RFH and DHW with solar

Tony Oosten

I have lurked on the wall for many years, and have now finally completed my new home with all of the ideas you have all talked about over the years.

The house is standard canadian structure 2x6 walls with batts, all windows are double pane low E argon, 9ft stud with R40 in the ceiling. The system is over 3000sqft of radiant floor heating consisting of 20 individual balancing zones (no zone valves just constant circulation). House temperature is controlled by a Tekmar 362 with outdoor reset and indoor sensor in the main living area controlling a 4 way valve and the slantfin 12kW electric boiler (electricity is $0.06/kWhr here on Vancouver Island BC).

The DHW is via a Viessmann B300 dual coil indirect the top coil and aquastat control the electric boiler. (Note the bathrooms have heated towel warmers which steal heat from the DHW using the top coil when the boiler is not running) The bottom coil is for the solar supply. We have hot water recirc with the grundfos comfort timer pump.

The solar is 60 evacuated tubes, which work best in our cooler cloudy weather. The water for the collector comes from the bottom of the two 120gal tanks in the garage, the return from the collectors returns to the tanks just above the supply suction. Hot water from the tanks is taken from the top and is sent via two different pumps and controllers to either the DHW or the 4 way mixing valve for the RFH. The RFH Tekmar 362 does not have any link to the solar control it just fires the boiler if it thinks the mixing valve is too open. To stop the boiler water from being carried out to the solar tanks an OR relay is used to pickup the RFH boiler call and shutdown the RFH solar pump. The Solar pump is powered by a battery backup system as we get frequent power outages in winter and summer. Because all of the solar water is open to the RFH and our temperatures do not get too cold here no antifreeze is used as the cost would have been prohibitive.

I apologise for the sideways photos but they are fine on my end.

Unknown

Without a schematic I can't understand this. Your electric sure is cheap, do you have solar controls that monitor btu transfer?