Fit new Potterton Suprima PCB - doesn't work - please help!

[sebh007]

Thanks all for pointing out how stupid I was not to note the terminal positions properly at the outset.

You now have me worried that the two blacks with the loose red sleeves which presumably feed the pump can be connected 'back to front' and fry another board.

Is there any way of telling which way round they should be before another £150 goes down the drain please?

(By the way, I have checked that the boards are fused and they are but it seems that whatever I have done to the board it wasn't the right kind of thing to blow the fuse - the fuse, when tested on a meter is untouched.)

Thanks again for all your help.

 

[gas_man_gaz]

mite be worth ringin bg n askin for a on call assistance, they charge £168 ish (dependin on location) for a fixed price repair which includes parts n labour...

 

[D_Hailsham]

When I removed the old PCB, the two blacks were connected to the pump terminals on the main terminal block - to the Pump Live and - I thought - to Pump Neutral so that's what I reconnected when I put in the new unit.

On reflection, your suggestion simond seems sensible and that I mis remembered where the second black with red sleeve went and it should have gone instead to Switched Live.

Is your pump remote from the boiler, e.g boiler downstairs and pump upstairs in the airing cupboard with the HW cylinder etc? If so, the pump is probably getting its neutral connection locally and, as simond suggest, one black will be the pump live and the other the switched live.

You will need a meter which measures AC voltage to find out what each black does.

1. Turn off electricity to system
2. Disconnect the black lead to the pump at the pump end (probably at a junction box)
3. Disconnect both black leads at the boiler end (this will stop the boiler running) and keep them clear of each other and any metal parts.
4. Turn electricity on
5. Turn the CH or HW thermostat up so the boiler tries to light (it won't!)
6. Measure the voltage between each black and neutral at the boiler end. (one of them will be live 240vac, so take care.
7. The one which measures 240vac will be the switched live and, by process of elimination, the other black will be the pump live.
8. Turn the thermostats right down.
9. Turn electricity off.
10. Connect the blacks at the boiler (correct way round this time!) and reconnect the pump black at the airing cupboard junction box.
11. Turn electricity back on.

The system will now work, provided you have not fried your new circuit board.

If you do not have a manual for your boiler, you can find it Here

 

[sebh007]

D_Hailsham - thanks a million! What a fantastically clear and logical explanation - thank you!

As a newbie I am most impressed by the knowledge and kindness from all the contributors to this topic. I hope that other Suprima Potterton PCB sufferers will find this a useful reference in the future.

The moral of it all is that it is not difficult - the instructions are clear and well presented and with a little patience and dedication you CAN do it but ONLY if you note your connections correctly before you disconnect them and don't get interrupted by children, animals, telephones etc.

Thank you all so much!

 

[Agile]

Without getting too involved, I would recommend that, as I advised earlier, you should check for the presence of the pump by measuring its resistance across the proposed wires you assume are for the pump!

I also prefer the pump to obtain its neutral from a connection at the boiler.

Tony

 

[mickyg]

Im surprised that the corgi nuts haven't started jumping up and down yet about the OP doing this job. The new harness that comes with the PCB requires taking the sealed case off to change it.
Can't believe he's doing it to be honest, BG fixed price repair seems best option if you ask me. Cost about an extra £20 and all the hassle taken away.

 

[D_Hailsham]

D_Hailsham - thanks a million! What a fantastically clear and logical explanation - thank you!

But does it work

 

[Kristoflampie]

Million dollar question has just been asked......... once we had all the info whats the result?? Does it work??..... has all the help been worth it???

 

[sebh007]

I'm afraid that I'm going to have to tease you with an 'I don't know'!

I definitely fried the board when it was misconnected and have to wait for its replacement to arrive to be able to answer the question.

I hope and trust that now that I know how to test which way round the pump connections should be it should be fine. The rest of the operation seems to be comparatively straightforward and had I been more careful about the *****y connections in the first place I wouldn't have needed to trouble you all.

