Attached is a diagram of a heat recovery system using a wood-fired (or any type of) pizza oven to heat water in a 800 gallon atmospheric tank, which in turn provides heat to a RFH (radiant floor heating) system and/or for DHW (domestic hot water). This setup is based off of a drainback solar hot water system in that when the controller senses that heat is in the flue and needed in the tank, the pump turns on and water fills the flue’s heat exchanger (FHE) tubing. When the tank reaches the desired temperature (140 F) or the water exiting the FHE is cooler than the tank, the pump turns off and all water is drained out of the FHE into the tank via gravity. The FHE can be easily removed from the flue for inspection and cleaning with CSST (corrugated stainless steel tubing) unions and ‘liner to liner’ flue connectors. The FHE is constructed with 50 feet of coiled 1” CSST so that it barely constricts the flow of the exhaust gases. Condensate that may develop on the CSST can drip down in a small reservoir, hence the angled top & bottom FHE housing. This condensate should steam off when the oven is turned back on.
I plan to make the FHE and install this system this fall to complement my solar hot water system being installed in a new pizza restaurant in Lake Arrowhead, CA. I have installed many solar hot water systems on apartment buildings, including building my own tanks in various sizes & shapes. I may put this oven system in after inspections since I am not sure how the building/health inspectors will react to this system. Anyone have comments or experience with such a system?