Gas boiler Potterton not heating up domestic hot water.

[willin]

My Potterton Gas boiler is not heating up my domestic hot water.When I turn on the central heating it hots up that side of things ok. So it doesn't appear to be the boiler. So I am wondering how I can tell if it is a motorised valve ( I have 2) or if it's the thermostat on the side of the hot water tank. Thanks.

 

[gas4you]

You need to test the HW valve, or the wire on it, with a multimeter. There should be 240VAC on the brown wire and consequently the orange wire when there is a call gor HW.

I suspect that you will have 240V on the brown, but not on the orange, which points to the valve microswitch being broken.

If there is no power on the brown, then it points to the programmer or cylinder stat at fault.

 

[willin]

You need to test the HW valve, or the wire on it, with a multimeter. There should be 240VAC on the brown wire and consequently the orange wire when there is a call gor HW.

I suspect that you will have 240V on the brown, but not on the orange, which points to the valve microswitch being broken.

If there is no power on the brown, then it points to the programmer or cylinder stat at fault.

Thanks for the reply,
If I were to slide the lever across at the back of the valve would that tell me anything??

 

[mickyg]

what make of motorised valve is it?

 

[willin]

what make of motorised valve is it?

It doesnt say. Just a lot of numbers and Made in Canada for replacement.

 

[mickyg]

try pushing the lever really hard, you can sometimes get it to briefly make contact with the microswitch, the pump will then pulse, that will tell you that the cyl stats ok. Prob just the motor thats duff, depends what type of valve you've got as to how easy fix will be.

 

[D_Hailsham]

My Potterton Gas boiler is not heating up my domestic hot water.When I turn on the central heating it hots up that side of things ok. So it doesn't appear to be the boiler. So I am wondering how I can tell if it is a motorised valve ( I have 2) or if it's the thermostat on the side of the hot water tank. Thanks.

Four possibilities: 1. Faulty HW thermostat; 2. switch in valve not closing; 3. HW valve not opening;4. HW valve sticking.

If you have a multimeter and know how to measure AC voltages, you can check the voltages from the timeswitch HW terminal to the valve.

Disconnect the valve brown wire and temporarily connect to a permanent Live. If the HW gets hot, then no power is getting to the valve through the HW thermostat. Reconnect brown wire.

Disconnect the wire from timer HW On teminal, connect to a permanent Live, turn HW thermostat to max. If boiler lights and HW gets hot,the HW thermostat is OK. Fault is in the timer.

If Programmer and HW stat are OK but water does not get hot, find the grey and orange wires from valve. One will connect, via a terminal, to the boiler; the other to a permanent live terminal. You need to connect the boiler temporarily to the permanent live. This bypasses the switch in the valve between grey and orange wires. The boiler should light and. when you turn the HW thermostat up the HW should get hot. If this happens, the switch in the valve is faulty. Replace the Valve actuator (box on top of valve.

If all tests fail, remove the actuator and check the spindle of the valve can be rotated easily. It will only move throught about 20 degrees. If stiff, a small amount of WD40 may help.

 

[willin]

I've pushed it over as far as it will go, after half way it meets a resistance as though I am turning something then it slowly returns itself to it's original position. Nothing came on or juddered. The lever is round the back of the valve.

 

[willin]

Just as a matter of interest, I gave up and got a heating engineer in. Despite me moving the lever to no effect, it turned out to be the motorised valve, although the engineer wasn't sure, as the tests he did were'nt coclusive.
Anyway I'm a bit poorer but the problems now solved .Thanks everyone for the advice, cheers.