Radiant Heat Experts

[Frank Mopar]

My house was built in 1956. It had a central floor furnace which needed to be replaced.

I installed a radiant heat system which I bought from a company that makes the complete systems. It is a single zone. The tubes are completely covered with heat transfer plates, reflective paper and fully insulated.

the house has a full basement, updated siding, house wrap, insulation and windows.

The question is what to run the floor heat at because when it gets real cold say under 30 this system wont keep up. I have head no more the 90 but also up to 105. Whats the correct answer??

 

[Moms68]

You don't mention if you're running NG or oil. If you're replacing the boiler, and it's a condensing gas boiler you can run it at lower temperatures. Outdoor reset which will modulate boiler temperatures based on outdoor air temperature (OAT) is the best way to go. If you have a mix of radiant and regular radiators you'll need a mixing valve when OAT drop in the dead of winter. A range of 80-120 degrees is what is recommended for a radiant loop. Of course it will differ based on feet of head, insulation, and site conditions.

 

[Burnout68]

Is the system all under floor, or do you have base board radiators
If underfloor (wood floor) 120ish if have carpet may go a little higher if not feeling it
If not holding up on the coldest days probably want to make sure you got the right capacity
Might need a heat loss calc done on your home
And then make sure you got the proper capacity
Make sure you have all the air bled out the system also

 

[Burnout68]

Looks like you have four zones piped in
If in future got it working properly you could put some zone valves and break it up into four zones if wanted looks like

 

[Frank Mopar]

Thanks everyone for the replies.

The system was designed based on where I live but Radiantec.com.

I actually have 5 circuits (One wasn't finished when I took the picture) all approx 120-140 ft and its one zone

Im running a dedicated hot water tank. Water going in at 130 and comiing back at 115. I have plenty to go on the water heater thermostat. Also have a wall thermostat that can control ambient and floor heat

probably 65% of the floor is carpeted.

 

[fewillys]

Most of your typical tank style "water heaters" will not be able to keep up with the demand once it gets cold out , that is most likely your weak link at this point . Another weak point that most people do not adequately address is the insulation under the tubing . Go to this site I have linked and do some research , even if your components are not their brand . I have 3 systems currently and have had others in the past .https://www.tacocomfort.com/product/radiant-systems/

 

[toolmanmike]

Wow, I'm surprised they system is designed with that large or tubing and only 2 per section. Plastic doesn't conduct/radiate heat well either. Copper would be best but cost a fortune. I have multizone hot water heat and 3 zones are radiant fin tube. They need 150° or so water temp to work efficiently. I have 1 zone with cast iron radiators that works well at 120°.

 

[Frank Mopar]

Most of your typical tank style "water heaters" will not be able to keep up with the demand once it gets cold out , that is most likely your weak link at this point . Another weak point that most people do not adequately address is the insulation under the tubing . Go to this site I have linked and do some research , even if your components are not their brand . I have 3 systems currently and have had others in the past .https://www.tacocomfort.com/product/radiant-systems/

All the piping is totally covered with transfer plates, reflective barrier and insulation under that.

 

[Moms68]

Thanks everyone for the replies.

The system was designed based on where I live but Radiantec.com.

In my opinion, running this system with a HWH will not work when the temperatures drop below freezing. Not sure where you live but here in New England it’s a hard no on this setup. If you have a boiler and want to use the tank for a storage vessel then it’ll work with the proper tempering valve.

 

[Burnout68]

Yup most likely that water heater being used as a boiler
I’m guessing it’s not a high recovery either
Would recommend getting a real boiler and you can put a zone to make domestic hot water also
Typical water heater is like 30/40,000btuhs
You might need double that depending on your sqft
And your loop pipe like mentioned above is way smaller trying to feed 5 loops with the same size trunk going to loose some capacity there also I would imagine

if want a much more efficient system for your application I would pipe in baseboard radiators but that’s redoing your system
The design is the issue it looks like

 

[Burnout68]

I don’t see no air vents or air catcher either
Can you hear the water moving through the system/pipes

reg temps on floor heat is around 120 up or down depending how comfortable on your feet
Baseboard usually 140+for hydronic heat

 

[Frank Mopar]

I don’t see no air vents or air catcher either
Can you hear the water moving through the system/pipes

reg temps on floor heat is around 120 up or down depending how comfortable on your feet
Baseboard usually 140+for hydronic heat

lines are completely purged of air. Maintain 20 psi and there is an expansion tank.

the question is answered that I can ramp up my floor temp way above what Im running now. Btu’s baby

This is why you ask the guys in this forum. Proper answers and no bullshit!

 

[bm02tj]

I use max water temp 130F but biggest temp concern is surface temp of floor no more than 94F as it is bad for your body
so flooring makes a difference with heat transfer
Water flow should be set for a 20deg delta T
1/2 in tubing max length 250 feet

 

[Frank Mopar]

I use max water temp 130F but biggest temp concern is surface temp of floor no more than 94F as it is bad for your body
so flooring makes a difference with heat transfer
Water flow should be set for a 20deg delta T
1/2 in tubing max length 250 feet

My 5 1/2 tube circuits are 150 ish. Water in at 130 back at 115.