radiant heat water speed to fast

sacandaga

i need to know what pump to use to really slow down water speed. my situation is i recentently added a new addition to house and the new side is heating beautifully , the old side is not. reason being the loops are 200feet and im getting a delta of about 7. not enough energy being released. i read 4 years ago when i did the old side that 200 feet was the perfect length and the information could not be more wrong. the new side is all 300 feet and im getting a delta of 22 and like i said it heats up 2000 sf faster than the old side of 500 sf. i am using the taco 0015 on both zones with the variable speed. i have the variable speed set on low for everything. once again they are different zones with their on manifold and their own circulators. i have adjustments on manifolds that i am experimenting with now but would like to know if there is a ultra slow circulator on the market? i believe that will solve my problem. also i even added another run in between each bay of the old side and it did not work, so i have 3 tubes running down each 16 on center bay with transfer plates on the old side and still cant meet the thermostat temperature.

Zman

Slowing down the water will not increase the heat output. It will more than likely decrease it a bit.
Your 300' runs have a higher delta because the water is moving more slowly and there is more tubing surface area to release the heat.
BTU/hr = GPM x Delta T x 500
Decreasing the GPM will increase the Delta T but will probably decrease the BTU output slightly due to lower average water temp and less turbulent flow.
Maybe the new space is better insulated and therefore recovers more quickly?
Can you increase the water temp?

archibald tuttle

i'd be interested in the differences between the sides, total feet of pipe to square foot. I know your runs are shorter on the old side but you didn't mention the ratio (albeit you did mention adding additional length per run).

and as @Zman mused, besides the delta, it's interesting to know what the temperatures actually are to consider the practicality of raising the temp. and i presume but maybe wrong you are controlling them with outdoor reset?

the new side, aside from being 300' runs, plate heat exchangers also? snap ins or u groove? 3 runs per bay or 2?

any difference in floor materials that would slow the heat transfer on the old side to living space?

I probably could keep coming up with more questions but you get the point. you gotta think about everything. slowing down the pump won't impart more btus, it will give you a wider delta but you need btus.

also, you may be speaking the 'thermostat' of comfort. I don't run most of these systems on a thermostat, just with outdoor reset which ,depending on relative insulation and position in house of the two spaces you are comparing I would just be constantly circulating and balancing flow to get comfort levels across the home.

Robert_25

Did the old house heat correctly before the addition? If it did...what changed?

Your issue is not the delta across the zone, it is probably the temperature of the water in that zone.

sacandaga

New side has 2 runs per bay and both sides have u style transfer plates stapled to bottom of subfloor. I do not use outdoor reset( I literally threw it out) the water temperature is 128. I hate to go higher due to wood floors everywhere.  Right now I have no insulation under new side, soon to be r38. Old side I have r30 insulation. Old side built in 60s with a 7/8 subfloor plus wood floor on top. New side has no floor over it yet. I do understand that new side only has 3/4 subfloor with no woodflooring yet so it will heat quicker but old side (500 sf ) runs 3 times longer than new side. I can turn the boiler heat up but I figured its already pretty high. Funny thing is in the beginning I ran the 2 zones one one thermostat by jumping it in my taco computer board and left for 2 weeks only to come back to old side at 63 degrees and new side at 87 degrees,  I had icicles everywhere on new side eaves.

sacandaga

Yes the old side did heat before but it probably ran the boiler alot. I didn't pay attention till new side was hooked up. I have navien boiler and it would run at 9k btu all the time and it didn't cost much to run. Then I needed a bigger navien and then I started to see money go out the window. First navien was a 60k and new is a 80k boiler. It still modulates down to 11k heating old side only when other side isn't running.  

Jamie Hall

Back to basics. Do you have any means at all of determining the actual flow rate, in GPM, of the two sides? You need that information. Pump speed is quite irrelevant, as the actual flow which a pump produces is related both to the speed at which it is operating and to the head loss through the circuit. The pump you are using can produce anywhere between no flow at all and 16 gpm, depending on the head loss.

Frankly, your off hand comment that the recommendation of 200 foot loops " could not be more wrong" does not give me great confidence in your understanding of how water flows, but we will try to help here.

