Potterton performa 28 combi

[Christopher buzzard]

Hi all. Got called to the above boiler which had an intermittent hot water fault. Had it for 2 weeks and gradually getting worse. Went on Friday and couldn't get it to fault. Had it running for 5 minutes and it didn't drop out once. Kept turning tap on and off but still no fault. The customer said that the radiator icon on the front panel flashes and boiler has to be reset to get it working again. Done usual checks, burner pressure. Checked fan which seemed ok. Rang technical and without it going to fault they weren't much good. Customer has rang again today to say it's playing up again. Can anyone point me in the right direction for things to check or has any1 experienced this fault. Regards to the Heating side, I tried that and it didn't go to fault but female customer said it would go to fault on Heating also, where as the male says it's hot water only that fault occurs.

Regards

 

[ShaunCorbs]

If rad symbol is coming on check the diverter is working correctly

 

[Christopher buzzard]

I could see when hot tap was turned on the pin from the hot water pressure differential valve was operating the micro switch to bring on the boiler. Just couldnt tell if it was going down the Heating as it was already on when I got there. Number 28 on the picture would come on so customer said.

 

[ShaunCorbs]

Depends could be a fault eg over temp or a ch fault

 

[Christopher buzzard]

Ok thanks. When I ran it on hot water it went up to 80 degrees light and maintained the temperature for 5 mins. No issues.

 

[DGT plumbing]

Had an intermittent fault on the equivalent Baxi a few weeks ago. Turned out to be the pump was at fault. It was running ok but didn't have a lot of grunt left in it. You could stop it rotating with a screwdriver. So it wasn't distributing the heat fast enough when it was getting up to temp and going to fault. Just a thought.

 

[Burger]

I take it the fault is lukewarm water? You haven’t actually said.

 

[Christopher buzzard]

No water temp is fine. The fault is that after running the boiler on hot water the boiler will just Randomly cut and go to fault. The radiator icon with line through it( see pic) Water will run cold until the boiler is manually reset. It will then fire up. Sometimes it is fine and others it will go back to fault again. They can run a bath 1/4 full with hot water. Like I say it wouldn’t do it when I was there.

 

[Christopher buzzard]

He has just txted to say when hot water is running he can hear the igniter continually clicking away. After the boiler has ignited am I right in thinking the ignition process should stop once flame has been established.
Not sure if related. Just thought i would say

 

[ShaunCorbs]

correct shouldnt go more than 5 secs once flame

 

[AMGasServices]

If it’s attempting to ignite then either it’s the gas valve or PCB.

 

[Christopher buzzard]

Sorry if I’m confusing people. He said He could hear it trying to ignite when the flame was present, established and hot water coming out from the tap. I’ll check it out on the board tomorrow when I go round and see what what’s happening. Wasn’t sure if this had anything to do with the flame going out mid way through running a hot tap and going to fault.

 

[Last Plumber]

If it's continuing with the ignition once lit for any amount of time or even stopping and starting intermittently, then it could be that there is no continuity through the flame or the probes are corroded (coated). Did you test for continuity through the probes and did you test the high and low gas flame?
If all seems well with those and it has a good flame current I would suspect the board, especially with it throwing a sensor fault code. Have you tested the heating sensor resistance?

 

[Christopher buzzard]

Hey. Thanks for that @Last Plumber I’m going back tomorrow to check the heating sensor. Read I need around 11 ohms when cold.

 

[Last Plumber]

Hey. Thanks for that @Last Plumber I’m going back tomorrow to check the heating sensor. Read I need around 11 ohms when cold.

11ooo (11k) Ohms cold. (normally around room temp 20 degrees ish).

I think (don't quote me as it's been a while since I worked on those) the DHW sensor and the CH sensor are the same part. If they are at the same temp then they should read similar. Just saying as sometimes a bit of thought when fault finding can save time.

 

[Last Plumber]

They are the same, I just checked.