Hi,
Having wired my own new central heating/ hot water system I got roped in to helping out a mate with his existing system which is round 15 years old.
It's plumbed as a y plan system with the usual mid position valve etc. His timer allows him to switch both HW and CH independently but when he switches the CH only on, the boiler does not fire unless the HW is also ON.
Initially I thought it might be a faulty mid-pos valve, but having replaced this the problem was not solved. I've now discovered that at the timer wallplate there is no cable to the HW off terminal.
This seems weird, as surely with the mid-pos valve already in place the system was designed to operate in a Y configuration, and therefore the wire should be there?
At the terminal box near the cylinder there is a spare blue wire which is simply terminated, it does not connect to anything in the terminal box, however I can't trace where this goes! The grey wire from the valve and the yellow from the cylinder stat are connected to number 7, but there is no connection on the other side of the strip. It's almost like the spare blue should go to the 7, but without this terminating back at the wall plate it makes no sense.
I suppose the question is, where could the spare blue be going to? I can't see it at the back of the stat or the controller wallplate, and if I can't trace this wire, would simply adding a wire from the number 7 terminal back down to the HW off terminal on the wallplate work?
Sorry for the convoluted question!
Cheers
Robbie
Having wired my own new central heating/ hot water system I got roped in to helping out a mate with his existing system which is round 15 years old.
It's plumbed as a y plan system with the usual mid position valve etc. His timer allows him to switch both HW and CH independently but when he switches the CH only on, the boiler does not fire unless the HW is also ON.
Initially I thought it might be a faulty mid-pos valve, but having replaced this the problem was not solved. I've now discovered that at the timer wallplate there is no cable to the HW off terminal.
This seems weird, as surely with the mid-pos valve already in place the system was designed to operate in a Y configuration, and therefore the wire should be there?
At the terminal box near the cylinder there is a spare blue wire which is simply terminated, it does not connect to anything in the terminal box, however I can't trace where this goes! The grey wire from the valve and the yellow from the cylinder stat are connected to number 7, but there is no connection on the other side of the strip. It's almost like the spare blue should go to the 7, but without this terminating back at the wall plate it makes no sense.
I suppose the question is, where could the spare blue be going to? I can't see it at the back of the stat or the controller wallplate, and if I can't trace this wire, would simply adding a wire from the number 7 terminal back down to the HW off terminal on the wallplate work?
Sorry for the convoluted question!
Cheers
Robbie