Worcester 28CDi Increasing Pressure

[daveA66]

Hi

Seen a few topics on this subject on this and other sites, but I have the above boiler, and the CH pressure keeps incresing up to the max 3 Bar.
I let some water out and it creeps up again.

I am suspecting the Water to Water Heat Exchanger, and to prove, have turned everything off today while we are all out of the house to see if the pressure increases when the CH and HW are not being used.
( Incidentally, when I last took the cover off the boiler and dropped the control panel down, had a look and put back, the problem seemed to go away for a while....? odd)

Anyway, if my diagnosis is correct (any pointers welcome) my main question is really:
Am I able to replace this part myself? I have seen them for sale on merchants websites for about 65 quid + VAT. and cash is a bit tight at present. Or should I call in a CORGI engineer or suitably experienced plumber?

Thanks

Dave

 

[doitall]

Does the pressure drop or fluctuate when you open a tap.

Easy to change, but very fiddly, probably take you a couple of hours the first time.

Protect the sparky bit at all cost.

 

[daveA66]

I will have to check the pressure when the taps are open - havent thought to look.
What would this mean?
Sparky bit? would I need to access the burners?
Hoping not to touch anything Gas related - I like my house as it is!

Dave

 

[superdupergasman]

sounds like a pinhole in the DHW HE.

Pressure riseing when all is off and no CH or DHW water being drawn.

Its an easy one to do, just follow the manf instructions,
drain down both HW and the CH water,a screw and a clip, and a nut,
plastic bag over the drop down panel to save the electrics!!!!

Pull off the HE then refit in reverse using NEW o rings and Washers with plenty silicone grease on them.

Also worth adding a bottle of inhibitor to the system through a radiator.

 

[daveA66]

Hi

Thanks for that - yes, will find out when I get home later - I thought by the sparky bit he meant the piezo!

Yep - wouldnt want water all over the panel....

Cheers

dave

 

[daveA66]

Well, after the house had been empty nearly all day, CH Off, the pressure had gone from 1 Bar to 2.6 Bar.
Does this confirm my suspicions of the HE?

Dave

 

[daveA66]

Ok

Changed the heat exchanger - got a drip from the HW out pipe on the heat exchanger - took it all to bits again - can not find any locating dip for a O ring should there be one - cant see how this should seal.
Got no HW, no CH and its a cold cold day!
Had the thing to bits 4 times now, but every time I put it back the leak get worse.
Sure I am missing something, but cant see what

Any help appreciated!

 

[nickso]

the hw inlet and outlet are just pushfit with o-rings on the end. did you use new o-rings?

 

[daveA66]

everywhere I could see to put one - could not see a suitable place on the HW outlet from the HE - the push fit doesnt seem to be too good either...

 

[daveA66]

there seems to be plastic ring on the spigot, but not a O ring

 

[nickso]

they always feel loose when they go on. the o-ring is on the end of the pipe just before the hw thermistor, i can't see how you can have missed it. they go flat to the same size of the pipe i suppose.

 

[daveA66]

I should have a replacement - I bought the manufs spare kit. - I take it the plastice flat ring, is not in fact a plastic ring, but a flattened hardened O ring?

 

[nickso]

number 38

http://i30.photobucket.com/albums/c321/ChrisPlumber/28-cdi-parts.gif

 

[nickso]

I should have a replacement - I bought the manufs spare kit. - I take it the plastice flat ring, is not in fact a plastic ring, but a flattened hardened O ring?

yes, its probably flat and hard, get a screwdiver in and prise it out....carefully!, ive never been impressed with the floppyness of the outlet connection on the backplate....always gives me the fear even though ive never had it leak yet.

 

[daveA66]

That great, thanks for your help! Ive been looking for a diagram like that all afternoon - off to have another go - I'll let you know, but thanks for the advice..

Dave