Direct Pump TT Solo 110 with 3 zones

ivanator2

I have 3 zones with the following flow requirements:



Zone 1: 4.6 GPM at 30 degree delta-t.

Zone 2: 1.8 GPM at 30 degree delta-t.

zone 3: 1.0 GPM at 30 degree delta-t.



Oversized, cast iron radiators in all three zones.



I've been watching the ongoing discussions on circulators ....



If I were to direct pump the TT Solo 110, what circulators would you suggest I take a look at? My question primarily centers around maintaining the required flow through the heat exchanger. - there would be times each zone would be the only zone calling for heat.

CMadatMe

Based On

Triangle wants a min of 5.5gpm across the HX at High Fire. Hence, when everything is calling. You need a pump that will move 7.4gpm based on your posted flow rates and delta. Which by the way exceeds the btu/hr out put of the boiler. 7.4 x (30 x 500) = 111,000 Btu/hr. Your head loss across the boiler is 5' now add the head loss of that longest zone and you need a pump that will move 7.4gpm @ X Ft of Head.

ivanator2

I'd rather be slightly undersized

We plan on installing two 20,000 btu gas fireplace inserts at some point, so on design days we'd use them if needed, or sweaters. Third floor won't have installed radiation for a few years yet and will be used sparingly.



I'm mainly wondering about outcomes when all the below are promoted.



1.  Zoning, with some some zones having fairly small GPM requirements.

2. Avoiding over-pumping.

3. Large delta-t's, which I would assume regularly mean zones with very low flow requirements.

4. Direct-pumping.

heatpro02920

Bumble bees

may work, are you doing 3 separate circulators or zone valves...

SWEI

if you balance the system correctly

and tune the ODR curve well, those zones should run almost continuously.

ivanator2

If the following were assumed

- Zone valves.

- Well-balanced to match heat loss of each room.

- Minimum flow through boiler.

- ODR.

-Direct-pumped.



Can I really take advantage of a more sophisticated circulator such as the Grundfos Alpha, or shoudl I just get something that meets GPM and X ft. of head.



Why is direct-pumped better than primary-secondary?

TonyS

A couple of reasons

1. With a single ECM pump running 24/7 it is a bit cheaper than running 2 pumps.

2.Your supply sensor is in the proper spot sending exactly what your ODR is calling for.

3. Because the boiler is heating the water to exactly what is being called for the boiler will run at a lower temperature than if it was heating the water hotter then mixing it downstream.

CMadatMe

Why is Direct Better

It isn't in America. Why? Because we need to make our boilers cheap and affordable so we can sell them. Our boilers don't offer the control logic to control the speed of the pump for the most part. Lochinvar at least offers the ability to limited control but nobody else does.



Viessmann tried it here with the WB2A but the boler was so expensive compared to the competition they ditched it here in North America. Across the pond it's standard practice for the boiler to control it's pump.



Stay tuned for the Vitodens 222F in the next few months. It will sport a 30 gal indirect below a Vitodens 200 in a single cabinet, floor standing all pre piped and ready to go. No more Power Pump Module, 120 Volt Ready and a Control set up for North America out of the box.



Triangle, Burnham and Lochinvar all offer supply sensors to midigate the mix stream temp. Nobody uses them for the most part. Viessmann forces you to use them which along with also wanting boiler pumps sized for a 40 Rise reduces the elevated return temps seen in the majority of condensing boiler applications.

TonyS

Your return temps

are already determined by your existing radiators and your heating curve. It doesn't matter how you heat your water or mix it, in order for your system to match the heating curve, the temperature of the water entering the radiator and leaving the radiator is pre determined by your heat loss and the size of your radiator. Heating some of the return water  hotter and then mixing it downstream to the temp required by the ODR only serves to increase your vent temperature and lower efficiency

There is nothing more efficient than a boiler replacing exactly what was used at the lowest possible temp Your TT boiler can do that because it has a low pressure drop exchanger because of modern computer controlled robotic welding. Casting, bending and stamping just cant accomplish this nomatter how you try to twist the math.

CMadatMe

Not True

Your return temps are influenced by the gpm that fixed speed boiler pump is moving. In a Pri/Sec piping arrangement it kills you because the system side can rarely take the gpm made by the boiler pump out into the system side. What goes into a tee must leave a tee.



In a direct pipe system it is also dictated by the operation point on the curve of the given circulator. In a multiple zone application your zone flow rates are never the same so at some point your are over pumping.



