What temperature difference is typical from the start to the end of a heating loop?

hotdog

hotdog

I am only dropping 2-4 degrees in a 35 FT loop. Does that seem right?

hot_rod

What type of heat emitter? Pipe size?

The hotter the average temperature across a fin tube, hot water coil, or radiant loop the greater the heat output.

A 20° drop might look like 180+160 divided by 2 = AWT of 170

An 8° drop 180+172 divided by 2 = AWT of 176 which of course equated to more heat output.

If you have a design condition you want all the energy transfer possible.

On lower load conditions the flow, and heat output could be ramped down. Often this with temperature modulation controls like ODR.

Limiting factors would be the velocity or speed the fluid is traveling. For hydronic stay below 4 feet per second.

So the pipe size determines how many gpm and BTUs can be transferred. Here is a table with common pipe sizes and accepted flow rates for hydronics.

Look up the manufacturers output tables for fin tube baseboard, hot water air coils or radiant loop and you will find increased flow and AWT results in higher output.

http://www.pmmag.com/articles/85239-the-water-s-moving-too-fast

An older but still relevant article.

http://www.pmmag.com/articles/85239-the-water-s-moving-too-fast
Limiting a

Rich_49

That there is some nifty math Rod . Same circuit delivered 12* less but somehow delivered more heat . That's kinda comparable to this manipulation , 500x5x20*=50K or 500x0.5x200*=50K , 500x1x100*=50K . All that math works but that is not how we design . Or is it ?

bmwpowere36m3

Rich said:

That there is some nifty math Rod . Same circuit delivered 12* less but somehow delivered more heat . That's kinda comparable to this manipulation , 500x5x20*=50K or 500x0.5x200*=50K , 500x1x100*=50K . All that math works but that is not how we design . Or is it ?

So a 20 vs. 200 delta... my limited understanding says yes, if the AWT is the same. However one would require a much higher supply temp with a HUGE drop in return temps.

hot_rod

Don't know how you design, but I'm convinced a hotter emitter gives off more heat energy, do have evidence to the contrary?

What do you mean by manipulation above, looks like multiplication But it is only part of the story when it comes to energy transfer. The energy transfer from a fluid to a pipe and emitter also depends on the flow condition, turbulent flow transfer energy from a fluid stream more efficiently than slow, laminar, yes or no?

One step at a time, it takes a temperature difference to transfer heat energy, yes or no?

Trying to heat a cold space with a cold rad is going to get some customer complaints.

Hotter surfaces, pipes, radiant surfaces, panel rads, HXers, etc transfer more energy to colder surfaces, yes or no?

It doesn't matter how the emitter gets hotter, increase the supply temperature, or increase the flow rate. If you increase the AWT across the emitter, the heat output increases, yes or no?

Use an indirect tank as an example, if you want more DHW production would you increase the boiler supply temperature to the coil, or decrease supply temperature to the coil?

Could you also increase the flow rate, bump the pump speed up, for example, into the coil to get additional energy transfer, or would you reduce the pump speed, and try let those BTU linger and get off the train when they are darn good and ready. Personally I'd rather push them off a fast moving train and go grab some more.

A solar thermal collector, do you reduce flow rate to get additional energy from the collector, or increase? Don't you want to scrub the heat energy as fast as the sun is adding it, or let it just linger in a hot absorber, until the surrounding air temperature grabs it out of the box.

Don_197

There is a delta t that no one ever talks about......and that is the difference of the water or emitter and the other medium being transferred TO. I have observed (and been fascinated by) that the bigger the difference between the temperature of the water/emitter, and the temperature of the medium being heated by the water/emitter (usually air.....but in pure radiant it would be the floor or ceiling, objects in the room, people etc etc) the more "energetic" the action. In other words, the larger delta t between the two mediums the faster the btu's "jump" from one to the other. Above a certain point however, that can get pretty uncomfortable, and without really good convection current, or forced air (ick!) temperatures in the space can become unstable, uneven and most of all UNCOMFORTABLE!

icesailor

Before the days of Delta T and ECM circulators, because I had installed Tridicator gauges on the supply and returns of some boilers I installed, I could measure the Delta P and Delta T when the system was running to see how my design came out.

I could watch a Delta T and see the high limit differential working. You could see the thermal lag, but the Delta T stayed the same. With all zones open. Start closing zones, and the Delta T went down, but the Delta P went up. I think. I never worried about the Delta P. But, it was conclusive that the emitters worked just as well with the hotter, faster water than it did with the slower water.

