Temperature Sensor location for radiant floor heat

JohnInNewHampshire

I have a house where with three zones radiant hot water heat. Two of the zones of baseboard hot water radiators and use wall thermostats. There is an addition off the back of the house that has floor hot water radiant heat. There is no in floor temperature sensor, and previous owners used a Nest wall thermostat (two wire back to boiler). The Nest is programmed for floor radiant heat.

The heat in the addition with floor heat is super difficult to control with long time constant causing either too hot or too cold. Any suggestions for how to retrofit a thermostat and temperature sensor to better control the floor.

I was thinking to get a Honeywell thermostat and add a remote temperature sensor that would be as close to the floor as possible and not on an outside wall. E.g. Honeywell T9 with remote sensor.

Any suggestions? Thank you!

hot_rod

is this a slab radiant, or can you get under it to add a sensor? Mid room between two pex runs.
Does the room get a lot of solar gain causing over-heating.

I would consider a thermostat that is radiant specific and includes sensor options. Uponor, tekmar, HBX.

How is the supply water temperature controlled? Sending too hot of supply can cause over-heating. Ideally it would be controlled by an outdoor reset function.

A sensor installation video.

https://www.youtube.com/shorts/mP-5JZ0IM_4

JohnInNewHampshire

Thank you for your response! Unfortunately, it is on a slab, so no easy access to install a sensor in the floor.

Also unfortunately, the addition ceiling is not well insulated and difficult to add insulation due to limited access (no crawlspace). So room gets hot in the summer, too.

Hot water goes thru mixer coming out of boiler to get lower temp for floor heat circuit than the baseboard radiators zones.

Thank you for the suggested vendors for thermostats! I will research.

JohnInNewHampshire

Also, the flooring is ceramic tile planks, so slight pain to rip up the floor… :-)

DCContrarian

I'm not a fan of floor sensors because it doesn't really address the problem.

I'd be looking at getting an automated mixing valve that allows you to adjust the water temperature for outdoor temperature.

JohnInNewHampshire

OK - thank for responses re: outdoor temp control. That makes sense. We are in New Hampshire with some pretty extreme (low) temps, and the overshoot is definitely worse on those relatively warmer days.

The mixer valve is manual & Boiler zone controller is an older Taco system which I was thinking might benefit from an upgrade.