The boiler btu/hr out put is dictated by the boiler rise period. You must maintain the minimum flow rate required to move the min boiler btu/hr output. Those stupid charts mean that is the flow rate needed to get the full btu/hr output of the boiler at that given rise.



Boiler rise is a moving target and never stationary with a fixed speed boiler pump. Too many guys are hung on water temp. Btu/hr doesn't care about water temp and flow is just the conveyor belt that moves btu/hr. Water temp is what the emitter requires and has nothing to do btu/hr deliver by the boiler. The temp difference between a given supply temp and return temp does.



You cannot get around no matter how hard you try, gpm = btu/hr / (delta-t x 500) when a system is running on 100 percent water. Add glycol and we change the 500 number.

Eastman

@Chris

How will your advice change when (if) variable speed pumps become standard?

TonyS

Chris, I believe

That you believe what you say is true......so good luck with that theory.

CMadatMe

Good Luck?

Let's look at the Triangle PT 110 which has an output of 87,000 Btu/hr.



Flip that manual open to page 82. Here are the listed flow rates at different Delta-ts.



20 Delta - 8.7gpm so 8.7 x (20 x 500) = 87,000 Btu/hr

30 Delta - 5.8gpm so 5.8 x (30 x 500) = 87,000 Btu/hr

40 Delta - 4.3gpm so 4.3 x (40 x 500) = 86,000 Btu/hr



The min flow rate at high fire is 5gpm so we know we cannot run a 40 Delta. So if that is a fixed speed pump flowing a fixed flow rate every time it comes on and your not moving 8.7gpm or 5.8gpm on your system depending on what delta-t you are using where does the rest of the gpm left over go?



Because your a top notch installer you are using a pressure differential by pass on every installation that is direct piped as show in every diagram in the Triangle Application Guide right? If not your beating up that boiler pump which will eventually fail but it will be the pumps fault right?



So now that we know at operating points in the system we are not taking that full flow given by the boiler circulator we can never keep our BOILER return at the 20 degree or 20 degree temp difference between boiler supply and boiler return unless the system is taking the full flow rate and all zones are operating on the same delta-t. That happens ONCE if EVER and that is when your system needs 87,000 btu/hr.



Eastman my theory wouldn't change with a variable speed pump being controlled by the boilers logic. The boiler is doing the math for me, telling the pump what gpm to move across it's HX at that given time. The boiler is going to fire the burner to the btu/hr required based off what the system wants, ie the difference between boiler supply temp and boiler return temp.

TonyS

Ok Chris lets keep this simple

We go into a single room home to replace the boiler, we measure the house the glass ect and do a heat load calc. The calc says that this home needs 2080 btus on a 9 degree day to maintain 70 degrees inside. OK

On the wall we see 4 feet of Burnham 9a baseboard. Its already there, we are not adding to it, subtracting from it. It is our job to figure out how we can make that board heat the house on a 9 degree day. So we go to our little baseboard fact sheet( ill include a link) and we find that if we heat that board to 170 degrees we get 520 btus per foot.

So what I would do is send 180 to the board then adjust my flow so 160 is leaving. This would be an average of 170 across the board with a flow of .20 gpm.

Forget about outdoor reset, forget about the fact that the closer the water temp gets to ambient the slower the transmission of heat. Today it is 9 degrees and thats all we care about. Now tell me what temp and flow you would use to heat that house?



http://cdn.usboiler.net/products/baseboard/slenderized/assets/literature.pdf

CMadatMe

And Where Did

That other 6.7gpm that boiler pump flowed across the HX go? It's a fixed speed pump and you can't change the 8.7gpm it is flowing.



Now back to your question. I agree with you. The basis of the entire post has to do with the effect the fixed speed boiler pump has on the boiler delta-t (Temp Rise) not the systems. In the scenario you posted that boiler would be short cycling to death.



Is it not also the installers responsibility to make sure the entire heating system is operating efficiently and not getting beat up, or is it just about one facet of the heating system?



Would it not be nice if your boiler pump only flowed the 2gpm you needed in your scenario instead of 8.7gpm and then when the next zone called and you needed 4gpm the pump ramped up to meet the demand all done through the boiler controls logic to match the burner btu/hr out put?

unclejohn

You should not

Direct pump that boiler with that piping design. You must primary secondary.

TonyS

I used a flow valve to regulate

my gpm. Thats how you adjust flow through different circuits. Forget about short cycling the boiler, we will pretend we have a mini modular that fits inside our mini house that modulates to 0.

