Low Gas Pressures at Boiler

Blueboo979

We recently had our annual boiler service (2year old Valient Combi boiler), and were advised that the gas pressure at the boiler was low approx 11mbar. Whilst the pressure at the gas meter was found to be 20mbar. The engineer felt that the internal gas pipe was too narrow (22mm) and that to improve the pressure he advised that we had the pipe replaced with 28mm pipe.

However, I’m am reluctant to have the pipe replaced as two separate gas engineers have said that they felt the 22mm pipe was more than sufficient, especially as the distance from the gas meter to the boiler is minimal. They both felt using wider pipe wouldn’t guarantee improved pressures, additionally to do this would mean exposing the pipe from a recently boxed in area, which will then need reboarding, plastering and painting.

The governor was replaced last year by Transco and so the other line of thinking is a blockage in the pipe.

So my question is, whether it is possible to clear the pipes to check if there is any blockage, or has anyone any alternative ideas why the pressure may drop so much between the meter and the boiler?

Thanks in advance for any help/advice

Alex1983

What output in kw is the boiler, if you have a working pressure of 20 at the meter and 11 at the boiler it has to be undersized pipe work or a blockage.

Alex1983

Also how many meters is it from the boiler to meter roughly and do you have any other gas appliances?

Blueboo979

It’s approx 8m from the meter to the boiler, and the only other gas appliance we have is a gas hob. Can’t tell you the KW of the boiler off the top of my head, but once I’m home I’ll post it.

Do you know how blockages can be cleared?

Thanks

Alex1983

There’s not a lot that will block a gas pipe, water in the main possible, iron shall possibly or kinked pipe from installation. Apart from checking the boiler inlet or the inlet of the boiler gas valve you can only really cut the pipe and look for the blockage.

I’d check the working pressure at the cooker and trace the pipe as far as possible to check for damage or any lead pipe.

Blueboo979

Many thanks for you advice. Will get the gas engineer to consider these options before hacking into the boxed in pipe work!

Gas_masters

Sounds like the original guy who installed the boiler has soldered a 22mm fitting with a smaller 15mm fitting inside the larger fitting. Seen it lots of times.
Get your local gas engineer to check the pipe work fittings near the boiler.
This will reduce the pressure to the boiler.

Regards:

MX5huggy

I’m not sure it’s on there but were the reported pressures on the commissioning report when the boiler was installed?

bris

Had dirty installs a few times. Some engineers have apprentices or labourers run the pipes under floors etc to get them into position for them. They don't tape up the ends so dust and crap gets scooped into the pipe and soldered in place.


The gas pressure then forces this crap along the pipe and into the gas valves filter. Have an engineer take the gas valve apart at the inlet and check the filter.


Whilst he's got it apart open the gas for a couple of second to force any other crap out.