In floor heat. What temp?

[breymeyerfam]

I just finished with my boiler build/ install last week. The boiler and the furnace hx seems to be working well, but just now installing the themostat and zone pump control for my in-floor heat in my basement. What water temperature is everyone introducing to their concrete slabs? I know that boiler temp water is way too hot and installed a mixing valve in the floor heat circuit, but not sure exactly what temp to set it at... I've heard a few different temps, but I don't want opinions, I want real world temps from guys that have it. I don't need to pop my damn ceramic tile off the floor or anything like that.

Also, how long does it take to bring your slabs up to temp?

 

[AGoodSteward]

Don't have it personally but my friend had one professionally installed and it was set at 90. It took half a day each winter to get the slab warmed enough that you could feel it.

 

[Mustang71]

I've always seen 140 as the highest heat for in floor heat in the hvac world. 180 would be way to hot. If you are heating with the radiant floor 140 should be good but if it's just for warm floors 120 usually works we have put in water heaters for in floor heat

 

[rancher2]

I run the floor in my shop floor at about 140 seems to work good. I just run a manual mixing valve and check it a the start of the season. I haven't had to adjust it since I installed it years ago. I do run my floor threw a flat plate heat exchanger and have antifeeze in the floor. Last winter I didn't spend a lot of time in the shop as I was working 70 hours a week at my normal job so I didn't use the floor heat a lot. I also have a air handler with a coil in it and I would just used it when I was out their working. Hoping to be home more this winter.

 

[ChoppyChoppy]

80-90* is what mine normally runs at with a max of 120* (the mixer adjusts based on outdoor temp).

Was told 130* or more will soften pex. Dunno?

I rarely use the floor heat though, aside from the garage. House is heated with a Blaze King for much cheaper than the gas boiler can.... though I do happen to know a guy that delivers firewood. Haha

 

[NSMaple1]

I didn't reply last night, because I don't have it.

But there are some replies here based on a concrete shop floor, whereas the OP mentioned ceramic tiles on his inside the house floor. Night & day differences.

IMO 140 is way too hot for that. I would start out at the 90 area, then see how it goes & go from there. Like I said, I don't have it, but have read quite a bit about it. Based on that, I don't think I would run hotter than 110. Warmup time would depend how thick your slab is, & how well it's insulated around & under. I wouldn't be surprised on a couple of days - slow & easy is best.

 

[Mustang71]

If you are trying to heat with the radiant floor then warmer will work better. Just because the temp is set to 140 doesn't mean the floor will get anywhere near that temperature once the thermostat reaches desired temp the zone valve will close. It will heat up faster than 90 degrees will. If you just want a warm floor then 90 may be fine. I know most shops run 140 in the slab to heat the building I've seen 170 once or twice too but I wouldn't recommend that.

 

[Mustang71]

Also depends on your loop size. If you made 1 large loop the water will enter at 140 and leave pretty cold which is bad for the boiler. If you made several smaller even length loops it will heat the slab evenly but the temp entering and exiting will still always be different

 

[woodfarmer]

I'm heating 1800 sf, running six loops of pex(300' per loop max) 4" Dow styrofoam with the px on top and covered with 3" of concrete.
Run max 140* although try to keep it down at 120*. It takes a good day to bring it up to temp. I still haven't determined if the basement slab is a good heat sink to store heat.
I built the house in the winter, had the basement at 84* but when you went Upstairs it was only in the low 50's.

 

[ChoppyChoppy]

Also depends on your loop size. If you made 1 large loop the water will enter at 140 and leave pretty cold which is bad for the boiler. If you made several smaller even length loops it will heat the slab evenly but the temp entering and exiting will still always be different

Not an issue for a properly plumbed boiler. Need a primary/secondary loop and mixer. Boiler runs at 160-180, floor heat at 90.

My house is heated the same way as the garage when I use the floor heat.
I have 5 zones. Water heater, garage, living room/kitchen, master bedroom, 2 other bedrooms.

Takes about 12hrs from 45* to 70*... (we turn the heat down when gone out of state)

 

[Kevin in Ohio]

I run 135-140. Been online 13 years and not a single crack in a 36'x50' slab.

 

[ChoppyChoppy]

No flooring in your house?

 

[Kevin in Ohio]

No flooring in your house?

If your referring to me, I heat a 36' x 50 attached garage with radiant floor heat and a 36' x 50' 2 story with full basement via a plate heat exchanger. Heat exchanger ties into existing baseboard heat which is circulated with oil furnaces circ. pump.

 

[ChoppyChoppy]

Oh. My house and garage have floor heat. No idea what my house slab looks like, have carpets, laminate, etc.