The point is Chris, in order to heat this house we must deliver a certain temp water in order for the radiation to do its job. Therefore no mater what boiler or piping strategy we use, the return water temp from our radiation will be the same, in this case 160.

Now if we take that 160 at .20 gpm and just add enough btus to bring it back up to 180 or we could do it like you say, take our 160 return and pull .10gpm through the boiler and heat it to 200 and let the other .10 gpm go through the t's and mix them downstream to regain our 180, which one is more efficient?

Your boiler is operating at 200 and mine is 180, you have two pumps and I have one.

Also, as our outside temp goes up and we get closer to our condensing temps on the boiler. We both will be pulling the same temp return water in, but I will be pulling in twice as much causing my boiler to condense more...making it even more efficient.

TonyS

What Boiler???

Your missing the point. This was a hypothetical question using real easy numbers, it wasnt about any boiler just temps needed to serve a space.

But I know what your going to say and I dont agree with that.

Lets say I actually was talking about putting a 110 prestige on that 4 feet of board(Which I wasnt) Our ultimate goal is to have the boiler fire at a rate equivalent to what the house is losing, So how is pri sec going to change that? If the boiler cant modulate low enough for the demand it is going to short cycle just as rapidly on pri-sec that it does straight through....to the second.

This is why the tt110 has selective blocking times and a larger...3-1/2 gallon exchanger

TonyS

Sorry, not a flow valve a balancing valve!

I meant a balancing valve.

CMadatMe

No You Will Not Condense More

Your leaving out the fact that the boiler pump is fixed to move an X amount of flow across the HX. If your using flow meters then you are using a pressure differential. You have to or the boiler will continually go off on high limit (short cycle) because you cannot pull out the btu/hr it is making. Pipe pri/sec and it;s the same.



You cannot just disregard the boiler pumps flow rate in your math. Yes your zone will be running on a 20 but your boiler will not.



You still haven't answered the question as to where the left over gpm the zone isn't taking goes to?



Take the attached as an example. This could be your two closely spaced tee a low loss header of even what happens with a pressure differential by-pass. You have to account for the boiler pump flow in your math for the boilers not the systems return temp.



In this example my boiler supply water temp may be 6 degrees higher then yours but I'm condensing and your not. So what's more important boiler supply water temp or boiler return as it pertains to efficiency?



When you pipe the Prestige direct your suppose to be using a pressure differential by-pass at a minimum in multi zone applications. Why? Because you'll kill the boiler pump and force short cycling of the boiler. That on board pump is moving 8.7gpm across the HX always even on low fire.



It seems to me that a lot of installers think that the system side return temp is always going to match the boiler return temp and that is just not the case.



The second attachment shows where the boiler operates in btu/hr output at different BOILER Temp Rises or it's delta-t.



How can you say running a boiler not the system on a 20 is better then running it at a 30 or 35. I'd say the sweet spot for the Prestige is running a 30 on the boiler side, pipe pri-sec and run the system side on a 20.



The 3rd attachment is all 3 rises running a 145 Supply flowing 5gpm on the system side. System side flowrate based on a 20 degree delta in all 3 examples.

Eastman

Here is my concern Chris:

I think a lot of people are reading your posts and coming to the conclusion that the best course of action would be to get a couple of dT pumps and enforce various combinations of different primary and secondary temperature deltas.  But clearly there is no point to this, since that would ensure the primary and secondary flow rates are never in synchronization.

CMadatMe

Who Says

They have to be Eastman? In essence when piped pri/sec or LLH you have three different systems or segments to the complete heating system. System 1 being the boiler system moving a fixed gpm of x amount of btu/hr at a certain water temp to System 2 the secondary or distribution side takes it's x amount of btu/hr at a certain water temp to System 3 the emitter which delivers it's btu/hr out to the space. How much btu/hr system 3 takes from system 2 dictates the delta-t. System 2's only job is to move the btu/hr. Well I made it in system 1, gave it to system 2 so now it's up to system 3's to take what it needs.



Flow rate is nothing more then a conveyor belt moving btu/hr around the system and since we are hydraulically separated system 1's flow rate has no influence over system 2's. System 2's does though have an effect on system 1's return water temp. We are after btu/hr are we not?

TonyS

There is no leftover GPM

I have throttled my flow rate down to obtain my 160 return through the board!

