Electric hob prewired with 13A plug.



LOL!!! I've actually seen it done, so don't knock it. LOL!!! And they wonder why Part P is now in circulation. :-)
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BigWallop wrote:

... so these bodges stay in use for longer before getting rewired safely.
NT
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A ring circuit made from Flex and with each flex protected. Should be fine and at least as safe as a ring main provided you glue the plugs together so you have to remove them both. ;-)
You could always do the job properly and use a bigger connector that's designed to take 6kW.
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snipped-for-privacy@meeow.co.uk wrote:

Hey, don't laugh. I did that once. Temporarily, of course. I had designed and built (with a colleague) an interactive exhibit which used four or six hot air guns to heat the air for a hot air balloon. The final install location was to be near a distribution board where we could quite easily sit a 32A breaker and proper take-off, but for "proof of concept" purposes we had to make do with a couple of standard 13A sockets in the workshop...
Worked a treat in the workshop, but they made me redundant before I could install it properly, and the people who did the installation didn't really have time to get it right. I gather it still (two and a half years later) isn't working. Getting a 10ft high balloon to fly on demand and within the sort of attention span a typical 11 year-old has is no easy task.
Hwyl!
M.
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Hmmm! Two 13A plugs and a relay or two and it wouldn't have been a bodge.
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Two 13A plugs, and a whole cabinet full of DIN-rail mounted connectors, contactors and a transformer. Transformer was for LV remote switching of the contactors, one contactor per hot air gun, four installed, but contactors for two more. Even I was impressed.
Hwyl!
M.
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wrote: <<<snipped>>>

There is a large house in Ravelston, Edinburgh, with remote switching for curtain closing, light switching, TV switching Etc. Etc. Etc. And it's all done from a bank of LV relays and alpha-numeric keypad panels sited around the house. It took us four weeks of very long days to create it, but the finished product is pretty impressive, though I say it myself. :-)
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So why weren't the guns split across two mains feeds then? Then it would run without overloading and wouldn't need any special work to fit it.
Just make sure you use a couple of connectors that have to be removed to get in so no idiot leaves one plugged in while working on it.
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Several reasons:
Firstly, your last point, which *is* a bodge when there is a better way.
Secondly the fact that there were no socket outlets near the intended point of use, so we were going to have to wire something up, also this would be a large point load on any existing sockets circuit and so would probably be treated to its own circuit anyway.
Thirdly there was a not-full-utilised distribution board a mere couple of yards away, with a nice knockout on the side perfectly sized for a 32A connector.
Fourthly, if it had been installed somewhere else I didn't want someone plugging it into two phases.
Fifthly the guns were 2kW each and intended to be used at full power, so it wouldn't have been a couple of sockets, it'd have been four or six.
Shame it seems that it never worked once they built a proper (rip-stop) balloon for it.
Erm... come to think of it (look, this was two and a half years ago and my memory's dodgy at the best of times) I don't think it *was* wired for 32A single phase. I think I wired it for 20A three phase. That would have made more sense (two guns per phase) but without going digging into my (unsorted) photo collection (I did take one of the innards) I can't be sure.
Hwyl!
M.
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Done that with a PC to program sequences and to allow for control using a web browser. Didn't bother with keypads though.. much more impressive using a tablet PC running a flash program.
You could dim lights, switch appliances, change channels on the TV, etc.
It even had face recognition and took videos when people went into certain places. It sent SMS and email alerts if it decided you were an intruder.
I was working on routing the TV to the tablet PC when I had to leave it all.
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Martin Angove wrote:

Guaranteed method: teach them a maths class while the job's being done outside on the lawn. It could take half the day, you'll have their attenmtion alright.
NT
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snipped-for-privacy@meeow.co.uk wrote:

As I may've mentioned before, I knew an 'official' University electrician (he'll have retired by now ;-) who did this for real to run 5-6kW of stage lighting for smaller gigs in the individual colleges (York Uni). He was ever so careful to plug the two plugs into separate sockets with the individual switches *off*, and then turn the switches *on*, reversing the proceedcake when tearing down.
He had some 32A 'commando' style sockets fitted in at least a couple of the colleges (Goodricke and Vanbrugh, IIRC) shortly after spreading the load across a couple of sockets in separate rooms.
Which were on different phases...
Stefek
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<snip>

of
the
Ouch, Oops !... :~(
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Stefek Zaba wrote:

sure it can. In most cases. For limited time.

would they? It should all run no more than lukewarm at 13A, so in most cases it would be fine at 20C, well within limits. Whats being eroded is the safety margin more than the working ability.

