Replaced motorised valve now nothing works!

[dubmuffin]

Hello, can anyone help me.

We have a potterton prima 50e which was installed about 20yrs ago. After some overheat thermostat cutting out problems last year we replaced the 2 port CH valve, so when the same thing started to happen again this year we replaced the (original) HW valve (as a precaution - not a scientific deduction)). Since then we can't get the system to work.
Power seems to be present at the wiring board when the timers switch on, but neither valves are operating. If we change the HW to manual, the boiler does fire but goes off after 30secs or so (maybe because the pump doesn't start to run).
The pump is a replacement but about 10yrs old. If for some strange reason it failed when we put in the new valve, whould this prevent the valves from operating.

I don't think it would and feel the wiring is a bit iffy, but OH thinks it could and wants to buy a new pump. I await any help with interest
Thanks

 

[jackthom]

There may be problems with the wiring but having made the boiler fire by pushing the valve across to manual this should get the pump running.

Is the pump wired directly into the Potterton boiler terminal block or is it connected to the external wiring centre? If the wiring can be identified a multimeter or mains tester screwdriver should show if the pump is getting power.

 

[DeltaT2]

I wouldn't recommend using a neon tester type screwdriver to test electrics. If it gets wet, it could be a SHOCKING experience!! That's what happened to my mate years ago, wet Plumber's tool box, with a neon tester lying at the bottom!!!.........Daft git..........

Use a multimeter & check your getting 240Vac at the circulation pump, if you are & the pump's not working replace it.
When you have your programmer HW&CH on, room thermostat & cylinder thermostat calling then both motorized valves should swing open.

 

[jackthom]

I wouldn't recommend using a neon tester type screwdriver to test electrics. If it gets wet, it could be a SHOCKING experience!! That's what happened to my mate years ago, wet Plumber's tool box, with a neon tester lying at the bottom!!!.........Daft git..........

I'd have to agree, considering how cheap multimeters are these days every home should have one.

 

[DeltaT2]

I'd have to agree, considering how cheap multimeters are these days every home should have one.

Yeah, even an autorange one for just over 20 quid.
Unlike my Fluke 116??!!!.........

 

[dubmuffin]

There may be problems with the wiring but having made the boiler fire by pushing the valve across to manual this should get the pump running.

Is the pump wired directly into the Potterton boiler terminal block or is it connected to the external wiring centre? If the wiring can be identified a multimeter or mains tester screwdriver should show if the pump is getting power.

The pump is connected to an extrenal wiring block. It doesn't come on when we push the valve to manual - but the boiler fires for a bit. If the pump was faulty, would this stop the valves working automatically, and if so how?
Only had one of those screwdriver testers to hand last night, looked like there was power on all terminals of the ext block!

 

[jackthom]

If all terminals looked live it's possible the neutral connection has been left disconnected but I'm really just guessing here.

No neutral would allow the boiler to fire but the valves and pump would have an incomplete circuit.

If the pump wires can be identified on the terminal block, one of them should be at 230V and the other close to 0V

Does the wiring look anything remotely like the diagram at the end of this PDF ?....

http://www.honeywelluk.com/Documents/All/pdf/937.pdf

 

[dubmuffin]

Your guess is as good as mine!

I love the diagram, if only it looked like mine it would help. It is based on the same system tho and is really useful. My two greys are not in the same teminal block like that, and I feel like they should be, one of mine is in with some blues, I don't like it, but as the wiring is quite old it is difficult to replace them in the wrong holes accidentally. The block is badly positioned and difficult to work with as all the wires are quite short. I'm going home now to do a bit more testing, the diconnected neutral idea sounds like a good place to start. I'll let you know.

 

[dubmuffin]

jackthom,

I have drawn a wiring diagram of my set up and it is not close enough to the diagram you gave me to compare. I thought that the sequence was timer comes on, powers stat which powers valve then pump & boiler, is that correct?

I've dug out my multimeter (needle type not digi) but now realise am a bit rusty on AC testing! so I'm not sure where to start especially as everything seems to have a live when using the testing screwdriver.

I appreciate your time trying to help, I know it's a bit of a long shot as the wiring is not as simple as earth/live/neutral

Further investigation, if I measure across the live/neutral of the pump I get a reading. I can't seem to get readings for the brown switched lives for the valves when testing them with the neutral of the pump (neutrals of both valves in same connector). I may be testing this incorrectly.

What puzzles me is that the timer in on, both stats come on and are below required temp, but neither HW or CH valves activate. Should I be looking for a common power element for both of these?

 

[matt1e]

hi dubmuffin can you post a photo of your wiring centre as it would help to tell you where to place your meter probes and give you guidance

I have drawn a wiring diagram of my set up and it is not close enough to the diagram you gave me to compare. I thought that the sequence was timer comes on, powers stat which powers valve then pump & boiler, is that correct?

on s-plan, yes and posting your diagram would be useful

I've dug out my multimeter (needle type not digi) but now realise am a bit rusty on AC testing! so I'm not sure where to start especially as everything seems to have a live when using the testing screwdriver.

don't use the screwdriver, use your meter

Further investigation, if I measure across the live/neutral of the pump I get a reading. I can't seem to get readings for the brown switched lives for the valves when testing them with the neutral of the pump (neutrals of both valves in same connector). I may be testing this incorrectly.

what reading do you get at the pump?

What puzzles me is that the timer in on, both stats come on and are below required temp, but neither HW or CH valves activate. Should I be looking for a common power element for both of these?

I have to agree with jack, at the moment it looks like a missing neutral
turn on hot water and central heating select ac volts on your meter (at a range that covers 230v) put one probe on the valve live and the other probe on earth

do you now get a reading of around 240v?

Matt

 

[jackthom]

Yes I'd also like to know the actual voltage measured across the pumps live & neutral wires. I'm betting it won't be 230V.

 

[dubmuffin]

Thanks to everyone for their input today, I have just got back from work and will follow your suggestions.

The pump was replaced today as we thought it wasn't working, (not my idea!) but it was v old and noisy and didn't seem to be operating. This is where we are at moment.

When the Water is switched to manual, the boiler fires but soon switches off
When the CH is switched to manual, nothing happens.

I think the pump is now running continuously, but it is so quiet now I can't be entirely sure.

I will try and take a photo of the wiring block (you will wish you never asked) and show you my version.

 

[dubmuffin]

I have uploaded 2 pics to my wiring album, is that how to do it?

Bear in mind that nothing has been rewired, and we have successfully installed a replacement valve previously, using like for like connections but the block is tricky to work with and looks nothing like the standard S plan schematic I have seen!

On the PDF file the cable I called Boiler is marked B on the actual cable so I guessed and the one marked Supply has no markings

I'm not sure which G/Y one is an actual earth as for instance, the water stat earth seems to go to the Water MV brown which i thought is a switched live?

I am of course no expert!

P.S. the pump is running constantly, the boiler PCB was replaced 2 years ago

 

[dubmuffin]

Yes I'd also like to know the actual voltage measured across the pumps live & neutral wires. I'm betting it won't be 230V.

Voltage is measuring 150v, takes quite a bit of wiggling the probes to get a reading

 

[dubmuffin]

PDF of my interpretation of the wiring block now uploaded as a jpeg (what have they got against PDFs huh!)