may not be reached at a condition you want, and a limiting control prevents dangerous operating conditions. An oversized boiler is one example of equalibrium being reached at a dangerously high temperature.

With too much emitter we could run in dangerously low operating temperature conditions for a cast iron boiler.

Remember the heat emitters dictate the operating condition of the boiler "The system doesn't care if it is delivering the proper amount of heat to the room or operating safely. It only cares about finding the balance between heat input and heat output."l

Steamhead

Hatterasguy said:

Anthony...(snip)......Your anecdotal evidence suggests that the system efficiency of an overpumped CI system is far lower than we typically project using the boiler's combustion efficiency.

This is quite an important point because, every single contractor on this site strives to get the net output of the boiler to match the heatloss of the building.

If this data is accurate, these contractors are going to get into serious issues with insufficient boiler size as the energy available to heat the building is significantly less than the net output of the boiler. It's an important discussion.

A very interesting discussion. I've been posting about this for quite some time. Here is an early article about an extreme case that took me longer to figure out than it should have. It's older than the date shown on the page, having been thru several versions of the site:

https://heatinghelp.com/systems-help-center/adjusting-the-flow-rate-for-an-old-gravity-hot-water-system/

That was one of the projects that I used as the basis for this article:

https://heatinghelp.com/systems-help-center/sizing-circulators-for-old-gravity-hot-water-heating-systems/

We replaced that boiler in 2006. Here is the thread, unfortunately minus the pics:

http://forum.heatinghelp.com/discussion/96753/thee-olde-spencer-has-retired-gordo-steamhead

After we got FLIR guns, we used them to show over-pumped radiators- pics here:

http://forum.heatinghelp.com/discussion/140472/seeing-inside-an-over-pumped-radiator

Question for the ΔT circ guys: As I understand it, this type of circ will slow down to increase the system's ΔT. However, since a converted gravity system won't circulate well with a too-low flow rate, it seems possible that a ΔT circ might slow down past this point until the boiler warms up enough to speed up the circ. This would make the system heat unevenly. Thoughts?

Paul48

I've considered the problems with using a DT circ with a gravity conversion, and wondered whether you would wind up dropping the most remote radiator(s). Balancing can be an issue with these systems, and there is usually problems with radiator valves. Replacing valves in a 100 year old system can get quite expensive, when you calculate the created leaks and the valves that don't match up well with the configurations of the old valves. The best solution I could come up with, is to put the supply and return sensors on the risers to the most remote radiator.

Gordy

Hatterasguy said:

Gordy said:

Does anyone here believe it to be possible to hold the same system delta every time at the end of satisfying a heat call with a simple CI boiler, single zone radiant emitter type of system, wet rotar dumb circulator,no outdoor reset. No matter what outdoor temp that imposes a load on the structure?

Probably not with radiant due to the much higher mass. The DT is changing constantly throughout the heat call.

This is quite unlike fin tube that heats quickly and has little mass.

The statement that the CI boiler maintains a constant DT is dependent upon reaching equilibrium. This really doesn't occur on a radiant system unless the system can run for an extended period of time (at lower SWT's).

Your own system is a good example. The DT is probably changing throughout the call and the call ends before equilibrium is ever established.

The emitters not the boiler. In a radiant emitter system with a ci boiler the emitters are mixed down temps. Plus this whole discussion has been about the emitters as far as I'm concerned. Not the boiler delta. Yes low mass emitters are different than higher mass radiant. Yes the boiler of a CI variety with, or without ODR will mirror the fintube, ci baseboard, or radiator system temps.

So mass plays a crucial role. With a CI Radiator setup especially a gravity setup. Lots of mass. The large water content in the larger piping, and ci rads can can be considered buffering to the system. Fintube, and ci baseboard not so much. The only way to add mass is a lot more emitter, or a buffer tank.

SWEI

The higher velocity circs make perfect sense if you're using a conventional thermostat to control a converted gravity system with a non-modulating boiler.