Water temp for heated floor.

I have two connected pole barns that share a Navia on demand water heater. One building has an overhead box heater with radiator, fan, and louvers. The other building has tubes in the cement radiant heat.
The floor heat is off. The overhead box has been keeping both shops warm with 150 degree water. Last night it was colder and the OH box didn’t keep up.
What is my more efficient option? I can raise the water temp to the OH box (180?) or drop the water temp so I can run both heaters as the floor can only take 120 or so.

140 was the magic number I was explained as to spalling Concrete or causing cracking.

There are different systems for different purposes. Insulated building with constant use a heated floor works as well as forced air or a furnace.  For an uninsulated building and intermittent use it is best to use radiant heat as it heats the objects (you) quickly.

set the boiler at 120 degrees. The floor heat will work great and do 50% of the buildings.. The 120 degree water in the radiator heater for the other building should heat that 50% to an acceptable temp.

Ok I need to be more clear. The two buildings have a shared 30 ft wall and a 10x10 door. The old 10’ side, fully insulated, has the overhead box heater.
The 14’ side, also insulated, has the heated floor.
With the door open between the two the overhead heater has been keeping up with both sides until today.
I tried turning up the water temp today but it seems the OH box is struggling to maintain temp.
I am trying to be as efficient as possible. My options appear to be turn the temp up for just the OH box or lower the temp and put on the floor to help the box. The above suggestion of a mixing valve is what I need. The OH box is nice with 172 degree water going in and at that temp the return temp shows 154.
I’ve sat here and decided to drop the WH temp and put the floor on with the thermostat set at 62 and see what that gets me.

I put the floor at 62 and the OH box at 66 and the floor didnt turn on because the ‘floor side’ thermostat was still reading the 66 degrees the box had been providing.
I left it with both box and floor both set at 66 when I came in. I will check the return temp when I go out. Hopefully there is more than 20 degrees of temp drop.
Thinking about a mixing valve…. If the OH box is putting out hotter air than the floor thermostat is set to the floor would not turn on unless I had the door between buildings closed.

Jay, the floor has 4 250' zones with 1 pump and a wall mount thermostat. The commercial built OH box has a 'radiator' about small car size, fan with shroud, 5 louvers and has a pump and wall mounted thermostat right under the box. The system was new a year ago but until more recently the building lacked insulation and a fair 'test' of what worked the best wasn't really possible. I just re-discovered the water pumps have an adjustable speed so that opens new possibilities. 

Sorry but who cares what the temperature of the floor is? Your goal is usually to make a room feel comfortable ( or at the temperature you want), not to heat a floor to some point.   So measure and control the room. I suppose it might be interesting to see what temperature the floor is at times but I wouldn’t bother with trying to control with a thermostat in the floor. Our house has in floor heat like this for the basement and garage with thermostats on the walls. Works perfect. My niece and her husband and a little child lived in the basement for close to a year including a hard winter. Comfy cozy 0 complaints. The one thing I’ll say, if you are normally comfortable in a 70 degree room, you’ll probably be comfortable at 66-67 in a room with a heated concrete floor.

Edited by Tbone95 - 02 Dec 2024 at 12:08pm

Tbone is right you don't set on the floor you want the temperature to be what is confortable at the level you are working.

Edited by DaveKamp - 02 Dec 2024 at 10:40pm

Dave,

Steve I turned down the overhead to 62 and left the floor at 66 last night. This morning the thermostats read 62 and 66 and neither had the "heat on" light lit.

About five years ago I was dragged out of retirement to engineer a unique in-floor heating system for a new elementary school for a religious group. They wanted in-floor heating as the children would be spending a lot of time on the floor. There were no engineers in the area that had designed in-floor heating systems. The secret to the system was a special thermostat designed for in-floor heating systems. It had two sensors, one measured slab temperature to prevent damage to the concrete from over heat and a second sensor measured room temperature. The last challenge was to educate the staff how to use the thermostat as in-floor system has a very slow response time compared to a forced air system.

thats what i was thinking Scott... IF your two thermostates are measuing AIR TEMP on th wall near the radiator box unit, then when you set the hot air unit ABOVE the floor heater unit, the air gets warm and shuts off hot water to the FLOOR heater........ I think you set the FLOOR heater where you want it because it is slow reacting ( maybe 66 degrees)... And set the radiator unit at 62 to keep it "ok to work"... and if you want more instant heat, you just tern the radiator unit up while you are working.......... but 62 should be GREAT for most working conditions......