Taco Question

Paul48

I never attempted to justify it John. Bob asked a question...I answered it. Rich asked where the other 7* went.....I answered that too. In this example, it stayed in the boiler.

Eastman

A lot of the boiler documentation I have seen shows significant efficiency gains at partial modulation rates.

Eastman

There's also other system variables that can be optimized when supply and demand can be met in real time.

Eastman

Why limit your self to just 20 degrees?

4Johnpipe

In a cold room you will have more heat transfer...in this case it will heat quicker.
Delta T is the result of heat being transferred...The BTU's were not left in the boiler or returned. We have this as shown by the SWT and RWT...
If we supply with a fixed temp for both rooms and 1 room returns with a cooler temp the BTU's were left in the room.
I did not state this with orginal example because I do not know the characteristics of the room. Assuming all are identical the wider DT between supply and return left the BTU's in the room...
Unless physics ceased to exist that is...

Eastman

@4Johnpipe

You're way over thinking this. The heat transfer into the room is a direct consequence of the difference in room temperature and floor temperature.

The one with the higher AWT is emitting more heat because there is a higher deltaT between the floor and the air. The example doesn't really add anything to the discussion, I wish hot rod hadn't posted it.

4Johnpipe

Thought is stated that the assumption is both rooms and characteristics are identical...

hot_rod

Eastman said:

@4Johnpipe

You're way over thinking this. The heat transfer into the room is a direct consequence of the difference in room temperature and floor temperature.

The one with the higher AWT is emitting more heat because there is a higher deltaT between the floor and the air. The example doesn't really add anything to the discussion, I wish hot rod hadn't posted it.

I should have added more info with the example, sorry about that, here are some numbers to better clear up the point of the piping circuit comparison.

And here is the main point. As Hatt mentioned it cannot be just delta T, the flow rate needs to be part of the calculation.

The temperature drop along the baseboard naturally changes as the flow rate through the baseboard changes. The notion that any heat emitter “wants to,” or even can, remain at a fixed temperature drop as the flow rate changes is not supported by these results.

Step through the entire process here.
http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_16_na_0.pdf

4Johnpipe

Isn't the main point that delta T is not a thing...Delta T is only the evidence that heat has been transferred? We don't create it we measure it...What I have come to love is the fact the Taco has found a way to measure it and adjust a flow rate to keep one aspect of all the different delta T's occurring in a system constant. We are not making a delta T with these pumps we simply can monitor it and vary the flow to an optimum pre set range / point. If your system design wants 10* give it 10*. If it needs 35* give it 35*...
Let the flow rates work in harmony with the aspects or requirements of the whatever emitters we are using...

hot_rod

4Johnpipe said:

Isn't the main point that delta T is not a thing...Delta T is only the evidence that heat has been transferred? We don't create it we measure it...What I have come to love is the fact the Taco has found a way to measure it and adjust a flow rate to keep one aspect of all the different delta T's occurring in a system constant. We are not making a delta T with these pumps we simply can monitor it and vary the flow to an optimum pre set range / point. If your system design wants 10* give it 10*. If it needs 35* give it 35*...
Let the flow rates work in harmony with the aspects or requirements of the whatever emitters we are using...

Delta T is a thing, and an important thing But it works with other things going on in the system. It's not just delta T that make it all work successfully and efficiently. You cannot ignore flow rates and how they effect heat transfer, in conjunction with the ∆T.

Yes there is a role for VS ∆T circulators, we have asked for them for a decade or more now. But it is not a fix all for every system. Actual experiences shared here by the installers points to some conflicts when the pump is trying to do one thing and the boiler control another, they need to be on the same page working together.
Knowing how to apply it correctly is what we are all trying to understand and communicate.

Going to be in the Colorado area in early December? Siggy will be clearing up some of the misconceptions and questions on this topic.

Paul48

..

