OWB piping diagrams

ALH_4

There are many ways to do this, so I assume this will be a mod/con? I would control it similar to a solar heating system. I would probably use a Tekmar 155. You have to sense the temperature in the wood boiler and the temp of the return pipe to the gas boiler. When the wood boiler supply is hotter than the return to the gas boiler, actuate a 3-way valve to direct the gas boiler loop flow through the wood boiler heat exchanger. Doing it on the return to the gas boiler lets you use the wood boiler down to the outdoor reset temperature of the boiler minus the delta-T. Be careful of the Cv of the 3-way valve. That valve could also be a circulator if there is significant flow resistance in the heat exchanger or if the required flow rate is high enough to cause significant head loss through a standard diverting valve.

Rob Blair

OWB piping diagrams

I am looking for some boiler piping diagrams for OWB with a gas boiler backup. It would be through a HX on the boiler side. I was trying to think of the scheme that when the OWB would drop below a certain temp the boiler would fire and make up the difference. But I also thought that I would want to stop the OWB flow through the HX.

Help Please.

Rob