In Floor Heat - Water Temp Setting using Heat Exchanger

[ShiftedSolutions]

So for my 32X40 I am using an in floor heat. The heat source is an AO Smith tankless hot water heater. This heater is used to heat both my domestic hot water I use out there and then also heat floors through a brazed plate heat exchanger (my floors are on a separate loop since they have a glycol in them).The garage is well insulated. Typically the garage is set at about 58 degrees, and I live in Michigan.

The question I have is what temperature I should set my water heater at as it runs through the heat exchanger? I don't know if it is best to set the water temp (from the tankless heater) at 90-100 degrees and it circulates longer, or if I should have it run much hotter to transfer the heat to floor loop quicker. Which is more efficient (this is an LP system...)? Has anyone used this set up and what do you set your temps at?

 

[Kaizen]

Low and slow. 100 to start and adjust as needed. Let it warm slow


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[Chris705]

I don’t have your setup. I do use an indirect wh to make hot water from my condensing boiler. I was very close to doing what you have. I recommend setting your hw to what you would expect to have available at your hw faucet ....120 to 140ish. Then use a mixing valve on the floor heat side set to about 110,using a tee on the return water side of the floor heat as cold water input for mixing valve. Control the floor heat pump and heater with switch relay (Taco or similar) and t-stat.

 

[86turbodsl]

You won't want your floors much above 100F, or they start to get uncomfortable.
I don't know what your plumbing loops look like, so it's hard to give advice on what you're doing here.

 

[Chris705]

T-stat will reach set point long before floor reaches water set point temperature....

 

[tdkkart]

You won't want your floors much above 100F, or they start to get uncomfortable.

If you're floor is 100*, the floor is gonna be the least of your worries because your air temp will be 90-95* in short order.

T-stat will reach set point long before floor reaches water set point temperature....

Exactly. In a "well insulated" structure with reasonable heat loss, your floor shouldn't be much more than about 5* warmer than your desired air temp.

Consider this when deciding what your supply temps should be. Hotter is not necessarily better, or needed.

 

[86turbodsl]

If you're floor is 100*, the floor is gonna be the least of your worries because your air temp will be 90-95* in short order.

Well, with the typical 4" floor, that much thermal mass is hard to move fast. At least on my floors, i can put 100F water in if i'm trying to move the slab temp in under a couple days.