Vent hissing on boiler shutdown

Steve Garson_2

I have a newly installed WM SGO4. Each of two mains has two Gorton vents. The radiators have Gortons as well.

When the boiler shuts down, one of my radiator vents hisses for around ten seconds while air goes back into the radiator. This radiator is at the end of the main.

Shouldn't the main vents allow the air back into the system when the systems cools? Could the fact that the main is well insulated and the feeder to the radiator, which is in the wall and perhaps not well insulated (five feet or so) be the cause? I never had this problem with the old boiler, which I now realize was probably underfired.

Steamhead (in transit)

The main vents are still hot

so they remain closed, while the steam may or may not have reached the rad vent. I think you may still have some bare pipe somewhere, and not necessarily in the runout to that rad. Happy hunting!

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