Cooker / Induction Hob isolation

[DetlefSchmitz]

Believe me - most people who found they needed to operate the switch wouldn't even know it was there - plus the thought of having to get to it would just result in more panic if you knew it was there somewhere and had to empty the cupboard.

I think you have to have been there.

But even so. With a switch moderately in view - my people didn't think to turn it off.

 

[JohnW2]

In those days it was in the garage, a long way away. House would have burnt down before we located the key.

I suppose I should have considered Sod's Law before I asked the question However ...

In the current kitchen (new extension), probably 4 metres away.

.. and I would imagine that we can probably agree that such is far more 'the norm' in the average domestic property?

The isolation is more like 30cm from the hob, but I guess we now have the choice.

With due deference to the OSG, I would personally feel that was too close (certainly in the case of fire), for the reasons I've given.

At least in the day time. You wouldn't want to throw the main switch off on a fire at night time.

... but you wouldn't want/need to. We're not even talking about an electrical problem (in the fat fire case). I'm sure that I would ignore all this obsession with 'DP isolation' (even in my TT installation ) and just flick the cooker's MCB!

I don't have an electric cooker, so can't indicate whether I practice what I preach but, FWIW, the CU which serves the kitchen is about 6 (unobstructed) paces from the cooker.

Kind Regards, John

 

[DetlefSchmitz]

John. You would turn off the cooker mcb.

My wife (to avoid any personal references to your situation) would not even know it was there.

 

[JohnW2]

John. You would turn off the cooker mcb. My wife (to avoid any personal references to your situation) would not even know it was there.

I'm sure the same is true of my wife (indeed, she refuses to touch anything to do with a CU!). However, nor do I think she would approach a burning fat pan in order to operate a local isolator, even if it were visible - she'd be running in the opposite direction and screaming!

I accept that there are pros and cons. I suspect that the oft-cited 'chip pan fire' (such as you have experienced) is about the only common situation in which there is really a need for an 'isolator' at all. Burning food in an oven can normally be dealt with using the normal cooker controls, and any electrical fault will probably cause a protective device to operate.

Kind Regards, John

 

[DetlefSchmitz]

That probably says it all. People should be able to make their own decisions from that.

When the chip pan fire happened to my mother a long, long time ago, the flames reached up to the ceiling and set fire to the polystyrene tiles. Somehow or other it then extinguished, but the smoke damage was much worse.

I think we are making some progress.

 

[JohnW2]

That probably says it all. People should be able to make their own decisions from that.

Indeed.

When the chip pan fire happened to my mother a long, long time ago, the flames reached up to the ceiling and set fire to the polystyrene tiles. ...

It's not really an electrical issue at all. As far as I can make out, hob-top chip pans have got an awful lot to answer for. Electric fryers are so much safer, with a primary thermostat and secondary thermal cutout - and, even if that all fails, the lid presumably offers some 'oxygen starvation'. As I said/implied, if it weren't for hob-top chip pans, I think the argument for a cooker needing a dedicated 'isolator' would become pretty weak.

Kind Regards, John.

 

[bernardgreen]

My mother in law's oven thermostat failed in the closed position. Seeing smoke she opened the door to investigate, the internal side walls were glowing dull red. She was lucky that the carbonised food did not ignite as the fresh air entered the oven.

The heat meant a broom stick was needed to turn the cooker unit switch off as it was directly above the cooker.

The collection of switch fuses ( no CU ) was in a cupboard behind a heavy arm chair.

 

[JohnW2]

The heat meant a broom stick was needed to turn the cooker unit switch off as it was directly above the cooker.

That's why I keep saying that if one is going to have a 'local' switch/isolator, I think that it should be well away from the cooker - I really don't think that the OSG's 300mm is anything like enough in the face of a fire or near-fire in/on the cooker.

Kind Regards, John

 

[RF Lighting]

Isn't every hard wired heating element required to have a local DP isolator?

 

[JohnW2]

Isn't every hard wired heating element required to have a local DP isolator?

Is it? Where does that come from? Also, are you saying that it needs a DP isolator, even in a TN installation (for which the regs say that isolation, in general, doesn't have to be DP)?

As I've been saying, a built-in flaw in any such arrangement (or requirement) is that if the isolator is DP is too 'local' it will become inaccessible if that heating element seriously overheats and/or results in a local fire. If there were such a requirement, I therefore think it would logically impose a minimum distance from the load (as well, perhaps, as a maximum).

Kind Regards, John

 

[RF Lighting]

I'm sure I was taught this as an apprentice.

That's why you would always install a DP isolator for an immersion heater, cooker, shower, panel heater, storage heater, etc.

 

[JohnW2]

I'm sure I was taught this as an apprentice. ... That's why you would always install a DP isolator for an immersion heater, cooker, shower, panel heater, storage heater, etc.

It's certainly the sort of regulation one might expect to exist, but I haven't seen it in BS7671, have you? Of course, many MIs may require it, which somewhat forces the situation.

Having said that, as I mentioned, it would seem a bit odd if there were a blanket requirement for DP isolation in such situations, when BS7671, in general, says that isolation does not have to be DP in TN installations, wouldn't it?

Kind Regards, John

 

[RF Lighting]

I'm beginning to wonder if it's one of these hangovers from older regulations, which still gets passed down the generations.

I can't find any specific reference to it in BS7671

 

[EFLImpudence]

I can't find any specific reference to it in BS7671

There is none.

 

[ban-all-sheds]

John. You would turn off the cooker mcb.

My wife (to avoid any personal references to your situation) would not even know it was there.

I should hope not.

If she did you should wonder how she's so familiar with the layout of John's kitchen.