Glowworm 18si Pressure Constantly High

Heroditas

Hi everyone,
Hope you might be able to point me in the right direction here.
We have a Glowworm 18si in the house and it's been running fine since we moved in about 6 years ago. No issues bar the usual bit of servicing.
I had to top it up a bit in October because the pressure was too low (<0.8bar) but since then, the boiler constantly seems to be at too high a pressure.
I bleed the system to bring the pressure down to 0.8bar, the boiler runs but after a while there's a reasonably sized puddle of water on the ground where the discharge safety valve has released some water from the system while it's been running.
Once the boiler has switched off, the pressure is up at around 1.5 to 1.8bar and remains there.
Again, I bleed the system to bring it down to 0.8bar but, again, after the boiler has been running for a while, the pressure builds up again and it releases water from the system through the valve out onto the ground out the back of the house and the pressure is back up again at around 1.5-1.8bar.
It's getting a bit ridiculous because this seems to happen every time the boiler is running and it never happened before this winter. There's a sizable puddle of water under the discharge safety valve outlet pipe out the back.
It appears to be constantly topping up the system automatically and then draining the excess.
Any suggestions?
Thanks in advance.

corkgsxr

You need to get a rgi to top up the pressure vessel

Heroditas

corkgsxr wrote: »

You need to get a rgi to top up the pressure vessel

The pressure vessel is a diaphragm at the back of the boiler that "absorbs" the build-up in pressure, isn't it?
Relatively straightforward job?

sullzz

It's not a DIY job , boiler needs to be drained and casing removed , hence the previous reply , get a rgi to it , if the vessel can't be recharged a new vessel needs to be fitted.

Heroditas

sullzz wrote: »

It's not a DIY job , boiler needs to be drained and casing removed , hence the previous reply , get a rgi to it , if the vessel can't be recharged a new vessel needs to be fitted.

Oh God no, I've no intention of doing it myself!!

Only reason I'm asking is I'm trying to gauge the cost involved and how intrusive/how long the work would take.

Also, is there any danger of damage being done to the boiler when it's in this present state?

corkgsxr

yes needs to be done sooner rather than later as new water all the time will corrode everything and give ya rust and sludge over time.

a hour at most. but the safety valve prob needs to be replaced too as its very common they never stop dripping. and the manufacturer ones are 20-30 euro

Heroditas

Safety valve was replaced just before Christmas because I mentioned the problem when the boiler was being serviced and they reckoned that was the problem. Cost me over €100 including the call-out to get it changed IIRC.

Ah well, more expense...


EDIT: thanks for the help!

corkgsxr

id bet he never checked the pressure vessel at the service.

Heroditas

Heroditas wrote: »

Safety valve was replaced just before Christmas because I mentioned the problem when the boiler was being serviced and they reckoned that was the problem. Cost me over €100 including the call-out to get it changed IIRC.

Ah well, more expense...


EDIT: thanks for the help!

A leaking safety valve is purely a indication of a problem, not the cause of the problem.

I'd contact your RGI and explain to him/them that your boiler is still having problems with a leaking safety valve due to increased system pressure that is temperture orientated, indicating a defective expansion vessel, hopefully they will come out and put it to bed with minimal cost.

Heroditas

Thanks for all the help, guys.
Have sourced an RGI and as soon as I explained the problem, he said the same thing as all you guys and is calling over first thing in the morning.

Heroditas

Anyway, looks like the problem is solved.
Pressure vessel was ruined so instead of dismantling the boiler etc, a new pressure vessel was fitted externally and it is doing the trick.
Also the cut off valve in the hot press to top up the system was faulty and that was causing water to continually trickle into the boiler, hence why the pressure kept building up.
Everything seems to be working ok now.
All I have to do now is whitewash the wall out the back because it's absolutely destroyed from all the water escaping the system and splashing it for the last couple of months!!