View Full Version : solar home heating with AC
03-21-2010, 12:33 PM
Anyone ever try solar hot water through an airhandler coil then have an AC coil too?
Or would 2 coil resistance kill the airflow? Seems like it.
This would be for a home in TX, what are the electric rate and Nat Gas
Thanks in advance for your responses.
03-21-2010, 12:48 PM
i service several office buildings with air handlers that do this, except the hot water is made threw a boiler. U may be looking at a commercial grade coil air handler.
03-21-2010, 12:50 PM
We have installed air handler/HP units and left a space in return for customer's hot water coil for outdoor wood furnace. Only problems we encountered was the wood furnace installer screwed up the low voltage wiring and burnt up our low voltage transformer. Are you installing the solar system? If you are, then should not be a problem especially if you oversize the blower right off the start.
03-21-2010, 01:59 PM
With right sized ductwork I'd think this would be good application for variable speed blower.
03-21-2010, 02:09 PM
there are units already designed for use with hydronic coils. many manufacturers make them. biggest issue is what to do when solar is not available.
03-21-2010, 03:44 PM
It's already a product, been out several years. Goodman makes one we've installed several times. Although a hot water heater has been used to heat the coil in the jobs we've done.
You'll need a second source of heat - natural gas if available or propane.
Make sure that the air handler has an ECM blower if the house is going to be off the grid.
03-21-2010, 07:34 PM
We've done it with a geo system. It works up to a point but in our area the 2,000 gallon solar tank gets pulled down pretty fast. You have to be careful about the Btu load and not depend on the solar for extended times when the sun isn't out and it's low in the sky, such as January and February. Having said all of that, the main problem we ran into was controls. Seems nobody builds a control/t-stat that will handle both the air handler blower and cycle the pump for the solar as primary and the heat pump as secondary. We got into some special control applications there. The other two issues were that the HP was to be used for cooling in the summer (2-stage) so we had to be able to run the system without the solar at all above 65F. Also, we had to be careful to turn off the solar when the tank temperature dropped or we'd be using the geo HP to heat the solar coil, which is neither efficient nor what is intended. The static is only a little higher but that is primarily due to the limited space we had to squeeze in both the air handler and the solar coil.
We came onto the job late, after the solar installer was already at work when they realized they couldn't heat the house all winter with the solar. So in the future, my geo jobs will have PV solar rather than water solar. That way we can offset the electrical component cost of running the geo system and the net is a zero cost of operation heating/cooling system.
12-15-2010, 08:30 PM
Skippedover is right in the point that a forced air system will zap the heat quickly from a solar storage tank. In most cases, the storage will only last for 2-3 hours in cold weather. If you want to heat with solar, the best way that I have seen is radiant floor heat. The temp settings for most floors is so low (85-100 degree range) that the cushion of heat in the storage tank is pulled down slowly. Even at that, you should still have some secondary way to heat the solar storage tank in the event of several cloudy days or unusually cold weather.
12-16-2010, 05:54 AM
Just a matter of having enough ESP for an existing duct system with the added coil, or having sized the duct with the available ESP with a new duct system.
Doesn't seem more complicated than that, or did I missed something?
12-16-2010, 06:23 AM
I work on a old hydro heat that has a ground water cooling coil, a heating condencer coil, and a outdoor boiler heating coil. System works fine.
12-16-2010, 06:25 AM
things can get screwed up to. I was on my third warranty call on a water heater and suddenly noticed that I had plumbed it backward.
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