It really proved my point when someone claimed (because he was told by his BIL Plumber) that the boiler was too small. Because the soffit and ridge vents in his new house and recessed can lights in the cathedral ceilings of his new house, were sucking the heat right out of the rooms.

At 16 degrees OAT with no wind, the building would go to 70 degrees and the boiler would cycle on high limit. Regardless of how high I set it. And maintain a 20 degree delta T. Days later when the OAT was 30 degrees but the wind was gusting over 30 MPH, the building wouldn't go over 60 degrees, the boiler was still cycling like it was when it was 16 degree OAT.

Never underestimate the effects of unknown infiltration.

OBTW, the system was designed for -0 OAT with 15 MPH wind speed, and all emitters rounded UP to the next longer piece.

The owner blocked off the full length soffit vents and things improved. His "expert BIL plumber still claimed the boiler was too small. Not good for my reputation.

Just because you are right, can still mean you are wrong. In the eyes of some "experts".

hot_rod

Don said:

There is a delta t that no one ever talks about......and that is the difference of the water or emitter and the other medium being transferred TO. I have observed (and been fascinated by) that the bigger the difference between the temperature of the water/emitter, and the temperature of the medium being heated by the water/emitter (usually air.....but in pure radiant it would be the floor or ceiling, objects in the room, people etc etc) the more "energetic" the action. In other words, the larger delta t between the two mediums the faster the btu's "jump" from one to the other. Above a certain point however, that can get pretty uncomfortable, and without really good convection current, or forced air (ick!) temperatures in the space can become unstable, uneven and most of all UNCOMFORTABLE!

Exactly, which is why you sometimes see streaking on a fin tube, baseboard convector when you run them at very high temperatures. Higher fin tube temperature, increased convection, faster air movement across the fins.

The increased air movement moves more dust and pet hair across the fins, and enclosures.

This the concept behind a forced convectiors, put a fan under or behind a finned coil and drive more heat transfer.

The data and performance is out there, pick up the performance spec on a kick space heater for example, hotter temperature, faster airflow = more heat transfer.

Anytime you move heat energy with air, you have stratification potential.

icesailor

"" Exactly, which is why you sometimes see streaking on a fin tube, baseboard convector when you run them at very high temperatures. Higher fin tube temperature, increased convection, faster air movement across the fins. ""

Or, why (where I worked) when we installed Cast Iron Baseboard radiators, we always stapled foil faced craft paper to the wall, and bent it over the top of the baseboard with a piece of 3/4" cove molding on top of the paper and a piece of 3/4" 1/4 round on the bottom. To stop the hot air from running up the back side ot the heater and staining the wall with black streaks. If the wall was uninsulated, we turned the foil to the front. If it was insulated, you turned the foil to the back. So you didn't see the foil between the openings on base ray.

Rich_49

Hot Dog , is the loop including supply and return piping 35' or are we talking about the emitter itself ? Would love to know this to show some math . What circ is this ?

hotdog

We are talking about a loop off a main loop. circ is old B&G

Rich_49

Rod said ,
"The hotter the average temperature across a fin tube, hot water coil, or radiant loop the greater the heat output.

A 20° drop might look like 180+160 divided by 2 = AWT of 170

An 8° drop 180+172 divided by 2 = AWT of 176 which of course equated to more heat output. "
Rod , question ? Since Delta T is the sum total of how much heat was delivered , where did the other 12* go to if the 176* loop delivered more than the 170* loop ?
Cannot wait to hear the wisdom that will explain this . Always learning from you Bob .

Rich_49

Oh , the hell with it ! They both delivered the same 10,000 BTUs . The only difference is that Rod's higher temp loop increased head , consumed more electricity that gave no benefit to the space since we moved fluid without delivering energy , we will certainly make the boiler reach high limit faster thus cycling more . Did I miss anything ?

icesailor

How does the same amount of flowing water, in a closed loop, running hotter water, increase head pressure?

If the circuit was pumping with a 6# Delta P at 180 degree water, it will go down if the water temperature drops to 120 degrees?

hot_rod

Rich said:

Oh , the hell with it ! They both delivered the same 10,000 BTUs . The only difference is that Rod's higher temp loop increased head , consumed more electricity that gave no benefit to the space since we moved fluid without delivering energy , we will certainly make the boiler reach high limit faster thus cycling more . Did I miss anything ?

increased head in 3/4 copper going from 1 to 2.79 gpm That additional energy is ??? Put a dollar amount on that, probably take an Alpha from what 17 to 20 watts.

