WB 28CDI DHW Problem

[mad_angler1]

Hi All after some advice with a problem with a WB 28cdi, this is an older one installed about 2003,not condensing, First thing first i am not repairing this boiler its my parents, its covered by a BG insurance and so far they seem unable to solve the issue, i am spark by trade and work in the white goods industry and over the year i have learnt a lot of boilers so i know my way around a combi wether i should or not is whole other discussion.

First thing first on this boiler the internal expantion vessel failed a few years back and instead of replacing the internal one BG decided to fit an external one in the loft, bloody annoys me this as i fix white goods for a living and some jobs are a pig but it should be done so the appliance works as it should not a work around but hay its been done. the original is still connect internal from the look of it.


The issue is this, Only on DHW when you run a tap, the boiler fires and start to heat the water, next minute it start making all sorts of banging noises, the pressure gauge jump rite up then I'm guessing the PRV opens and lets some water out(definitely water at the outlet, very little though) gauge drops and it shuts down, burner light goes out, no error lights though, if you keep the tap running a few second later it will fire back up and work normally, no noises just heating as it should, some times when it start to happen you just shut the tap off and back on and it works fine.

This does not happen every time, some days it won't do it at ll then some its 4 or 5 times a day only DHW.

Thus far BG have been out 4 times and the problem is still not resolved, first 2 calls the engineer could not replicate it, the first time he basically did nothing, the second time he pumped up the internal expansion vessels even when told it was failed, third time removed the pump and checked it and all seemed fine, on the last visit they have ordered a pump and are due back this week.

now I'm not convinced its the pump, sound more like blocked heat exchanger ?, the ch system was drained and refilled a few months back by my self, water is good, inhibiter added ect.

one question i have in my head is can the combi work with out a expansion vessel on DHW, its connected so that its in circuit both CH and DHW, would this cause an issue ?

As i said i am not touching this thing i just need to get BG to pull their fingers out and sort it.

Thanks In Advance

 

[leethegasman]

The external expansion vessel was probably done like that as the materials and labour would have been cheaper for BG that way,
As for the other issues with your boiler It's forum rules that no advice can be given for safety reasons,Its in BG interest to get it sorted as it's costing them every time they come out perhaps you could try asking for a lead engineer,Or maybe they are hoping you will have a new boiler I'm sure they must have done you a quote normally standard procedure once the appliance gets older and going wrong.
Hope you get it sorted.

 

[Aquazone]

I agree with Lee, they will be trying to fix the boiler, but maybe as suggested, try asking for managers number and a lead engineer or the like.

As you have a combi, all the parts are inside the case, and thus as per forum rules, we can't give any information regards fixing it.

Hope you get it sorted. Could try asking a local independent engineer with a good reputation if you don't get anywhere with BG.

I know you shouldn't have to, but I assume getting it fixed is more important.