When to start floor heat?

[will02]

I put up my new shop last winter and ended up turning on the heat in Febuary during the longest cold spell of the winter. Below zero for a week or so. It took about 5 days to get up to heat and sent the electric meter spinning like a top. After it got up to 60*, it settled in and worked like a champ. I leave it at 62* in the winter. 40x60x14 with a 15x22x9 office on seperate zone, Floor heat, electric tankless heater, Seisco brand, average Oct temps here are highs of 60* and lows of 38*. It fluctuates alot this time of year, had a hard 29* frost Sat morning and was 92* Monday! My question is, when do you turn the heat on? Is it easier and cheaper, on the system, to turn it on when the floor is still not much below 60* or do you wait until it is cold in the shop? The floor is now @64*, should I just flip it on now with the thermostat set at like 58* or maybe even 50* so it won't run until the floor hits that temp? Thanks-Dan

 

[oldgoat]

Just guessing but I'd be turning it on now and just set the thermostat down to 50. Shouldn't take much to keep it at temp once there and far easier to get it up to the temp you want when you need it.

 

[PhantomEB]

Was talking to a bud who has infloor heat, he turns it off during the spring/Summer, apparently pretty quick here, hes gonna be turning it back on and running it at 10* above freezing, just to insure that he dont get any frozen pipes.

 

[Franz©]

Floor heat operates on the basic concept of making the entire slab a thermal battery. When the floor is hotter than the room, the floor givces off heat to the room.

That said, you have 2 choices. You can either maintain the heat already stored in the slab by adding a small amount of heat to the slab as ambient temperature falls off, or you can let the slab chill, and add a huge amount of BTUs to the concrete when you decide to begin heating the room. BTUs tend to be getting more expensive as time goes on regardless of the fuel used to generate them.

My thinking would be to use an infrared thermometer to determine the true temperature of the concrete floor, and begin adding heat to the concrete when it falls 10° below the desired room temperature. That would maintain what's called flywheel effect in the heated area, and probably require less BTUs than bringing the slab up from freezing.

 

[will02]

Thanks Franz, that is what I was thinking also. I plan on running it about 62*,so I will keep an eye on it and turn it on when the floor hits about 50*.

 

[sneezer41]

last year I set my garage under radiant garage to run for 1/2 hour [IIRC] a day to keep some heat in the slab. I find that 50 something with a warm floor is pretty comfortable.

 

[kbs2244]

Why would you ever turn it off?
If it is at temp the boiler won't come on, will it?
Radient seems like the ultimate "set and forget" set up to me.

 

[BowtieNut]

I leave mine on year round. Why would I ever turn it off? If it's warm out, it won't run. If it gets cold, then I want it to run.

Besides, my controller will automatically cycle the system for 5 minutes per 24 hours (or something like that, maybe it's 5 min/week I can't remember) just to keep the pump from seizing up. If I shut it off completely, I just disabled that useful feature.