Rich_49

@ Eastman . Exactly where in the room did the heat go in both examples . Next question , since the Delta between the exterior wall and the hottest water and the flow rate was slowed is it possible that more heat transferred at that point and those 7* went toward raising the MRT ? Again I ask , where did the 7* go ? I cannot believe that nobody figured it out The biggest factor and reason for installing radiant is to warm the surfaces , the coldest surface is the outside wall and the higher flow rate did not allow that transfer to take place as effectively as the lower flow rate . The colder surfaces in the room had time for heat tgransfer to take place in a beneficial way

Does anyone disagree that this is what happened ?

hot_rod

4Johnpipe said:

Isn't the main point that delta T is not a thing...Delta T is only the evidence that heat has been transferred? We don't create it we measure it...What I have come to love is the fact the Taco has found a way to measure it and adjust a flow rate to keep one aspect of all the different delta T's occurring in a system constant. We are not making a delta T with these pumps we simply can monitor it and vary the flow to an optimum pre set range / point. If your system design wants 10* give it 10*. If it needs 35* give it 35*...
Let the flow rates work in harmony with the aspects or requirements of the whatever emitters we are using...

Isn't the main point that delta T is not a thing...Delta T is only the evidence that heat has been transferred?

Delta T IS a thing. Its a number you pick to design the system around. Then you select a circulator to provide that ∆T based on GPM,the required flow, and the pressure drop established in that circuit, the pump curve and system curve intersect at the OP, operating point.

Steve Thompson (Taco)

Sorry, I can't resist...

I've always said, variable speed (flow) circs should directly communicate (on the same page) with a modulating boiler (Vdc for example). Two separate brains not communicating is a bad thing (just ask my "X").

But short of that, the closest "separate brain" communication is temperature (boilers react to temp as does a delta T circ). But then there is a potential in different reaction times, PID etc. that could cause issues. The last thing we would recommend as a dedicated boiler circ (remember we have both and believe it or not are unbiased on this point) would be a VR 1816 (or equivelant delta P circ) set on proportional pressure or the VR 3452 (larger delta P) set on "Auto" - definitely asking for trouble with low mass boilers.

BTW we've had both 0-10Vdc and delta T standard AC circs for over 10 years for outdoor reset applications. Didn't understand their value as a delta T circ until Mr. Barba came along.

Just sayin...

Paul48

So you cooled that room and even selected the boiler type?

Rich_49

Bob ,

Mis application and improper use are very important things also . What could Siggy clear up that he has not written in MHH3 ? The book states it all quite accurately , especially the ideal heating curve which I just described from figure 10-6 where the heat transfer characteristic showed much or most of the heat being offloaded at the cold walls where the greatest Tw / Ts Delta lives , or am I mistaken about maintaining MRT being the major part of radiant ? Radiant energy goes to surfaces and not ambient T air , correct ? The greater the Delta the more heat will be transferred .

Maybe some folks need clarification and I am quite sure Siggy will accomplish that without contradicting himself as many often unwittingly do because they lack an understanding . Think I don't get it ? Maybe you can ask John how I did during the first ever Mastering Hydronic System Design course he offered . Yeah , I know a bit about John's writings and beliefs

hot_rod

Rich said:

@ Eastman . Exactly where in ten room did the heat go in both examples . Next question , since the Delta between the exterior wall and the hottest water and the flow rate was slowed is it possible that more heat transferred at that point and those 7* went toward raising the MRT ? Again I ask , where did the 7* go ? I cannot believe that nobody figured it out The biggest factor and reason for installing radiant is to warm the surfaces , the coldest surface is the outside wall and the higher flow rate did not allow that transfer to take place as effectively as the lower flow rate . The colder surfaces in the room had time for heat tgransfer to take place in a beneficial way

Does anyone disagree that this is what happened ?

I think thiis is where you are still confused.

The higher flow rate did not allow that transfer to take place as effectively as the lower flow rate.

You need to get over that BTUs not jumping off a train at certain (faster) speeds misconception. It's just not so as every example above shows.

And yes we agree that getting to a 2∆T from a 20 will not be worth the energy expended to get there, unless as Hatt mentioned it's free energy.

Gordy

I do not disagree about the radiant slab to exterior wall delta transferring more at the beginning of the loop, but then are all the walls exterior? Assumptions we can assume a window, and even a door in a wall are exterior walls, and even walls with out them unless known.

Deltas can tell us other things not just btus delivered to the emitter , but also btus delivered from the emitter to the room, the rooms emitter to mrt delta It's a 2 part delta. If the room is 60 and the radiant slab is 85 in one case, and another room is 70 and the slab 85 which slab will lose btus faster? No flow rates needed for that one.