Now if we both have a return coming back at 160...ahhh forget it, I have to go weed wack my driveway!

CMadatMe

How Did You Throttle

Down the boiler flow rate? It's a fixed speed pump moving 8.7gpm at all times. You do have a pressure differential by pass when direct piped correct? CH Blocking is just a fancy name for post purge. They put in in there because of exactly what I'm trying to get across.



They know and understand that the on board boiler pump flows more then the typical system is able to pull out. We like zoning here in America. If you had ACV's Pretisge from across the pond that pump would be controlled by the boilers control logic. Like everyone else over there does. The boiler pumps flow is matched to the boilers btu/hr output via variable speed. Less btu/hr pump slows down, more btu/hr pump speeds up.

Jean-David Beyer

We are after btu/hr are we not?

We sure are after btu/hr!



I assert that whether you use direct or primary-secondary, there are two (sub) systems in a heating system: the boiler and the emitters. I further assert that the heat produced by one subsystem is equal to the heat consumed by the other under steady state conditions.



Heat enters the system by the combustion in the boiler.

Heat leaves the system by radiation and convection from the emitters.

Heat is measured in BTU and heat flow is measured in BTU/hour, not by temperature difference between supply and return (there is a relation between temperature difference and water flow on the one hand and heat flow on the other, but that is not relevant to the present discussion).



By the high-school laws of physics, if the heat entering the system is the same as the heat leaving the system, the system temperature will remain the same. If the heat entering the system exceeds the heat leaving the system, the system temperature will increase without limit. If the heat leaving the system exceeds the heat entering the system, the system temperature will drop without limit.



Of course, there are limits. If the temperature goes up too far, an aquastat will stop the fire, or the water will boil and the pressure relief valve will work. If the temperature goes below the room temperature of the emitters (actually impossible) the emitters would absorb heat from the zone and return it to the system.



Therefore, in normal operation, the heat added to the system is equal to the heat removed from the system and the system temperature remains the same if the environment remains the same.



So we do not really care about temperature drop through these systems. What flow rate gets the most heat out of an emitter with a given input temperature? The maximum flow rate it makes sense to use, because any lower will cause a fixed size emitter to emit less heat. This flow rate will, in fact, have the lowest delta T.



Now consider the boiler. Here we want the boiler to absorb the most heat from the fire. Similarly to the case of the emitters, what flow rate is required to do this? To get the most transfer between the fire and the water, we want the maximum temperature difference possible between the fire side and the water side of the heat exchanger. And how is this obtained? It is obtained by using the maximum reasonable flow rate, because if you use less, the temperature at the exit of the heat exchanger will be hotter than if you used a higher flow rate, and less of the heat would go into the water and the rest would go out the venting system. This flow rate will also have the lowest delta T.



Notice what is going on.



With high flow through the boiler, the gradient between the fire and the water will be highest, resulting in maximum absorbtion of heat (and minimum temperature rise).



With high flow through the emitters, the gradient between the water and the air will be highest, resulting in maximum emission of heat to the load.



Now if the load is taking the maximum heat, there will be less heat returned to the boiler. Its temperature will be higher than with lower flow, but the heat will be less due to the greater flow. We are returning less heat to the boiler.



If the boiler is taking in its water from the emitters at a higher temperature, but at a greater flow rate, such that the actual heat is less that at lower flow rates, the actual cooling of the boiler will be greater than otherwise. So the entire system delivers the heat at a lower temperature. That helps everything in a system such as these.

CMadatMe

I Quote

"The water within the system is neither the source of the heat nor its destination; only its "conveyor belt". Thermal energy is absorbed by the water at a heat source, conveyed by the water through the distribution system piping, and finally released into a heated space by a emitter.



"The overall hydronic system consists of four inter-related subsystems. The Heat Source, Distribution System, Heat Emitters and Control System."



"For example, if you observed the operation of a hydronic heating system for an hour and found no change in the temperature of the water leaving the boiler, although it was firing continuously, what could you conclude? Answer. Since there is no change in the water's temperature, it did not undergo any net gain or loss of heat. The rate the boiler injected heat into the water was the same as the rate the heat emitters extracted heat from the water."



"It has been stated the every circulator in a primary/secondary system operates as if it were installed in an isolated circuit. The primary circulator (boiler circ) does not assist in moving flow through any of of the secondary circuits, or vice versa. The function of the primary loop is simply to convey the output of the heat source to the secondary circuit, "pick up" points, while operating at or close to a selected temperature drop."



