Problems with shared return on new oil heating installation

melro

I'm really hoping someone can offer some advice. I recently had installed a new oil heating system. Its a large installation with 3 zones and water. All the zones have a shared return due to lack of space for individual returns for each zone, therefore a shared return for all zones has been installed. It now seems that when an individual zone is on that the water returning from the heated zone migrates through the return to the other zones which are off, causing the radiators in the zones that are switched off to heat up. My question is how can this be resolved?

Robert O'Brien

Flow check on return

Jamie Hall

Robert O'Brien said:

Flow check on return

before they join together to create the shared return. Slightly less effective, but will also work, is a flow check on the feed.

Steamhead

Robert O'Brien said:

Flow check on return

This.

Big Ed_4

You have a missed place return pipe . The zone that is split needs to be rejoined back to single pipe before its connected to the mutual boiler return ... Or throw in checks

Mike_Sheppard

@Big Ed is right. If you split one zone the returns need to connect back together before entering the common return. Otherwise you will need check valves. But eventually check valves will fail.

Two pictures attached from B&G system design manual.

melro

Thanks very much for all your helpful replies. I would be interested to know why you think the check values will eventually fail?

Jamie Hall

sad experience..

Mike_Sheppard

> @melro said:
> Thanks very much for all your helpful replies. I would be interested to know why you think the check values will eventually fail?

Because time is cruel and eventually everything fails. I’m sure they’d last a good long while though.

Big Ed_4

Adding a more complicated device to correct a simple solution just increases the odds of failure ....