I'm considering doing a solar water heater and getting a large storage tank to let me partially heat the house by doing a heat exchanger from the tank for our furnace. Is it worth trying?
By installing a heat exchanger in your A coil you would pull heat from the solar first.In order to do this you need to size the solar properly.You'll need more than just a 4x10 over an 80 gal. tank.More than likely you would at least need say 2-4x8s maybe even 2-4x10s over a 120. This all depends on where you live too. Below is a good site for figuring size and cost.
USA Not enough info. First, you need to be in an area where you will get plenty of sunlight. You mention a furnace - that means you have a warm air heating system. Instead of a heat exchanger, why not put a hot water coil in the duct at the furnace? Actually, the coil is a heat exchanger, but I assume you mean a water-to-air heat exchanger mounted external to the furnace. Feed hot water to the coil from the storage tank. It is definitely worth trying. If you have a hot water heating system with a boiler, in lieu of heat exchangers and tanks, why not run hot water heating pipes through a solar collector, and tie the solar heated water directly to the boiler hot water return piping. By using thermostatic controls on the water pipes, you can open / close valves to use or close off the solar supply.
