What makes flames on a gas hob start going from high to low ?

Question

I've got an electric over with a gas hob (4 ring). It has a glass lid. Its worked beautifully up until a couple of days ago, when suddenly turning it on high, after about 30 seconds it turned itself to low. I tried turning all four hobs on, same thing happened. It goes down (sometimes down then up again, sometimes just down) to 'low' as the flames stay on, doesn't go out altogether.

I've checked the lid - moved it further back etc - to check that it hasn't blocked off the gas.

The flames now have yellow ends, whereas they were blue before this happened. Can hear the gas drop (or at least hear the flames drop).

I've looked all over the net for hours but can't find anyone with this problem exactly, other than one person who's cooker (not hob) lowered after putting it on, and the answer to that was needing a new "FFD".

The burners are very clean, haven't had much use, kept clean after each use.

Really would appreciate help so much on this if anyone knows.

Hi to everyone thats contributed, and thanks :)

I've got a 'practical' friend who's going to take a look at in a couple of days. He'll look at the answers to help give him a checklist to go on.

Its mains gas that goes to all the flats in this apartment block, nobody else is having a problem apparently.

Shelty, I'm not sure what you mean (my fault not yours), there's 4 hobs and I've taken a couple of the plates off (its a Cannon Henley if that means anything) and there's a 'hole' and I can see what looks like a pipe a bit below and out of reach. I can't hear a whistling, what I can hear when a hob is on is the sound of the flame dying down to low. Sometimes also when lighting it it 'pops' first (which for some reason reminds me of the theory of 'air being in a pipe' like when there's air in a water pipe and it 'spurts'?).

Woodworker - I'm not sure how to ensure there's air to the hob - as in its 'in a room' and so much have air? Or is there some way of air having to flow 'in' the gas system somehow? I'm not the most practical being on earth :)

Martin - I haven't got any other gas appliance and the Caretaker (who also lives in the building) says his gas is fine and nobody else has reported a problem either so he doesn't think its a pressure fault. From what I can see over the top (I can't move it far) its attached by a pipe that looks something like a washing machine inlet hose (only a bit wider, but about the same 'stiff' look to it) from the cooker to the metal gas pipe. Re water (do you mean leadksfrom the water system, or gas 'creates' water like condensation?) flats built in 2001 so not sure that would happen?

To the person below Martin (copied answers to notepad - missed your name).
Theyre in the proper places.

Friend checking first cos of cost, will let u know.

Thanks to all :)

MARTIN: Thanks for the additional info.
Pipe isn't even black - it's light grey and I think you mean I can't call a corgi engineer out while that pipe is on there cos its illegal?

Friend didn't call, went fishing instead, but rang him this morning to read your message out.

He's going to ask around his 'group' of practicals to see if one of them does gas fittings first then see what happens.

Thanks again - and to everyone else too as it might be a combination of various things for all I know.

Hi Nosdda. I don't know if I pushed the lid back too far before it happened, I may have as it tends to vibrate very slightly but at high speed (and with an irritating noise to match) when the top oven fan is on. I did intentionally do so though when the gas hobs problem started. Good point though, as maybe the vibration, though slight, has dislodged the pipe a little or something. It's noted. Diolch yn fawr iawn :)

I see I'm running out of 'time' and have copied and saved t all the answers. I really appreciate everyone's replies, Thank You.

Martin, thanks again for your last 'additional information' comment. I'm a little nervous about doing that as it was a (different) friend who attached the oven for me at the time I moved in. He'd photographed the fitting at the back of the oven and the mains fitting, taken the pics to a shop and come out with what he understood to be the correct fitting. I wouldn't want him getting into trouble either. So I guess I'm stuck to having the 'hose' replaced with copper piping done by someone else, but the rate its going I'll be in the same position at easter time. I've got a carbon monoxide sticker now very close to the oven (its fine so far) and the detector just outside the kitchen door is supposed to pick up fumes as well as smoke.Thats working, it goes off every time I so much as slightly singe the very edge of a piece of toast :)

Answer 1

Hi. Check your other gas appliances and see whether the same fault happens. If it does then you have a supply pressure fault and require the services of your local gas emergency utility. If this is in the UK contact National Grid Gas on 0800 11 999. The pattern you describe may be a governor fault at your meter or water in the service to your property. When you start to use your gas, water surges along with the gas and causes the pressure to fluctuate. If you have only one appliance it may be as above, whereas if the fault is only with the hob and all other appliances are OK, you could contact a local CORGI registered engineer, or National Grid Gas who will check the appliance and advise. A hob should be rigid fix and not installed with a flex. Again seek professional advice.

