Req: Wiring diagram for a non-roomsat controlled system

[Hugo Nebula]

My mother's heating system is a balanced flue boiler, with a cylinder 'stat, a three way valve, but the heating is only controlled by TRVs with no room 'stat. The boiler is a replacement one, but I don't think it's been wired up correctly. When the cylinder's 'stat is satisfied, the whole system, pump and all, turns off, irrespective of whether heat is being called for by the radiators. The three way valve seems to be permanently centred (allowing hot water through both circuits).

I have the diagrams for a room stat controlled system, but I can't find one without room stat. Are the connections simply bridged as though the room stat is constantly calling for heat?

I've managed to get the installers to call back tomorrow, but on the 'phone they are arguing that it's the three way valve (which wasn't replaced by them), so I'd like a bit of ammunition to fire back at them.

[Set Square]

The wiring would need to be as per the Y-plan diagram in

but with 4 and 5 bridged in the junction box. Note that the cylinder stat needs to be of the changeover type which provides a "HW satisfied" signal to the 3-port valve - otherwise everything stops when the cylinder stat switches off. This could be your problem!

[Set Square]

Did you manage to get it sorted, Hugo?

[Hugo Nebula]

On Sun, 17 Oct 2004 12:23:07 +0100, a particular chimpanzee named "Set Square" randomly hit the keyboard and produced:

In the short term, yes. It was the 3-way valve.