Intermittent very hot and cold water

[deepham]

I have a viessmann combi boiler 35kW WB1B Series. around 7-8 years old.

Called an engineer and he replaced
Service cock hose from the main heat exchanger to pump, but this didn't resolve and came up with a FC fault so called
Viessmann engineer - came and cleaned inside burner and the Main heat exchanger, replaced fan, electrdoe, flue seal, temp sensor and said it shoud resolve the problem.
This didnt resolve and was then told that the boiler needs a new plate Heat exchanger but that didn't resolve the prolem either.

Any comments would be appreciated

 

[DP]

Not much else to replace
Might be an idea to replace what has not been replaced, that might cure the problem

 

[deepham]

someone suggested to check the pressure in the expansion vessel, not sure if this has anything to do with the very hot/coldwater issue

 

[ianmcd]

someone suggested to check the pressure in the expansion vessel, not sure if this has anything to do with the very hot/coldwater issue

No it doesnt, I would be looking at the pump, you should have just got a fixed price repair from Viessmann before you had all that changed

 

[deepham]

No it doesnt, I would be looking at the pump, you should have just got a fixed price repair from Viessmann before you had all that changed

The pump has been replaced too. (just noticed I had missed that in my op)

Viessmann did come on a fixed price repair when i got the FC fault and it was afterwards they said that there may be issue with the heat exchanger which has now been replaced.

 

[ianmcd]

The pump has been replaced too. (just noticed I had missed that in my op)

Viessmann did come on a fixed price repair when i got the F2 fault and it was afterwards they said that there may be issue with the heat exchanger which has now been replaced.

Just get them back and tell them they havent sorted the problem they wont charge you again if it is the same problem

 

[deepham]

Sorry just corrected my post the fault they came to fix was FC

 

[gasbusters]

I have a viessmann combi boiler 35kW WB1B Series. around 7-8 years old.

Called an engineer and he replaced
Service cock hose from the main heat exchanger to pump, but this didn't resolve and came up with a FC fault so called
Viessmann engineer - came and cleaned inside burner and the Main heat exchanger, replaced fan, electrdoe, flue seal, temp sensor and said it shoud resolve the problem.
This didnt resolve and was then told that the boiler needs a new plate Heat exchanger but that didn't resolve the prolem either.

Any comments would be appreciated

Pretty much the only thing left to replace is the boiler casing....

If they are changing all these parts surely would be more economical to just replace the boiler??

 

[picasso]

Any one checked the working gas pressure ?

 

[deepham]

had the boiler service 4 months back, so I presume that would have been checked.
looking at the report there is a mention of 3.15 against gas rate