Good Luck.

************* NEW ADDITIONAL INFO **************


Hi again, Hob fitted on a flex is illegal and will need to be re-piped in 10mm copper with an isolation valve in-line to allow for servicing - some companies allow a flexible fix, without the instructions to your hob as a guide you will need to refer to best practice. As this is a flex, should be black in colour, it is likely to be attached via a 1/2" BSP bayonet plug in connector (PIC). My experince of these are,if not connected correctly, will only be half open and will be the cause of your gas going up and down. The flex pushes onto the PIC and locks with a 1/4 turn with two small metal pins. It is like replacing a light bulb when you have to push and turn. I would advise that when you have had the flex replaced if you are still experiencing problems your CORGI engineer will be able to determine which side of the meter is at fault.

*********EXTRA ADDITIONAL INFO************

This pipe is definately not a gas carrying pipe and is most definately illegal. There are no grey coloured gas carrying pipes manufactured. You can still call a CORGI engineer as he will refit your hob, with your permission correctly or make it safe. Because it is illegal, it does not prevent you from getting a CORGI engineer. I would advise that you did as the fitting of such a pipe is RIDDOR reportable to the HSE. CORGI engineer would deal with this and there would be no comebacks on you as the customer. This is a common occurance in situations such as this and is laid down by law.

Good Luck.

Answer 2

OK what has happened is that the transfer pipe to the jet has come apart and so now you have more oxygen in the line. Lift the plate off and inspect where the ring and its attached pipe bed and join to the smaller gas pipe blower part. Most gas stoves have a small pipe abutting a larger volume pipe that is attached to the ring It is at this point that it has all come apart. You can probably hear a strange almost deep whistling sound? then that's the problem. Other than that there may be a kink in the feeder hose if its LPG bottle gas

Answer 3

You have yellow tips on the flames because the burner is not getting enough air to mix with the gas. This seemed to happen after you moved the top further back. I think that in doing that, you have moved the burner pipe very slightly and the burner pipe is not connected to the gas jet properly. The other fault could be that the burner tops are not seated properly.

Answer 4

It could be some piece of equipment on your hob, causing this,but in a boiler, or furnace, I have seen gas burners, changing from large burners , then to small burners, and back again repeatedly. The cause of this is a lack of oxygen, all carbon fuel needs oxygen to burn.If there is insufficient air, the burner will go small,then when there is an excess of air , theburner will increase in size rapidly, as it burns the unburnt gas, this might have nothing to do with your problem, but do make sure there is air to those burners

Answer 5

In addition to Martin above, and i know this sound obvious, but make sure the burners are on the correct places and correctly located. You would be suprised at how many times i have gone out and those have been a problem.
If you are in any dought, call the gas board, or preferbly get a Corgi registered engineer to check it out

Answer 6

your 'friend' who is going to take a look then goes out fishing should be shown the door. By the sound of things he has a come day go day attitude to life and if he looks at your appliance and makes a balls of things, you are the one needing the coroner, not your friend! Call in an expert, death lasts a long time, I know the natural gas isn't supposed to kill but it does go in for spectacular explosions.

Answer 7

Of course its regulated. All gas is. The regulator is probably defective. If you have natural gas, call the gas company and request that they change the regulator. If you have LP gas, call the gas company and ask them to check/change the regulator. Make sure your tank is not low if you have LP gas.

Answer 8

Get out of the house quickly!

Answer 9

turning the gas on n off!!!

Answer 10

this is a long question! hold on, I'll get back to ya.