vaillant turbomax 828e racing temp and recurring S54 error

[jenny1234]

My Boiler has a recurring problem in that the temperature D40 measured coming out of the heatexchanger, races up rapidly and the boiler goes into S54 mode and shuts down for 10 mins very annoying if you are in shower, it fires back up after 10 mins. Somtimes it continues to do this and gives a F24 error. Its an intermittent problem it doesnt continuously do it.

I was advised to have all my pipe work replaced from a one pipe to a two pipe system. All radiators ( just 4 years old) flushed out and an inhibitor put in the system. So all the pipework is new and the radiators about 4 years old. Vaillant have said they have replaced all components they can. 2 Thermisters, Pump, plate to plate heat exchanger, aqua sensor, divertor valve, gas value, the main heat exchanger was removed and checked for blockage and it came out completly clean, no black sludge at all.

Vaillant say if it reoccurs it mustbe my pipework design/config. The feed to the 4 radiators upstairs ( two of these are very small) is on 15mm, and he says this may be the problem. This has just been replaced and the central heating installer thought it was fine to run 15mm to upstairs.

What else can I do?
Luckily I have boiler insurance, but Vaillant are saying they can do nothing more to help.
Im loathed to buy a new boiler, if Im paying £140 per year to Homeserve for insurance

Any help gladly received

 

[picasso]

how old is the boiler ?

 

[jenny1234]

Its 9 years old, but now every component has been replaced, so it should be like brand new

 

[Beerlover]

I would have gone for blocked main heat exchanger, if they removed it from the boiler, why didn't they renew it?

Insist on this before binning the boiler

The radiator configuration is irrelevant as you have said it happens on hot water also. Point this out to the numb nuts when he comes back. He will be back, as Vaillant as a company will not accept a 9 year old boiler is beyond repair. Insist on a senior engineer, after you speak directly to a Field Service Manager.

Tell them an ex bunny told you so

 

[jenny1234]

Many thanks for that, the reason the heat exchanger wasnt replaced was he ordered the wrong one and brought the wrong one with him, but once he removed it he said it was clear. I agree it should have been replaced.
Boiler has been good for 3 days now, so Im just hoping it stays that way.