The BG info was very interesting and would probably be my recommended route for others. I was unaware of it being an option until it came up here. The guys who regularly service the boiler wanted ~£406 for the whole job. I assumed that they would be charging the going price and that others would want the same - I didn't think to look at BG or anyone else - I just thought it was way too much.

At that price, I could almost get three PCBs for the price of their one fit so even buying two and junking the first one I'm still quids in compared to going with the regular service people. I shall now be looking for a competitive service mob!

Will post when there is news.

Thanks, Kristoflampie, for asking!

 

[sebh007]

Well here's the next, but sadly not the final instalment.

The good news is that the board has arrived and been installed and shows no sign of being fried. D_Hailsham's diagnosis for the two black leads that go to the pump was spot on and thus far I am extremely happy and grateful. However...

...the boiler is failing to light.

It goes through all the motions correctly but tries five times to light and then goes into lockout. Pressing and holding the reset button gives me the LED diagnosis of 'Ignition Lockout'. When I go to the Ignition Lockout page, in layman's terms, it suggests that the gas is not getting through the gas valve and tells me to test that I'm getting 240v in the multiway connector going to the valve.

Well I tested that and I am getting 240v so that's OK. I suspect the problem however is the multiway Molex connector and I would really appreciate some input here. The old connector slides on and off in a typical 'stiff' sort of a way - just as you would want a multiway connector to go on and off. The new one however slides on rather too loosely for comfort. When I look at the black and white photo in the installation instructions, it appears as if the black cable is going to the top of the valve and the red to the bottom but the plug is handed so that is going to be impossible to achieve without some reasonable force. Given my previous experience of swapping the blacks, I'm not keen to do this unless I have to. Have any of you experienced this and do I just have to be brutal or is there something I'm missing? It seems so unlikely that there would be a geometrical mismatch in the connector that would 'encourage' you to reverse the polarity or to have such a loose connection that it might leave open circuit...

Both the new PCBs have identical Molex connectors, both wired the same way and both handed the same way and both are loose when connected the 'easy' way.

All input most welcome! Thanks in advance.

 

[Agile]

I think there are only two wires to the gas valve.

If thats the case it does not matter which way round they are if the connet to the same pins.

You can measure the resistance of the two windings in series and confirm they are on the pins the wores are on. About 4.4 K I expect.

Tony

 

[D_Hailsham]

D_Hailsham's diagnosis for the two black leads that go to the pump was spot on and thus far I am extremely happy and grateful.

One black lead goes to the pump; the other is the switched live which makes the boiler run. I hope that's what you meant!

I gave you the link to the installation manual for your boiler, but here it is again:

Boiler Manuals

(You will be asked if you want to install a plugin - you need to and it is safe)

There are several version of your boiler so you have to select the right manual. They all show the gas valve and the fan sharing the same connector, so you need to get it the correct way round. The earlier models had a 9 x 1 connector; the later models had a 5 x 2 connector.

 

[ollski]

You have probably missed the connector when you put the ignition wire into the back of the pcb.

 

[sebh007]

OK guys. Thanks for all your help so far but I am still a gnat's whisker from success I'm afraid.

Following ollski's comment, I thought I had better double-check and the connector was properly connected. So that suggested to me that either the gas valve was failing to open or the igniter was failing to spark. Very reluctantly therefore I took the front cover off the burner to establish which of them was at fault. Imagine my amazement when I found that neither was - the igniter was sparking for England and the gas was coming through and indeed the boiler lit. Fantastic I thought and hurriedly turned it off before anything that shouldn't get hot, got hot.

I then replaced the burner cover and switched on the power again. The system went through the ignition cycle, but failed to light (there was no reassuring dull boom when ignition actually takes place). So I removed the burner cover again and retested in case I had nudged something. Again the boiler lit first time. So I replaced the cover and tried again - same result: no ignition.

I wondered if I had somehow managed to earth the igniter with the cover but all the igniter parts seem very well clear and I can't think of any other reason why having the cover on stops it lighting and taking off the cover lets it light.

All input most welcome!

 

[sooey]

Quick, go outside and make sure that a short sighted pigeon hasn't rammed itself into the end of your flue.