Been trying to choose between electric cookers. Back in June 2004 there was a thread "Electric Hobs which type?". General conclusion was that induction was the best but unfortunately it lost its way by bringing gas into the debate.
Of the 4 types available: Ceramic; Induction; Halogen; Solarglo:
Q1 How does each one work (or is supposed to work)? - the only indication in the thread was that induction operates by electromagnetic induction at around 50kHz and requires cast iron(?) pans to operate. But as for the others, which techniques do they use to get hot?
Q2 Speed?: thread indicated that induction has more or less instant start and stop heating up. & the others?
Q3: Reliability? How tolerant is each one of a ring being left on?
BTW I am trying to see through the sales fug & work out just what are the pros & cons of each type. Also gas is NOT an option & is not being considered.
Radio 4 had a couple of famous posh chefs on recently arguing the merits of hobs. Not electric types vs. other types, but actually electric vs. gas, Although they both clearly thought the only sort of eelctric hob worth bothering about was induction, one thought this was better than gas and the other was barely disagreeing.
It surprised me - I've always hated electric hobs (but never used an induction one).
You missed the traditional curly element. Don't know but isn't Solarglo just a type of Halogen?
Induction sets up a magnetic field through the pan and the "element" in a manner very similar to an electric transformer. The pan becomes part of the circuit and is heated by eddy currents flowing through (or something like that). Cast iron isn't necessary, but a magnetic pan is; i.e. aluminium and some stainless steels won't work. Halogen types (lightbulbs) heat mainly by radiation, partly by conduction. Ceramic and traditional ones work mostly by conduction.
I would imagine that there is one big disadvantage to induction (other than cost), namely that the pan base has to be in contact with the ring area in order for the magnetic coupling to be efficient. It is thus impossible to cook with a bowl-shaped wok (to be fair, it is only possible to use a bowl-shaped wok properly on gas) and if you're in the habit of handling your pans during cooking (i.e. moving and shaking them about) then every time you lift or tilt the pan the magnetic coupling reduces and therefore so does the heat. Again, this can also be a problem with other types of electric hob but not so much of gas.
The heat lag of an induction hob is *mainly* in the pan. So the thicker the base of the pan, the longer it takes to cool down but other than that, yes, switch off and the source of heat is very quickly removed.
Halogen types often (always?) have *two* heating elements. One is identical to halogen lamps as found in security lights (though circular rather than linear, obviously) and thus switches on and off very quickly. This gives the impression that halogen hobs are fast. The problem is that this element only contributes a half or less of the total heating supplied by the whole "ring". The other half comes from a standard resistive heating wire which, should you operate a ring with no pan on top, you will see slowly heating up and then slowly cooling down. Their lag is thus greater than induction, but not all that bad. These hobs have a glowing indicator to show "hot hob" as the red glow disappears quite quickly but the glass plate can remain very hot for some minutes.
Ceramic and traditional rings are purely resistive. The only real advantage I can see of a ceramic one is that it is "sealed" and so less difficult to clean. I suppose it also spreads the heat more evenly
- but decently thick pan bottoms should do the same for traditional rings. Ceramic, due to this top plate, is the slowest of all hobs both on heat up and on cool down.
Ceramic and traditional rings are (IME) extremely reliable, probably giving decades of service. Traditional rings are dirt cheap and very easy to replace. Ceramic a little more expensive and difficult. Leaving them on won't damage the rings, but as ceramic rings don't glow red it isn't obvious that they are on and this could be the cause of all sorts of problems.
Halogen rings seem to be reasonably reliable, but they are very expensive to replace should they fail. For one I looked at a year or so ago, a new ring would have cost almost the same as a whole new ceramic-type hob. Again it's obvious when they've been left on as they glow very brightly.
I haven't a clue about the reliability of induction as I don't know in detail how they work. As they are unlikely to include miles and miles of very thin resistive heating wire though, they are quite likely to be reasonably reliable. My hunch (though I've never used one for long enough to need to find out) is that removing the pan breaks the magnetic circuit sufficiently for the ring to switch off when no pan is present. This would co-incide with the fact that induction hobs won't switch on if your pan isn't a suitable type.
Shame about the gas. Personally it'd have to be next to impossible to install gas for me to consider an electric hob. Even if the only option were great orange bottles I'd look to gas as the first choice.
One other thing to (possibly) consider is that while "normal" hobs are fairly standard in their electrical rating - they usually have something like a 3kW, two 2kW and a 1kW ring - induction hobs, being aimed at a "higher class" market (compare the costs) sometimes have greater requirements. One I saw had a 10.5kW rating for four rings - compare this with 8kW above. Having said that, this is mainly a running-cost issue. A standard 32A cooker circuit, although only continuously rated at 7.6kWish is good for a diversified load of up to around 18kW if there's no socket fitted, or 14.6kW if one is fitted. (OSG table 1A -
10A +30% of remaining f.l. +5A for a socket).
Also induction hobs, with their electronics, need a chunky filter on their supply terminals to stop all the HF noise getting onto your mains wires. This filter will introduce some (small) amount of earth leakage into your electrical system which might need to be taken into account if for any reason the cooker supply is fed via an RCD. Resistive heaters also often leak slightly, but the PSU in an induction hob is (effectively) designed to leak.
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