Thermostat Question

dbornhorstjr

Two years ago my wife and I purchased our first house. It was old and needed updating. It had a fuel oil boiler in a small basement that took up a lot of space. So we ended up replacing that with a on-demand combi unit run by natural gas to free up space in the basement to create more living space. I recently had the concrete floor dug out and replaced and while doing this had radiant floor heat put in the basement. This is the only heat in the basement and has been working great this winter. before I finish the work on the basement I want to put radiant heat in the floor above, for comfort measures only just, to have a warm floor. I will not be removing the baseboard heaters upstairs. My question is how do go about putting the radiant floor heat upstairs on a thermostat. My fear is that whatever room I put the thermostat in when that zoned area reaches the temperature for the baseboards it is going to end up turning off the radiant floor heat thus not giving me that warm floor feel. I have thought about setting the radiant floor heat thermostat 1° higher, however, wouldn't the two systems just then be in competition. In searching online I have found Tekmor thermostats that have a slab thermometer and also control the room temperature at the same time maintaining the room temperature but not allowing the floor to fall below a certain temperature. However I believe these are 24 volt and my system is typical to wire I believe 12 volt. Any help is greatly appreciated

Jamie Hall

Check your voltage -- I'd be much surprised if the whole system weren't 24 volt controlled. If you can find the transformer, it may have a label on it which will give you the voltage and rated output.

That said, your best bet is some sort of slab or surface thermostat to control the floor. You can retain the present thermostat for the baseboard and all that valving and piping and pumps just as it is now. There are many possibilities; hopefully someone will chime in with some suggestions.

dbornhorstjr

Jamie Hall said:

Check your voltage -- I'd be much surprised if the whole system weren't 24 volt controlled. If you can find the transformer, it may have a label on it which will give you the voltage and rated output.

That said, your best bet is some sort of slab or surface thermostat to control the floor. You can retain the present thermostat for the baseboard and all that valving and piping and pumps just as it is now. There are many possibilities; hopefully someone will chime in with some suggestions.

Thank you, I am not sure what my current system voltage is, maybe it is 24. I know i only use 2 wires now, but maybe it is 24 and i can just use the others. I just started looking into a slab or surface thermostat

any recommendations for brand?

mattmia2

Control the water temp with outdoor reset and undersize it a bit so that the output won't be enough to heat the room fully and the controls for the baseboard will control the room temp. add a t-stat to shut it down if it overshoots.

Most of your control should be in the design of the loops and the water temp. Use an electronic mixing valve with an outdoor sensor to provide the mix for the floor.

HVACNUT

Install a 2 stage heat thermostat. First stage radiant. Second stage baseboard. You'll need to run a new thermostat wire though, or go wireless.

dbornhorstjr

Thank you everyone!

HomerJSmith

And, how do you plan on doing that? Do you want the fuzzy warm floors to operate 24/7? How do you plan on regulating the flow and temperature of the two systems, upstairs? Is it going to be underfloor? Baseboard usually operates at 160-180 deg and radiant at about 85-120 deg. Baseboard flow can be as much as 4 gal/min and radiant 1/2-1 1/2 gal/min.

How are you currently regulating the flow and temperature of the boiler water in the radiant slab in the basement?

dbornhorstjr

Once I get the piping hung I will have the company that installed the boiler come back. When they installed it the left 2 zones for radiant heat. They already came and hooked up the slab heat. I'm not sure what was used, but I know there is a mixing valve, not sure how any of it really works. A manifold.

Zman

If you have in-floor radiant, why would you want the baseboards? Unless you have a very high heat loss, running both will just make the floors feel less warm.