vokera combi boiler pressure issues

[aeu99217]

Hi,

Got a vokera 20-80 flowmatic boiler. The pressure reflief valve was leaking even when down at 1 bar, so replaced that. Then pressure shot up straight away, so recharged expansion vessel. Difficult to do with the valve where it is but on 3rd attempt, seemed to have got it. But pressure rose to 2 bar from 1.5 bar, so called corgi guy out. However, in the 1- 1.5 hrs it took for him to get here the pressure maintained its level (when switched off). Guy took filling loop out and reduced pressure to 1 bar (nothing was coming out of the filler loop valve so that was ruled out.). When boiler fired up the pressure rose to 1.5 bar but guy said that was normal so possibility that i over pressurized system. Bloke gave instructions: advised that i should run with heating on with hot water off and check pressure in a couple of hours, if pressure rose then new expansion vessel needed. Alas when checked pressure was at same 1.5 bar level.
Following instructions, i then switched on hot water valve, used water and then checked after couple of hours and the pressure was back up to 3 bar and discharging from relief valve. Bloke reckons it might be heating exchanger.

Called him and he advised to reduce pressure back to 1 bar keep water valve open but not use hot water, then go and check in morning. If pressure ok then reckons it will be thermostat, but bloke reckons this is an outside chance.

Just wondering if anyone had any thoughts on this?

Thanks

 

[twgas]

with water valve turned off and no pressure rise, on and pressure rises, sounds like secondary h/ex to me.

 

[aeu99217]

thanks twgas, how much would be reasonable to replace the secondary heat exch?

 

[twgas]

dont know, I've never changed one, I dont even know if you can get them, it is quite an old boiler.

 

[aeu99217]

Hi twgas,

just searched for the part online and its come up with 139 ex vat for heat exchanger and 92 for domestic heat exchanger

http://www.heatingspareparts.com/Bo...ierId=26&ApplianceId=9762&SparePartsTypeId=92

which one is a secondary heat exchanger?

Thanks again

 

[DP]

OP, suggest you get the diverter valve checked before splashing out on a HW heat exchanger. Changing HWHE is not for the faint hearted. Do not poke and hope, do it right.

A service would be better option as a host of bits and bobs are checked during service.

Have never had to change a HWHE on the Flowmatic.

 

[aeu99217]

hi dp, thanks.

wasn't going to change the hwhe myself. called out a corgi guy today and spoke to him tonight about it. he said that he didnt want to change the hwhe in case that didnt solve it. should i suggest the diverter valve? is this something he should have picked up on before?

Thanks again

 

[DP]

Would it not make sense to call someone who offers advice and operates in the same city as yourself?

 

[twgas]

Would it not make sense to call someone who offers advice and operates in the same city as yourself?

nothing like a subtle hint Don, and we all know if it's vokera you can fix it

 

[aeu99217]

Hi DP,

didnt realise you were in Glasgow. Can't seem to find the message facility. Could you post/message your number and i'll give you a call. Thanks

 

[kevplumb]

look here

 

[aeu99217]

thanks Kev.

DP, I've sent you an email.

Cheers