Central Heating Prevents Hot Water Coming On

[newcube]

Hi all,

I've got a new issue that I wondered if anyone can shed some light on.

I've got a Potterton 2002 controller that seems to be intermittently unable to kick off the hot water in the afternoon. The timer is set for 4:30pm, at the allotted time, the orange light comes on, but the motor value doesn't move and the boiler doesn't fire.

The central heating is always "on" but controlled by the room stat via a Drayton DigiStat SCR. The stat is low at the moment so although the Potterton CH light is on, the boiler and motor valve are off - as expected.

What's not expected is that if the water SHOULD be on but isn't, but sliding the Potterton CH switch to OFF seems to allow the HW to come on!!

What might cause this? I've had a fair amount of work done to the system recently and am suspicious of the wiring job the plumber left behind.. Could some crossed wires cause this behaviour?

Any suggestion most welcome!

Thanks in advance,
Nic

 

[1983]

The 2002 was bad for the slider switches not working after a while, sometimes its the contact on the back of the switch that gets bent in and doesnt make. However, you seem to suspect that the plumber has done something wrong? If hes been mucking about with the wiring its possible hes not wired it properly. That would certainly cause the problem. you would have to check for voltage at the boiler/pump/valves to see if the timer is actually powering them. Is it a gravity system then, ie you have to have water on to get ch?

just read your post again! it does point to a faulty 2002 but you would have to check before replacing.

 

[simond]

If you are handy with a multimeter the EP 2002 has a lift up flap, so you can insert probes into the terminal blocks while it is still connected.

We dont fit Potty programmers as they are Prince of Darkness. hW on is usually pin 3.


You can get the front off with difficulty by inserting a wide flat screwdriver in the slot located on the bottom edge right hand side. You push the driver up and try to swing the lower half of the prog up at the same time.

The test slot has a hinged strip cover at the top edge.

 

[newcube]

cheers, i'll give this a go.