Boiler Setpoint for Radiant Flooring Heat

retiredmt

I've got a propane boiler that provides heat for a hydronic flooring radiant system throughout the house. The setpoint temperature is 125 F and yet I just found out that the flooring manufacturers recommend 80-85F. The flooring consists of carpeting, tile, engineered wood (floating floor), and LVP. I also live in an extremely cold climate. I'm wondering if the set point is too high? Any thoughts?

hot_rod

A pic of the boiler would shed some light. A conventional boiler would need to run hotter and have a mixing valve for the radiant temperature.

How is the tubing installed? If it is below a subfloor, for example, the supply temperature is not what you would expect to see on the floor surface. There is some r-value between the tube and actual flooring.

80- 82 is about a hot as you want to see the top surface of the flooring. Beyond that it becomes uncomfortable to a barefooted person, even if the wood could handle that or higher temperature.

Additional reading here:

http://www.healthyheating.com/Thermal_Comfort_Working_Copy/Definitions/floor_temps.htm#.Y7hkeOzML9E

retiredmt

hot_rod said:

A pic of the boiler would shed some light. A conventional boiler would need to run hotter and have a mixing valve for the radiant temperature.

How is the tubing installed? If it is below a subfloor, for example, the supply temperature is not what you would expect to see on the floor surface. There is some r-value between the tube and actual flooring.

80- 82 is about a hot as you want to see the top surface of the flooring. Beyond that it becomes uncomfortable to a barefooted person, even if the wood could handle that or higher temperature.

Additional reading here:

http://www.healthyheating.com/Thermal_Comfort_Working_Copy/Definitions/floor_temps.htm#.Y7hkeOzML9E

The boiler is a Lochinvar WHB155N. All tubing is blow some type of sub floor, whether it's OSB or concrete. I'm just wondering why 125F? Why not 140 or 90? I talked with the Lochinvar tech support and they said that the setpoint should be what the floor manufacturer calls for. But that doesn't make sense. Or am I crazy?

hot_rod

Ideally with that boiler, if it only supplies the radiant I would connect the outdoor sensor. So then the boiler temperature would automatically modulate, raising as the temperature outdoor drops.

This will also raise the efficiency of the boiler. On mild days maybe 90- 100 is all that you need. On the coldest days maybe 125- 130 or more.

To know exactly what you need to supply on that coldest day, you would need to determine the heat load for the worse case room, calculate the thickness of the subfloor and flooring. With that you come up with required supply temperature.

If you can find one of these RadPads they allow you to try different inputs for determining requires SWT.

Or just p[ick some numbers, start at maybe 100 for the low end 130 for the high end. if on a cold day it doesn't keep you warm, bump the high to 135.

Do you know how to get into the control and make adjustments?

The manual takes you through the steps, or some videos at the Lochinvar website.

retiredmt

I do know enough to get into the system to make adjustments. But I want to make sure that I won't damage any of the flooring. At this time, everything is working fine (outside temp is 25F). This system also has an outdoor sensor (which I know how to disconnect, if needed). But I think you are indirectly telling me what I need to know. That if the outgoing water temp is 125, then by the time it circulates, the temperature may drop. And this is a function of type of flooring, type of sub flooring, etc. I will say that the house temperature has been great unless it gets super cold (I have another post about being too cold outside). But my discussion with Lochinvar assured me that the current set-up of the boiler is correct. They suggested next time there is an issue, try disconnecting the outdoor sensor.

Hot_water_fan

You can just try lower temperatures with the outdoor reset curve. If 125 is fine for the coldest weather, lower will work at warmer outdoor temps. It'll just result in better efficiency.

hot_rod

You could also get one of the point and shoot temperature guns and shoot the floor in different areas. The hottest point will of course be over the tube. If it is at or below 82F I don't see any problem with solid wood, laminates or engineered flooring.
If you know the type or brand of wood, check with the manufacturer.

Longtime RPA member, www.launstein.com has done a lot of testing of the flooring they sell with radiant, check them out.

It depends on how the tubing is attached, or not, to the subfloor. With aluminum transfer plates you can run the lowest supply. Stapled tube, no plates, needs higher supply. The early suspended tube or UltraFin product may need 160F or higher.

Throw rugs can really put a damper on floor output.

Here is an example of plates or direct tube staple up. As expected the aluminum transfer plates even the floor temperature better, as a result better BTU output.

The IR pics also show pex in plates, vs staple up bare pex, same flow rate and supply temperature. The back 1/2 of these test panels has carpet.

retiredmt

hot_rod said:

You could also get one of the point and shoot temperature guns and shoot the floor in different areas. The hottest point will of course be over the tube. If it is at or below 82F I don't see any problem with solid wood, laminates or engineered flooring.
If you know the type or brand of wood, check with the manufacturer.

Longtime RPA member, www.launstein.com has done a lot of testing of the flooring they sell with radiant, check them out.

It depends on how the tubing is attached, or not, to the subfloor. With aluminum transfer plates you can run the lowest supply. Stapled tube, no plates, needs higher supply. The early suspended tube or UltraFin product may need 160F or higher.

Throw rugs can really put a damper on floor output.

Here is an example of plates or direct tube staple up. As expected the aluminum transfer plates even the floor temperature better, as a result better BTU output.

The IR pics also show pex in plates, vs staple up bare pex, same flow rate and supply temperature. The back 1/2 of these test panels has carpet.

Thanks

Mosherd1

In the middle of designing my moms system right now.  All the rooms require about 22 btus per square foot, it’s all staple up pex with heat transfer plates under 3/4” plywood, but in order to achieve needed output and keep the wood floors, tile floors, and carpeted floors from exceeding temperature limits; the engineered wood floors need max 105^ water, tile floors need max 120^ water, and carpeted areas need 160^ water. If you have wood floors, carpeted floors, and tile floors, it’s most likely you will need more than one supply water temperature.  

hot_rod

Supply temperatures10 degrees of one another are ok on one mix valve. Run the boiler at 160, then one mix station.