If the boiler reaches high limit, it shuts off, no fuel consumption, no $$ expended.

If the boiler short cycles it indicated you need a buffer to cover the micro zone, or modulate it down to the load of the zone. That's why we have modulating equipment, adjust the heat input to the heat extracted.
Or a nice HTP tank style heater, one of my favorite choices for multi, micro zoned hydronics.

Rich_49

Hatterasguy ,

Please show us some manufacturer's specs showing those assumed outputs . Slant fin # 30 puts out 504 BTU/hr/ft @ 180* and 1 gpm . The same baseboard puts out 530 BTU/hr/ft @ 180* with a flow of 4 gpm . I removed the 15% Heating Effect factor ( 580/1.15 , 610/1.15) . Just in case you were not aware that should be done . Please Sir , explain to us now how a flow rate of 2.79 gpm(?) put out more BTU/hr/ft than with 4 gpm flow .
* Hey , since higher water temps are better and promote more heat transfer maybe we should run systems at a 1* Delta , then we'd be delivering all the BTUs right ?
* Imagine a system having 2 zones , 2 manifolds with parallel piping to the emitters and trying to flow 4 gpm through all of them at a head loss of say 7 feet . Get out your pump curve cvahrts boys and girls and let us see what pump we would need to evenly heat an 8 room house where every emitter needs even 2.79 gpm x 4 = 11.16 gpm @ 7 ft. hd. x 2 zones . Boy , we sure have made this system efficient .

hot_rod

Rich, nobody is proposing RUNNING the system at 1° ∆T, the numbers presented are to prove the concept or the effect the various AWT have on output.

You get to chose what ∆T works best for the emitters you are installing. It a balance between heat output and pumping requirements.

We know and agree 2-4 fps is a very comfortable and quiet flow rate in pipe size up to 2". That could be the guide for your piping design.

Rich_49

Does it somehow seem to you that I require help in design Bob ? Throwing around numbers for the sake of doing so does nothing to further the discussions that people will learn from . What you have said will be taken as gospel by some who will google you and we will have been responsible for more bad systems .
That's my point , maybe these philosophical discussions need to be had in private . Hell , you have this hatterasguy posting stuff that has absolutely no mathematical or hydronic value .

hot_rod

Calm down Rich, I can feel your blood pressure ∆P rising from here.

All heating and engineering can be defined by numbers. It needs to be or we are all just guessing and "throwing darts" trying to hit a target.

I stand behind the concepts, math, and reality of the concepts I presented here.

No heat transfer discussion needs or should be held in private. we all learn when we discuss different opinions.

We have been transferring heat to spaces since Roman times the concept of heat transfer and thermodynamics is fairly well proven and understood.

If you knew it all you would not keep coming back here, same for me.

icesailor

@Rich:

I've played around a lot to learn what I have learned, right or wrong.

So, if I have a small baseboard system with the standard smallest oversized boiler, running at whatever I chose to set it. say 170 degrees, and it is pumping into 4 zone valves (I like zone valves) through one 007 circulator, and all the baseboard emitters are so hot I can't put mi finger on the pipe but the water is returning ay 155 0r 160 degrees, why are the elements and heaters hot? I don't have any idea what the flow rate is, but because I have a full sized ball valve for purging on the return, I can throttle the flow. I throttle the flow way down, and the return temperature starts to drop. If I throttle it enough, I can get it to a 40 degree drop. But the first baseboard is still really hot, but the last ones around is cooler. If I open the throttling valve, the return gets hotter again.

Many use shade tree engineering. If it works, that's how I do it. How many times have we herd someone say "That's how I was taught". If it works, no one questioned it.

Its like the chicken and the egg. Which came first.

A bigger pipe and heat, then the engineer who decided how it worked?

The biggest problem the Wright Brothers had with trying to fly, was that no one knew how to fly one, or build one. They had to do both.

James Watt invented the Steam Engine. Not to drive a locomotive engine, but to run pumps to de-water coal mines. The engineering came later.

4Johnpipe

Rod said...

If the boiler reaches high limit, it shuts off, no fuel consumption, no $$ expended.

