Hi all,

[valleygas]

Hi all, just had my annual gas safety check as i live in rented accomodation owned by local authority. I have recently qualified in gas ( domestic ) after a few years out of the industry. I decided to check the boiler inlet working pressure which i recorded at 15.5 mbar at maximum output ( hot water ). I mentioned this to him. After the safety check was carried out he told me he had checked the working inlet pressure and it was just shy of 17 mbar, all depends what is being delivered at the meter at the time he said.The combustion ratio was within acceptable levels so the pressure is not having any adverse affect on combustion. Any way just out of curiosity ( i'm not a cat) i checked it again and recorded 15.5 mbar. M.i's state that if pressure lies outside the 17 - 25 mbar range ( NG ) then do not put into servive. Any thoughts on the matter would be appreciated, thanks.

 

[Chuck]

Any thoughts on the matter would be appreciated, thanks.

Are you using a good quality pressure gauge with an in-date calibration certificate?

Have you calculated the pressure drop between meter and boiler?

 

[valleygas]

I was using a water guage that was zeroed correctly. Working pressure at meter test point is 19mbar

 

[valleygas]

Am i missing something here? It has a 22mm feed. approx 5 elbows and 2tee's on first 3m of pipework. my first guess would be undersized pipework.

 

[valleygas]

Hi, by the way the boiler is a Vailant plus 831.

 

[valleygas]

vailant ecotec plus 831.

 

[ShaunCorbs]

You can’t test from the gas valve point vailants can have a massive pressure drop

 

[Timmy D]

How much 22mm between meter and boiler? Just 3m and 7 fittings you mention? If so, pipe size is fine.

Where did you measure? At internal gas valve or under boiler (does this boiler have a test point on the gas isolation valve?).

As Shaun said, if measured internally, you can lose 2-3mb due to internal restrictions.

 

[king of pipes]

You are 2 mbar shy at the gas meter test point so that's not helping , as a rule cut a test point in the gas supply before the gas valve on the boiler, as the guys have said there can be pressure loss through the valve . Kop

 

[valleygas]

How much 22mm between meter and boiler? Just 3m and 7 fittings you mention? If so, pipe size is fine.

Where did you measure? At internal gas valve or under boiler (does this boiler have a test point on the gas isolation valve?).

As Shaun said, if measured internally, you can lose 2-3mb due to internal restrictions.

Hi, pipework run is 6.5 meters between meter outlet and appliance inlet. There is no test point at isolation valve.

 

[valleygas]

Appologise for wrong pipe sizing, equivilant Length is 15.3 meters with all fittings taken into account and actual pipe run of 8.1 meters if this makes a difference. Thanks for all your help.

 

[Timmy D]

Appologise for wrong pipe sizing, equivilant Length is 15.3 meters with all fittings taken into account and actual pipe run of 8.1 meters if this makes a difference. Thanks for all your help.

31kw can go about 15m equivilant in 22mm, so the pipe size is just about ok.

I’d bet the engineer just added 1.5mb to the 15.5mb reading due to the pressure loss through the gas valve.

 

[valleygas]

31kw can go about 15m equivilant in 22mm, so the pipe size is just about ok.

I’d bet the engineer just added 1.5mb to the 15.5mb reading due to the pressure loss through the gas valve.

Thanks for the reply, i was not aware of the pressure loss through the gas valve. If this is an issue then why don't all manufacturers include a test point at the isolation valve?

 

[Timmy D]

Thanks for the reply, i was not aware of the pressure loss through the gas valve. If this is an issue then why don't all manufacturers include a test point at the isolation valve?

Some do/some don’t. Guess it all comes down to cost.
I add them during install.

If you call the manufacturer technical they will tell you the expected pressure loss through the valve, different boilers from the same manufacturer can have different pressure losses.

 

[ShaunCorbs]

This also has resistance (test point in the valve)