Radiant Heat not Heating

smittyal06

This past winter we were not able to keep your house warm with infloor radiant heat. This was our first year in the house as we bought it as a foreclosure.  I have had 3 heating companies over and I was given this site by the last for some additional assistance. None of them seem real up to radiant systems. The house is heated by an outdoor wood boiler which is an open system. It comes through a plate exchanger to a closed system. The basement (about 1000sq concrete) stayed plenty hot with the system. However, the main floor (1000sq.) and upstairs (800sq) only would make it to 60 degrees. This was with everything running 24/7. The infloor tubing is 3/4 inch and has one run between every joist. It has insulation under it. The water coming in was hot so you could not hold on to the tubes, and on the return it was still warm. However, it was not heating our house. I have included a picture of the current set up. I know this is very vague, but I am not sure exactly what other information you may need to know. If you have any suggestions as to how to make this work better so we can actually stay warm, I would greatly appreciate them. Thank you.

JStar

Heat

What model and size boiler? Any pictures from a view with the boiler as well?



I see at least a handful of problems already.

smittyal06

Boiler

We use an outdoor wood boiler. The brand is subzero. Not sure on model, but it is plenty large to heat the house.The electric boiler does not get used.

Zman

Emitters

Without a drawing or a wider view it is hard to tell what is going on in your boiler room. I agree with J star that there are some things that look suspect.

One 3/4" tube every 16 inch does not make for much of an emitter. Is it stapled or hanging? Does it have plates or fins on it? I would guess that a bare tube assembly like that would have trouble making more than 10 btu/ft. I imagine your house loses more than that.

Have someone do a heat loss calculation and add the appropriate emitters. Panel radiators come to mind.

Carl

Gordy

+1

On the emitter side. You have insufficient tubing centers to heat the space. Plates, or no plates.



Need data on floor detail.



What are your floor coverings on main, and second floors. The higher the r value the worse it gets.





Also what temps are being run through the loops? Flow rates?

Rich_49

Sounds like

the Company with the Orange dominant logo has struck again . Have had homeowners ask me to install internet purchased systems before .  Not good .

Tom_133

Smitty

The first thing I would check is the plate exchanger, I had this problem on a house in New Hampshire. His plate exchanger was so plugged it you couldn't blow through it. If its possible for you to remove it without a professionals help thats where I would start, if there are no valves then I would call someone to come do that. If it's plugged you can try cleaning but it may be beneficial to replace keep the old one toss it in a bucket of calcium eating fluid and in a few months you have a back up.

Zman

Exchanger

If the exchanger is bad, you would not be getting enough heat or flow. Since the slabs work fine and the staple up is too hot to touch., it seems unlikely. How hot is the return on the staple up?

Carl

smittyal06

Exchanger

The exchanger was just put in last October. I wouldn't think it would be plugged? The lines were all run when the house was initially built, but the pix you see was all done last October when the outside wood boiler was connected. 

smittyal06

Return

The return is a little warm, but nothing like the supply. I wish I had thermostats on each end.

smittyal06

Emitters

It is a staple up system. There are some generic fins on it. I don't think they radiate much heat away from the tube.

Zman

Piping

How about posting some pictures of the piping.

It sounds like your delta t is high between supply and return.

You may also have low flow. If the zone has a mixer, what model.What size circulator?

Carl

Tom_133

Smitty

In the New Hampshire job I couldn't touch the supply because it was so hot. It flowed just enough to get the supply screaming hot but not enough to flow to circulate through the system and get any return temps. Could be a system pump problem or piping or plate exchanger. I agree with Zman lets see some pics.

CMadatMe

You Have Flow

House wouldn't heat to 60 if you didn't.



The first thing to do is to re engineer the radiant system. Have a radiant heat loss and design calculated using the existing loops lengths etc. How would you be able to determine the needed water temp without it? Room again, is heating to 60 so you are transferring btu/hr out of the radiant.



Look for the 2" air gap between the tubing and insulation. No gap, no transfer of heat. Basically in the is application you are creating a convection oven in the bay. Need that gap.



You can stare at the boiler room all that you want, means nothing without knowing the heat loss and water temp required.

Zman

Where to start...

I absolutely agree with Chris that the emitters are suspect. Some investigation and math should be done.

Any time you have a supply temp that is too hot to touch (140+?) and a return temp that is slightly warm (90-?) , I am going to think you have a flow issue. The flow issue needs to be addressed either way , so why not start there. The delta T will only get worse as the emitters improve. I would expect a delta T in the single digits in the system he describes.