The slower flow rate room allowed more passengers of the btu train to get off at the beginning, and the higher flow room allowed the same at the beginning
It was also able to carry some btus deeper into the room do to the higher flow rate.

So it's quite possible both rooms have the same flow rate and the room with the higher delta the extrerior wall is poorly insulated with a single pain window, and the lower delta room is highly insulated with a much better quality window.

But if envelopes are equal the btus got off the train sooner in the low flow room,

What Rich seems to be trying to say is the higher delta delivers more btus per the universal formula can't beat the math. So in saying that I will assume that you are saying an emitter with a high delta of any kind is dumping more btus than one with a lower delta. Again the math. But having the whole emitter at an even temp means something even if it's a narrow delta. The bigger the emitter surface the more it comes into play. That is the emitter to room delta. If the beginning of the emitter is hot it will transfer more to the room than the end which is cooler.

Gordy

Something I have thought about @Hatterasguy strap on temp sensors, and their delayed response time verses well sensors. Especially in laminar flows. The water to pipe pipe to sensor sensor to circuitry chain. Is it enough to make the circ chase its tail.

Rich_49

Both rooms are one room at exact same conditions . Bob would not even suggest other , I hope . Walls extending outward from ends of room that are perpendicular with tubing would suggest they are interior walls . Many guys space tubing closer in to approximately 4 feet , what do we suppose the reason for that is ? Take a look at this excerpt

Q.
I realize that existing software packages vary the density of radiant floor tubing by having more closely spaced sections relegated to outside wall proximity, while increasing the spacing towards the center of a room. The logic of this is simple and understandable, but my question is this: what factors are derived from the input information that drives this design? Is it merely that consistent spacing yields inadequate capacity in certain rooms and thus increased density (closer widths) merely accommodates the load? Or are there other factors that influence the decision to do so?

A.
Richard,

There are likely various opinions on this.

I will often use close tube spacing in floor areas about 4 feet in from exterior walls with lots of glass, just to boost the mean radiant temperature in proximity to the glass.

You can also use methods in chapter 10 to calculate the output of the close tube spacing versus wider tube spacing, and then determine the area required for the close tube spacing based on meeting the total room load (assuming the entire available floor area with the wider spacing can't handle the design load).

On high end houses, I will often go with close tube spacing throughout the project. My justification is that the extra tubing doesn't add much to the total installed cost of the system (perhaps 2 or 3 %). The closer spacing reduces variation in floor surface temperature, and brings down the supply temperature thus increasing heat source efficiency. High end house = close tube spacing.

seems what I stated above is not just my opinion but others as well . Anyone care to take a satb at who answered this man's question ?

Gordy

What I find interesting is convective emitter charts raise their btu output ratings according to water temperature, and incoming air temp. An convective emitter can have the same flow rate, and put out a variety of different btus per Lin. Ft. Depending on water temperature. So why can't a radiant slab?

We get to hung up on the delta t, and the fact that a wide one will allow more output to an emitter, and we are,forgetting about AWT so the full area of the emitter can give the same output.

4Johnpipe

@hot rod said
Delta T IS a thing. Its a number you pick to design the system around. Then you select a circulator to provide that ∆T based on GPM,the required flow, and the pressure drop established in that circuit, the pump curve and system curve intersect at the OP, operating point.

Not exactly...mother nature provides the outdoor design temperature based on historical data...the client picks the indoor target temperature and we measure / calculate the delta T. My intention was to point out that we do not manufacture the delta T. We use the delta T that occurs as our driving force behind the heating system. After all the delta T between us and our environment to be in the comfort range is our goal. We try do achieve the comfort range as efficient as possible. Wish I could say that each and every time we commission a new system set to the math performed it runs perfect from day 1. Not so I allow return trip(s) to make adjustments as to real time expectations.

Rich_49

With identical EWTs only flow rate can increase AWT in same baseboards . A well known author of all things hydronic believes , as that's what he wrote , just like the manufacturers did . 1 gpm SHOULD BE USED unless you can guarantee equal to or greater than 4 gpm flow rate . Again I state and in agreement with the author , you must remove the 15% HEF and a 300% increase in flow will only give you a net gain of .057 or 5.7% . Thats alot of squeeze for no juice , not even worth the effort or mention and I wish it would not be brought up again . Can anyone say Obfuscation ?

