Nov 14, 2010 02:06 pm
Re: Plumbing schematic for interface with existing propane boiler.
Charles, it's amazing your plumber cannot figure this out, it's only 3 to 4 valves. Basically use two cold water feeds, one to the solar tank and one to the propane tank, each with their own shut off and vacuum relief. (valves 1 & 2 respectively) Pipe the HW outlet from the solar tank into a tee after the cold water inlet shut off(valve 2) to the propane tank and to a tee on the hot water outlet side of the propane tank going to the house. Install a valve on the HW outlet of the solar tank, on the branch of the tee going to the HW line out to the house. (valve 3). Then install an optional valve on the HW outlet of the propane tank, before the tee from the SHW going to the house. (valve 4)
This gives you the option of;
SHW preheating the propane tank.
Open valve 1, and 4, close 2 and 3.
open valve 1 and 3, close 2 and 4.
open valve 2 and 4, close 1 and 3
Sorry no drawing, if you can't figure it out I will try to insert one for you...
As far as the radiant heat goes, I usually hook up the heating portion directly to the loop returning to the panels instead of using up a tank of hot water. The volume of hot water stored in the tank is usually not sufficient to use for heating. If you hook it up as I suggest, basically install a bypass on the return line back to the collectors forcing the collector fluid through the radiant zone. This will heat the tank first and use any residual heat to pass through the radiant before returning to the collectors. An aquastat can be used instead of a bypass to turn on a secondary pump to the radiant when a certain temperature is reached in the solar return loop making sure that domestic hot water is made first.
If you haven't installed the radiant yet, use a double loop. One for solar and one for conventional heating, for times when solar is not available.