If the boiler short cycles it indicated you need a buffer to cover the micro zone, or modulate it down to the load of the zone. That's why we have modulating equipment, adjust the heat input to the heat extracted.
Or a nice HTP tank style heater, one of my favorite choices for multi, micro zoned hydronics.

I would offer that during times when OD temps are at or below freezing the mod con boilers will ramp up every time to the max setting of 180 degrees...They do this in seconds. The boiler would not have time for physics to begin condensing and even if it did the boiler will shut off rapidly (short cycling).

The HTP Pioneer type boiler will never do this because it has built in buffer by design.

Buffer tanks are a necessity to prevent short cycling. I have seen 2 year old systems that may have had very little run time and exaggerated ignition cycles in poor shape because of the short cycle condition.

Let the boiler modulate and condense with a buffer or an HTP.

Rich_49

The fact that 170* AWT with a 20* Delta T should have clued you in if that's your excuse . I also deal with running SYSTEMS at their most efficient throughout the entire range of conditions offering the best value and comfort to the end user . If you or others would increase head , flow , electrical usage and short cycle boilers because some pot head left the door open so be it . I will never agree with that line of nonsense .
We deal with system efficiency , not emitters only . Simple statement is that it is easier to maintain than ramp up and down Hatterasguy or whoever you are .
People on the site always talking about Delta Ts that make no sense and against what so many teach in an effort to help an industry's future is counter productive . Running high Delta Ts through equipment that does not condense , low Delta Ts at high temp through condensing boilers . advocating against industry values .
By the way , instead of making lame excuses Mr. I don't understand Veissmanns logic . Why don't you show us the math that gave a 2.79 gpm flow and 8* Delta through the same emitter length that delivered less at a higher flow .

Gordy

It's all natural dudes. Mother Nature wants to equalize in every aspect hot to cold the larger the difference the faster it happens. High pressure to low pressure the larger the difference the faster she wants to equalize. Where ever those delta P's and T's exist Mother Nature will resist those differences, and TRY to reach equilibrium. We just invent ways to prevent it. Become one with it.

Rich_49

Well there we have it . I thought that we designed for an hour or at least strived to achieve all components of the system to run for an entire hour (all of them) at design conditions .
We should have a boiler that fires at correct output , emitters that delivered every BTU the boiler sent out and every BTU in the mechanical system was transferred to the room .
What nobody has identified in Bob's stupid little game is the fact that his imaginary , nonsensical system that defies the teachings of great instructors of the past and present did not run for the entire hour or maybe it did because Daniel Thomas , Colorado brownie eating , pothead extraordinaire , left the door open . But how long did he leave it open for ?

Let's make the system water a bit higher AWT for the sake of simple math and to make use of the chart Hatterasguy has provided us . and break it down like this . AWT 180*F
We were able to deliver 166.667 BTu per gallon of fluid moved at a 20* Delta t . The system ran for an entire hour and all of our components ran at peak efficiency with minimal wear and tear .
The system using a 5* Delta as the ratings chart would suggest delivered the same 10,000 BTUs at a rate of approximately 55.556 BTU per gallon of fluid moved in 45 minutes . In that 45 minutes we used more electricity , more fuel because the boiler short cycled , we put undue wear and tear on all of our components .
I will say that Bob's magical boiler although it ran at the same AWT had to produce only 182.5* fluid while mine had to put out 190* water .

How confused do you think future heating techs will be when given this type of information and they apply it thinking it is correct because the very well known "HOT ROD" taught it to me ? Bob , you really may wanna think about some of the garbage you put out there because your station makes most people believe that whatever you say is gospel . This industry will only get worse . There are 7 kids somewhere right now planning that 8* Delta T system because that old dude on heating help said to do it this way .Thanks for your contribution Rod . You have successfully transformed efficiency into a top fuel dragster , Really fast and as inefficient as possible , all for your entertainment .

Hatterasguy , maybe you should have used a calculator and wiped something with that napkin , like the brown spot of Missouri morning pudding off your nose .
Look at that , I can be funny too .

Gordy

Remember when this question was a pretty simple straight forward answer. Use it in your design but never expect that design number to be an actual reality for a number of reasons. That it being delta t.

Now we have the tools to enforce it.

We can talk all day long about theoretical, what counts is reality.

hot_rod

Your statement Rich

The industry's response. Shown in their data sheets below.

Better get on the phone call thousands of manufacturers and have them pull all this info. Or in your world flip all the numbers to show lower flow results in higher output

The thread was about delta t and what how it relates to heat transfer.

