Potterton Combi 28i - no hot water - advice please

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Hi there.

My Potterton combi 28i boiler has stopped providing hot water since yesterday, however central heating is working fine. Initially, the boiler stopped working for hot water demand from shower but was starting when kitchen tap was open. However, now it doesn't register the hot water demand from any tap or shower. I have tried resetting and increasing the water pressure but no effect.

I have British Gas cover for boiler repair but they can't come for another week. Any help or advice would be appreciated if I can do some more checks myself for fault finding and fixing the problem.

If it helps, the boiler hasn't been serviced for at least 4 years and the PCB was changed 3 years ago. Haven't had any other problems until now since moving into the property 3 years ago.

Thanks in advance.

Dan.
 
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DP

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If boiler not serviced for that length of time, gas valve will have drifted, electrode gap london bus will pass through, condensate rap will need cleaning, diverter cartridge could be weeping too.

When you run a hot tap, does the HW demand light come on?
 
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Thanks for quick response.

The hot water demand light does not come up but you can hear the water going through the pipes.

The central heating is working fine with boiler registering the demand, firing up and circulating the water.

The boiler was meant to be replaced last year in the grand scheme of things but didn't happen unfortunately.
 
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Sorry to rain on your parade even further but check that BG repair contract- I'll be amazed if there isn't something in there about 'boiler must be serviced annually by BG for repairs to be covered'
 
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It's a BG homecare product. I have checked the key requirements and servicing is not in there and BG have booked an appointment for a weeks time without asking for servicing history.

I will read the full terms though. Thanks.
 
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It looks very old, I have just taken a picture of the internals to give you an idea. Can't see a diaphragm as such.
 

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It looks very old, I have just taken a picture of the internals to give you an idea. Can't see a diaphragm as such.
That is because your boiler doesnt have one, you have a diverter cartridge and actuator motor, here lies your fault, most likely the cartridge, but motor might be water damaged too, remove the motor, no need to drain anything, its just a clip , have a look or post a pic to see if it shows signs of water ingress
 
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That is because your boiler doesnt have one, you have a diverter cartridge and actuator motor, here lies your fault, most likely the cartridge,
Could it not be the microswitch/worn diaphragm?
 
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Have checked both actuators, the lower one looks fine but the upper one has water leakage with solid deposits. The actuator motor had some wetness and deposits, photos attached.

Cleaned the visible parts and put the actuator back, still not working.
 

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DP

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It looks very old, I have just taken a picture of the internals to give you an idea. Can't see a diaphragm as such.

You will not see the diaphragm because it is inside a brass manifold with 4 screws on it. All that gunge has been leaking for a while. When you run the hot tap, does the silver spindle push out?

image 2394, use a match to operate the microswitch whilst the hot tap is running. Does the light come on indicating hot water demand and burner fire? Giving you hot water?

Service well overdue. You do not need to replace the boiler but a thorough service will make this boiler like new.

What you call actuator is a microswitch. Silver spindle pushes out with hot tap running, operates the switch, starts the boiler sequence

PS, if someone holds a door open for you, do you thank them for it???
 
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Thanks a ton. :D

Checked and the spindle doesn't move at all. The matchstick test did work meaning microswitch is working.

Presumably the cartridge/diaphragm can be cleaned/replaced using the four surrounding screws. Or the whole brass assembly would need replacing??

PS - I was meaning to thank all for their contribution at the end of the thread.:)
 

DP

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If boiler not serviced for that length of time, gas valve will have drifted, electrode gap london bus will pass through, condensate rap will need cleaning, diverter cartridge could be weeping too.

When you run a hot tap, does the HW demand light come on?

I too was thinking this boiler is a band A steamer:notworthy::notworthy::notworthy::notworthy::notworthy:
Gas valve drifting and spark electrode gap not an issue- boiler is essentially a Baxi 105E instant with a recuperator.

You could open the manifold, might need a new diaphragm but certainly that spindle needs cleaning and lubricating with silicon grease. If you are not careful you could get wet and if unlucky, the pcb will get wet and replacement will be required. Wish you good luck with your repair
 
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Thanks again with the fault finding. Have ordered a repair kit from Ebay as the bush might need changing anyway to stop the leak. Will attempt to clean tonight while awaiting delivery as I got few guns pointing at my head.

Thanks for your advise for water. Supply isolation and plenty of rags should help. Will update later on how it goes.
 
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Quick Update.

The repair kit arrived promptly today. Replaced the diaphragm which was well worn out and had a tear as well near the disc edge. Couldn't change the bush as the old one didn't want to come off.

Had to open manifold twice as had lost the washer for the sensing tube first time around and it started leaking. No water came out first time but plenty second time. I was off-guard based on first time experience so had water everywhere. Dried everything and used hair dryer on PCB to be sure and waited couple of hours before restarting the boiler.

Couple of resets and boiler started operating then sudden drop in water pressure to the extent that boiler won't start hot water. Even filling loop didn't work. Spent two hours of my life stressing about what had gone wrong and what can i do to fix it. Only then found out through local forum that supply pressure was reduced by Thames Water. They couldn't have timed it any better.:(

Supply pressure restored now. Everything seems fine and both CH and DHW are working. Overall great outcome with thanks to all the contribution and guidance from this great forum. Adding £5.4 cost and few hours of my time has led to a happy family which otherwise would have to wait at least until 2nd for a proper shower.:D
 
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