WB Greenstar 35HE high pressure problem

[Dustyy]

Hi,
As post title suggests I have a high pressure (3.5bar!) problem with my boiler when central heating firing .
Cold pressure is about 1bar but rises to 3.5 over about 6-7 minutes with PRV activating before I turn down thermostat for fear of damage.
Reading round the subject I thought it may be the expansion vessel but when pressing the valve only air comes out with no sign of water as I'm lead to believe this is indication of failed vessel.

Could it still be the E.V. or is there something else possible?

I looked at the condensate trap and it's literally full of grit like substance, could this cause similar symptoms if condensate can't escape quickly enough?

Boiler is 14 years old do not sure if its worth repairing?

Appreciate anyone's help / advice.

Cheers.

 

[terryplumb]

EV needs re pressurising .condensate trap needs cleaning ,but not related.

 

[Dustyy]

Thanks for your reply. Do EV's sometimes lose pressure without needing replacement?
Is it a case of getting pressure down to zero in system and in boiler itself, re-pressure the EV 0.75bar as spec'd in manual and then top up to 1-1.5 bar via filling loop?

 

[gasbanni]

Pressure vessle lose their charge and you can pump them up with a bicycle pump, but if the diaphragm is pin holed, on the air ( initial charge is nitrogen) side water will come out of the schraider valve when depressed ! Press it down when pressure is high nothing coming out of the valve means it can be recharged ....If water comes out its failed.

When re charging drop the pressure to zero. If the pv is goosed use a rad in a spare room by draining it and only half bleeding it as a stop gap measure to act as a temporary pressure vessle.

 

[Dustyy]

I depressed the valve but only air seemed to come out. Probably did it just short of 2 bar. Does pressure need to be a higher to be more sure if there is a pin hole letting water through?

 

[Dustyy]

Ok, so I've got the trap off, cleaned it out and put back on. Took approx 200ml water out of system, pressure at zero on gauge and pressed EV valve....just air, no water.

Used pump to get EV to 0.8bar and switched back on. Boiler went through trap fill procedure and then fired up to meet demand call from thermostat.
Pressure gauge rose slightly during trap fill procedure but then as soon as burner kicked in properly then gauge gradually rose to 2.5bar and I turned thermostat down as obviously not sorted.

At 2.5bar I then pressed EV valve, air came out, no moisture.

Is there anything else that can cause high pressure at the gauge??

Don't mind changing the EV but at £80 I want to be sure it's that and not something else.

Cheers

 

[Dustyy]

Couple of pics of boiler, some crud around flue join where black bit meets the grey plastic, not sure where that's come from.

 

[Daveydub]

Ok, so I've got the trap off, cleaned it out and put back on. Took approx 200ml water out of system, pressure at zero on gauge and pressed EV valve....just air, no water.

Used pump to get EV to 0.8bar and switched back on.

So when you pumped up EV, did you check gauge? Still on zero? Probably not so drain to zero, inflate to .8, drain to zero etc etc.
Alternatively leave drain off open while you inflate EV
The ev should be at .8 with the gauge at zero, then re-fill system

 

[Dustyy]

Ahh, ok. I'll take the reading direct off the EV with a tyre pressure gauge.
Thanks alot for your advice.

 

[Dustyy]

Daveydud, I've cycled through 3 times, draining off but as i do so the EV pressure goes down to zero too? Have I got too much water in the system?

 

[terryplumb]

Drain the c/ heating system and leave the drain cock open. Then pump the EV until you get 0.8 bar pressure in the ev ,do not pay any attention to the boiler pressure gauge at this point ,but take a pressure reading at the ev with a gauge attached to the ev. Then close drain cock and fill system until 1 bar achieved on boiler gauge once all air has been bled from all radiators.

 

[Harry Singh]

Drain the c/ heating system and leave the drain cock open.

Hi Terryplumb when you say drain do you mean open the drain cock and then repressurise forcing water out of the EV - rather than drain as in empty the whole system?

 

[Dustyy]

That makes sense, Thanks.
Can I save some of the system fluid by shutting the rads and just draining the pipework and leaving drain cock open as i repressure the ev?
Do EV's often lose pressure without actually failing?

 

[terryplumb]

I mean drain water out of the central heating system at a lower point than the boiler ,and leave the drain cock open ,whilst pumping air into the ev Harry.

 

[terryplumb]

That makes sense, Thanks.
Can I save some of the system fluid by shutting the rads and just draining the pipework and leaving drain cock open as i repressure the ev?
Do EV's often lose pressure without actually failing?

If ev loses charge " often " theres something wrong. Bit like a car tyre !! Should work fine for years. My boiler at home is twelve years old in november and the ev has never needed to be recharged.