I'm looking to redo a bunch of plumbing this summer to get to a my plumbing to run more efficiently. But I'm wanting to keep a heat dump zone for potential boiler over fire. I know most dump zones are gravity systems for power outage. we never lose power but I have been known to over load the firebox. It doesn't happen often but if it does I would rather dump the heat then have the boiler idle. My boiler is in a shed just outside the garage there is a FPHX that the storage water is charged through. So while boiler is batch burning the storage circ is running water to the boiler shed through underground lines then to the HX then back to storage tank. I'm wanting to use my existing garage heating loop as my dump. I will use an aquastat to control when my boiler goes into over heat mode. If over heat situation happens the aquastat will close a relay that will simultaneously open my diverter valve to dump side, turn on my garage loop circ and my garage loop fan. The "storage charge circ" will remain running in series with my garage loop circ to help with the added head of the garage loop. I have a drawing of the plumbing I think will work. I'd like some feedback to see if you guys agree.