Gas Pipe - How do I caculate pressure drop?

[mark]

Hi I have a 120BTU Boiler which is connected to my gas meter. From the meter it go's 22mm copper straight into 25mm PVC pipe. Lengeth is 120ft . One straigth through coupler 3 natuarl pipe bends (long 90%) the into

15mm pipe straight into boiler. Gas board measured 21.5mb's at the meter (static and working) at the boiler before the gas valve static was 21.5mb but drops to 12mb under working conditions!

Question is can I get around this problem by getting a different gas meter(if this is possible) or what pipe size should I have?

Problem I have is the flame keeps going out at strange intervals, the pressure on the other side of the gas valve on the boiler I can only get to 10mb which I also find strange, I guessed I would have got this to 12mb?

Thanks in advance

[Dr Wu]

[john.stumbles]

Firstly it sounds as if your installation is dangerous and you should not use it!

The pipework will need to be increased to 28mm for much of the length of the run.

No offence to you (but this is the law as well as common sense and safety first) it really sounds as if you don't know enough about gas fitting to DIY it. If you're competent at general plumbing in soldered copper pipe you can read Ed's gas fitting FAQ and if that is 101% clear to you and you operate and test everything by the book then you could correct the supply problem yourself. Even so you still need to (re)commission the boiler correctly since it clearly was not done properly in the first place. (Who set it up like that? They should be reported to the HSE.)

For your own sake as well as that of anyone within explosion range of your property you should get someone competent in to put it right.

[Andy]

There is a website that you ought to look at:-

[mark]

the gas meter has been move since the boiler was set up, and as you know the gas board do their bit and thats it. You could connect the other end of the meter to an open flame and they would not care!

Thanks for your comments, out of curiosity how would this setup (at present be a danger)?

The boiler is working within its designed parameters just on the very min side.

Cheers

[Andy]

As I understand it boilers are designed to operate with an inlet gas pressure of 19-21mBar. I've seen it said that they'll cope with a wider range of pressure, I believe 15mBar was mentioned as not causing too much trouble. I suppose it depends on the boiler.

I would have thought 10mBar was pushing it though. Your boiler may not be capable of delivering its full rated power, it may not combust efficiently, and it may therefore put out CO, or NO or what have you. Probably not dangerous as such, but daft to leave it like that IMO.

Andy.

[Ed Sirett]

This is quite unacceptable. It's one thing to have the pressure a little low (most houses in the UK would probably have some pressures a _little_ under the limit some extreme circumstances). This is however completely out of order.

Whoever recommissioned the boiler after the meter move was at fault.

The appliance inlet working pressure limits are 18-22 mb (they have been widened in the last couple of years). Some manufacturers might well allow

17mb.