Thermostat

Charlie_9

I've installed a new hydronic heating system which includes both hydronic baseboards on the second floor and radiant heat in several rooms that are adjacent to each other on the first floor. These rooms also have supplemental hydronic baseboards. The floors are 3/4" oak over plywood, with the Pex-al-Pex radiant tubing attached to the top edges of the joists. Looking for a recommendation for a thermostat that will control both air and floor temperature, incorporating a floor sensor.

STEVEusaPA

Well Tekmar makes a t-stat for that, but what kind of boiler control are you using?

Charlie_9

I have a Navien tankless boiler with Taco controls

Rich_49

Could you take a picture of the tubing placement or describe a bit better where the tubing is attached ? One pass per joist bay or two ?

How is the baseboard / radiant arrangement piped ? Is the Navien a combi or is it strictly a boiler , what is model number ?

Pictures of the boiler and near piping please . Yes it does make a difference

Mark Eatherton

Charlie said:

I've installed a new hydronic heating system which includes both hydronic baseboards on the second floor and radiant heat in several rooms that are adjacent to each other on the first floor. These rooms also have supplemental hydronic baseboards. The floors are 3/4" oak over plywood, with the Pex-al-Pex radiant tubing attached to the top edges of the joists. Looking for a recommendation for a thermostat that will control both air and floor temperature, incorporating a floor sensor.

Do you still have access to the tubing from below? I hope so, because fastening to the sides of the floors joist is not an approved method of installation, and there's not a control logic on the market that can straighten that problem out.

Tubing should be stapled 8" on center in the joist bays, and fastened as often as possible to ensure good tube to subfloor contact.

Ideally, the tubing should be installed in good quality extruded aluminum heat transmission plates.

If access is not available, the best you can expect is floor conditioning, where the floors are not ice cold...

Good insulation is also a critical detail commonly overlooked on these joist bay installations. I'd require a minimum R 15 insulation in tis situation, and NO BUBBLE FOIL BUBBLE crap. Junk science.

ME

Ironman

Charlie said:

The floors are 3/4" oak over plywood, with the Pex-al-Pex radiant tubing attached to the top edges of the joists. Looking for a recommendation for a thermostat that will control both air and floor temperature, incorporating a floor sensor.

You won't get 1/2 the btu output that you could with extruded plates installed.

Mark Eatherton

Nice chart Bob. Where'd you find that gem? (I see who did it, wondering if there is anything else to accompany the chart)

ME

Ironman

It's from Rehau's training manual and summarizes the results of a study done by VA Tech's engineering department.

Mark Eatherton

Cool, thanks.

ME

Ironman

Mark, I'm sure you can find the entire study somewhere on line, but coming from engineering it's overloaded with verbage.

SWEI

I emailed Mark a PDF of the study.