If you want to talk distribution efficiency, first you need to understand the very basic, AWT increases heat output.

Actually you're not all that funny, just rude and mistaken.

Tune in tomorrow along with 400 or more registered attendees to get a non biased look at Analyzing Circulator Performance in a Hydronic Circuit.

Rich_49

I'm guessing I won't attend , but maybe I will . I spent over a hundred hours studying and performing calcs based on the presenters latest published theories , methods , equations and preferences just a year ago . Doubt much has changed in that time . Mistaken , no , funny , depends , rude , as rude as you want me to be or deserve to receive . Always funny to see where your demeanor turns Bob ,usually around the same time in every discussion .

hot_rod

"Rude as I deserve", Thanks Rich for the support.

What I do have going for me is history and reality. 52,000 ASHRAE members since something like 1894 teaching hot goes to cold, the rate of heat transfer increases as temperature increases. My one and only point inn this thread.

I have presented the above drawings and teachings to over 7,000 folks in person, 40 webinars, we have a couple hundred thousand Idronics on the street.
I've stood in front of 60 ASHRAE and ASPE engineers sweating like a fountain, presented to Boeing rocket scientists in Seattle.

My training partner the esteemed Jody Samuell presents this exact same material weekly to engineers specifically across the US and Canada, closing in on 1 million You Tube hits. I have the support of 1100 Caleffi colleagues across the world that help assemble the idronics.
I always credit and show competitor products in my presentations by the way.

An you, I must say are the very first to accuse me of "some of the garbage you put out there" and "confusing future hydronic techs"

Regardless of you valued opinion, I'm staying the course, even going to kick it into a higher gear in fact

You don't like or agree with the numbers, gpm flow rates, delta Ts, radiant loop design temperatures, used in all those idronics pages I posted, Take it up with the engineers at Slant Fin, First Company, Uponor, etc it THEIR numbers used in the calculations.

I NEVER suggested or implied a 8F be used in a baseboard system, the number 8 was used to make the heat output comparison, in fact I stated it is up to the designer to chose the "sweet spot" delta T he or she is comfortable with.

On another topic that you wantbto drag into this thread, I embrace Delta T circ pumps and currently have 4 different brands in my shop dating back something like 20 years to the short lived UFC circ.

We are not in the pump business at Caleffi, but we understand how vital it is to then operation, the wheels on the BTU train.

A sample slide from todays webinar, should you chose to attend, Everything from Einstein to Alpha and much in between.

hot_rod

me too.
I agree efficiency should be a big part of the discussion, it could be delta p or T but we should have a goal of the most efficient circulation and heat transfer.

I have always been of the opinion we need reliable, efficient boilers and circs that can modulate from near zero, maybe 500 BTU/ hr up to design output.

Chatting with Dave Davis I understand the complexity of a stable flame etc across a wide turn down. Not to forget how fuel suppliers constantly play around with fuel quality, the boiler needs to recognize and adjust to the fuel value change without a service tech constantly adjusting mixture screws. Looks easy in the chat rooms, not so easy to build.

What my point to the efficiency pumping question is how low can you go and still transfer some energy. There is a point that heat transfer slows and stops based on conditions inside the tube or emitter. You can see, predict, model and even watch that with inferred cameras for example.

Is it best to truncate the curve, lock out the condition potential? Or re-examine emitter design like Jaga is doing for low flow, low operating temperatures, Dynamic Boost I think they call it.
From what I'm reading here adjustments are still being made to some circs to find that workable balance.

Plenty of strong opinions as you can tell.

Important for us at Caleffi that components be produced or tweaked to still remove air, dirt, magnetic particles, flow control and balance, etc if we are going to below 2fps design velocities.


Some of the devices currently used will not work so well when we start cranking down flow velocities, vortex principle separator for example that need high flow rates to spin the fluids.


I don't have a suggestion as far as 17, 20 or 25.5 as the design ∆T number. Certainly different emitters have different "sweet spot" operation conditions. What works well in a panel rad for ∆T flow rates doesn't necessarily translate to pex radiant loops.