This is nonsensical in our discussion because at those flow rates most boilers will stack heat and shut down . Can you guarantee 4 gpm at the same EWt when the burner has shut down and will not fire again until the temp is below . This cannot be guaranteed except in a fantasy world . I can tell you this , the UFT will certainly shut down it's combustion operation at 5* above the water temp at a given time based on your needs as progra\mmed in the ODR curve . Yes guys they control burner by temp and not just high limit temp . feel pretty abd for those who do not really know what they are doing .

hot_rod

4Johnpipe said:

@hot rod said
Delta T IS a thing. Its a number you pick to design the system around. Then you select a circulator to provide that ∆T based on GPM,the required flow, and the pressure drop established in that circuit, the pump curve and system curve intersect at the OP, operating point.

Not exactly...mother nature provides the outdoor design temperature based on historical data...the client picks the indoor target temperature and we measure / calculate the delta T. My intention was to point out that we do not manufacture the delta T. We use the delta T that occurs as our driving force behind the heating system. After all the delta T between us and our environment to be in the comfort range is our goal. We try do achieve the comfort range as efficient as possible. Wish I could say that each and every time we commission a new system set to the math performed it runs perfect from day 1. Not so I allow return trip(s) to make adjustments as to real time expectations.


Maybe we are talking two different ∆T. you are saying the ∆ between outdoor and indoor, so 0 outdoor, 70 indoor 70°∆T, agreed.
Of course you could still change those numbers if you expect global warming or global cooling. Or if the customer is older they may request 72F indoor. So you the designer still chose that ∆. That elps determine the heat load.

I'm talking about the ∆T of the fluid supplied to cover the load. 110 supplied to the emitter -95 returned to the heat source, that is the design ∆T for sizing pipes, pumps, and determines, along with flow rate the heat transfered.

hot_rod

Gordy said:

I do not disagree about the radiant slab to exterior wall delta transferring more at the beginning of the loop, but then are all the walls exterior? Assumptions we can assume a window, and even a door in a wall are exterior walls, and even walls with out them unless known.

Deltas can tell us other things not just btus delivered to the emitter , but also btus delivered from the emitter to the room, the rooms emitter to mrt delta It's a 2 part delta. If the room is 60 and the radiant slab is 85 in one case, and another room is 70 and the slab 85 which slab will lose btus faster? No flow rates needed for that one.

The slower flow rate room allowed more passengers of the btu train to get off at the beginning, and the higher flow room allowed the same at the beginning
It was also able to carry some btus deeper into the room do to the higher flow rate.

So it's quite possible both rooms have the same flow rate and the room with the higher delta the extrerior wall is poorly insulated with a single pain window, and the lower delta room is highly insulated with a much better quality window.

But if envelopes are equal the btus got off the train sooner in the low flow room,

What Rich seems to be trying to say is the higher delta delivers more btus per the universal formula can't beat the math. So in saying that I will assume that you are saying an emitter with a high delta of any kind is dumping more btus than one with a lower delta. Again the math. But having the whole emitter at an even temp means something even if it's a narrow delta. The bigger the emitter surface the more it comes into play. That is the emitter to room delta. If the beginning of the emitter is hot it will transfer more to the room than the end which is cooler.

If it shows up at your end, the coloring of the tubing tries to show the temperature difference. The tighter ∆T, higher flow example has a more consistent color from S to.R So the average temperature across the slab from one side to the other will be fairly consistent. So that 15∆ falls between the 10- 20 shown by many of the radiant design manuals, it would provide a very comfortable slab to live on, across the area.

With the lower flow, wider ∆T, the front end of the loop is warm, but the tail end is cooler, blue colored. I'm down to 88F at the end of the slow flow example, 22∆. The higher flow has 95 at the tail.

In the slow flow example the first 1/2 will fell nice, the last 1/2,or so has a lower fluid temperature= lower output, cooler surfaces, may be acceptable, or customer may notice the surface temperature difference, your call.

The supply temperature is not the slab surface, by the way, we shoot for 82 ish at design for floor surface temp. Below that it may not "feel" warm, but it is still delivering energy. The ICF home conundrum, cool floor but still warm ambient

In super insulated homes some suggested leaving the tube away from the exterior walls, load it in the center where people congregate to assure they "feel" the warm floors, never tried it myself, makes some sense.

