Vaillant TURBOmax plus - code F.28 and pressure loss

[ianmcd]

Well... warranty is not a concern, that's for sure. I wish, right? I'll talk to the Engineer when we're face-to-face... and gauge his comments. I suspect part of the issue here is - a leak in the system might be the reason for the pressure loss, and it might not be - but tracking it down (if under floorboards etc.) could be difficult - so not necessarily inexperienced, maybe more pragmatic and time-aware?

You have already been told that the majority of pressure loss is caused by expansion problems, so just stick leak sealer in and give it a few weeks then start replacing boiler parts, the expansion vessel should be properly re-pressurised every annual service, and pressing your finger in a Schraeder valve is not servicing it, I would bet your has never been done

 

[dpm_dpmartin]

Agreed, I bet that too. Thank you very much for all this guidance. I think it will end up being a replacement part too and the expansion vessel has been called-out.

 

[Gasguru]

Thanks. This sounds like experience accumulated over years of war-weary engagements... and extremely valuable to boot, but how on earth do I justify (if anything bad happens in the future) deliberately asking my Engineer to go against the "book value" (I assume that means the manual? maybe the installation one?) if something / anything goes awry? I did not select this boiler (as with so many people) I inherited it... but I was kinda pleased with it - sure, it looks rather old and clunky, but reputation says it's a workhorse and will just keep going and going and going... I like that. It appeals to me.

I will mention "ignition burner pressure is the same as the minimum burner pressure" to the Engineer tomorrow and see what his reaction is. You know how it'll be - he'll ask me where I got this and I'll say "a forum" and he'll raise his eyebrows at me.

Any gas eng. that repairs Vaillants should be well aware of this issue although upping the pressure a little is normally done to resolve F22 issues (temperature gradient across the heat exchanger problems).
It's a Vaillant "approved" fix so he's only got to phone their technical line.
These models can also have a failure to ignite due to the flue restrictors..I've had issues when they are on a vertical flue so that's another area to be looked at.

 

[dpm_dpmartin]

Only an update... the Engineer was delayed until yesterday, but the boiler did work adequately until yesterday morning (lucky coincidence, who knows?)... the GSC and Service was done on it - passed. A TF1 Omega filter was fitted and an external filling loop. We tested all that out - pressure changes now in seconds, rather than half an hour. They did not bother with the leak seal, as they went around looking for visual issues and found nothing - they said it did not need it. They said the F28 code was not related to pressure. It could be a) the gas supply, b) the gas valve, c) the igniter... no way to know yesterday, but for a) they obviously had a gas supply yesterday and throughout their tests I saw the boiler ignite first time, every time over 15 times. They left saying the boiler was in good order and warned that the most likely issue was gas supply - credit on the pay-as-you-go meter!!! Effectively warning me to double-question this aspect every single time an issue like this is reported to me. As we were out at the van he said his eagle-eyes had scanned the smart meter in the corner of the living room on the way out and it read something like "low gas credit"...

At least, if that is the real issue, then I have some actual improvements to the system for the roughly £400 I spent... and I did not get the dubious leak seal put into the system. They advised me not to replace this boiler if I could help it.

Fingers-crossed.