Potterton Gold Combi 28HE A fluctuating DHW :(

[anomaly]

Hi guys, long time reader, first time poster.

I'm scratching my head here; I've got a Potterton Gold Combi 28HE A which was installed about 5 years ago, initially without any CH filtration. For the last year the DHW temperature has fluctuated making showers a nightmare and the CH would get hot whilst using the DHW.

Last month I did some major service work on it, replacing the plate HE, diverter valve, diverter motor, DHW sensor & CH sensor as well as installing a Fernox TF1 on the CH return. I've circulated Fernox F3 for about a week now, sometimes on constant CH, sometimes on timer.

Anyway, the temperature in the hot water seems much better and the fluctuations in the DHW seemed much less frequent, but they still happened.

One issue that kept happening was when using the DHW the boilers CH & DHW green LEDs would flash sequentially and the temp display would alternate between the boiler temp and the code "SF", which I've come to understand means that it is in calibration mode. This also happened today whilst I was in the shower: Hot water one minute (albeit fluctuating) then cold mains temperature water! When I went down to look at the boiler the temp had shot up to 59C and the LEDs were flashing with the display again alternating between the temp & "SF".

Any takers? Any help is very much appreciated

 

[anomaly]

Bump... Anyone

 

[gigz]

Sounds like a pcb error, but an expensive part to change without proving it.

 

[anomaly]

That's where my suspicions lie at the moment as well. I've read online about others having issues with Baxi/Potterton boilers and similar symptoms all coming down to dry solder joints on the PCB.

Think I might look for anything obvious on the board before replacing

 

[DP]

That's where my suspicions lie at the moment as well. I've read online about others having issues with Baxi/Potterton boilers and similar symptoms all coming down to dry solder joints on the PCB.

Think I might look for anything obvious on the board before replacing

Dry joints? Not had any on this model type (all I do is boiler repairs)

 

[Agile]

These PCBs are very sensitive to giving random fault codes.

After all those parts have been replaced the DHW should be stable.

But as a DIYer you will presumably not have had anyone checking the gas settings. Nor have you apparently had any professional service done lately.

Tony

 

[DP]

These PCBs are very sensitive to giving random fault codes.

After all those parts have been replaced the DHW should be stable.

But as a DIYer you will presumably not have had anyone checking the gas settings. Nor have you apparently had any professional service done lately.

Tony

What other codes apart E168?

 

[anomaly]

Hi again guys, I've got an update.

I bought a new PCB, part number: 5120218. Changed it over and initially had an E168 error, I suspect because power was interrupted. Reset boiler and called for CH & DHW and the error cleared, then switched to DHW only and error didn't return, great! The boiler is still doing the same thing though

I opened the kitchen tap and watched the boiler (I'd set the temp to 37). Burner comes on and heats water all the way up to about 47/48C before burner cuts off and water drops back down to around 36/37C and then it repeats; burner comes on, temp goes up to 47/48C and then cuts out. Feeling this at the tap is the usual fluctuating DHW that I'm accustomed to in the shower. Why is the water temp going so far beyond the 37 that I had set it to??

Re-fitting the original PCB yields the same results...

You're right Tony, gas settings have never been checked (since installation) and it's never been serviced. It's my parents house and the old man's reluctant to ever get anything serviced/shell out any cash.

In your experience, with everything that's been changed and the current symptoms I've described (including heating the water beyond the preset temp) what do you think the cause(s) could be? With the condition the plate HE was in (full of black magnetite) could the primary HE be scaled up as well causing localised boiling/kettling albeit without the banging? Could it be something to do with the gas valve?

Thanks again guys

 

[bazdaman]

Measure temp at tap, the display on boiler shows internal boiler temp not hw delivery temp

 

[Agile]

Boiler repairs involve a composite assessment of all boiler functions.

The first step is to check all gas settings because unless they are correct then any other problems cannot be correctly assessed.

As for someone who is too mean to get their boiler ( or car ) regularly serviced then I would expect they deserve every problem which they encounter!

That's the "polite" description!

Tony

 

[DP]

These PCBs are very sensitive to giving random fault codes.

After all those parts have been replaced the DHW should be stable.

But as a DIYer you will presumably not have had anyone checking the gas settings. Nor have you apparently had any professional service done lately.

Tony

What other codes apart E168?

..????????

 

[DP]

Any advance on 168 tony

 

[Agile]

I intentionally don't remember fault codes in case I get them wrong.

That means I look them up every time!

Part of my error avoidance strategy!

 

[Agile]

According to the maker's information, E168 is not triggered by a specific fault but FOLLOWING on from another fault.

Because I see it so often I really wonder if that is really always true.

 

[DP]

Tony I am quite sure E168 is an umbrella fault code that may well be a software issue resolved when the board is replaced. I have yet to get any respect E168 from the new board so it would appear the issue has been watered down of resolved even

These PCBs are very sensitive to giving random fault codes.

Seems to suggest there are other fault code failures