Vokera Compact SE - rising pressure

[al4567]

I have a Vokera Compact Se 24, combination boiler of about 5 years old.

It has recently started suffering rising pressure in the CH side, I have replaced the safety valve and inlet valve on the filling loop very recently, and left the filling loop unattached this time as the old valve was leaking mains pressure through albeit very slowly. The safety valve I replaced because the old one partially jammed allowing the pressure to rise much higher than usual before it overflowed.

I can set the base pressure to 1/1.4 bar, and yet the system still becomes overpressured after a few hours, whereupon it leaks out through the safety valve.

Does this model have a diverter valve that might have failed? I cannot work this out from the user manual, and am keen to get the problem fixed rather than shell out for a new boiler. The filling loop is not attached now as I mentioned.

Any help would be much appreciated.

Alex.

 

[nickso]

its either the expansion vessel or the heat exchanger. pray its not the latter.

check the FAQ's on how to repressurise the expansion vessel.

 

[al4567]

its either the expansion vessel or the heat exchanger. pray its not the latter.

check the FAQ's on how to repressurise the expansion vessel.

Thanks for the response, I really appreciate it. Surely though the expansion vessel is purely on the CH side of things, and has no connection with the mains water supply?

The alternative being that there is a pathway between the DHW and the CH side now within the heat exchanger?
http://www.vokera.co.uk/download.asp?id={252216DF-4714-4865-B82D-52DF3916557E}&type=literature shows on page 19, the heat exchanger. It appears that the DHW circuit runs within the larger diameter CH piping. The appropriate connections being either side.

The above being the case, it looks like it's a new heat exchanger!

Any further thoughts?

Alex.

 

[spacethegas]

as nickso said check expansion vessel.

 

[nickso]

its either the expansion vessel or the heat exchanger. pray its not the latter.

check the FAQ's on how to repressurise the expansion vessel.

Thanks for the response, I really appreciate it. Surely though the expansion vessel is purely on the CH side of things, and has no connection with the mains water supply?

depends if the pressure is rising all the time or only if the boiler is on.

if its rising all the time then its a new heatex, they are quite pricey for this boiler if i remember right, at least you will get a few quid back for the scrap heatex as the weigh quite a bit.

 

[al4567]

The pressure rises all the time. If I leave it all alone for an hour or two until the boiler is completely cool, and then re-pressurise to 1 Bar or so, over the next hour or two the pressure will slowly rise back up to the red, and begin to slowly seep through the safety valve.

I looked at the Heat exchanger yesterday, and it appears to have one set of pipes running within the other set for CH and DHW. A little like some Automatic cars having their transmission oil coolers within the engine radiator.

It strikes me looking at it, that I could drain down the CH, and then remove the pipes into the heat exchanger for the CH and having dried it out a little, check to see if water builds up and flows out of them. That being the case, it can only be a leak in the heat exchanger.

They seem to be about £180 or so, but an easy job to change over.

Am I making sense with this?

Alex.

 

[spacethegas]

if you leave the boiler isolated off with the filling loop disconnected.

if the pressure rises at all, the plate h/e will need replacing.

 

[nickso]

it doesnt have a plate h/e, thats why its so expensive.

disconnect the fill loop as space says, if its still rising change the h/e. its easy anyway.

 

[spacethegas]