How to light hob

[Owl]

I'm completely new to boating and having trouble with something very basic which is lighting the hob for cooking. It's a vanette 4000/2 and at the survey a few weeks ago the hob rings were working happily which I saw with my own eyes. However now I can't get any of the rings to light and haven't been able to do so since moving in a couple of days ago. There's four rings  and I can't get any of them to light. 

 

There's no ticking sound for the ignition suggesting it might not be working which I don't mind, but I've tried manually lighting the hob with a long lighter which I'm also used to using at home and nothing happens. I do feel like I can smell gas coming out of the ring as normal when the switch is turned, although I can't hear it flowing.  I've only tried this for at most 5, 10 seconds at a time as I'm scared of filling the boat with gas. 

 

Does anyone have any ideas what might be happening? No suggestions too basic as like I say I'm a complete novice and feel like it's probably something obvious as the surveyor a few weeks ago got the hob working with no problems. 

 

 

 

[Athy]

Welcome, Owl. You are wise not to leave the switches turned on for too long; but I wonder if you are pressing them down as you turn them? That's what we need to do when lighting a gas ring on our boat. Keeping the switch depressed for a few seconds after the flame ignites seems to ensure that it will stay lit rather than going out as soon as pressure on the switch is relaxed, though I don't know why.

[Mike Hurley]

Are the gas bottles turned on at the regulator? Is there any gas in the bottles?

[MtB]

Can you hear the hiss of gas coming out while the rings fail to light?

 

If not, the gas supply has failed. Did you realise the gas comes from gas bottles that run out and need refilling?

 

do you have any other gas appliances? Do they still work? How about the oven and grill?

[Ray T]

Has your gas hob a fail safe thermister? You need to keep the knob pressed until it warms up.

[Owl]

Hi all 

 

Thanks for your suggestions so far. 

 

In terms of the hob, on this set up there's no way to turn the switch/ dial without pressing it down. My process has been to switch on the lighter and hold it by the flame ring, press down the dial and turn it to flame and then wait for a few seconds but nothing happens or, rarely, it feels like it might be starting to ignite but stops without me turning the switch off. 

 

In terms of the gas I can't hear the hiss but can still smell it a bit. I knew about the gas bottles possibly running out but was thinking it would be too much of a coincidence for them to run out straight after the survey, maybe not though! I've got two gas bottles and from weight they seem roughly the same which could either mean they're both empty or both relatively full.  The hob is my only gas appliance.

[Mike Hurley]

Is the regulator turned on?

[MtB]

7 minutes ago, Owl said:

In terms of the gas I can't hear the hiss but can still smell it a bit.

 

Classic description of an empty gas bottle. 

 

When ‘empty’ a gas bottle will often deliver a few more millilitres of gas when a gas tap is turned on. Enough to smell but not enough to light, or to make the classic hissing noise of a gas ring runnning. 

[Jen-in-Wellies]

5 minutes ago, Owl said:

 knew about the gas bottles possibly running out but was thinking it would be too much of a coincidence for them to run out straight after the survey, maybe not though! I've got two gas bottles and from weight they seem roughly the same which could either mean they're both empty or both relatively full.  The hob is my only gas appliance.

Coincidences have to happen sometime! Check that the pillar valve is open on top of the gas bottle. Follow the pipe in to the cabin and check there are no valves on it that may be shut. When you do change the gas cylinder, you need the correct size spanner. The nut needs to be turned the opposite way to disconnect the bottle. Clockwise to undo, anticlockwise to do up.

 

On my boat, the gas usually runs out in the middle of cooking tea. Outside it will be dark and either raining, or sideways sleet!

 

Jen

[nicknorman]

Although I think an empty gas bottle is the most likely explanation, do check everything is turned on. Try rotating the knob on the top of the cylinder. It should rotate several turns when you rotate it clockwise (viewed from above). If it will only rotate anti-clockwise if it was turned off. Rotate fully anti-clockwise to turn on.

 

Usually there is a separate gas isolator valve near the regulator. They can vary but ours has a flat (butterfly) knob that rotates 90 degrees. On is in line with the pipe, off is at 90 degrees to the pipe.

 

 

[Boater Sam]

51 minutes ago, Owl said:

 

 

at the survey a few weeks ago the hob rings were working happily which I saw with my own eyes.

Has the surveyor done a gas test? If so the pipes will be full of air, it will take more than a few seconds to get sufficient gas to light, give it 10 seconds with the doors open and see what happens.

[Dr Bob]

30 minutes ago, Owl said:

Hi all 

 

Thanks for your suggestions so far. 

 

 

 

In terms of the gas I can't hear the hiss but can still smell it a bit. I knew about the gas bottles possibly running out but was thinking it would be too much of a coincidence for them to run out straight after the survey, maybe not though! I've got two gas bottles and from weight they seem roughly the same which could either mean they're both empty or both relatively full.  The hob is my only gas appliance.

