Domestic Appliance | Self Repair Guides
- Published: Tuesday, 30 November 1999 00:00
- Hits: 12452
There are of course many different types of gas hob that utilise many different ways of, more or less, doing the same thing but, what we show you below is a typical blow-out diagram of a typical four burner gas hob to sow you all the different spare parts on it.
It is worthwhile noting that this is what we see when we look up spare parts for almost any appliance (at best) and all the numbers shown relate to a part number, a brief description and that's it! We get very limited information other than that, if we get any more information at all.
So that's what we see, let's walk you through the main elements of the hob. For the purposes of this exercise we'll ignore the main body of the hob, the hoptop itself and the base plate.
All the parts shown in red are gas carrying spare parts and the gas supply would have to be interrupted to replace these, for that you will require a Gas Safe operative. We will not supply these spare parts without evidence that you are qualified to carry out such repairs and test safely.
You can also see that there are a lot of parts that you would just never use and, we hope understand, that this is why we don't list all spares for all machines as a lot of the parts would be pointless to have and simply confuse people.
Gas Hob Model Numbers
Because most manufacturers go for as clean a look as possible for the hob, the model number will be on the underside of the hob which often isn't so easy to get to and very often you will have to remove drawers or an oven to see the rating plate, which is where all the information is.
DO NOT trust the numbers on the instruction manual as it will almost certainly cover a huge range of machines and, if you order spare parts off that then you may well get the wrong ones.
Without a correct model number it will be very unlikely that we would be able to find the spare part that you are looking for.
But, spare parts from the top...
230 - Pan Supports
Pan supports are the bits of iron or metal that you will actually sit your pans on in order to cook . These are often unique items to one particular gas hob or range of hobs and can be ludicrously expensive to replace.
Pan supports get really dirty as they are subject to extreme heat from the gas burners and, over time, spillage tends to build up on them causing a layer of seemingly impossible to shift grease.
The only way that these usually fail as such is that some of them are bonded together and this can break causing the pan support to break or simply fall apart.
210-221 - Gas Burners
This is probably, aside from control knobs, the most requested spare part areas for a gas hob.
The burner will usually consist of either two or three actual parts in most cases, or at least the parts that you can see and replace at any rate. The three can become two where the burner ring (shown as item 217 as an example) is built into the moulding of the burner body (shown as 212 as an example) to become one, usually, aluminum part.
If this case, the front left burner consists of item numbers 212, the burner body, 217, the burner ring and the all important 220, the burner cap or flame spreader as it is sometimes known.
120 - Gas Hob Control Knobs
The control knobs are usually very easy to replace, they just push on and pull off. Which is good as they do tend to break a fair bit.
Do note that, for most hob control knobs, we will need the model number to identify the correct knob or knobs for your hob or cooker.
160 - Ignitor or Spark Plug
The spark plugs or ignitors are the parts that deliver the spark that will ignite the gas to the burner. Usually this is done by a high voltage ignition or spark generator (the next item we'll look at) by making a high voltage spark "jump" from the spark plug to the gas burner ring or burner body where that is integrated.
In order for this to work several things come into play. To start with the ignition spark generator has to be working obviously to actually create the charge that makes the spark, that bit's easy to suss out.
The other things that are often missed is that the spark plug itself has to be clean. By this we mean the metal that protrudes from the top of the actual ceramic plug as, if it is dirty then there may be too much resistance for the spark generator to overcome and it will fail to spark. When this happens you will usually get one or two rings of a hob not igniting or, igniting intermittently.
Likewise the burner ring also has to be "clean" as well. If it is caked in dirt of grease then it is all too possible that the spark produced will have nowhere to go and simply jump to the case or hob top.
For the spark plug, it can be cleaned with a mild abrasive such as Emery cloth or suchlike to ensure that it is good to go. Obviously cleaning the burner elements takes a little more care but, a Brillo pad can work wonders and these two tips can save you some money replacing parts that really don't need changed.
147 - Ignition Spark Generator
This is the actual ignition spark generator that pretty much does what it says on the tin.
These do fail although most are pretty reliable for the most part, it tends to be more the bits around about them that fail more. In this example you can see the little ignition button (Item 148) attaches directly to the ignition unit itself but, increasingly this is becoming less common on modern gas hobs.
As usual there's good and bad in this.
The system shown is very simple and easy to understand but, increasingly, we see more complex systems that will use a remote ignition unit that it operated by an electrical signal. This works as there are mini switches under the gas control knobs (Item 120) that make contact as you press them down to turn the gas on. That contact closure causes the spark generator to get a current and come alive and, generally, all the rings will then spark to ignite.
The other way is a "bar" that sits under the control knobs that, when you press down, makes contact with an electrical switch which then operates almost the same as above or that presses the ignition button as in the case shown in the diagram. This way is prone to silly failures as these bars do go out of line and don't make contact so well.
In the automatic ignition systems if the control knobs are faulty it can cause the burners not to ignite properly as well.
All The Other Parts and Safety
All the rest of the parts shown, largely in red, are what we consider to be "Non-user Servicable"‚"Gas Carrying" spare parts.
This is for your own safety!!
Should you interrupt the gas supply there is a danger that the hob can leak gas. It doesn't matter how good you think the seal is, it can leak.
If, for example, a gas tap leaks inside the hob the gas can build up in there and, as soon as it gets a spark... BANG!
We see, almost on a weekly basis, the malleable connection at the back fitted incorrectly and left leaking by "fitters" these leak and are a danger. In fact, when we get a report of a newly or recently installed gas hob leaking we just assume that this is the issue.
The point it, it's too dangerous to take risks with if you don't know what you're doing and have the proper equipment and knowledge to properly ensure that the appliance is safe to use. It is certainly not worth the potential risk to life and limb to save a few pounds fitting a spare part yourself.
Therefore, we can and do sell gas carrying spare parts, but only to people that can produce the relevant Gas Safe identification as we don't want to live with anyone being injured or worse on our conscience.
If you are working on the internal of the hob do be careful as on some models you cannot lift the hop top without breaking the gas supply. This isn't common, but worth noting. If you get any resistance trying to lift the hob top, stop and call a qualified engineer.
Also, if you are inside, make sure that the power is off before you start!