Carl

smittyal06

Air Gap

There is a 2" air space between the insulation and tubing.

smittyal06

Pictures

Here are some additional pictures of the system.This first is the piping coming from the outdoor wood boiler to the plate exchanger. The second is the other side of the plate exchanger. The top is the incoming and the bottom is the return. It goes up then to the 3rd picture to the tank. From there it goes down to the 4th picture. It head to the right through the mixing valve to the circulation pumps and down to the basement loop which is working good or the return. The 5th picture is the 2 pumps. One controls the main floor and one controls the upstairs. The 6th picture is the return from both the main floor and upstairs. That heads up to the top of the 7th picture to the top right just below the mixing valve. That then goes down to the basement loop or return as in previous picture. The 8th picture is the tubing in the joist. There is a little over a 2" gap from the tubing to insulation, and then the ceiling boards. The tubing is hearing hardwood floors on the main floor and laminate on the upper level. Please let me know which additional pictures you need or information would be beneficial. I appreciate the input.

smittyal06

Delta T

I feel the Delta T is high. How do you lower this? Is it a matter of shorter loops?

SWEI

Pictures 1 and 2

appear to show a heat exchanger which is bypassed on both sides.

smittyal06

Pictures

Yes, that is true in the picture. Sorry for being misleading. When in work, the valve in pix 1 and in pix 2 are both closed. They are open b/c we used the electric heating unit at the end of the season to try to heat the house to see if it was a boiler issue. However, the electric boiler did not produce any better results.

CMadatMe

Chasing a Ghost

Your chasing a ghost and putting the cart before the horse here. Take the time and have a radiant heat loss and design performed based on what's in the floor. You don't even know what water temp you need. As a matter of fact you don't even know if the existing system can even get you to where you want to go. Like any lost sole in a jungle, a map comes in real handy and that heat loss and design is your map..



Willing to bet there isn't enough tubing in the floor. Heck, you don't even know if those pumps are sized right. How would you, you don't know the needed gpm and at what head loss you have to overcome..

Zman

Cart

I am really not seeing the harm in spending some time seeing if there are issues in the mechanical room before deciding to tear into a full redesign. Right off the bat with very little effort it seams obvious that the delta t is too high, indicating low flow. It could be that the position of the valves on the heat exchanger bypass is the entire issue. Maybe it is something else that is real simple.

It is kind of like tearing apart your motor looking for a problem only to find out the car is out of gas.

Carl

SWEI

Just checking

having missed my share of (even more) obvious details.

Gordy

High delta t

Could also mean that there is insufficient emitter, and the btus are getting pulled off the train before it reloads at the station. May be beginning of loop is in a high load area.



Could also mean excessive loop lengths for the tubing size, and circulator.



But then again these could all point to flow rates. Like Chris said your only guessing.



If we are guessing though, and tube centers are 16". Supply is to hot to touch, and return is a lot cooler. Then it's a combination of not enough flow, emitter,possibly insulation detail is not correct.



I'm only seeing 4 loops seems like not enough loops for three floors worth of radiant even at 16" on center. Long loops?



To add those plates are not the best let alone the installation of them.

Gordy

To the OP

The best thing you can do is invest in an IR temperature gun. Install thermometers on supply, and return of each loop, and calculate loop lengths.



Along with the heat loss of your dwelling.



Once you know the heat loss of each zone, or loop. We can then do the math to see if what you have can be enhanced to meet the loads required.



This could mean larger circs, extra loops, higher average water temps, insulation detail etc.



With out the load call we are stabbing at it.



I think you are producing the btus needed, you just have to get them where they need to go.l

CMadatMe

Exactly

The OP says he can get the thermostat to read 60. He is moving btu/hr. In my opinion that large delta is being caused as to one of your points Gordy, being taken off the train. Another issue I see with those plates is that a portion of the tubing may be right up against the sub floor. Wood is an insulator and may be stripping out the btu/hr so Gordy's IR thoughts to shoot the floors would show high surface temps where tubing is.



I saw the four loops as well and that tells me there is either no way enough tubing in the floor and/or loops lengths are awful long and pumps may not be sized correctly as well.



All is mute without the heat loss and doing the math.

Rich_49

Delta T

seems to be the issue here .  Install the appropriate 00VDT from Taco , set the Delta for 10* Delta and call me when you are toasty .  I know it's not quite that simple but the Delta T 00's have made plenty of horribly designed / installed jobs where there were unknown factors a snap for me . Some used the 0013 , most we used the 008 , but in most instances they worked real good and made us look like geniuses . If more work is required after that step the pump stays and is a great feature on any install because you are controlling closely the Designed For Delta .   

