Combi boiler high pressure / dripping overflow pipe problem

Hi. I have a pressure problem with my Ariston MicroGenus 24kW combi boiler. The pressure gauge reads 2.2 or 2.3 bar when the boiler is cold. It has also come to my attention that there is a constant dripping coming out of the overflow pipe at the back of the boiler, which is dripping down the side of the building.

I think it has been like this for a while as I was aware there was some water dripping into the common area behind my flat but didn't realise it was anything to do with me . This is made even more annoying by the fact that my 2 year guarantee ended just a couple of weeks ago .

Therefore I am hoping that this will not be a big problem to fix. I left a message with the original installers of the boiler but haven't heard back yet. I know that pressure can be relieved by bleeding one of the radiators, but does the constant dripping (even when the boiler is switched off) suggest that there is a more serious problem that requires professional assistance?

Any help gratefully appreciated

Johnny

It could simply be that as your cold pressure is 2.2 ish, then when your rads come on this will increase to above 3Bar, thereby opening the prv which is set at 3 Bar.

Once this has opened it could be that a bit of crud has stuck on the valve seat preventing it from closing and producing this drip.

Reduce your cold pressure to just over 1 Bar and if it still drips then you will probably need a new prv.

Until you have done this you will not be able to tell if there is another underlying fault.

I attempted to reduce the pressure in my system by bleeding a few of the radiators, but unfortunately the pressure has remained above 2 bar. Does this mean that I need a new PRV? I think it may have another name on the Microgenus - safety valve? Is this difficult to replace? I have fitted spare parts to my electric shower in the past, but haven't fitted anything to my boiler before.

Try draining a bit off from a drain cock under the boiler or a radiator.

You'll be forever doing it vis a rad bleed nipple.

Make sure the filling loop is fully turned off as well.

If it is still dripping at 2 bar then it sounds like a new prv is needed first.

Never worked on one of these so can't tell you if it's easy or hard.

If the filling loop is fully closed and not letting by,when the discharge pipe leaks does the system pressure decrease? if it does than it sounds like the prv.The prv is quiet easy to change as long as you remove the right hand side panel, however there is a problem, to remove the panel you have to remove the burner chamber cover. Unless you are an RGI, you should not attempt this.The boiler drain valve is situated behind the condensate trap, and can be accessed by lowering the front facia. As Gas4you suggested, make sure you fully close the filling loop valves, also there have been a few instances where they let by even when the taps are closed. When you do get the prv changed make sure that the expansion vessel is pressurised between .75-1 bar.

Thank you for all the advice. I wasn't really familiar with the filling loop, so I hadn't closed it previously. Is it correct procedure for it to remain attached and open during use?, as this is how the installing engineer left it, and how it has been for the past two years.

I switched off the gas and the boiler and closed the filling loop. Upon closing both valves of the filling loop the pressure began to decrease. At first I thought that this was due to the water continuing to flow from the overflow pipe to outside but I also noticed another slow drip, this time coming directly from the filling loop valve at the central heating flow side of the loop.

By the time 50ml had dripped out the pressure had dropped to 0.5 bar, so I reopened the valve at the central heating flow side to stop the dripping, and the pressure seemed to remain constant. I briefly opened the the valve at the water inlet side to increase the pressure to 1 bar but subsequently noticed that when I left the water inlet side valve closed and the other valve open the pressure slowly dropped towards zero.

I again opened the water inlet side and it repressurised up to 2.5 bar initially, but again it soon decreased. Would switching the boiler back on make any difference i.e. enable the pressure to be maintained? Although I guess it's not feasible to have one side of the filling loop open and the other closed. Does the dripping valve at the left side of the filling loop when both are closed indicate a faulty valve? What would you say is the problem with my system?, what action would you advise now?

thanks again for all your help

The filling loop should be removed when not in use according tot he water Regulations but few people do.

Disconnecting it does show that the valve is turned off though.

Tony

OK, but should both valves have been left open though? (i.e. with the clips sitting in a position parallel to pipe) If the filling loop was left open could this be why the overflow pipe is always dripping? - i.e. PRV becomming jammed in open position as always getting rid of excess water.

Once pressurised to about 1.2 Bar BOTH filling loop valves should be closed fully.

Yes this would cause the prv to drip.

Thanks a lot for all the advice. After belatedly closing my filling loop a full two years after it was installed, I've enjoyed a big slice of luck in that my PRV isn't actually jammed (despite being open all that time!). It seems to have closed and the overflow has stopped dripping down my wall.

I've re-pressurised to 1.2 bar and, fingers crossed, that's everything fixed now. I still don't have an earthly why my plumber left the loop open after installing the boiler, but considering his minions first drilled a massive flue hole in my wall in the wrong place! (and had to fill it up with cement), then put a foot through my ceiling from the loft I guess it's a good lesson that even if you're a poor student the cheapest quote is usually not the best quote.

regards

johnny