Worcester Bosch 35CDi - High Water Pressure Problem

[gamza]

I have a 2-year old WB 35CDi mark II. The pressure showing on the system pressure gauge regularly exceeds the 1-1.5 setting to as high as 3.5-4. I have tried to release the pressure from the radiators to bring it back down but it continues to go back up and remains at the high pressure even when the central heating is off. There is also water leakage from the overflow pipe when the heating is switched on. Central heating works fine and water heats up ok.

I called in a Corgi engineer who suggested that the pressure relief valve may have gone and that the expansion vessel may also need to be replaced.

Some basic questions:

1. What check can I do to determine whether the PRV is faulty and/or that he EV is no longer functional
2. Is it an expensive job to replace these parts. I do not want to spend the £170 odd to call out a Worc. Bosch guy if I can help it.

 

[COG]

If your pressure rises but does not fall after water loss then it cant be your expansion vess as it would fall down to zero ,you have one of two problems,first your filling key is in place and the tap is passing(easy to check) second your plate heat exchanger is cross leaking,thats to say the mains water is leaking through the plate into the system water ,the bad news is the £170.00 n you said does not cover a plate heat ex the charge would be £225.00 ,but have a word with worcester and explain its only two years old .

 

[gamza]

Many thanks COG. The filling key is definitely not in place. So it sounds like the heat exchanger. I spoke briefly to the WB tech support guy who confirmed that is the likelihood. I'm calling one of their engineers out this week. Will let you know how I got on.

I'm really peeved off about the fact that this has happened to a boiler just 2 years old!

 

[gamza]

By way of an update -

It turned out to be the Plate Heat Exchanger that was cross leaking. The Pressure relief valve was also replaced. Seems to have solved the problem. Thanks again COG for ur advise.

 

[COG]

8)

 

[jgsmuzzy]

the bad news is the £170.00 n you said does not cover a plate heat ex the charge would be £225.00 ,but have a word with worcester and explain its only two years old .

I used to work for the company that produced the heat exchangers for Worcester and Potterton Myson. They are the E series and for the E5 (small domestic boilers), they cost the boiler producers £7.20, and for the E8 (for larger output boilers) £9.90. This was 7 years ago, but selling them to the public for £225.00 is price gouging at it's very worst.

(Wierd first post, but I have a problem with my 35 CDI and am trying to figure out whether it is a common fault or not!)