EV or PRV problem?

[MANDATE]

Just keep the PRV open, as you say it can't make it any worse.

Once you have charged the vessel correctly (0.8bar) and water pressure set to 1bar afterwards the rise in pressure when heating is on should be about 1bar.
The problem then transfers to the PRV. If any sediment is trapped between valve seat and washer, there is going to be a small leak and you could lose pressure regardless of whether the heating is on or not.
For example heating is off at midnight pressure 1bar. following morning pressure dropped to 0.5 due to PRV.
Its one of those situations where one problem creates another

 

[shamilt1]

Just keep the PRV open, as you say it can't make it any worse.

Once you have charged the vessel correctly (0.8bar) and water pressure set to 1bar afterwards the rise in pressure when heating is on should be about 1bar.
The problem then transfers to the PRV. If any sediment is trapped between valve seat and washer, there is going to be a small leak and you could lose pressure regardless of whether the heating is on or not.
For example heating is off at midnight pressure 1bar. following morning pressure dropped to 0.5 due to PRV.
Its one of those situations where one problem creates another

Thank you for your help. If the PRV is faulty, will there be a drip all the time, or only when the heating is on? At the moment it drips whilst it is on, but not when off and cool.

 

[shamilt1]

Actually, it is dripping all the time- about 1 drip every 5 seconds when cold. It's only about a tenner for a new PRV- is the procedure for fitting quite straightforward?

 

[gigz]

In the meantime, open the prv, then open the filling loop and give the prv a good flush, this sometimes gets rid of any crud on the valve seating (only works sometimes though)

 

[Agile]

Even better to turn it until it clicks quickly about 6-8 times!

Then repressurise to 1.5 Bar when cold.

Tony Glazier

 

[shamilt1]

Okay, I had another go at pressurising the EV. This time I held the PRV open whilst I pumped some air in ( .8 Bar). The water pressure stayed at zero this time. Now the system is running well, going from 1 1/4 cold up to 1 3/4 Hot. The PRV is still dripping though. Can someone tell me the correct procedure to change one of these please?

 

[David937]

Glad you got the pressure problem sorted Well done.

 

[shamilt1]

Glad you got the pressure problem sorted Well done.

It was your advice on filling the EV whilst holding the PRV open that seems to have done the trick ( so far so good anyway). Thanks a lot for your help. Have you any experience in fitting a new PRV? The part looks easy to fit- (one side threaded and the other a push fit), but its more the procedure I am wanting to know.

 

[David937]

I have but not on the boiler you have, it was a fairly simple job, you will need to drain the boiler again, will be fine to use the PRV since it's already leaking!

All I done was drain the boiler with the PRV, remove old PRV, fit new one and re-pressurise the system.

 

[shamilt1]

Thanks again. The instructions with my boiler tell me to 'drain the central heating circuit' - that means just the boiler then and not the whole lot including radiators?

 

[David937]

No need to drain the system, make sure the radiators have no air in them, screw down the automatic air vent, drain the boiler and carry out your repair, water can't escape unless air replaces it, hence making sure there is no air in your radiators and screwing down the AAV.

 

[shamilt1]

No need to drain the system, make sure the radiators have no air in them, screw down the automatic air vent, drain the boiler and carry out your repair, water can't escape unless air replaces it, hence making sure there is no air in your radiators and screwing down the AAV.

Thats great. Ill give it a whirl when I get the part. I know where the auto air vent is, but when you say screw it down- is there a screw to turn on it or something?

 

[David937]

There is a little cap on it which is usually left slackened to allow air to escape

 

[shamilt1]

Thanks mate. You've been a great help

 

[David937]

If it wasn't for this forum I wouldn't have been able to give you much advise tbh .