gas hob pressure

[dme]

I have just installed a replacement hob which will be checked by a corgi man. But I have a problem. I have 20mb at burner jet but this drops drmatically when I turn another burner on. With the gas lit you can see the flames reduce in size when more than 1 burner is on at a time. This happened with our old hob but I put it down to the age of the thing.

I did an extension some years ago and then about 5 years ago moved my boiler to the garage.This was checked by a corgi man, he actulaly made the final gas connections. I think the gas hob problem coincided with boiler move but as I say, i put it down to the age of hob.

Here is a diagram of the pipes (approx including allowance for elbows)

2mtrs @ 22mm 10mtrs @ 22mm Meter-------------------------TEE----------------------------------------------------------------------BOILER 1.6m3/hr | | 12mtrs @ 22mm 14mtrs @ 15mm

|---------------------------------REDUCER--------------------------------HOB

1m3/hr

I used the following link and calculations for pipe sizes all look ok? Any ideas what the problem may be? I'd like to know whether Corgi man will need to lay new pipes etc.

[John Stumbles]

Meter-------------------------TEE----------------------------------------------------------------------BOILER

The 15mm pipe from your Tee (I think - the formatting doesn't work as ASCII art for me) will drop all your allowed 1mbar on its own if the hob is taking 1m3/h (that's a big hob, isn't it?). Thus, taken with the 12m of

22mm and shared 2m of 22mm to the meter your pressure drop will be more than what it should be. Even so you shouldn't be getting a radical drop in flame size at the other burners. What does the pressure at the hob drop to? (Stick your manometer hoze onto the burner jet of the smallest ring if there isn't a test nipple anywhere, which there usually isn't on hobs. Oh and mind out for the spark ignition as you're holding the tube in place!)

If you're getting more than say 2mb drop I'd suspect a blockage somewhere.

How much do the burner flames drop by when another burner is lit? Is it enough for a burner set low to go right out? And do the burner flames drop when the boiler fires up?

whether Corgi man

By the book, yes, and if one were commissioning the new appliance that's the way to do it. If it's an existing appliance one might raise a 'not to current standards' warning notice to cover one's backside if the appliance wasn't showing any problems with the pressure. However the problem you describe would definitely have to be addressed.

BTW you will shortly be receiving advice from a regular on this group to re-do your pipework right the way back to the North Sea (or maybe Russia) to avoid this problem. :-)

[woodglass]

Meter-------------------------TEE-------------------------------------------

---------------------------BOILER

|---------------------------------REDUCER--------------------------------HOB

I think you should re-do your pipework right the way back to the North Sea (or maybe Russia) to avoid this problem.

woodglass :-)

[Gav]

Meter-------------------------TEE----------------------------------------------------------------------BOILER

has anyone bothered to check the gas rate of the appliance to see if it is burning correctly???

[Gav]

Meter-------------------------TEE----------------------------------------------------------------------BOILER

oh and i think you might need 99 mm gas pipe for this hob!!!!(that was a joke before you start)