New CH system - combi boiler pressure down to zero

[taz777]

I'm getting a strange problem where the pressure in my boiler goes down to zero or close to zero under certain cisrcumstances. It's a new CH system and the boiler is a WB 30CDi combi.

I switched off the CH (via the thermostat) a few days ago when I went away from home. I returned after three days and checked the pressure and it was at around 1.5 bar (which was what I was told to set it to by the CH installers).

So, all good I thought - there are no issues. I then had the heating on for many hours. This morning I heard running water sounds through the rads as if there was a lot of air in the system.

I checked the boiler and the pressure was down to 0.5 bar.

I bled the radiators and lots of air came out of the upstairs ones. I then refilled the boiler and set the pressure to just over 1 bar.

So, it looks like the system loses pressure after it is used for many hours and the rads have been hot for a while. It does not lose pressure if the CH is switched off for several days.

Any ideas?

 

[denso13]

Could be pressure vessel at fault, but whatever is wrong you need to get the installers back. It shouldn't happen on a new system and it needs to be fixed before it leads to further problems.

 

[TheGasMan26]

Its likely the above, try letting it heat up fully then have a look at the pressure gauge on the boiler front, if thats going high when its hot its probably your expansion vessel, another ones is the have a look around the pipe that comes out the wall the boilers mounted on(probably) for signs of leakage, this the pressure relief pipe for when the system pressure gets to high.

But if its just been fitted, get em back.

 

[bengasman]

...It's a new CH system and the boiler is a WB 30CDi combi.

How old is new?

 

[Happyplumber]

Get the installer back if it is few weeks old,or call worcester customer services ,they will guide you through preliminary tests and if necessary send out one of their engineers to repair the boiler if necessary

 

[taz777]

...It's a new CH system and the boiler is a WB 30CDi combi.

How old is new?

Around 8 weeks old. The CH company have been in a total of 6 times to fix other issues with the CH system that they installed.

I'm loathe to call them in again!

 

[mysteryman]

You need them in again. The expansion vessel precharge pressure is almost certainly too low [or possibly too high]. Tie a poly bag over the end of the pressure relief valve pipe with an elastic band. If it collects water, the expansion vessel is suspect.

If all else fails, find someone else to check and sort it out.

 

[bengasman]

Seems to be a matter of put up or cough up.
The problems is if anyone else works on it, regardless of whether that is a pro or not, they can claim third party interference and refuse to do foc repairs.
In other words: ditch the company and you may have a problem with warranties.