Hot goes to cold, and the rate of transfer from hot to cold is driven by the temperature difference, (laws of Thermodynamics.)

With the slow flow, the average temperature across the entire slab is lower, so the ∆ between the ambient and slab is lower, less heat transfer.

In this example we are talking 1 gpm or 2 gpm, not a huge difference in pumping power, but more output and better comfort with the higher flow, tighter ∆ example.

With more pumping power we could design that down to a 10∆ as Uponor suggests, or offers as an option on their graph. That would show up as even higher temperature at the end of the loop, higher AWT across the slab, and higher slab output. 110S, 100R, average slab temp bumps up again.

Increasing flow rate, increases AWT across whatever emitter, and that in turn increases the output of said emitter.
Ya get to decide if you like the 22, 15 or 10∆ design, or any other number based on pumping requirement, expected slab comfort, etc.
Same as you get to decide what gpm thru fin tube, it could be either of the choices on the literature, or anything in-between, you decide, there are not BTU police.

We want efficient systems, but also high comfort, that is what will keep customers coming back for radiant system. Efficient, comfort, and low operating cost, juggle them as you wish.

Paul48

When I look at those 2 diagrams, I see an obvious difference in flow. Rich sees an obvious difference in slab temperature.

Gordy

hot rod said:

If it shows up at your end, the coloring of the tubing tries to show the temperature difference. The tighter ∆T, higher flow example has a more consistent color from S to.R So the average temperature across the slab from one side to the other will be fairly consistent. So that 15∆ falls between the 10- 20 shown by many of the radiant design manuals, it would provide a very comfortable slab to live on, across the area.

With the lower flow, wider ∆T, the front end of the loop is warm, but the tail end is cooler, blue colored. I'm down to 88F at the end of the slow flow example, 22∆. The higher flow has 95 at the tail.

In the slow flow example the first 1/2 will fell nice, the last 1/2,or so has a lower fluid temperature= lower output, cooler surfaces, may be acceptable, or customer may notice the surface temperature difference, your call.

The supply temperature is not the slab surface, by the way, we shoot for 82 ish at design for floor surface temp. Below that it may not "feel" warm, but it is still delivering energy. The ICF home conundrum, cool floor but still warm ambient

In super insulated homes some suggested leaving the tube away from the exterior walls, load it in the center where people congregate to assure they "feel" the warm floors, never tried it myself, makes some sense.

Hot goes to cold, and the rate of transfer from hot to cold is driven by the temperature difference, (laws of Thermodynamics.)

With the slow flow, the average temperature across the entire slab is lower, so the ∆ between the ambient and slab is lower, less heat transfer.

In this example we are talking 1 gpm or 2 gpm, not a huge difference in pumping power, but more output and better comfort with the higher flow, tighter ∆ example.

With more pumping power we could design that down to a 10∆ as Uponor suggests, or offers as an option on their graph. That would show up as even higher temperature at the end of the loop, higher AWT across the slab, and higher slab output. 110S, 100R, average slab temp bumps up again.

Increasing flow rate, increases AWT across whatever emitter, and that in turn increases the output of said emitter.
Ya get to decide if you like the 22, 15 or 10∆ design, or any other number based on pumping requirement, expected slab comfort, etc.
Same as you get to decide what gpm thru fin tube, it could be either of the choices on the literature, or anything in-between, you decide, there are not BTU police.

We want efficient systems, but also high comfort, that is what will keep customers coming back for radiant system. Efficient, comfort, and low operating cost, juggle them as you wish.

Hot rod I think you misinterpreted my response. Yes I know the supply temp is not the slab temp.

Gordy

Glad we are not at the bar all the tappers would be dry.

SWEI

Anyone got an aspirin?

Gordy

Hungover already?

SWEI

The mere thought of being at that bar gave me a headache.

Gordy

I was ready to roll over to the barber chair for shots.......lets go!

hot_rod

Gordy said:

hot rod said:

If it shows up at your end, the coloring of the tubing tries to show the temperature difference. The tighter ∆T, higher flow example has a more consistent color from S to.R So the average temperature across the slab from one side to the other will be fairly consistent. So that 15∆ falls between the 10- 20 shown by many of the radiant design manuals, it would provide a very comfortable slab to live on, across the area.

