Raeburn to replace boiler/hob/oven

On 15 Sep 2014 07:07:59 GMT, Huge wrote:

Ours is not perfect at simmering but it's a damn sight better than the solid hot plate electic cooker, that *cannot* simmer. Even on "1" if you leave anything without stiring for more than 5 mins it will burn.
The cheapo induction on "1" is a bit more than a gentle simmer and things will stick after 5 mins but stick only they won't have burn't, the bottom of the pan just doesn't get hot enough. It also has a "temperature" mode, set that to 80 C and it's a "keep warm", I might try 100 C for a gentler simmer below "1" but I might have already tried that.
All sounds complicated but as the settings and controls behave in a consistent manner, ie set it to X it will do Y, irrespective of pan size or duration it has been on or since last change it is easy to pick up the settings you like.
Other electric hot plates are very inconsistent in use due to the high thermal mass. Pans can be fairly rapidly boiling 5 mins after you turned the ring off! And the crude ON OFF control means that if you look at a pan set for "simmer" (ha!) just before it's about to switch ON it looks too low or if you look just as it switches OFF too high. You simply can't just look at a a pan and say too high/low you need to look twice 30s to a minute apart.
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That isnt true of the glass topped electric systems with a decent thick based stockpot on them. You don't need to stir them anything like as often as that to stop it burning with stuff like marmalade once you have made sure that all the sugar has dissolved before you heat it again.
And you boil it anyway, not simmer it.
Same with the relish.
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Yep, it does. Just went and tried it.
So why don't Al pans work?
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On 15/09/14 09:31, Huge wrote:

Well I suspect that actually they do.
I am beginning to think that the iron slab is more about making pots work BETTER.
And that the manufactures statements are there to (a) cover their arses and (b) ensure that only pots that are definitely designed with induction hobs in mind are used and (c) help boost sales of new pots. Preferably made in Germany ..
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Perhaps the notion is that they will, but not as well. Perhaps also there is the risk of damage to the coil in the ring? Poor impedance matching?
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On 15/09/14 09:43, Tim Streater wrote:

Mmm. I very much doubt it would damage them. After all you can expect people to take pans off completely without switching off the hob.
One manufacture whose manual I skimmed seemed to have a telltale to indicate when a pot was 'good' I suspect this means 'a decent amount of primary current being drawn'
Presumably al, especially thin al would not draw as much...
Making the relationship between power setting and actual heat outpout rather problematic and pot dependent. Of course software to keep primary in phase current steady, would sort that, but white goods manufacturers are not very sophisticated really.
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On 15/09/2014 10:06, The Natural Philosopher wrote:

Induction hobs detect removal of pans and switch off the ring.That operates pretty quickly.
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This is interesting, if a little noddy;
http://home.howstuffworks.com/induction-cooktops3.htm
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On 15/09/14 10:03, Huge wrote:

MM. there they say its iron's specific resistance that helps it be effective, plus a bit of hysteresis loss.
The specific resistance is non-essential. You can design for any specific resistance you think likely.
The hysteresis you cant. But solid iron at the sort of frequencies in play is useless anyway die to eddy currents dominating things.
I am beginning to lean towards the magnetic thing as being 'has iron in it, which has decent resistance, so works better' and nothing to do with its magnetic properties as such.
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The two induction hobs I've tried both had this function.
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On Mon, 15 Sep 2014 09:19:30 +0100, The Natural Philosopher wrote:

doesn't

and

I assumed you already had or knew... B-)

Which are *induced* by the varying magnetic field. B-)

A flat piece of foil gets kicked into the air, crumpled just sits there. It does get just warm but there isn't much mass to heat up. But the ring sulks, displays ERR and beeps. About every 5 seconds or so it tries again with a very short burst. Think "tick".

'cause at least my hotplate complains and refuses to work. That's with a copper bottomed (about 1mm thick) stainless pan or plain stainless one. I might see if I can find a thicker bit of ali to try, we don't have any ali pans.
<later> Found an offcut of 2 mm thick ali sheet about 6" x 2". It just sits there, doesn't get warm, the ring complains.

That's an odd statement stainless steel isn't magnetic. Or do they mean stainless steel with iron/ordinary steel inlay?

That's probably it, also to get decent I^2R losses in copper/ali needs somewhat heftyier currents than the same losses in iron. ISTR from investigating CCS "CW1308" that the restivity of copper v steel is 1:7. Not only do you have more resistance you also have higher flux density to drive the eddy currents. I think...
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On 15/09/2014 21:34, Dave Liquorice wrote:

Not quite true:
http://www.scientificamerican.com/article/why-dont-magnets-work-on/
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