Gas pressure question

[ShaunCorbs]

By 'appliance working', do you mean the measuring device (e.g. this one) is connected to the boiler itself, while the boiler is running?

yes under full load and this is how i normally do it

turn boiler and any other appliances on on to full load / high burn
test pressure at meter
test pressure at boiler (allowing for restriction through the gas valve listed in the manufacture instructions)

say you have a inlet meter working pressure of 21 mbar
at the boiler you have 18 mbar working
you look in the instructions and your gas valve has a restriction of 2 mbar

21 - 2 - 1.5 = 17.5 mbar max so your pipework size is correctly size

 

[Wormwood]

You would not have known .

No, but if the pressure is high enough for my existing boiler (Glow-Worm), I don't see why it's not high enough for a new boiler (any ordinary/standard replacement).

The Glow-Worm has only ever cut out twice in the 10 years I've owned the house and that was in extremely high winds - the wind blew the pilot light out by coming in thorough the large (cage type) flue, which is an exposed place on the outside wall. The boiler has never cut out due to low gas pressure.

 

[Wormwood]

yes under full load and this is how i normally do it

turn boiler and any other appliances on on to full load / high burn
test pressure at meter
test pressure at boiler (allowing for restriction through the gas valve listed in the manufacture instructions)

say you have a inlet meter working pressure of 21 mbar
at the boiler you have 18 mbar working
you look in the instructions and your gas valve has a restriction of 2 mbar

21 - 2 - 1.5 = 17.5 mbar max so your pipework size is correctly size

How do I find out the figure for the bits I've highlighted red Shaun?

I should mention that the chap who measured the pressure at the boiler did it twice on two different days - and he got two completely different readings. This was using the same digital measurement device. Why would that happen?

I think the readings were 11 and 16mbar (boiler working) - but that was before National Grid changed the regulator (which raised it by 4mbar at the meter outlet).

I'm wondering if there's a partial blockage in the pipe between the gas meter cupboard and the boiler (distance is around 12 feet). I did think of getting someone in to blow compressed air through the pipe - i.e. disconnect at the regulator & boiler ends and attach a high pressure air hose to one end.

 

[Chuck]

It's not common, but gas pipes sometimes get partially blocked by water. Have there been gas main repairs in the area in the recent past?

Whatever the problem, the solution is to get a GSR in to diagnose and fix it. Do not be tempted to try DIYing this one.

 

[snowhead]

I did think of getting someone in to blow compressed air through the pipe - i.e. disconnect at the regulator & boiler ends and attach a high pressure air hose to one end.

Air and gas in the right mixture (with added ignition) = potential explosion.
No GSR would carry out your request.
Only a GSR can break the pipework.

The meter doesn't belong to Nat Grid Gas, now called Cadent.
Your energy supplier owns it and would need to be contacted if there is a suspected problem.

The new boiler would probably work quite happily on a lower pressure, the manufacturers spec would probably show that, but all appliances and pipework installed today have to conform to the Regulations in force today.
As above that means no less than 1.5mb drop

 

[Wormwood]

It's not common, but gas pipes sometimes get partially blocked by water. Have there been gas main repairs in the area in the recent past?

Whatever the problem, the solution is to get a GSR in to diagnose and fix it. Do not be tempted to try DIYing this one.

Part of the pavement/road was dug up last year - I didn't pay any attention to it though, so I'm not sure if it was gas, H2O or electricity.

As far as I know, no other house in the road has had to resort to swapping to a 22mm pipe when they've had a new boiler fitted - hence my suspicion of something partially blocking my pipe, either upstream or downstream of the meter. Or, the meter itself is restricting gas flow (more than meters normally do).

I'm not tempted to DIY it. I know what gas can do when it goes off!

Air and gas in the right mixture (with added ignition) = potential explosion.
No GSR would carry out your request.
Only a GSR can break the pipework.

How else can they check if the pipe is partially blocked then?

The new boiler would probably work quite happily on a lower pressure, the manufacturers spec would probably show that, but all appliances and pipework installed today have to conform to the Regulations in force today.
As above that means no less than 1.5mb drop

The chap who tested the pressure at the boiler did not test the pressure at the meter.

The other chap tested the pressure at the meter (when he changed the regulator) but did not test the pressure at the boiler.

In other words, both points have not been tested at the same time. Hence, I have no idea whether the drop from meter to boiler is more or less than 1.5mb. All I was told is that the pressure at the boiler end of the pipe is too low and a 22mm pipe would solve it.

 

[Wormwood]

My current plan is this.

1. Ask the supplier to change the whole meter for a new one.

2. Get someone in to measure the gas pressure in and out of the meter. Then measure the working pressure at the boiler.

Sounds reasonable to me.

 

[snowhead]

I'm out after this, but you'll end up with 22mm up to the new boiler whoever fits it and whatever size it is.

Has anyone checked whether you have Earth Bonding to the gas pipework?
Even tho' your boiler may have worked fine without it for 30yrs, you'll still need to have it if it's not in place.

 

[Wormwood]

I'm out after this, but you'll end up with 22mm up to the new boiler whoever fits it and whatever size it is.

Has anyone checked whether you have Earth Bonding to the gas pipework?
Even tho' your boiler may have worked fine without it for 30yrs, you'll still need to have it if it's not in place.

Why will I end up with 22mm?

Yes, there is earth bonding on gas & water pipes and it's ok (it was checked & certified by an electrician in June).

 

[king of pipes]

Do not attempt anything on your gas supply contact a GSR he will diagnose your problem and if you should need a vist from cadent he will arrange another vist . cheers kop