With the lower flow, wider ∆T, the front end of the loop is warm, but the tail end is cooler, blue colored. I'm down to 88F at the end of the slow flow example, 22∆. The higher flow has 95 at the tail.

In the slow flow example the first 1/2 will fell nice, the last 1/2,or so has a lower fluid temperature= lower output, cooler surfaces, may be acceptable, or customer may notice the surface temperature difference, your call.

The supply temperature is not the slab surface, by the way, we shoot for 82 ish at design for floor surface temp. Below that it may not "feel" warm, but it is still delivering energy. The ICF home conundrum, cool floor but still warm ambient

In super insulated homes some suggested leaving the tube away from the exterior walls, load it in the center where people congregate to assure they "feel" the warm floors, never tried it myself, makes some sense.

Hot goes to cold, and the rate of transfer from hot to cold is driven by the temperature difference, (laws of Thermodynamics.)

With the slow flow, the average temperature across the entire slab is lower, so the ∆ between the ambient and slab is lower, less heat transfer.

In this example we are talking 1 gpm or 2 gpm, not a huge difference in pumping power, but more output and better comfort with the higher flow, tighter ∆ example.

With more pumping power we could design that down to a 10∆ as Uponor suggests, or offers as an option on their graph. That would show up as even higher temperature at the end of the loop, higher AWT across the slab, and higher slab output. 110S, 100R, average slab temp bumps up again.

Increasing flow rate, increases AWT across whatever emitter, and that in turn increases the output of said emitter.
Ya get to decide if you like the 22, 15 or 10∆ design, or any other number based on pumping requirement, expected slab comfort, etc.
Same as you get to decide what gpm thru fin tube, it could be either of the choices on the literature, or anything in-between, you decide, there are not BTU police.

We want efficient systems, but also high comfort, that is what will keep customers coming back for radiant system. Efficient, comfort, and low operating cost, juggle them as you wish.

One more ∆T to throw out and I'll call it quits.

Let say in the high flow, tighter ∆T example I got a consistent 85 surface temperature, warmer at the start, cooler at the end, average 85.

My room ambient or MRT if you wish is 70. 85-70= 15°∆ between radiant emitter and room ambient. I'll transfer around 2 btu/ sq ft for every degree difference, so my slab has a 30btu/sq ft output. We see that number as a reasonable radiant floor output often.

With the low flow, wide∆ my surface only gets up to 80F - 70 ambient, 80-70=10 X 2= my output is now down to 20 btu/ sq ft.

That where I leverage the wider delta T where the rubber meets the road. Wider on the higher flow system = higher heat output.

As for outside wall loads, I can compensate by adjusting my tube layout maybe a serpentine with hot tube, cold tube, hot tube, etc.

If I have 2 outside walls I may use an L shaped serpentine layout to put energy at the higher load areas first, same average slab temp still.

Hot rod I think you misinterpreted my response. Yes I know the supply temp is not the slab temp.

hot_rod

hot rod said:

Gordy said:

hot rod said:

If it shows up at your end, the coloring of the tubing tries to show the temperature difference. The tighter ∆T, higher flow example has a more consistent color from S to.R So the average temperature across the slab from one side to the other will be fairly consistent. So that 15∆ falls between the 10- 20 shown by many of the radiant design manuals, it would provide a very comfortable slab to live on, across the area.

With the lower flow, wider ∆T, the front end of the loop is warm, but the tail end is cooler, blue colored. I'm down to 88F at the end of the slow flow example, 22∆. The higher flow has 95 at the tail.

In the slow flow example the first 1/2 will fell nice, the last 1/2,or so has a lower fluid temperature= lower output, cooler surfaces, may be acceptable, or customer may notice the surface temperature difference, your call.

The supply temperature is not the slab surface, by the way, we shoot for 82 ish at design for floor surface temp. Below that it may not "feel" warm, but it is still delivering energy. The ICF home conundrum, cool floor but still warm ambient

In super insulated homes some suggested leaving the tube away from the exterior walls, load it in the center where people congregate to assure they "feel" the warm floors, never tried it myself, makes some sense.

