Hi guys, new here on the forum, looking for some advice. I'm thinking about replacing my standard on/off set point thermostats in the rooms with radiant, and the rooms without radiant to programmable. I currently have radiant in the basement and garage slab and under a mix of hard wood and tile, run off a boiler. The boiler is a propane boiler and is a backup/ transfer from an outdoor wood boiler which carries the load for the whole house and hot water. I've got approx. 8 zones. Any help is appreciated!

typically slabs are not worth setting back unless you are setting them back for days at a time. However, it can manage your demand periods if you are trying to do something like make sure the wood boiler is still hot in the morning for domestic or something.

I guess I'm looking for ideas for ones in the living areas (living room & entry foyer) that are hardwood and tile. Thanks for the help

Posted By Mingom on 26 Nov 2012 05:04 PM
I guess I'm looking for ideas for ones in the living areas (living room & entry foyer) that are hardwood and tile. Thanks for the help

How thick is the cement/mortar under the areas you wish to control?

Standard tile/ 1/2 to 3/4 in hardwood, then subfloor the radiant between rafters with aluminum plates and fiberglass insulation.

We use standard heat only thermostats to control most of our radiant floors and ceilings. If setback is called for (rare) we use boiler controls to setback design water temperature.

Setback thermostats are made to overcome the many shortcomings of forced air heating and are for the most part incompatible with properly designed radiant floor heating systems.

If you are trying to save operating costs with your existing radiant floor heating system look to a weather sensitive controls.

I do prefer thermostats with floor sensing like tekmar 508s if I'm doing radiant floor, personally. one more lever to control comfort with.

We're doing setback with high and low mass here at our shop as an experiment to try to shift our demand periods to warmer times (air source heat pump). Last night it dipped below 20 F here, and even initiating our setback recovery period at 530 AM this morning, our internal temps are still trying to catch up 4 hours later.

not a lot of opportunity for "lower indoor temp energy savings" here. the more swing I'm willing to tolerate the more of my demand I can shift to sunny times, but if I were running a GSHP or a boiler of any kind, this setback would be a waste of time.

if you're running a high temp boiler, some very fancy thermostats like "TekmarNet 4" or "Net 2" systems can do indoor feedback and raise water temps temporarily to come out of setback faster... as long as running hotter doesn't hit your heat source efficiency that can be a strategy that works. but that's more involved than just thermostat selection.

The boiler is a Crown Cayman, setpoints now are at 150 hi and 140 lo. Each radiant loop has a mixing valve to control the temp going under the floor. My current thermostats are Braeburn 300 series. Thanks for all the information, I really appreciate it!