Greenstar 28i Junior pressure problem

[GrahamM]

Attended the above 5 year old boiler for annual service.
Cleaned through the magna booster and brought pressure back upto 1.5bar and left boiler on as elderly customer feeling the cold.
Went on to service fire and as I went to turn boiler off to gas rate fire, noticed pressure was up at 2.5bar.
E/V checked and again pressurised boiler to 1bar removed fill loop key and left boiler on as filled out paperwork. Pressure was soon back over the 2 bar mark within 10 mins.

Mains water entering the heating system through burst heat exchanger???

 

[Billy Bob Bob]

could well be it can happen,you need to turn the cold off to it,record the pressure reading and return to it within a few hours if its stays the same phex has failed

 

[mfgs]

Sounds like a plate heat exchanger has pin holed to me aswel. As Gasman said, you need to isolate the cold into the boiler to test. Perhaps it could also be the flexi to the expansion vessel blocked? Not seen this on a Worcester but had it on a few vokeras before,

 

[Billy Bob Bob]

Sounds like a plate heat exchanger has pin holed to me aswel. As Gasman said, you need to isolate the cold into the boiler to test. Perhaps it could also be the flexi to the expansion vessel blocked? Not seen this on a Worcester but had it on a few vokeras before,

good call on the flexi

 

[neily01]

Had plates on cdi pin hole wouldnt be suprised if this is the same.

 

[hammers4spanner]

i had a few flexis on these boilers block up with crud last year which had the same effect a pressure rise . Annoying thing is that you have to get boiler off the wall to do something that takes 5 mins ,,,,grrrr worcesters = tat !!

 

[vern]

If flexi, drain boiler, undo clip, use a long cable tie (point on end helps) to feed up and unblock, get wet, mop up black crud, replace hose and test, 10 mins job done......

 

[R1CKY]

How did you check the expansion vessel?

 

[GrahamM]

How did you check the expansion vessel?

Remove schrader and fill system. No sign of water from valve usually indicates the vessel bladder is sound.
Put in new schrader, open drain valve and pressurise to 0.8-1 bar. Refill system. Job done......usually!

 

[arran197]

Could be the phex, but is the filling loop completely disconnected? If not, could be passing. If you isolate the cold to the boiler and open the hot tap, the pressure might go down, so would confirm phex fault.