Worcester Bosch Style 8000 Combi Boiler losing Pressure

mazibee

Hi Everyone,

I need some help/suggestion from seniors

We moved into our new home in 2019 and got the existing system boiler replaced with a new combi boiler fitted in September 2019.

I started my central heating a few days back and the boiler went in the Siphon Mode, I googled and found that it can happen when the central heating is tarted after a long time and after approx 15-20min it was normal, few later it went in Air purge mode, which also cleared after 15-20 minutes.

Since then the boiler is losing pressure, I refill it to 1.3 -1.4 bars when it is cold when I start heating, on the display, the pressure slowly starts increasing 1.4......2.8/2.9 bars it, when the system cools the pressure drops to 0.5/0.6 bar and on the display, it appears System pressure too low.

In the morning at around 07:00, I refilled it to again 1.4 bar and before leaving for office it has dropped to 1.1 bar even without using the heating.

One more thing I noticed was when the pressure was 2.9 bar on display, the gauge was showing around 2.1 bar

I have attached few photos.

Any idea what can be the reason for the boiler losing pressure and when turning on the central heating it's going to 2.9 bar, what need o be checked and what is the solution to this.

Thanks in advance.

Bendy_House

See the green band on the analogue gauge? That's where your needle should be pointing.

2.9bar is at the limit of the in-built safety valve, so almost certainly what is happening is that this valve (Pressure Release Valve) is being forced open to dump the excess pressure. Once dumped, your sealed system now has less water in it, so when the system cools down again, the pressure will be lower than when it first started.

Your system has a fixed volume of water in it. When water heats up, it expands. To prevent the system pressure increasing due to this expansion, the excess is taken in to an 'Expansion Vessel', and is returned when the system cools down again. So it seems very likely that this EV is faulty.

Your boiler is under warranty, and checking the EV - and re-topping it with air - isn't a normal DIY task. So call out the installer.

You also mentioned that the boiler went into air-purge mode? If the rubber diaphragm inside the EV has burst, then a good amount of air would have been sent into the system water.

Finally, there should be a 15mm copper pipe coming out through your exterior wall near the boiler, and either pointing down at the ground, or else bending back on itself. That is almost certainly where the water is being ejected. Have a look - see if there are drips at the end.

mazibee

@Bendy_House Thanks for your reply.

There is a pipe (white plastic ) running down the wall outside and going in the garden, water was dripping from it, I put a small empty container ( approx 450ml ) day before yesterday it was filled to the brim (might be overflowing), I emptied it again last night and before leaving for office today when i checked it was already 1/4 filled.

So it means there is something wrong with the expansion vessel of my combi boiler?

Does it need repressurizing or replacement?

Shall I contact the installer or directly contact the Worcester Bosch as it's under warranty?

Also is it safe to turn the heating on, as it will be cold tonight?

Bendy_House

The white plastic pipe is the condensate, and this will trickle when the boiler is running - it's moisture condensed from the burning gas. That is not the issue.

There should be another pipe - 15mm and copper. Usually located in the same general area as the condensate pipe. (Not sure if they can fit these internally now?) See if you can find it. That one shouldn't have any liquid coming from it.

plumb1_2

Ya most probably be EV,  it could just need pumping up to the correct pressure.
phone manufacturer to check it’s still under warranty 
You might have to prove it’s been serviced, before they carry out a free repair?
Also I have heard some now check the water in the heating system to make sure there’s been inhibitor put in it.