Garage floor heat control

[JTownLogger]

I was wondering how you guys were controlling the temperature in your garages with Pex in the concrete slab. All I have right now is an inline Honeywell thermostat that turns my circulation pump on and off. I thought this thermostat would be a good idea but last night the temperature in the garage must have dropped below 45F and the OWB ran all night and was out of wood in the morning. This is my first year with an OWB and garage heat that doesn’t consist of torpedo heaters! A friend of mine has pex in the floor, but he has a dedicated coal boiler just for the garage. His pump runs all the time, and he regulates the temperature of his garage by the temperature of the water.

 

[pwl]

Mine is controlled with a thermostat also. I do run my water through a temperature control valve however. 180 degrees out of the OWB and 135ish in the floor.

 

[woodman6666]

I circulate continuosly just have your thermostat open or close a zone valve, to either the floor or back to the boiler. Very simple and works great.
www.procutfirewood.com

 

[firewood guy]

I was wondering how you guys were controlling the temperature in your garages with Pex in the concrete slab. All I have right now is an inline Honeywell thermostat that turns my circulation pump on and off. I thought this thermostat would be a good idea but last night the temperature in the garage must have dropped below 45F and the OWB ran all night and was out of wood in the morning. This is my first year with an OWB and garage heat that doesn’t consist of torpedo heaters! A friend of mine has pex in the floor, but he has a dedicated coal boiler just for the garage. His pump runs all the time, and he regulates the temperature of his garage by the temperature of the water.

Check out the controls available from Growers supply . I have three greenhouses for our nursery operation and get all of controls from them. Great pricing and a staff that knows their stuff!! Growers supply was formerly known as Farmtek. Hope this helps!

 

[Ambull]

I put pex radiant floor heat in my garage as well, and I soon after regretted it. Too slow to respond. Also, it will create too much humidity in the garage if the floor is wet. Also, a lot of heat can be lost if it is not properly insulated below the slab.

Well, anyways, to deal with it I would try to keep the water criculating more regularly, so that the slab temperature stays warmer. If the slab is ice cold and the heat kicks on, it will take FOREVER, just as you stated. You hate to run the pump all the time, as it will shorten it's life, but perhaps there is something that could be done.

Not sure exactly why, but I have been told that it is not good to run hot water through the pex. It should only be warm water, 135 degrees max. Maybe hot water causes the concrete to crack or something.

Hope this helps.

 

[JTownLogger]

Check out the controls available from Growers supply . I have three greenhouses for our nursery operation and get all of controls from them. Great pricing and a staff that knows their stuff!! Growers supply was formerly known as Farmtek. Hope this helps!

I went to Growers Supply's site to check out their stuff. I found something that got me thinking. They sell a DuroStat™ Electronic Thermostat (Item# 102720) that has a remote sensor. I was thinking if I put the sensor in the floor, and monitor the concrete temp, I wouldn’t get a big temperature swing, like what I do from monitoring the air temp. Then maybe the OWB wouldn't idle all day and run full tilt at night. Has anyone tried this?

I dont understand how you are getting the water down to 135F before going in the slab. If I could get it down to 60F and run it continuous thats how i'd do it.

 

[Steveguy]

I have a mixing valve in mine that takes the 175 degree water coming from boiler and blends cool water returning from the floor into the floor supply side, mixing it to around 100 degrees. This slows the heating a little and doesn't pull down the boiler as hard. So even if the floor calls for heat in the night it won't burn up all the wood in the stove as quick. Also it gives a little more time for an air sensing thermostat to work before overshooting the setpoint. I do think a remote sensing thermostat sensing slab temp would be much better, I'm too cheap to buy one to try it.

 

[JTownLogger]

Steveguy,
Can you get me a Make and Model of your Mixing valve? That seems like a pretty nice set up. My buddy who has the coal boiler heats the water to 85F and it circulates through the slab continuously. That works real nice. Do you know how low can you adjust the valve? Thanks

 

[Steveguy]

It is a honeywell AM-1 series mixing valve, I don't have the exact part number.
I also have a similar one on the domestic hot water that says it will adjust from 80 to 130, this one is supposed to be special for domestic hot water so if it fails, it fails cold instead of scalding anyone. The heating mixing valve was a little different as i recall. I'm not sure how low it will go, around 90 to 100 in my system. Here is a listing from pex supply. You maybe want one that is listed as heating only, temp 80-180



www.pexsupply.com/Honeywell-AM-1-Anti-Scald-Mixing-Valve-1474000

 

[JTownLogger]

Ahh, I just installed one of these for my domestic hot water now that I'm heating my water with my OWB. Thanks. You gave me some options. Now I need to figure out what to try first. The thermostat with a remote sensor is actually cheaper than the mixing valve...

 

[Steveguy]

One other thing iI have done is use a cheap plugin timer to regulate when the floor can heat. I have a Line Voltage thermostat to run the pump directly, and I have that plugged in to 110v . I have plugged a timer in and then the thermostat, and set up times of the day to allow heat when the wood use isn't a big deal. I try to save heat in my shop because I don't have foam under the whole floor. I heard you could do a perimeter insulation and then use the ground as heat storage (thermal mass) but I am disappointed with the performance of this setup. I may run the floor just a little and set up forced air also to bring up the temp while I'm in the shop. My attached garage has foam under the whole floor and I keep that at around 60 all the time, it works great.

 

[JTownLogger]

Well, I ordered a mixing valve. I like the idea of when the pump does kick on, there won't be as big of a load on the furnace. I think the thermostat with remote sensor and the mixing valve would make everything work perfectly, but I'll just have to try one thing at a time right now. Thanks everyone.

 

[brushfire]

My heating guy and I installed pex in my new garage floor a couple weeks ago. The carpenters finished framing and now the heating guy has to set up the different zones. Each zone should consist of 300' or less of pex. I put 2" blue Styrofoam under the whole floor and on the outside of the frost walls along with 2" foam over the outside edges of the footers extending out to prevent cold from creeping up the frost wall from the bottom.

I also ran reflectix all along the perimeter where the slab edge will join to the frost wall and stapled it to the blue under the floor so it would stay in place during the pour. The idea being to totally insulate and isolate the slab from the ground and the frost walls to prevent any heat flanking to the sides or ground.

The concrete contractor told me to heat the slab very slowly. Attempting to heat green concrete quickly can cause it to crack.

 

[coyotencuttin]

+1 for brushfire!! when i install slab heat i run a 1/2" conduit in the slab for the remote bulb for a honeywell T6031A1136 or an electronic remoted thermostat. when the area has a call for heat this remote thermostat acts as a limit switch keeping the slab from overheating. you will still need the tempering valve to keep the water temp to 120 degrees but the stat will only allow the slab to heat to 70 degrees or so. too much hotter a slab and it becomes uncomfortable on the feet to be working on all day. good luck, harold

 

[brushfire]

+1 for brushfire!! when i install slab heat i run a 1/2" conduit in the slab for the remote bulb for a honeywell T6031A1136 or an electronic remoted thermostat. when the area has a call for heat this remote thermostat acts as a limit switch keeping the slab from overheating. you will still need the tempering valve to keep the water temp to 120 degrees but the stat will only allow the slab to heat to 70 degrees or so. too much hotter a slab and it becomes uncomfortable on the feet to be working on all day. good luck, harold

That's a great idea coyote! I passed it on to my heating guy for his consideration on future jobs.