Gas burner takes ages to stay alight ???

[Jobs a good un]

Hi All

My gas stove when igniting takes about 1-2 mins before you can release the button so it stays on ,can anyone tell me why ? and what part i would need to replace etc etc

Many thanks

Mark

 

[VicS]

Flame failure device ! If only one burner affected look at the positioning of the sensor.

 

[Allan]

One of my burners was a little slower than the other. I found that the flame closest to the sensor was not working properly. Taking the burner apart and cleaning the area around that flame sorted things out. Now both of my sensors are now in flames as soon as the burner is lit.
Allan

 

[Conachair]

I've had the same problem , turned out to be the small solinoid at the knob end (ooo err ). cleaning that solved it but getting bad again, now i have to push the knob quite hard in and release it gently for the flame to stay alight. That's on a force 10 cooker.

 

[Sans Bateau]

May also be the thermal coupler (I think thats what its called) that sits in the flame and tells tap if the flame is lit. They do burn out, same at home when the central heating wont stay on, that usually happens on the coldest day of the year though.

 

[Jobs a good un]

Thermo couples

Someone said it could be the thermo couple where ? what is it ? Anyone know ?

 

[vyv_cox]

When this happened in my camper van a few years ago I paid a Corgi man £20 to solve it, after driving a long way to find one who could work on caravans. He waggled the electrical spade connections, which fixed it.

The thermocouple is the closed tube, about 1-2 millimetres in diameter, that protrudes out of the burner assembly into the flame.

 

[Allan]

The thermocouple could be the sensor that sits in or near the flame. I'm not sure how it would work as no power is connected to cookers.
Allan

 

[oldharry]

When this happened in my camper van a few years ago I paid a Corgi man £20 to solve it, after driving a long way to find one who could work on caravans. He waggled the electrical spade connections, which fixed it.

The thermocouple is the closed tube, about 1-2 millimetres in diameter, that protrudes out of the burner assembly into the flame.

Lost me there Vyv, the sensor is (usually) a sealed capillary going back to the tap. When the sensor heats up expansion pressure holds the tap open. If the flame fails the pressure drops and the tap closes. Least thats how all the ones I ever saw worked. When they develop a leak on the capillary or wherever you dont get your morning cuppa! One that is slow responding as in OP, is not in a strong enough flame.

Were yours electric? Must have been if waggling an electrical connector did the trick. annoying to have to pay £20- when thats all it is.

 

[lenseman]

Hi All

My gas stove when igniting takes about 1-2 mins before you can release the button so it stays on ,can anyone tell me why ? and what part i would need to replace etc etc

Many thanks

Mark

When you look down on the burners on the hob, can you see a greyish slab of metal close to the burners usually at the back and below the flame area? This is the flame failure device which needs to get hot before you can let go of the gas knob on the front.

If you turn the gas up too high when you try and light the gas ring, some times, like mine, this grey slab of metal only gets the blue part of the flame and this, as you know is the coldest part. I discovered that by turning my gas control down to simmer the yellow part of the flame heats the flame failure device and it lights very quickly.

Also sometimes on my stove, the two gas flame jets directly above the Flame Failure device do not light properly and this is the reason that I cannot let go of the gas knob!

 

[pete]

Thermocouples are usually copper outside and are in fact 2 conductors inner and outer that are insulated from each other apart from at the hot junction (tip).
Heating the tip produces millivolts at the other (nut) end to hold a electromagnetic valve open. because of the small voltage the nut end has to be clean and tight, but don't over tighten or kink the wire as you may damage the internal insulation and they must be in the flame.

Mercury vapour valves have a thin wire with fluid/gas inside that expands when heated and opens bellows in the valve. (commonly fitted in domestic ovens which light on low then boosts up after a few seconds) with these you have to change the complete valve when they fail.

Hope this helps
pete

 

[Martin_J]

As per David's post a couple above...

I have found that with the gas turned up full the flame seems to be too far away from the flame fail devices to make them effective... You have to count to ten very very very sloooowly before you let go of the knob ~(and even them it sometimes goes out).

If however you turn the knob immediately to low when first lit.. then the very small flame cups around the flame fail device so much quicker. Count to six and it's lit!

Hope this is an easy fix.

 

[DownWest]

Thermocouples are usually copper outside and are in fact 2 conductors inner and outer that are insulated from each other apart from at the hot junction (tip).
Heating the tip produces millivolts at the other (nut) end to hold a electromagnetic valve open. because of the small voltage the nut end has to be clean and tight, but don't over tighten or kink the wire as you may damage the internal insulation and they must be in the flame.

