JoelP
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| posted on 20/12/06 at 10:59 PM |
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question for the corgi boys
hi guys, just a small query for the corgi chaps on the forum. I fit kitchens for a living, recently did one and got my gasman to plumb in the range
cooker. He moved the bayonet a few inches and signed it off as all good. Next day the customer told me that the 15mm pipe that was visible was only
connected to 6mm pipe under the floor, i told him there was no visible pressure drop at the cooker. He then rang back complaining that he couldnt cook
his spuds!  So we drove back (2 hours each way) only to find that it was actually 10mm pipe, and only about 3 feet at that before it got back to a
22mm ID steel main. Further inspection shows no sign of a pressure drop when all the burners are lit, but the cooker doesnt have a pressure nipple on
it to do a proper test.
Now my gas man tells me its just fine to leave it like that, going through a 10mm pipe for about 3 feet. Is there anything in the regs that specifies
exactly what pipe must be used, or is it all just done from 'whatever works' etc? I know that with wiring regs its pretty much all done
via specific wires for specific currents etc, no idea about gas regs though.
Any ideas? Never know when to believe my gas man cos i know he can be a bodger when he's being lazy.
Any pointers appreciated. 
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Wadders
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| posted on 21/12/06 at 12:15 AM |
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The regs only state that you are allowed a 1 mbar drop between meter and appliance, when the appliance is working at full capacity. The actual pipe
size is irrelevant, as long as it can deliver the correct rate of gas. So if you have 21mbar at the meter nipple when the appliance is running, you
should have no less than 20mbar at the appliance. If you dont have a nipple at the appliance, you must gas rate the appliance at the meter according
to the manufacturers data plate. i.e the plate will state that the appliance uses so much gas over a given time, usually these days in Metres cubed
per hour. If when you time it at the meter its not using the stated amount, then its likely the pipe size is inadequate.
clear as mud?
Your mate is risking his ticket if the cooker is
not getting enough gas.
[Edited on 21/12/06 by Wadders]
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MkIndy7
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| posted on 21/12/06 at 12:48 AM |
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quote:
Originally posted by Wadders
Your mate is risking his ticket if the cooker is
not getting enough gas.
[Edited on 21/12/06 by Wadders]
Agree'd its not good practice.. and I'm not defending it but a cooker is atmospheric appliance so it won't be burning dangerously or
be "at risk" if its under gassed.
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fesycresy
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| posted on 21/12/06 at 09:01 AM |
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I'm industrial not domestic, but, I assume the prinicipal is the same.
After the initial pipe from the meter you can't 'increase', only stay the same, or 'decrease', i.e. if you've
3" BSP from the meter you can't then jump upto 4".
We have data plates on everything to set the gas pressures and they must be correct i.e. not over or underfired.
Bear in mind, if the guy is complaining it only takes one call to Corgi and they WILL investigate. Unlikely they'll be happy with 10mm !
-----------------------------------------------------------------------------------------------------
The sooner you fall behind, the more time you'll have to catch up.
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Aboardman
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| posted on 21/12/06 at 09:28 AM |
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this may help you.
http://www.cda.org.uk/megab2/build/pub124/sec3.htm
it says that a 10mm gas pipe can supply a max of 0.86m³/h of gas at a max 3m length. (you need to take into account the number of bends).
so if you gas hob requires more than 0.86m³/h of gas then 10mm is not big enough.
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mookaloid
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| posted on 21/12/06 at 10:06 AM |
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I am not a gas engineer, but I have accompanied several engineers performing Landlords gas checks in properties for let.
The test for adequate supply which I like to see is the one where they put all the gas fires on and all the rings on the hob on full except the small
one which is on minimum then they turn the boiler on to check that the small burner stays lit - if it goes out the supply is inadequate......
Cheers
Mark
"That thing you're thinking - it wont be that."
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