If both cylinders feel about the same weight, then I would guess they are both either full or empty. Most people don't switch cylinders until they are empty. It's good to learn how heavy cylinders are so you can estimate when they need changing. If they are the big ones and you can lift it with one hand then likely it is empty. Lifting a full one out of our locker is a two handed job. Get a neighbor to lift one and tell you whether it is empty.

[nicknorman]

2 minutes ago, Boater Sam said:

Has the surveyor done a gas test? If so the pipes will be full of air, it will take more than a few seconds to get sufficient gas to light, give it 10 seconds with the doors open and see what happens.

Why would the pipes be full of air? The gas tightness test is done with ... gas!

[Athy]

1 minute ago, nicknorman said:

Why would the pipes be full of air? The gas tightness test is done with ... gas!

That may be so - but I'm reminded that if we haven't used our oven for a while, the knob has to be held on for quite a time (20 seconds?) before the gas lights.

[MtB]

2 minutes ago, nicknorman said:

Why would the pipes be full of air? The gas tightness test is done with ... gas!

 

That's what I was going to post too!

 

A new gas system is supposed to be tested for soundness using air before introducing gas. A tightness test once commissioned MUST use gas not air, or the result will not be valid. 

1 minute ago, Athy said:

That may be so - but I'm reminded that if we haven't used our oven for a while, the knob has to be held on for quite a time (20 seconds?) before the gas lights.

 

You have a minor gas leak then, too small to detect during a conventional tightness test. And certainly too small to detect using the coarse resolution of a bubble tester.

[Boater Sam]

I think he may of had to turn the gas off at the bottle, removed his manometer and then searched his pocket for the test nipple plug, screwed it in and turned the bottle back on, during which time gas will leave the pipework to be replaced with air, His subsequent test that the nipple is gas tight will be fine with air in the pipes. Yes? It was only a suggestion not a declaration of war.

[DandV]

We had a non return pigtail, the flexible between the bottle and changeover valve fail, completely closed. No gas would pass  the pigtail attached to a full  bottle, valve open,

but completely open to air the other. Not sure how, but the non return valve was completely sealed both ways. New pigtail fixed the problem.

[Captain Pegg]

Sounds like someone has swapped out the full bottles for a couple of empty ones just before completion of the sale. Presumably the survey was done ahead of completion and therefore before the OP took ownership.

 

I suspect you would get a really big smell of gas if it was emitting and not lighting. That can happen if the top piece of the job isn’t seated correctly but it doesn’t sound like that is the case.

 

JP

[Machpoint005]

1 hour ago, Owl said:

There's no ticking sound for the ignition suggesting it might not be working which I don't mind,

The piezoelectric igniter might need a new battery (AA size, under the bottom front edge of the appliance).

[DandV]

1 minute ago, Captain Pegg said:

Sounds like someone has swapped out the full bottles for a couple of empty ones just before completion of the sale. Presumably the survey was done ahead of completion and therefore before the OP took ownership.

 

I suspect you would get a really big smell of gas if it was emitting and not lighting. That can happen if the top piece of the job isn’t seated correctly but it doesn’t sound like that is the case.

 

JP

Sounds credible 

[MtB]

6 minutes ago, Boater Sam said:

I think he may of had to turn the gas off at the bottle, removed his manometer and then searched his pocket for the test nipple plug, screwed it in and turned the bottle back on, during which time gas will leave the pipework to be replaced with air, His subsequent test that the nipple is gas tight will be fine with air in the pipes. Yes? It was only a suggestion not a declaration of war.

 

Nope! 

 

Gas under pressure will escape from the test nipple when the manometer tube is removed. There is no motive force to make air enter the pipe even once the pressure in the pipes has fallen to zero, UNLESS the plug is left out for long periods over which the ambient temperature varies. A rise then a fall in temp will suck in a bit of air, just as is happening with Athy's gas system with the tiny leak earlier in this thread. 

 

(Just explaining, not engaging in warfare!)

[Machpoint005]

16 minutes ago, Athy said:

That may be so - but I'm reminded that if we haven't used our oven for a while, the knob has to be held on for quite a time (20 seconds?) before the gas lights.

20 seconds is a good estimate - we have the same experience.

[Athy]

MtB, should we be worried about this leak? I would add that once the oven has been lit, it will subsequently (e.g. the next day) ignite immediately.

[MtB]

Just now, Machpoint005 said:

20 seconds is a good estimate - we have the same experience.

 

Another leaky system then!

 

We are talking really TINY leaks, that allow the pressure to drop to zero over several hours rather than the 60 seconds of a noddy bubble tester test, or the five minutes of a proper BS5482 Pt3 test.

2 minutes ago, Athy said:

MtB, should we be worried about this leak? I would add that once the oven has been lit, it will subsequently (e.g. the next day) ignite immediately.

 

No, no need to worry, unless you LIKE worrying. Obvs. 

[Athy]

3 minutes ago, Mike the Boilerman said:

 

 

 

No, no need to worry, unless you LIKE worrying. Obvs. 

For this relief, much thanks.