undersized gas to worcester junior 241

[CXR100]

only getting 31mb (LPG dungs valve) at inlet pressure when boiler is on at max. drops to 29mb when cooker is switched on , they are the only 2 appliances in the house. aprox 7 meters from regulator to boiler , all piped in 15mm with 7 or 8 elbows . why somebody would pipe it up in 15mm is beyond me. some idiot buit a wooden boxing next to the boiler so it had no side clearance , should have 5mm. flue pops up thru the roof clipped on to next doors gable end , so not getting its 500mm clearance from obstruction (was a bungalow in the middle of a row of houses stuck to each other). prv run in overflow pipework . around 1m of the flue was boxed in. asked customer to move some stuff out of the way so I could access it to have a look at flue inside "why do you want to do that? previous plumber did not open it on the last 3 cp12s he did" . Neither did he pick up any faults on the installation! so guys if I renew the pipework to 22mm do you think it will be ok? I AR the boiler as it was undergassed by so much, would you have done the same?

 

[IDCHAPPY]

What pressure of LPG will the boiler run happily on? Most NG boilers will run ok down to about 14mb.
Most cases the pipe is smaller because LPG at nearly 2 times the NG pressure.

Certainly sounds like a fair few errors, some gas related some not. Was there any joints in that 1M of flue boxing?

 

[Nostrum]

Minimum acceptable working pressure at regulator is 32mb. 2.5mb allowable drop on LPG across pipework, plus 1.5mb drop on boilers gas valve. So minimum allowed working pressure at boiler is 29 mBar.

This obviously depends on regulator working pressure being low and whether or not it was a Greenstar junior or non condensing?

LPG pipe sizing is much different to nat. gas so 15mm is often satisfactory.

 

[CXR100]

it was dropping to 29mb with cooker on, no joints in flue boxing but personally I feel he should have inspected it anyhow. quoted him to increase the pipe size and he is happy with doing that.

 

[Kevin D]

The real question here should be what was the smallest ring on the cooker doing when the boiler went into high fire? And are you sure about the dungs valve?