Wiring Help!!! for Heating Controls

[Smithmeister]

I have just changed the old satchwell dm 3601 3 port valve for a Drayton 22mm Mid-position valve MA1/679-3, all is working fine until the heating only is on, it wont go over to the CH and Stays on HW. When the HW is on it all works as it should.
The JB is also Satchwell wth the relay (sorry don't no the model No)

 

[stem]

My guess is you are missing a live supply on the grey wire to the motorised valve when heating only is selected.

The live for the grey wire should come from the H/W off terminal of the programmer. This grey wire is the supply responsible for operating the boiler when the hot water is switched off or up to temperature.

If the grey's not live, check the HW off connection from the programmer.

 

[Smithmeister]

My guess is you are missing a live supply on the grey wire to the motorised valve when heating only is selected.

The live for the grey wire should come from the H/W off terminal of the programmer. This grey wire is the supply responsible for operating the boiler when the hot water is switched off or up to temperature.

If the grey's not live, check the HW off connection from the programmer.

Thanks Stem. The HW off is connected to the programmer but comes into the 1970's Satchell JB with relay and thats where i am not sure, the only cables i disconnected were that of the valve and the new one has gone is earth-earth, N-N, orange-orange, yellow-white, white-grey.
Shall i get rid of the old JB with relay and wire into new JB.
Cheers...

 

[stem]

Not too sure how the relay was used, as it's a bit before my time. I have removed a couple of systems with them in the past and re-wired from scratch. From memory, I think the relay was used to switch the boiler on in the days when the motorised valves didn't have a microswitch to do the job.

Maybe someone else will be along in a while who knows a bit more about the relay. You may need to change your timeswitch/programmer as well if it's as old as the junction box as it might not have a hot water off terminal.

 

[bernardgreen]

Some systems had a relay fitted to remove the load of the boiler from the micro-switch contacts. The theory was it was cheaper to replace a relay than the micro-switch ( or the whole valve assembly)

 

[Lectrician]

Cyl stat should also have it's satisfied terminal to the HW off/valves grey.

Photos would be good.

 

[stem]

Cyl stat should also have it's satisfied terminal to the HW off/valves grey.

all is working fine until the heating only is on.

That would suggest to me that the cyl stat satisfied connection to the grey wire is OK. Otherwise the CH wouldn't keep working when the HW was on and up to temp. OP says it works fine in that mode. Problem only occurs when CH only is on.

 

[Smithmeister]

Thanks for the replies. Sounds to me that i should put a new JB in and reconnect everything. I suppose it also could be a faulty valve that i have put in?

 

[Smithmeister]

Cyl stat should also have it's satisfied terminal to the HW off/valves grey.

all is working fine until the heating only is on.

That would suggest to me that the cyl stat satisfied connection to the grey wire is OK. Otherwise the CH wouldn't keep working when the HW was on and up to temp. OP says it works fine in that mode. Problem only occurs when CH only is on.

I forgot to mention that if i put live on to the white the valve moves striaght to CH, i checked the voltage at the room stat and it was about 115v.

 

[stem]

I forgot to mention that if I put live on to the white the valve moves straight to CH

That's correct, the white wire positions the valve in the central heating position, the grey gives the supply that's switched by the motorised valve microswitch to switch the boiler and pump on.

I checked the voltage at the room stat and it was about 115v.

Hmm.. Room stat should be switching 230v, sounds like you may have something connected in series.