Tankless hydronic heat, 1 car garage

ketchgould

I am looking for the simplest way to heat 1/2" pex in a one car new garage build. I have propane and electricity, both 120AC and 12volt DC. I would like to simply use a tankless heater, expansion tank and circ pump. Can this system work? Would electric or propane be preferred?

EdTheHeaterMan

Tankless water heaters are expensive compared to a tank type water heater. LP gas is usually less expensive for heating water compared to electricity.

I have used a small residential gas automatic tank type water heater to do a small radiant job.  The smallest burner is about 30,000 BTUh and the smallest tank is about 40 gallons.  You can pipe it as you wood a closed system and set the water temperature thermostat to 110°F or 120°F to accomplish the proper floor temperature for the project.   

Look for the lowest price tankless heater and compare it to a tank type water heater and see the difference.  Also, the tankless water heaters are problematic with a closed system.  The circulator pump needed to move the water through the tubing may not generate enough flow to operate the flow switch that opens the gas valve on the tankless water heater.      There are hundreds of folks that come on HeatingHelp.com and other sites with the problem of no heat from the water heater.  That is because the water heater is not designed for a closed system operation.  It is designed to operate on an opens system. 

Ironman

A tankless water heater is not the right tool for the job. It’s not designed, controlled or approved for space heating. And for the size of a one car garage, it would be drastically oversized.

A small mod/con boiler would be the best choice, but if you wanna do it on the cheap, a tank water heater that’s dedicated only for that could be used.