Contrary to myths that exist in the industry, the primary circulator does not necessarily have to be the largest circulator in the system. It may even be the smallest circulator in some systems. The primary circulator also does not need to operate a flow rate equal to or greater than the total flow rate of all the secondary circuits that can operate simultaneously. The flow rate necessary to deliver the full output of the heat source using a specified temperature drop can be found using the Equation:



Required Flow Rate = Qhs (btu/hr) / (Delta-T x 500)."



" John Siegenthaler, Modern Hydronic Heating 2nd Addition." The 3rd is in my office and didn't have it handy to use.



I know some think I've been beating a dead horse but my whole point is to give the best advice on how to make THE BOILER operate more efficiently while still maintaining the comfort the customer needs and wants.

Zman

Correct

Chris,

You are of course correct.

This thread is a great example of why the manufactures have not taken this technology across the ocean.

 American heating contractors are just not ready to embrace (or understand) something this advanced.

Carl

Paul48

It's here now

I didn't know the argument was continued in this thread.

On reflection, I don't feel that either method is necessarily wrong, just different. The btus per hour will be used either way, and I can see applications for both methodologies. J-D's approach would work well with emitters in series, and Chris's approach would work better with emitters in parallel.

The only caviat I would add to J-D's approach, is, that you must stay within pipe sizing guidelines to avoid velocity noise.

Jean-David Beyer

Quotes from John Seigenthaler.

"The water within the system is neither the source of the heat nor its

destination; only its "conveyor belt". Thermal energy is absorbed by the

water at a heat source, conveyed by the water through the distribution

system piping, and finally released into a heated space by a emitter."



Sure.



"The overall hydronic system consists of four inter-related subsystems.

The Heat Source, Distribution System, Heat Emitters and Control System."



Sure, if it helps your understanding of this issue, divide the heating system into as many subsystems as you like. I thought two subsystems were enough, but if you need more to understand it, fine. I could say there are five, the kind of insulation the boiler jacket has, or the color paint of the cabinet. I just do not see that they matter.



"For example, if you observed the operation of a hydronic heating system

for an hour and found no change in the temperature of the water leaving

the boiler, although it was firing continuously, what could you

conclude? Answer. Since there is no change in the water's temperature,

it did not undergo any net gain or loss of heat. The rate the boiler

injected heat into the water was the same as the rate the heat emitters

extracted heat from the water."



Again: sure.



"It has been stated the every circulator in a primary/secondary system

operates as if it were installed in an isolated circuit. The primary

circulator (boiler circ) does not assist in moving flow through any of

of the secondary circuits, or vice versa. The function of the primary

loop is simply to convey the output of the heat source to the secondary

circuit, "pick up" points, while operating at or close to a selected

temperature drop."



Again: sure.



Contrary to myths that exist in the industry, the primary circulator

does not necessarily have to be the largest circulator in the system. It

may even be the smallest circulator in some systems. The primary

circulator also does not need to operate a flow rate equal to or greater

than the total flow rate of all the secondary circuits that can operate

simultaneously. The flow rate necessary to deliver the full output of

the heat source using a specified temperature drop can be found using

the Equation:



Required Flow Rate = Qhs (btu/hr) / (Delta-T x 500)."



" John Siegenthaler, Modern Hydronic Heating 2nd Addition." The 3rd is in my office and didn't have it handy to use.



Sure to all that. That changes nothing in this discussion.



I gave away my 2nd Edition, so I cannot check it, but since it is the same as Equation 4.7 in the 3rd edition, I do not dispute it except for two points.



1.) He does not say this is the Required Flow Rate. He is giving this as the Sensible Heat Rate Equation.



2.) He says IF you have a flow rate of f and if you get a specific Delta-T, then the heat transfer rate is be Q,  He does not say  you can get that. Furthermore, he does not say (at least not here) on what basis you should pick one temperature drop instead of another.



In my system, for example, the water temperatures I need to supply to make up the heat loss are such that if the outdoor temperature is 50F or above, I put 76F into the slab, so unless I heat that zone to less than 66F, I cannot possibly get a delta-T of 10 no matter what flow rate I use. So although his equation is correct, it does not apply in this case.