I doubt anyone in our industry has the final answer yet, searching the globe for partners with other options and opinions never hurts:)

Zman

This certainly is an exciting one. The OP was inquiring as to whether he has a correct flow rate for his system.
To the OP, what type of baseboard? What are your water temps? Is it 35' of actual emmitor?
As for the rest of this discussion which I am sure has the OP totally confused, why can't you just use the manufactures numbers to size the radiators and determine flow? The one thing that is missing in this discussion is the fact that low flow rates will usually produce adequate heat transfer at the first baseboard in series but will greatly effect the next baseboards in series. With small zones, the 1 gpm number will work just fine. If you have many in series you are going to need much higher flows or the last baseboard will suffer.
Carl


If you have a typical system with 35 if baseboard it might emmit 15,000 btu/ hr. At a 4 degree delta. That would be 7.5 gpm. Way too fast.....

Rich_49

Rod ,
Please don't misunderstand what I have attempted to drive home in this and the other discussion .
I have been taken aback recently by the suggestions or comments you have made . Maybe i lack the ability to present in a way that does not offend anyone in particular but what I do believe I possess is ways to make people think for themselves .
I must have missed the memo that we were now going to begin showing folks different things than lower water temps , proper flows whether ^T or ^P , how to make boilers operate at maximum efficiency , and how to build systems that as closely as possible match the load of the house the most % of the time where the system runs seemlessly and the occupants don't know what temp it is outside unless they watch the news .
Simple fact is that the circuit that started this whole s$%tstorm whether it was supplied with an AWT of 176* @ 8* Delta or AWT of 170* @ 20* Delta will provide the same BTU/h in a room with a thermostat in it or a zone with a thermostat in it . If we took the thermostat out and put it on a constant circulation parameter the 176* AWT /8* ^T the room overheats . I don't think anybody wants that on top of the system inefficiencies that go along with it .
I also believe that everyone here that assists folks in dealing with their issues know these things too . Our time would be better spent helping those that come here for heating help with heating help . My attempt was to make those future techs that may have been watching learn that we design for the heat load of the home on a room by room and hourly basis .
Please accept my apologies for being confrontational and pointing out how terribly wrong what you suggested would be . I do concede that the wider the Delta between room and system the more heat transfer , I never argued that point . Only that this is not the way design gets done .
I would point out that the charts you attached support the whole 20* starting point for Delta T for the Lochinvar (Knight) boilers but there are various choices for different types of emitters and your choice would depend on load , heat source type and circulator selection . Based on the statements in this discussion made by the both of us Rod might choose the KS 2004 with an entering temp of 190* and a flow of 3 gpm in a room with a 4300 BTU/h requirement where I might choose to install KS2008 with an entering temp of 130* and a flow of 1 gpm . I'm not going to get into the fan and it's operating points .
I guess the whole problem I am having here Bob id that I don't believe you would ever design and install that circuit in someone's home .
I'm done with this and will never again get involved in something this dumb . Sorry that I contributed .

Rich_49

THANK YOU Carl ! This is a single pumped circuit pulling fluid from a main , thus my frustration .

hot_rod

Rich, no need to apologize. We both have the same goal here, provide efficient, comfortable, reliable, understandable system. Our method or means to that end may differ.

If I was out of line with my attempt at lightening up discussion some humor, sorry. Humor and wit don't always come across the WWW wires so well.

I actually borrowed the open door concept from a Larry Drake at Think Hydronics comment when someone asked how to increase a radiant slab output. He suggested opening the window

Rich_49

Hatterasguy ,

It is also returning BTUs to the boiler , this is what will allow it to reach high limit faster .
Let's go back to the train .
At a 20* delta discussed in the debated circuit as with the 8* delta circuit the same amount of folks (BTUs) got on the train at a station , each of them paid the same fare . When the train arrived at the station at the other end 167 folks got off the train and another 167 entered and paid their fare . The second train arrived at the station and and 112 folks were sleeping and did not get off only leaving room for 55 folks to get on and pay a fare . The original station for train # 2 is now full to capacity and the fire marshall is on the way to slam the door shut before more folks enter and create a bad situation . Which of these trains burns more fuel , is in need of brakes more often and is profiting less ?

icesailor

@Gordy:

"" We can talk all day long about theoretical, what counts is reality. ""

Design for 20 Degree Delta T. Actual Delta T is 8 degrees. Building is warm. Reaches temperature no matter how cold it gets outside. Customer happy. Life is good.

Customers don't care about efficiencies when they think they are cold. Hotter system temperatures create more convection circulation. Humans can feel slight differences in temperature. Take a room with a high cathedral ceiling, that has adequate heat emitters in it with its own zone and thermostat. It will feel cold. Put a big paddle fan at the peak and blow the hot air on the ceiling down. Everyone is happy. Add a wall fan assisted heater. The room is warmer because of circulation and convection currents.

