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wall vs slab thermostat infloor heat
- Thread starter bwoody
- Start date
Do you have a good outdoor reset on your boiler? If so, the slab stat should deliver a better more consistent temperature. The ODR will modulate the boiler output temp and therefore the slab temp based upon outdoor temps.
I do not have an out door boiler reset. A little more back ground since I left off some details. This application is for infloor heat in my new basement. 1300 sq ft. Basement is framed out and spray foamed. 1 zone 4, 300 ft runs of pex, heated by a siesco electric 11kw boiler.
What determines the water temp?
The key is too use as low as possible -- the floor stat is the high limit.
Without the outdoor reset .......Sometimes you have to use the wall and floor together. Typically with only the wall .. a high mass floor will heat up too much before the room stat is satisfied -- when it is satisfied the floor keeps radiating heat and the room becomes over heated. The floor stat is used to cut off the boiler when the floor is warm and wait for the rest of the area to warm up. The wall becomes the high limit and the floor is what's adjusting the overall water temp -- it's like a manual outdoor resent with you in control. have to play with it a bit.
Even with outdoor reset -- sometimes having a floor stat is needed. High mass radiant needs overheat protection. I sometimes use one where I just want the floor to be warm .. but not fully heat the space. Since I also have ducts for AC -- I typically install a furnace. The radiant warms the floor and the furnace circulates air and maintains the temp.
The key is too use as low as possible -- the floor stat is the high limit.
Without the outdoor reset .......Sometimes you have to use the wall and floor together. Typically with only the wall .. a high mass floor will heat up too much before the room stat is satisfied -- when it is satisfied the floor keeps radiating heat and the room becomes over heated. The floor stat is used to cut off the boiler when the floor is warm and wait for the rest of the area to warm up. The wall becomes the high limit and the floor is what's adjusting the overall water temp -- it's like a manual outdoor resent with you in control. have to play with it a bit.
Even with outdoor reset -- sometimes having a floor stat is needed. High mass radiant needs overheat protection. I sometimes use one where I just want the floor to be warm .. but not fully heat the space. Since I also have ducts for AC -- I typically install a furnace. The radiant warms the floor and the furnace circulates air and maintains the temp.
stamanti
Well-known member
I have a Nest wall thermostat for the in slab heat in my garage, and another for the in floor radiant in my kitchen. Nest has a specific program for in floor radiant that self learns and works pretty well. The idea is that it learns the characteristics of your room and system so that it does not overheat the space.
In our basement we also have heat/ac ducts that is connected to our geothermal system, that is controlled by a thermostat up stairs. I guess I need to do some more research. Currently just have a wall thermostat but electrician recommended we get a slab thermostat.
water temp is just set at the boiler and not changed. unless I manually change it.
water temp is just set at the boiler and not changed. unless I manually change it.
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In our basement we also have heat/ac ducts that is connected to our geothermal system, that is controlled by a thermostat up stairs. I guess I need to do some more research. Currently just have a wall thermostat but electrician recommended we get a slab thermostat.
water temp is just set at the boiler and not changed. unless I manually change it.
You should figure out what's the max temp water you will ever need -- and lower the output to something just under. On the rare supper cold days you raise it manually.
With it being a basement the heat load should be small?
I would see of you can zone some ducts off the geo. keep the floors warm and do final heating with ducts. Its a great way to do it as the air is cycles and refreshed .. with air movement the small variations with radiant get smoothed out
I would guess our heat load would be pretty small. Only 3 feet of concrete exposed to outdoor air 10' basement. Whole basement is spray foamed (r21), 2 inches of insulation underslab and only a couple windows. We have ducts to all the rooms in the basement off the geo now.