 Quite possible the original installer did not account for the Cv through mixing valves and accumulated head losses through Hx , mixing , and long loops .  I do believe that 2 008's may very well solve the problem , like I said , it's a Good starting point . Start with the obvious . Anyone disagree ? 

Tom_133

All is "moot"

Chris just a heads up its "moot" not mute



If smitty is saying that with either system the house won't heat then a heat loss is a good starting point.



Smitty, maybe we can see a couple pics of the whole system, like entire piping layout at least another shot under the original post pic. Your symptoms could be a lot of things so it would be good to start at the first step then proceed. The way I see the system from the pic is there is no system pump or anything pumping the main loop. What's pumping water through the heat exchanger?

Rich_49

Whole system

from a distance is a great idea as opposed to segmented views . 

Gordy

Rich

Since the HX was bypassed using back up boiler with similar results we can conclude that the head loss from that component is not part of a flow issue. Cv from mixing valves etc yes.



Couple the fact it's 3/4" pex. I'm inclined to believe if the installer used 3/4 pex, 16" spacing, they probably had no clue on sizing circs, or maintaining acceptable loop lengths let alone understand water temps and flow rates .



Delta t pumps while a great tool when designed in to a system it troubles me when they are used as a bandaid for poor piping practices. Sometimes it's the most cost

Effective approach for righting several wrongs

smittyal06

Pump

The pump on the outdoor wood boiler pumps the water through the heat exchanger for the incoming. 

Rich_49

Agreed

that these pumps are much better when designed into a system . They are able to correct a lot of sins and let's face it often the only economically feasible fix . I honestly have to say that no matter what type of system I am designing nowadays I use them , only variable is whether I can get the losses down low enough to use the Delta T ECM .  I also wish that all are aware of what we are but we both know this is not the case .  Would you agree that this is a good starting point ?

smittyal06

Pumps

So replace the 2 current pumps with the Taco units and you think this may clear up the problem? I am getting the feeling from reading posts that there may not be enough pex running through the house to still supply enough heat? Could the pumps compensate for that if that is the issue?

smittyal06

Heat Loss

I used the Slant/Fin heat loss calculator app to calculate heat loss on the main and upper floor. I came up with a value of 37,000 BTU/Hr. Does that seam plausible? 

smittyal06

Options

With winter approaching I am not sure the route to take. I have no issue with tearing out the basement ceiling and rerunning proper loops with proper spacing and proper insulation. However, if that is the issue that only helps the main level. In which case the main level and basement would be heated. I have to still worry about the upper level. If I am already tearing out the ceiling in the basement to rerun loops, would it be a better option to use forced air on the main level as it would rise to also heat the upper level? Or would using water baseboard heating be a better option as the convection would also rise to heat the upper level? 

Rich_49

Replacing

the existing pumps with VDT's should solve the Delta T issue at which point you can determine if there are any other issues . It is a fine starting point and makes sense before undertaking a deep retrofit , which if that is necessary these pumps will make those fixes and the system proper as the system will have a very close to designed for Delta T at any condition .  Again , it just may solve the issue for small investment . Needless to say closer spacing and different install method could lower your temps among other things , the 16" spacing may work . Don't know how tight the building is . Personally I would not design for 16" ever .

smittyal06

Tubing

In reading the numbers on the tube, I could figure out that one run on the main level was 462ft. long. Which I know is too long. 

CMadatMe

HEAT LOSS!!!!!

Last time I say it. This thread is 8 days old and still no heat loss.

It's now time for you to take a few hours of your day, measure

the house and do a room by room heat loss. I'll even do it for you.



Need:

Coldest Day of the Year Temp. 0 Degrees?

Room sizes

Out side wall length

Ceiling height

Window sizes

Wall Insulation

Heat Above? If no, Ceil Insulation

Heat Below? If no, Floor Insulation

Finished floor surface in Room



Provide above for each room in the house.

smittyal06

System

Here is the entire system.

smittyal06

Already posted

I used the Slant/Fin heat loss calculator app to calculate heat loss on

the main and upper floor. I came up with a value of 37,000 BTU/Hr. Does

that seam plausible? Do you need it room by room or total like I have. I figured it out room by room and added them all together.

Gordy

20.55 btus sf

If your sure you used the right values then this is a starting point.



A value for each zone is helpful. You need to figure out what rooms are covered by each loop.



Next thing is types of floor treatments in each of those zones.



You will be lucky to get 15 btus a sf with your emitter set up depending on the r values of the floor covering. You are at .75 already with 3/4. Plywood



This is why you are only getting 60* room temp running 24-7



You are producing enough btus just can't get them off the train not enough stations to get off if that makes sense.