It is rather similar in my baseboard zone, although the differences are not so striking. On 50F outdoor days, I put 110F into the baseboard and get 108 to 110 F back. So delta-T is between 0 and 2. I calculate the flow rate to be a little under 3 gpm. It is not clear what flow rate I would have to use to get a delta-T of 10, for example, but if I used that, since the baseboards are in series and that cannot be changed without ripping out the floor of the two rooms, one will run with an average temperature of 107.5 and the other with an average temperature of 102.5. Since the heat loads of the two rooms are the same, one could be much warmer than the other and that would be unacceptable. Recall that the comfort is the real goal here, not mere boiler or system efficiency. And it might be even worse than that. If the flow rate to actually get a 10F delta T is so low that all the heat came out in the first room and none in the second, because as the temperature to a baseboard is reduced, its output drops faster than the temperature inside is reduced. So to get a delta-T of 10F, perhaps I would be getting 9F in the first room and 1F in the second. But whether this happens or not, if I reduce the average temperature in the emitters, the heat output is less than if the emitter runs at the same temperature from end to end. And increasing the delta-T necessarily reduces the average temperature of the water in the emitter, so the output from the emitter is reduced.



"I know some think I've been beating a dead horse but my whole point is

to give the best advice on how to make THE BOILER operate more

efficiently while still maintaining the comfort the customer needs and

wants."



I agree pretty much that that is the goal. I just do not think that that is the way to achieve it. With a mod-con, and probably all boilers, to get the efficiency of the boiler to go up, you need to have the water temperature of the water in the boiler heat exchanger to be as low as possible, and if you increase the delta-T of the water in the boiler's heat exchanger, then the average temperature of that water is higher than it would be with a lower delta-T and that will reduce the efficiency of the heat transfer. Similarly, if you look at the condensing in a condensing boiler, you want the average temperature of the fire side of the heat exchanger to be low enough to condense, you need as small a delta-T as you can get to keep the average temperature down, and that, too requires a higher flow rate.

TonyS

Incorrect

Chris is dead wrong!

TonyS

I am going to email John Seigenthaler

and see if he would put an end to this nonsense.

Jean-David Beyer

you must stay within pipe sizing guidelines to avoid velocity noise.

Absolutely right!



In this discussion, I am ignoring that because, while true, it does not affect the issue.



In a practical application, of course it must be considered.



I happen to run with very low delta-Ts in my system. It just happened, not by design, but because the installing contractor probably had a lot of Taco 007-IFC circulators on hand and used them everywhere. I observed the low delta-Ts and wondered if I should close the isolation valves down somewhat in order to raise the  delta T. I did not do this because I did not wish to harm the circulators. It may be that it would not harm them, but I did not want to risk it.



So then I wondered if I should replace them with smaller circulators, 3-speed circulators, or what. I did calculate the flow rates as best I could, but do not have great confidence in my calculations, because all the piping in my slab is in the slab, so I do not know how much tubing is in there, what elbows and Ts are in there, and so on. All I know is that five 1/2 inch copper tubes enter the slab and one 1 inch copper tube comes out. Similarly in the baseboard zone, I know for sure there is 64 feet of half-inch tubing, 24 feet of 3/4 inch tubing, 28 feet of 3/4 inch baseboard, lots of 90 degree elbows (I do not know how many, but lots more than 10, and some more 3/4 inch and 1/2 inch stuff. I did the best I could with that zone and came up with, I think, 2.8 gpm. I should be able to run that through 1/2 inch tubing and stay under 4 ft/sec.



In any case there is no noise from either zone except when there is air in the baseboard zone, and that has disappeared a few months ago now.

Eastman

NOOOOOO

These are the best threads.

Jean-David Beyer

I am going to email John Seigenthaler

Excellent idea! I hope he has the patience to deal with it.

CMadatMe

Tony and Jean

Are stuck on the system side. Everything I'm trying to get across is on the BOILER SIDE or primary. Even the Triangle piped direct with a pressure differential by-pass is going to elevate the boiler return temp. And, yes, your are suppose to use a pressure differential by-pass.

Jean-David Beyer

Tony and Jean Are stuck on the system side.

Are you paying attention? I believe neither Tony nor I are stuck on the system side.



I am paying attention to both subsystems: the boiler and the emitters. The considerations are the same. In both cases, you want as great a flow as possible to get maximum heat transfer at the lowest possible temperature. And this requires the lowest delta T.



If we consider the boiler subsystem separately, the easiest way to increase the efficiency is to turn it off: no heat wasted at all. But this is silly. That is why we must study both subsystems. But the considerations are the same.

CMadatMe

Ok Then

If you agree with every quote I posted then why do I have to move the same flow on the primary side as you do on the secondary side. My only job is to move btu/hr to the secondary side.