At first glance, I am somewhat suspicious that somehow in the piping there is now a bypass around the old side loops, and that much of the flow which should be going there isn't. Perhaps a complete diagram of all the piping, valves, pumps and so on would be helpful.

sacandaga

bui

sacandaga

First circulator is new area , following pipe second circulator is old side. Third is basement slab 4th is garage slab

sacandaga

Picture of old boiler on old side. Boiler is no longer there , just the manifolds with 1 inch pex supply and 1 inch return tubing

sacandaga

Now the old side has a 6 loop manifold not a 4. Hard to believe 3 runs in each bay cant get that thermostat satisfied 

neilc

in the new picture you're valved off where the copper meets the manifold,
still ?
and if so,
why?
indicators are showing no / low flow , , ,
they pull down for greater flow, correct ?
post a picture of the circuit setter side also

Zman

What temp water were you sending to the old zone before? What temp are you sending now?
Is the boiler able to maintain that setpoint?

The valve between the Tee's should be open in a primary/secondary setup.
How was the common boiler piping sized? I looks a bit small for the number of circs.
Do the circs all have internal check valves?

As for you original question, I suspect the original zone is underperforming due to lower supply water temps. The above questions are to help figure out why.

I am sure glad you threw out the outdoor reset. The improved temp control, comfort and fuel savings can be a real issue.

sacandaga

Picture was taken while I was assembling.  All the valves are open now. Believe it or not I was told by navien not to use the outdoor reset. They were having problems with them. 

sacandaga

Piping is 1 inch around  the boiler and I have temperature gauges on all the manifolds.  It is getting around 124 at the old side supply manifold. The others are getting 126 cause they are close to the boiler

sacandaga

How does outdoor reset work if one side gets heated no problem and the other doesn't.  How can it drop the water temperature if the one side never gets warm?

Zman

If you are positive that your Delta T on the old loop is 7 degrees, that indicates plenty of flow. Higher supply temp is the only way to significantly increase output.

sacandaga

I'm positive on the 7 delta t. I'll raise the temperature  to 135 to see what happens. Ty for all your help! Guess I'll see if I can dig out the outdoor reset and hook it up. Still dont see how it works with 4 different zones.  2 zones in concrete,  1 that heats no problem and 1 that has got my head in a pretzel . 

Ironman

Slabs and staple up all on the same Supply Water Temp zone? Probably not gonna balance out well.

Zman

I have found that slabs and staple up with plate will sometimes work OK.
Slabs and plateless staple up are a no go. Once you turn the temp up high enough to heat the plateless zone, you end up overheating the slabs and dragging the boiler temps down.

archibald tuttle

sacandaga said:

I'm positive on the 7 delta t. I'll raise the temperature  to 135 to see what happens. Ty for all your help! Guess I'll see if I can dig out the outdoor reset and hook it up. Still dont see how it works with 4 different zones.  2 zones in concrete,  1 that heats no problem and 1 that has got my head in a pretzel . 

two wood floors is 'work'. its not uncommon on staple up but that seems to be the obvious difference between your two sides. as far as your gas usage between new and old setup, it sounds like you have 4 times the square footage. even though you are conscious of the old floor 'running' more, with the turndown, runtime is only one part of the gas use equation. not sure your envelope or climate zone but your problem seems to be getting btus out of the boiler, not the number you are putting in.

i have single wood floors over concrete mass and, depending on outdoor temps will see water temps as high as 135 although your finish floor isn't seeing temps like that through the subfloor (which, in a way, is part of the problem). the balance between your loops is achieved by circulation usually regulated by by bypass/mixing or and the outdoor reset then controls system temp around the load generated by outside temps. that is a pretty straight line graph theoretically. were you making the thermostat or noticeably more comfort with the previous boiler in which case i suspect you were running at higher temps. so the difference with using reset is, instead of running to make temp and then shutting down with the temp set to the minimum needed at times when it is cold, you run all the time but at lower temps. your concrete masses especially are a helpful freewheel. I tend to run a buffer tank or DHW indirect tank as the freewheel for this and get the added benefit with the latter of keeping the pex separate from the boiler water although most modern material low mass boilers paired with barrier tubing have exterior degradation before interior.

it is a little late although sounds like you were back in the this old bays before, and I honestly haven't plumbed (sorry ) the wells of theory and experience here on the subject so i'm quite prepared to be told i'm full of it, but I do make my u plates full of siliconized caulk, well not full but enough of a bead to seat the pipe with more contact. Just wringing all the choke points out because wood floor itself is relatively resistant to heat transfer so the more of the heat that gets to it the better. obviously you are right

good luck at 135, report back.

sacandaga

So I got it at 130 and actually speed the water up to medium on the circulator.  Now my delta is 4 but it actually heated it up, sitting at a toasty 75 now. Thx for all the support! This is an extremely helpful site.