Is your system a two pipe or one pipe system? A two pipe system has a hot supply which feeds the radiator, and the cold goes back to the boiler. A single pipe system feeds through each radiator in a series. Turning off one radiator in such a system will defeat the whole zone.

If it is a single pipe system, it won't work until you fit the new radiator.

Hi there,

The answer is that I don't know for sure. But I looked it up on some website and I think that I have a single pipe. The water passes through in series (but with a bypass) and not directly back to the boiler.

But if the hot water is bypassing the missing radiator (which it is on the occasions that the system fires up) - why would that cause a problem?

Here's a little tip: try posting your problem in the Heating & Air Conditioning (https://www.askmehelpdesk.com/forumdisplay.php?f=150) forum. Someone over there may be more experienced in such matters.

Cheers,
Moishe

This question has been reposted over in Heating & Air Conditioning. Tom