gas / pressure drop when CH fires up

[Colin Wilson]

I have a gas pipe that runs from the meter under the stairs -> across the kitchen, before heading up to the first floor where the boiler is sited above the opposite wall (it was only fitted recently).

From this pipe at the point at which it enters the kitchen, there is a T which supplies the gas cooker and then on to a gas fire - these have been in since the house was built in the 30`s.

I think the pipework is 22mm or larger across the kitchen, but i`m not sure what the feed to the cooker / fire is (I think its smaller but its buried in a concrete floor).

When the CH fires up, there is an audible difference in the noise of the burner on the cooker, which I assume is caused by a drop in pressure.

Should I be noticing any drop ?

Ta

Bad ascii follows :-}

M (meter) | fire | | | | | | |------------cooker------------| | | | o (heads to the boiler directly above)

[BigWallop]

:-))

You will notice a slight fluctuation on the appliances, but it shouldn't be so noticeable that it causes the appliance to be hugely less efficient. So if the burner on the stove is actually being really affected, then have the system checked out by the supply company.

[Colin Wilson]

What flagged it up to me was the smallest burner is sometimes hard to light, and I think its the drop in pressure causing the problem...

[BigWallop]

Then have it checked out by your supply company to be sure. If it's causing problems now, you sure don't want them in the middle of winter.

[Andy Hall]

You shouldn't notice a difference really.

The spec is that there should not be more than 1mB of pressure drop as measured from the meter and then at each appliance with everything running. Typically it should be 21mB at the meter test point and 20mB at the test point of each appliance before the regulator.

a bit of background on this.

It is possible that the regulator/governor on the meter is going faulty. This can happen and mean that it is not maintaining pressure at the meter end either.

All of this needs to be tested using a manometer or digital pressure meter to determine what is going on.

For most boilers, unless very large, or the piperun very long, if the entire run from the meter to the boiler is in 22mm, it should adequately supply it plus a hob teed off from it.

You can also do a rough theoretical calculation using the info. in the link above. You willl need to look at the appliance rating information, work out gas volume and refer to the design guide if you want to do this.

My money would be on either there not being a problem at all and the hob is actually OK, pipework inadequate from meter to tee or faulty meter governor......

In any event it should be checked.

.andy

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[BigWallop]

> gives a bit of background on this.

Now that's a very handy site to have in the favourites folder.

Thanks Andy.

[Andy Hall]

.

There's a bunch of them linked from this page which also deal with how to size pipes in other applciations

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[Colin Wilson]

Thanks for the replies chaps... i`ll see how it gets on - the problem lighting might have been something daft like the top of the burner not being correctly aligned - there`s no "key" on the burner assembly to align to on the cooker we`ve got, just a slightly raised (0.5mm) ridge so i`ll keep an eye on it.

[Andy Hall]

Be very careful here.

Does the hob have a flame failure device?

If not, you have the risk that a burner on a low simmer setting could go out when the boiler fires up, leading perhaps to your rapid exit through one of the windows surrounded by the remainder of your house.

I don't want to be melodramatic, but this should be checked.

.andy

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[Colin Wilson]

Not sure about the hob, but i`m pretty certain the oven does

I know what you`re saying... once lit the audible pitch changes but it stays on quite happily.

[tarquinlinbin]

you need to ensure that your supply pressure is within spec. A simple call to Transco on 0800111999 will bring a man round to measure the working pressure. Report it as poor pressure. There are a number of issue with supply and you need to eliminate these first. The service pipe could be blocked/rusted up,the regulator could be faulty,the meter could be faulty.. joe

[IMM]

Take the fire and cooker supply directly back to the meter.

[IMM]

If it was working OK, and now the pressure has dropped, contact Transco. It could be the meter governor.