What to use for radiant heat source?

Old 07-28-06, 08:28 AM
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What to use for radiant heat source?

I'm not sure where to post this, so I'll start here!
I have a 2600 sqft ranch with a full, unfinished basement and 1400 sqft garage. When we built in 2000 we put in propane boiler baseboard heat upstairs and radiant tubing in the concrete floors of the basement and garage. We run the boiler for upstairs and have a mixing valve to mix the cool return water for the radiant floors in the basement (although it NEVER calls for heat) and garage (keep it about 50 degrees, just enough not to freeze the cat and it often calls for heat). We think that the boiler was undersized for the load and a couple of years ago had an opportunity to purchase a smaller boiler from a HVAC guy who thought that if we moved the floor loops off the big boiler and used the small boiler for just the floors, we would get better/ more efficient heat. Well then he retired and we never hooked the small boiler up.
We are getting killed with propane prices and have decided to install geothermal with regular duct work for upstairs and the basement. we will be on a .04 per kwh electric rate with the geothermal. Now we have the issue of how to provide minimal heat for the garage. I think it would be pretty inefficient to use the big whole house boiler. Not sure of the sizing of the small boiler. The electric company says it would be more efficient to use electric water heater for the garage loop due to the low electric rate. I'm not sure what size water heater would do it. Also not sure it is efficient with any heat source for radiant to be used just to keep the garage slightly above freezing.

Sorry this is so long, thanks for reading if you got this far! Please give any advice you have!
Old 07-28-06, 04:34 PM
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Heat for garage

You can do a heat loss calculation for $49 at http://hvaccomputer. com.
Once you determine the heat loss then it is just a matter of finding equipment to match the load.
Old 07-28-06, 06:30 PM
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yes, do the heat loss first.

I know nothing about geothermal systems, but I'm guessing if you are talking a total system changeover and new ductwork, that a properly sized and installed boiler would probably have a shorter return on investment. The new modulating/condensing boilers really shine on radiant systems. Check into them.

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