DIY Doctor UK DIY Forums

Hi, Can anyone help me please? i'm an electrician but have no knowledge about central heating! Since i've had my house i could only get the heating on by wedging the lever on the diverter valve. I've finally got round to replacing the Synchro motor which was connected from the junction box with a 5core flex. On inspection, the brown&blue were connected direct to the motor, and 2 cores (black&grey) were just taped up. I realise there's a micro switch (with normally open/ normally closed) connections in the diverter valve housing, but if i connect the feed to the motor through the switch first (norm closed), when it operates the valve thus opening the switch, wont the valve just keep on opening and closing?
I'd be grateful for any help!

What you need to do is google Honeywell for the wiring for the "S" or "Y" plan.

The internal electrics for the valve are quite logical once you understand the principle. When the valve has 230v supplied to the coil, the motor obviously winds the valve (three port) from only port 1 open, to both ports open, then to port 2 only open. (you don't mention whether it is a two or three port).

If the valve mid position is required, as the valve reaches this point, it operates a microswitch which removes the 230v, and diverts it through a resistor. The result is a reduced voltage of approx 60v across the motor windings. This is not enough to turn the motor, but sufficient to act as a brake and hold the valve in that position.

In fact, there are two microswitches in a 3PV. The second triggers the pump and boiler to fire.

Thanx Plumbbob,
I'll have a look on google. It is a 2-port valve.
Cheers![/b]