That's reality.

Rich_49

The circuit that the Op in the other discussion asked about has a Delta T between 2-4* Ice . He came here so is obviously not happy , if he was we would not have heard about this . His question was what should it be . Should we have told him about some fictional circuit or how most of us would design it to operate ? Glad you told me about they just want to be warm . I'll start offering 55 gallon drums with a flue and a fan and sell them a couple cords of wood a year . That'll be much easier

icesailor

@Rich:

Rich said:

The circuit that the Op in the other discussion asked about has a Delta T between 2-4* Ice . He came here so is obviously not happy , if he was we would not have heard about this . His question was what should it be . Should we have told him about some fictional circuit or how most of us would design it to operate ? Glad you told me about they just want to be warm . I'll start offering 55 gallon drums with a flue and a fan and sell them a couple cords of wood a year . That'll be much easier

I understand that.

My question that no one has asked is this. Is his low delta T because of a lack of emitters scrubbing heat energy from the water? Or is because of a high velocity through the zone.

My example would be if you have a zone with X amount of baseboard emitters with a kick space heater installed with a Monoflow Tee on the Series Looped zone. The fan is off. The Delta T on this imaginary zone is 10 degrees. You turn on the fan to high. You've added 4,000 BTU's to the loss of the loop. The Delta T goes up to 12 Degrees, Delta T. The velocity didn't change, the load changed.

At least, when I saw it, that was my explanation for it.

Rich_49

You really are just not that bright I guess . Hotter water returning to any boiler makes it reach high limit faster . I suppose you'll argue that this is not so also .

Rich_49

I certainly am not required to teach you how to design , install nor think . You can do this for as long as we have and make your mistakes and pay with your profits or you could pay different tuition and sit in someone's class . Not that you'd get anything out of it because you already know it all .
Nor do I need to convince you of anything at all , I need to help folks who truly require assistance to stay warm . I have spent more than enough time bantering about this nonsense . You'll figure it out . Maybe you should have attended the Coffee with Caleffi event today , you actually may have gained some insight into what gets discussed here instead of contributing to the confusion that has become the norm when qualified folks try to help visitors . this is a help site which you obviously do not need , so please allow us to get back to the business at hand and the mission that our host intended .
There is no anecdotal evidence from myself or Taco , just factual science on what the dead guys found out long ago . Although few have chimed in because they learned not to get involved with this garbage long ago I guess , what I have said is not foreign to those who know . You could easily verify what I have stated is true , you'll just have to pay for that knowledge in one form or another .
You are missing the point that everything designed and installed is based on the hour . If this system had a 10,000 BTU boiler when would it shut off on limit because you decided to deliver more BTUs in an hour than were needed . Ultimately we would like to have every BTU the boiler made during one hour be delivered to the space , every hour . There is your variable that happens not to be a variable . If you look at the kick space heater link Bob attached you will also see that the fan would shortcycle too , so to speak . Convective current may also be another variable you are looking for , the air entering the emitter becomes warmer throughout the cycle making heat transfer less as we progress . Although the air in the room may not be up to temp yet the actual heat transfer is taking place inside a cabinet that is much warmer than the room air , it has to be or no heat transfer can take place as the air inside is nearer the T system . that's how it works . Nobody ever said Delta T pumps were magic either , the statement is simply that they recognize the condition I just explained and react to it . Te 8* Delta has told us that we are not delivering the BTUs as designed . Listen to the system , you or I cannot impose our will upon it through any mechanical means or special math equations . It is what it is and when you recognize that the voices in your head with the M.E degrees will be at peace .
Good day Brian C .

Zman

The OP was lost a while ago....

If you are only looking at supply or return temps, it is hard to do the math on comparing flow rates to BTU's unloaded. If you look at the average water temp in the circuit you can look at the puzzle more clearly.
In my mind based on average temps a high flow circuit unloads BTU's at a similar rate to a low flow circuit. This is not completely accurate because if you go to extremes like 40 delta, you will find that the output chart is not quite lineal.
This is also undesirable because the radiators at the end of the circuit were likely not sized accordingly and comfort will suffer.

@hotdog if you post the type and length of your baseboard as well as the supply water temp, I promise your question about flow will be answered. Please come back.....

BTW
Looking down the list of contributors on this, all Very SMART people in my opinion.

Carl