Potterton combi 80 lockout problem

[martin99]

I have a problem with my Potterton combi 80 locking out all the time. For the last couple of years this has been intermittent. The boiler makes a loud gurgling noise from around the pump and then the flame goes and the lockout light comes on. Up until now, if I pressed the reset button it would start again and be OK for a few months.

Now it won't reset. When I first turn it on, the flame comes up and the radiators get very hot over a period of five minutes or so. Then the flame stops, there is a ticking for a few seconds and then the lockout light comes on. If I try to reset immediately, the lockout occurs again before the flame lights. If I wait a few minutes and reset, the boiler runs for a minute or so before cutting out.

I suspect from this that it is an overheating problem and probably due to either a sensor or the diverter valve. Does anybody have any idea what is most likely on this boiler and what would be the first thing to try?

Many thanks.

Martin

 

[ChrisR]

Run the hot tap and feel the CH (fat) pipes - does one get hot?

 

[Agile]

Unfortunately the poster has not identified the effect with reference to heating and Hot water.

Sounds as its its an electronic model and the overheat stat is tripping probably caused because the pump has seised.

Probably a CP53 pump. If so unscrewn the black plastic knob and pull it outwards catching the black water dripping out. Turn it to and fro to loosen it and then it will work for a while again.

Caused by dirty water in the system. Ideally needs power flushing to clean it out. Poster has known boiler has problems for last two years so is clearly someone who does not get anything serviced or maintained regularly!

Tony Glazier

 

[martin99]

Thanks for the replies Agile and Chris R. Apologies for the lack of useful information in my first post. Agile, it is an electronic model and it did seem like an overheating problem, but I had checked the pump and it was working OK.

I've found a solution to the boiler cutting out now and it does seem to be related to overheating. I followed the troubleshooting flowchart on the parts arena web site:

http://www.partsarena.com/baxi/

Follow the links to the combi 80 boiler and the flow chart is near the end. The third box of the flow chart says "Is red LED on modulator board". This LED was on. The suggested solution is "Replace hot water flow switch".

Before doing that I looked at the microswitch on the DHW flow switch. There is a diagram in the data sheet on the parts arena web site which shows the position and adjustment of the microswitch. On measuring the ga, it seemed a little small so I adjusted the gap on the microswitch to be the recommended 5.5mm and lo and behold, the boiler now works again. It does still have a problem with the hot water to the taps only working when the CH is on, and being very slow even then, but that is not new and I am going to post a separate question on that.

I hear what you are saying about the maintainence Agile. All I can do is admit to being useless at such things. The boiler is in the loft and, as they say, out of sight out of mind. I know you would think that having had minor problems, I would get something done but I seem to be the sort to wait for an emergency to act. I will get it serviced after this and try to be a bit more efficient about such things in the future.

 

[Agile]

It sounds as if you had a flow switch sticking on anf causing the boiler to overheat.

Coupled with that you seem to have a failed diverter valve! I am surprised you dont seem bothered about getting that fixed!

Tony Glazier

 

[martin99]

Do you think that moving the microswitch may have unstuck the flow switch?I guess that seems possible. If it happens again I would probably be best replacing the switch.

I think that the reason I have not fixed the HW problem is that it has only been a minor annoyance. The times when we want hot water are usually mornings and evenings when the CH is on. It may take a bit of time to come through, but that has not been too worrying. Now it doesn't seem to work at all I have a lot more incentive to do something.

 

[ChrisR]

The shaft which operates the mswitch passes through a rubber O ring seal, which can end up being half stuck to the shaft making the shaft stick. It is possible to dismantle and clean it. New whole flow switch without the mswitch is £40+

 

[hoorgi]

Martin,

I don't know whether you will receive this, but I saw your posting entitled as above and it describes my problem almost entirely. Is you boiler now ok? What was the best solution? (my exact problem was posted today on the same forum.

Regards

Paul

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