Radiant floor heat winter start up?

[jasondavidmann]

Good morning GJ,

I'm early in the process of my shop build and have a question about starting up the radiant floor heat.

With any luck I'll have the framing and insulation done before it gets too cold here in Manitoba. However if I am not able to meet my DIY deadlines it wouldn't make sense to turn the heat on without insulation. I would keep working in the cold until the building is ready.

MY QUESTION IS: Can I turn on the radiant floor heat (for the first time) in the middle of winter?

Once up and running my plan is to set the thermostat once and forget about it maintaining a constant temperature.

I'll be following up with my HVAC contractor but thought I would also ask the knowledgeable people here.

 

[Jackfre]

Yes you can. With a good outdoor reset program on your boiler it will regulate the necessary temps to maintain comfort and efficiency and have a min/max temp setting for best and safest operation of the system.

 

[Ak Jim]

Interesting question. Is the garage going to be heated by other means or will the slab be cold soaked to -30°?

 

[jasondavidmann]

I may run a space heater (forced air propane, not vented) while working. But likely the slab would be -30.
There will be plenty of insulation under and around the slab.

 

[yeldogt]

Go on heatinghelp and ask -- someone should be able to give an answer. I have never had to do a cold start in such a cold situation ...

I did do one where the outside was around 32F in the day ... but, the slab was above that --- so no danger of freezing the water as it went in. You also need to make sure there is boiler protection depending on the heat source and it's need. My guess is you need to use an antifreeze mixture for your climate anyway --- something I don't have to.

Some electric boilers can be direct piped -- fueled boilers typically need primary secondary and some required an exchanger w/ antifreeze.

Warming up a slab like that takes time and typically unless an industrial setting with a huge boiler you don't have to worry about the slab.

 

[Jackfre]

AK Jim possess the right question I did not consider. That’s the AK part The slab while insulated will be cold. You may need to run your supplemental heat source to moderate the temp of the slab. Once above freezing hook up a hose and run tap water through it. That will likely be in the 45-55* range. Then blow that out and add your heat transfer fluid and fire up the boiler.

 

[jasondavidmann]

Thanks everyone, part of my package purchase includes initial commissioning by the the HVAC company and thereafter warranty. My goal is to be insulated by October and then none of this will be an issue.

 

[Rc_Guy]

Go on heatinghelp and ask -- someone should be able to give an answer. I have never had to do a cold start in such a cold situation ...

I did do one where the outside was around 32F in the day ... but, the slab was above that --- so no danger of freezing the water as it went in. You also need to make sure there is boiler protection depending on the heat source and it's need. My guess is you need to use an antifreeze mixture for your climate anyway --- something I don't have to.

Some electric boilers can be direct piped -- fueled boilers typically need primary secondary and some required an exchanger w/ antifreeze.

Warming up a slab like that takes time and typically unless an industrial setting with a huge boiler you don't have to worry about the slab.

What do you mean freezing the water as it went in?

Wouldn’t the system be full of the water and glycol mix already?

 

[yeldogt]

What do you mean freezing the water as it went in?

Wouldn’t the system be full of the water and glycol mix already?

If it's cold out and the slab is in an unheated building --- the water can freeze as it's going into the pex to fill it initially. You can't fill the pex until you get at least some of the equipment in.

I had a bit of this issue last year ..... the floor guys hit one of the pex lines and the boiler lost pressure. The building has no water connection yet -- I had to feed the boiler from my outbuilding in 10 degree weather. My well water is very cold .... had about 5m to get the hose connected and get the water into the system before the hose froze solid. Not to mention it had to go in slow ...

Trying to fill a system in a super cold area has to be done correctly. In my area with proper insulation even at our cold temps it would take days for the slab to cool to 32. In an area w/ - 30 ..you have to use antifreeze solution

 

[Rc_Guy]

If it's cold out and the slab is in an unheated building --- the water can freeze as it's going into the pex to fill it initially. You can't fill the pex until you get at least some of the equipment in.

I had a bit of this issue last year ..... the floor guys hit one of the pex lines and the boiler lost pressure. The building has no water connection yet -- I had to feed the boiler from my outbuilding in 10 degree weather. My well water is very cold .... had about 5m to get the hose connected and get the water into the system before the hose froze solid. Not to mention it had to go in slow ...

Trying to fill a system in a super cold area has to be done correctly. In my area with proper insulation even at our cold temps it would take days for the slab to cool to 32. In an area w/ - 30 ..you have to use antifreeze solution

Yes, I know, I have antifreeze in my infloor heat.