Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Plumbing => Topic started by: jw on December 07, 2016, 07:53:33 AM
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So I'm finally getting around to adding a backup indoor boiler which will probably be used during shoulder season and when on vacation.
I'm attaching an image from the installation instructions that I've modified. The picture is exactly how my system is installed today with the exception of the indoor boiler circled in red. The indoor boiler is a high efficiency condensing boiler with its own pump and calls for specific pipe sizes and hydraulic separation of the boiler loop through closely spaced tees.
I'm fine with all that but want to put the boiler loop into the system after the plate exchanger and before the pressure tank. My reasoning is I don't want this boiler to kick on due to low return temps from zones when the first come on. Putting it after the exchanger means the zone return water will be brought up significantly before hitting the indoor boiler.
I've been told however that this is not an appropriate installation location since it would be "pumping against the pressure tank" and should be introduced after the air separator/pressure tank connection. That would require quite a bit of copper rework so was wondering if anyone else had an semi-professional opinion on the matter.
Easiest place to install it is where it is originally shown on the drawing however I don't think this will work as sometimes my return water from the zones is at 90-100* for a couple of minutes before warming up. This I feel would fire the backup boiler unnecessarily.
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Your friend is correct, the expansion tank and Spirovent should be on the low pressure side, keeping the gas boiler from coming on is easy, monitor the incoming wood boiler water temp with an aqua stat, remove one TT wire from the burner control or isolated end switch on the relay and run it through the aqua stat using the break on rise terminals and back to the burner control TT connection.