Hope this helps
pete

Second that, Never seen an expansion thermo-couple. The clue is in the name. All electric. And a slow take up is usually due to the nearest flame being iffy. As said several times above. They usually fail without any 'slowing down'.
A

 

[VicS]

Second that, Never seen an expansion thermo-couple. The clue is in the name. All electric. And a slow take up is usually due to the nearest flame being iffy. As said several times above. They usually fail without any 'slowing down'.
A

They call them "thermocouples" but they are not the electric gadgets described. You'll find them, some sort of expansion device, in gas boilers too.

Replaced one in one of our boilers ... even got the part from a DIY store.

Picture of one taken from BES website

 

[DownWest]

Vic, I may be a somewhat out of date, so thanks for the correction. When the Sunday Times crucified the Algarve for unsafe gas heaters, the fall out made ovens without flame failure devises illegal in rented villas. Since most british built ovens were prized, I got involved in converting them to flame failure systems, dispite the fact that they were not prone to the local built problems of gassing up to the top burners, then exploding and jumping out into the middle of the kitchen and frightening the horses. Happened to several people I knew when heating their pap secos.
A

And your edited pic, looks just like the thermocouple stuff I delt with then.
A

 

[pete]

They call them "thermocouples" but they are not the electric gadgets described. You'll find them, some sort of expansion device, in gas boilers too.

Replaced one in one of our boilers ... even got the part from a DIY store.

Picture of one taken from BES website

The most common expansion device on gas central heating boilers (mainly older ones) is the boiler stat.
Pete

 

[VicS]

The most common expansion device on gas central heating boilers (mainly older ones) is the boiler stat.

Flame failure thermocouple and thermostat equally common on my boilers . One of each on both boilers!

One is old ... the other even older!

 

[ianat182]

I second MartinJ's solution as I had this ignition problem on my Plastimo2500 and found out by accident, much quicker lighting now.

ianat182

 

[daveyw]

Ok, here's a free lesson on gas.
There are;
FFD's - Flame failure devices
FSD's - Flame Supervision Devices
and Thermostats.

FFD's are found on the burners on the top of the cooker, the grill and sometimes on the oven burner. They are indeed electrical devices. They generate a small voltage when heated, as Pete described, and this voltage holds open a magnetic valve that you manually hold open by pushing in the control knob.

Problems with these are;
They burn out at the tip
They are incorrectly positioned in the flame(should be in the blue part of the flame(Lensman, if you have yellow flames you need a service).
The contact where the nut screws into the valve is dirty and need cleaning.
Grease and dirt is preventing the knob being fully pushed in.
These are cheap items(£2-3) and easy to replace.

FSD's are only found in the oven. These are mechanical expansion devices.
When you turn on your oven a small amount of gas is immediately emitted and hopefully ignited. This small flame heats the sensor bulb. The resulting expansion then open the FSD valve and allows full gas flow(this should happen within about a minute). The FSD is normally located at the rear and bottom of the oven.

Problems with these are they burn out.
You will normally need to take the cooker out to access this.
These can be fiddlely to change. They can cost anything from £20 to £200.

Thermostats are found in the oven and boilers and is another mechanical expansion device. The heat from the oven heats the the sensor bulb and the resulting expansion operates a valve inside the oven control valve.

Problems with these are they burn out.

These again can be fiddlely to replace and can cost £20-£100

A lot of boat cookers do not have thermostats but merely a high and low setting on the control knob.

Back to the original problem, if it's taking a long time for the burner to stay lit. Check position of the thermocouple(looks like a thick pin). Make sure it's in the flame. Doubt the thermocouple has moved so maybe the flame is wrong. Are all the holes in the burner cap clean. Maybe the flame is lifting off(the thermocouple is in the part of the flame with unburnt gas. Turning the flame to minimum is a temporary solution but then chances are that the unburnt bit will reappear when you turn the flame up again and trip the flame off again. Lift off is cause by excess gas pressure(unlikely if the other burners are ok), restricted holes in the burner cap(likely) or lack of oxygen(unlikely if this is the first burner you are lighting).

Best of luck!
Try
http://www.gassaferegister.co.uk/about/gas_safe_register_engineers.aspx to find an engineer

 

[VicS]

Vic, I may be a somewhat out of date, so thanks for the correction.

In fact you were right.
Some further investigation reveals that they are electric. There is a junction at the tip between the copper outer casing and the wire ( iron ?) inside. The button on the other end makes the contact with a solenoid valve.

Obviously did not look closely enough at the one I replaced.

Quite surprising that you can get enough power to operate a solenoid but there you go apparently you can!