Whether I can move your boilers full 71,000 btu/hr with 7.1gpm or 4gpm to the secondary side what does that mean anything to the secondary side? You can still move what ever gpm at what ever flow rate you want on the secondary side. I just want to move out the btu/hr to the distribution system and get it away from b-lining right back into my boiler return at the closely spaced tee's thus keeping my boiler return from seeing an elevated water temp.



The problem is the majority of installers wouldn't know how to do the math and there are 4 boilers that I know of that offer a supply side sensor, Loch, Viessmann, Burnham Alpine and Triangle. One, Viessmann makes it so you have to use it the others list it as an option. There are some that are fixed that the elevated 5-6 degree boiler supply temp cuts down on efficiency. The math shows while I would have an elevated boiler supply temp I would be condensing while they would not. That 160 to 140 degree supply water temp in the majority of baseboard applications is the heart of the season and in most cases with large boiler flow rates and small system side flow rates condensing boilers struggle to get into condensing mode.





You case is different in the aspect that you don't need higher then 130 degree supply water temp so this really doesn't effect you. The majority of installations out there though it does. Even in your case you don't need a 007 as a boiler pump. You don't need flow from the primary side you need btu/hr. How I get that btu/hr doesn't make a difference. You said yourself you don't need the full output of the boiler. Why can't you limit the modulation rate and size your pump accordingly?



The only reason boiler manufactures give the pumps they do is because they are afraid of who is installing the product and the pump they give is based off the same math and pump they give with a cast iron boiler. That's what installers are use to working with, the standard 20 Degree Delta-t. Takes the thought process out of it.

Paul48

Chris

If the target temp is 130* and he wants to pump 15 gpm primary and secondary......What's the difference? Again, I am not arguing right or wrong,it's just a different approach. The boiler is producing what it should(based on ODR). The emitters will use what they need.

I might argue this approach with cast-iron radiators. We all know they suffer when over-pumped. But, for his baseboards in series, it's six of one, half-a-dozen of the other.

Jean-David Beyer

My English must be worse than I thought.

"If you agree with every quote I posted then why do I have to move the

same flow on the primary side as you do on the secondary side. My only

job is to move btu/hr to the secondary side."



You don't. I never said you do, and I do not believe it either. I think it would be unusual for the flow in the primary and the secondary loops to be the same. It could happen.



"Whether I can move your boilers full 71,000 btu/hr with 7.1gpm or 4gpm

to the secondary side what does that mean anything to the secondary

side?"



If I grant that you can, it would mean nothing to the secondary side.



"You can still move what ever gpm at what ever flow rate you want on the secondary side."



Not exactly. If I understand what you are trying to say, I have a fixed size radiant slab and piping, or a fixed size set of baseboard. In either case, I cannot reject the amount of heat I desire unless the flow rate is high enough that the heat emitted by the emitter is high enough, and there are only two ways of doing this, and one is not acceptable. The first way is to use a high enough flow rate so that the delta T is low, and the other is to raise the supply temperature so that it puts out enough heat in spite of the delta T loss from using a lower flow rate. And in the interest of efficiency, I do not want to raise the supply temperature.



"I just want to move out the btu/hr to the distribution system and get it

away from b-lining right back into my boiler return at the closely

spaced tee's thus keeping my boiler return from seeing an elevated water

temp."



Well, the way to get the most heat (not temperature) out of the boiler is to ensure that the heat exchanger is running at the lowest possible temperature. And to do that, you have to run a flow rate high enough that the delta-T through it is as low as reasonably practical. Now what prevents it all from coming back to the boiler is how much of that heat (not temperature) is picked up by the secondary loop and rejected into the load in the secondary loop. And, as I have said before, whatever the temperature being delivered by the secondary loop at the output from the supply-side of the closely spaced Ts (or the hydraulic separator) is going control the maximum amount of heat that will be rejected by the emitters. Lowering the flow in the secondary can reduce this, but cannot increase it. So when you are all done, the way to get low temperatures is to get the heat out of the boiler as fast as you can into the secondary, where you get the emitters to reject the heat into the load as fast as you can. And mainly, in most of the heating season, the only reasonable way to ensure low return temperatures is to reduce the firing rate so end up with as low as possible temperatures are delivered to the secondary loop as you can get, consistent with providing enough heat. The W-M Ultra does this by controlling the temperature with a sensor at the output of the closely spaced Ts.



