Reversing flow through boiler

jskubiz

Thank you. It didn't sound right to me, just the easiest fix for the installer versus changing the 6 zone valves he put in wrong. I'm calling the plumber who told me over the phone to check the zone valve direction as that could cause the loud water hammer I was hearing. He was right.

jskubiz

Reversing flow through boiler

Installer put zone valves on backwards (against flow) on hydronic return valve system causing siginficant water hammer when valves shut. His remedy was to reverse direction of pump so pump now pumps water from what was inlet through system then back through what was outlet instead of reversing zone valves. Expansion tank is now on return side. Is this okay? Water temperature seems to vary a lot more now.

Weezbo

i would say it is on the Not O.K. list.

jskubiz

I think I will call in another plumber to check out whole system since I now wonder what else might be wrong.

Unknown

Not a good idea!

With today's relatively low mass boilers it is not a good idea to reverse the flow. The reason for this has to do with the location of the temperature control for the boiler or aquastat. It is usually situated in the flow of the upper or supply tapping of the boiler to somewhat accurately sense the temperature going out into the system. When that temperature reaches a setpoint that the control is set for the boiler will shut off but the system flow will continue until the call for heat is ended.

By reversing the flow the cooler return water will always be washing the aquastat and the result will be overheating in both the boiler and system. You will see a dramatic temperature rise within the boiler when all is satisfied and everything shuts down. My advice would be to put things back the way they were and to reverse the zone valve bodies. Depending on the expansion tank size and location, when temperature increases so will the pressure in the system. This could become a safety concern if pressures begin to approach the relief valve setting. Hope this helps.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.