pressure problem with vokera boiler

[sb2210]

Hi , having recently moved into a new house everything was running sweetly until last night when i noticed water dripping from the pressure release valve pipe of the boiler ,after further investigation the c/h pressure was at 3.5 bar so using the pressure release valve i dropped it back down to 1 but after an hour it was back upto 3 bar , i then changed the top up valve for a new one believing this was faulty but still the pressure keeps building so i disconected the top up all together . the pressure builds up even when the boiler is turned off , any ideas please let me know , thanks.

the boiler is a vokera option combi

also noticed 1 radiator upstairs makes odd noises every now and again

 

[ArtfulBodger]

Expansion vessel lost its charge or diaphram ruptured - loads here on both - just use search

 

[sb2210]

Ok thanks will have a look at that

 

[weargas]

most likely cause is a perforated heat exchanger, it's bi-thermic so the dhw water runs alongside the primary water. get onto vokera, i'm sure there's a 5yr guarantee on heat ex's. simple test is to drop the pressure to around 1bar and then turn off the cold water inlet valve (square handled valve) and open a hot tap to relieve the back pressure. mark the pressure gauge and leave it untouched for a while . if the pressure doesn't increase turn the inlet valve on (hot tap off) and leave for another while to see if pressure increases. If it was artful bodgers suggestion of expansion vessel the pressure would only go up when the heating sytem got hot.

 

[sb2210]

ok thanks for the reply will try that , had a few beers so will leave it till the morning.

 

[sb2210]

ok i turned off the cold water inlet valve and the pressure stopped rising, also checked the charge on the expansion vessel which wasn't registering anything on the gauge off the foot pump so also recharged that to about 13 psi. noticed now that the pressure only builds when the hot water or c/h is running does this still point to the heat exchanger. thanks for your replies

 

[kevplumb]

where else do the two waters meet

 

[doitall]

Does the pressure rise with the boiler switched off.

 

[sb2210]

sorry pressure does still build when boiler is switched off but at a slower rate , also theres a mixer shower in the system

 

[doitall]

does it still rise with the cold mains turned off, theres a valve on the boiler switch it off and observe for an hour

 

[doitall]

should have said lower the pressure to 1bar and leave it standing for an hour

 

[kevplumb]

turn the water off that is supplying the boiler

 

[sb2210]

no it doesnt rise when cold mains is turned off

 

[doitall]

follow weargas instructions at the top

 

[sb2210]

ok will give vokera a ring monday morning, thanks to everyone for the help