Hot goes to cold, and the rate of transfer from hot to cold is driven by the temperature difference, (laws of Thermodynamics.)

With the slow flow, the average temperature across the entire slab is lower, so the ∆ between the ambient and slab is lower, less heat transfer.

In this example we are talking 1 gpm or 2 gpm, not a huge difference in pumping power, but more output and better comfort with the higher flow, tighter ∆ example.

With more pumping power we could design that down to a 10∆ as Uponor suggests, or offers as an option on their graph. That would show up as even higher temperature at the end of the loop, higher AWT across the slab, and higher slab output. 110S, 100R, average slab temp bumps up again.

Increasing flow rate, increases AWT across whatever emitter, and that in turn increases the output of said emitter.
Ya get to decide if you like the 22, 15 or 10∆ design, or any other number based on pumping requirement, expected slab comfort, etc.
Same as you get to decide what gpm thru fin tube, it could be either of the choices on the literature, or anything in-between, you decide, there are not BTU police.

We want efficient systems, but also high comfort, that is what will keep customers coming back for radiant system. Efficient, comfort, and low operating cost, juggle them as you wish.

One more ∆T to throw out and I'll call it quits.

Let say in the high flow, tighter ∆T example I got a consistent 85 surface temperature, warmer at the start, cooler at the end, average 85.

My room ambient or MRT if you wish is 70. 85-70= 15°∆ between radiant emitter and room ambient. I'll transfer around 2 btu/ sq ft for every degree difference, so my slab has a 30btu/sq ft output. We see that number as a reasonable radiant floor output often.

With the low flow, wide∆ my surface only gets up to 80F - 70 ambient, 80-70=10 X 2= my output is now down to 20 btu/ sq ft.

That where I leverage the wider delta T where the rubber meets the road. Wider on the higher flow system = higher heat output.

As for outside wall loads, I can compensate by adjusting my tube layout maybe a serpentine with hot tube, cold tube, hot tube, etc.

If I have 2 outside walls I may use an L shaped serpentine layout to put energy at the higher load areas first, same average slab temp still.

Hot rod I think you misinterpreted my response. Yes I know the supply temp is not the slab temp.

Paul48

I think hot rod's been at the bar. lol

Paul48

I guess I should lower the oven temperature to cook the turkey faster.

Paul48

...

hot_rod

shut the oven off, faster yet

Paul48 said:

I guess I should lower the oven temperature to cook the turkey faster.

Gordy

Hatterasguy said:

Gordy said:

Something I have thought about @Hatterasguy strap on temp sensors, and their delayed response time verses well sensors. Especially in laminar flows. The water to pipe pipe to sensor sensor to circuitry chain. Is it enough to make the circ chase its tail.

Actually, I prefer the delayed response time.

The boiler is quite slow to respond to changes in demand and it would be possible to smack into the HL if the circulator response is faster than the boiler response.

Slow response of the VT2218 is welcomed.

Depends if your coming down in modulation, or going up. Maintaining no big deal. Quick load changes. Weather, setback etc.

I see as an automatic transmission as the goal, and part of this being manual transmission. Even manual transmission when the passenger is telling the driver when to shift.

Harvey Ramer

Disclaimer, I didn't read every single post.

But..

I have a completely different veiw on dt pumping than anything I have seen here. I have experimented with it probably about 6 or 7 years ago.

Delta-t pumping coupled with ODR are like a hand-in-glove properly handled. I really don't care about the turbulence, laminar, or transitional flow. The DT gets dialed in according to the connected radiation in an effort to achieve the best comfort at acceptable pumping power. Don't go nuts. What happens is you create an animated system that is even more preemptive than standalone ODR can provide. Particularly well suited for high mass. I don't have to go in detail. Just picture the water temp rising or falling with the outdoor temp. What does the pump do? If the outdoor temp is dropping, it actually allows the boiler to inject btu's at a higher rate than fixed pumping with odr. The exact opposite occurs when the outdoor temp rises. It will go a long way to eliminate flywheel effect and prevent indoor temp fluctuations.

The only thing you have to be aware of is, your bottom end of the ODR curve may have to be held slightly higher. Depends on the emitter system.

The other thing is, the boiler electronics have to play nice.