Water Heater for radiant slab

Heatermon

Is that you really shouldn't run the water heater at 90 degree temperatures or the condensation you will be generating will eat up your water heater(s) to the point that a good condensing boiler would be a bargain. At the very least, you will have to provide some type of mixing arrangement to allow the water heater to get up over 120 degrees (and stay over it) while allowing the low temperature needed for your slab. Still can be accomplished, but be carefull.

Heatermon

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Rick Kelly

Water Heater for radiant slab

I'm bidding this job right now for a 1,200 sq. ft. slab in a tight well insulated building with few windows that's used as a shop.

I'd like to use a 40gal. Bradford-White sealed combustion/ direct vent unit as my heat source. It uses no electrical power to operate.

My simple scheme for temperature control is to use the heater's setting on very low (vacation) to deliver me 85 - 90 degree supply water. If I can achieve this, I only need a single circulator (1,600 ft. of tubing)and a relay control to receive my t-stat signal and activate the circulator. Throw on a strap-on aquastat for some overide protection, and it would seem like I have a very basic workable system.

Comments anyone?

[Deleted User]

Make sure

the manufacturer approves it for this use. I;d also suggest you strongly consider installing a low water fuel cut off using a thermoocouple stack device to interupt burner operation. Also make darned sure it's not dual use unless you don't mind being sued for generating Legionella.

In my own house, I use a single source water heater for doing the space heating. I cut a normally closed solenoid into the fuel line between the snap acting aquastat and the main burner and applied a tekmar outdoor reset control to increase its fuel efficiency.

Thats pretty tough to do when you have a gaping 4" hole running right through the middle of you...

ME

Alan(CaliforniaRadiant)Forbes

Jurisdiction

If this is a job that get inspected, talk it over with your inspector. None of the jurisdictions I work in will allow a run-of-the-mill storage-type water heater to be used for dedicated heating; it can only be used in conjuction with DHW. They don't like their water heaters to be connected to a closed system.



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