"The problem is the majority of installers wouldn't know how to do the

math and there are 4 boilers that I know of that offer a supply side

sensor, Loch, Viessmann, Burnham Alpine and Triangle. One, Viessmann

makes it so you have to use it the others list it as an option."



I do not know most installers; only two, and one does not understand mod-cons. Unfortunately, I picked them to design, supply, and install my system. My current contractor is much better than the first, though not ideal either. What math do you need them to do? They should be able to do the heat loss (that my installer did not do), but they can get computers to do that if they do not know which end of a pencil to press against the paper. It is only 6th grade arithmetic after all: tedious, but easy.



"There are some that are fixed that the elevated 5-6 degree boiler supply temp

cuts down on efficiency. The math shows while I would have an elevated

boiler supply temp I would be condensing while they would not."



It is not clear to me what you are talking about here. What elevated temperature? If you make a boiler run at a higher supply temperature, your efficiency is lower than if it runs at a lower temperature because the heat not absorbed by the heat exchanger goes up the stack instead of into the water.



What math and what does it show?



"That 160 to 140 degree supply water temp in the majority of baseboard

applications is the heart of the season and in most cases with large

boiler flow rates and small system side flow rates condensing boilers

struggle to get into condensing mode."



I do not understand what you are saying.



How does slowing the boiler pump help this at all? I see no difference between a high speed pump in the boiler loop pumping water up to the closely-spaced Ts and having most of it go right back down to the boiler on the one hand, and a low speed pump in the boiler loop leaving the heat in the boiler. There is actually a small benefit in the former case: the increased flow in the heat exchanger will reduce the possibility of local hot spots that could damage the heat exchanger before the control system could lower the firing rate, or cut off the burner entirely.



 If you use such high supply temperatures, I am not surprised that it is difficult to get much condensing. But lowering the flow rate in the secondary will not help. Doing that will cause the secondary to reject less heat, so the return heat will be more: just what you do not want. In such a situation, the best solution is to increase the size of the baseboard or add more radiant panel so the same amount of heat can be delivered at a lower temperature. That, for example, is why I took out the two three-foot baseboard units and had two 14-foot baseboard units put in. Just so I could get the heat I needed at a lower temperature.



"You case is different in the aspect that you don't need higher then 130

degree supply water temp so this really doesn't effect you. The majority

of installations out there though it does. Even in your case you don't

need a 007 as a boiler pump. "



I need the 007 boiler pump because W-M are so convinced that I need it that they supply it just so my contractor will not put something smaller in there. And if I change it, good bye warranty. I secretly believe that W-M know what they are doing. Also my calculations show that that size circulator will get the heat out of the boiler faster than a smaller one would.



"You don't need flow from the primary side

you need btu/hr. How I get that btu/hr doesn't make a difference. You

said yourself you don't need the full output of the boiler. Why can't

you limit the modulation rate and size your pump accordingly?"



I need the flow W-M specify because if the flow is too low, I am afraid the pins on the fire side of the aluminum heat exchanger would melt off, or burn off. I need the flow so that the amount of condensing is maximum. To get that I want the average temperature of the heat exchanger to be as low as possible, and that is with the maximum flow.



I can limit the maximum firing rate (not the modulation rate), and have done so because I cannot adjust the damping ratio of the feedback control system on the U-control board of the boiler; but that is not relevant here.  I cannot lower the firing rate below 20% and that is far too high if my baseboard zone only wants 1500 BTU/hour, or whatever it is, on a fairly warm day.



As long as that pump is big enough, and not so big as to cause noise, erosion of the pipes and fittings, and use way too much electricity, there is no point in changing it.



"The only reason boiler manufactures give the pumps they do is because

they are afraid of who is installing the product and the pump they give

is based off the same math and pump they give with a cast iron boiler.

That's what installers are use to working with, the standard 20 Degree

Delta-t. Takes the thought process out of it."



I do not believe it. I think the reason is that they do not want damage done to their heat exchangers and supply the pumps they do so they do not overheat.

Jean-David Beyer

What's the difference?

Right, and I doubt I get anywhere near 15 gpm out of those 007 circulators in my system. ;-)

Gordy

Poor Ivanator

Lost interest after his third post.



The poor horse hide is tanned, and stretched ready for making gloves.



I think we need a delta t section on the wall......seems to be a lot of this discussion this season for some reason say delta t circs? Trying to right boiler sizing wrongs.