I am new to the wood boiler world. Bought an old house that has an Earth 365 rancher. I am working on some issues. The main problem I have is that when I open the return valve it pushes water from the incoming water supply not from the pump. They have put a plate heat exchanger in before it hits the main heat exchanger. Could this be plumbed wrong? Possibly busted? The pump is pumping but when return is open it pushes solid stream of water out of my overflow...