I'm doubtful. I found it took 13A running thru thin 3A flex (IIRC) to reach that point. 13A flex would normally handle 20A no problem. Normally anyway...

yes, and the effective life of the user too. But not by much, even this bodge has only a very tiny chance of killing someone.
NT
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Stefek Zaba wrote:

sure it can. In most cases. For limited time.

would they? It should all run no more than lukewarm at 13A, so in most cases it would be fine at 20C, well within limits. Whats being eroded is the safety margin more than the working ability.

I'm doubtful. I found it took 13A running thru thin 3A flex (IIRC) to reach that point. 13A flex would normally handle 20A no problem. Normally anyway...

yes, and the effective life of the user too. But not by much, even this bodge has only a very tiny chance of killing someone.
Why not just uprate the cable and fit a heatsink to the mains plug? :) (joke)
NT
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I now have an image of the plug in the socket with a big sheet of copper stuck on its back. LOL!!! I Like it. :-)
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BigWallop wrote:

I see an Athlon CPU heatsink plus cooler fan on there, held in place with plastic ties round the plug, which is 2mm out to enable this. Fan is run off a wallwart in the next socket. The cable ties creep, ensuring poor thermal contact, the fan blows the hot air off the heatsink onto the wart, and the plastic round the plug pins slowly turns a shade darker each year.
NT
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Stefek Zaba wrote:

OK so far...

... No, for a *household* cooking appliance the "first 10 A plus 30% of remainder" rule appears in both Tables 1A and 1B of the OSG. Therefore it applies to *both* the design current of the cooker circuit itself and to the loading presented to the installation.

Well 5 kW is nearer to to 22 A. Applying the diversity rule gives you 13.6 A, so a 16 A circuit would be OK, but a 13 A 'spur' wouldn't. In practice though I guess most designers would opt for a 20 A radial circuit in 2.5 mm^2 giving a generous diversity factor of ~ 90%.
By your argument a typical free-standing cooker (12 kW, flat-out) would need a > 52 A circuit, meaning a 63 A fuse or breaker in practice. As we all know though, a 32 A circuit (~60 % diversity) is fine [OSG p. 154].
--
Andy

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Andy Wade wrote:

Ah, um, yes. I see. <soundfx="munch.wav">Delicious stuff, this pie. What did you say it was called again? Mumble? Dumble? Oh, *H*umble!</soundfx>

Fairy neurf. For an entire cooking installation - hob + oven(s) - it indeed seems entirely reasonable to me to consider the design load as diversified, as you simply can't draw the flat-out load for any serious length of time. For a 4-ring hob - well, it depends on your style of usage! Chez nous, it's common enough to be doing large pans of pasta, sauce, soup, and fried-things to feed medium-sized hordes of transient teenagers; again the simmerstats mean that the full-on load won't last long, but I'd still be chary of connecting through a 13A plug-n-socket and a 1.25mmsq flex (OK, I sneaked that headroom-lowering bit of spec in without any evidence just to bolster my point ;-) than a 20A DPsw and 2.5mmsq hob feed.
S'like that with diversity, innit - as the Good Book says, its values are 'only for guidance because it is impossible to specify the appropriate allowances for diversity for every type of installation... The figures given in Table 1B therefore may be increased or decreased as decided by the engineer responsible for the design of the installation concerned.' Applying which, I'd be happy connecting a 5kW hob to a 13A socket (well, FCU) for Granny, where Granny's been given such a hob as a Christmas pressie, there's no heftier cooker circuit to use, and she's living on her own; I'd be most *un*happy putting a 5kW hob on a 13A accessory in a communal-use kitchen (student kitchenette, yoof hostel, etc) - and to be fair the Good Book would be unhappy too, as it's not 'household' - and like the OP I'd be chary of the arrangement in a bigger-than-single-person household.
But thanks for the clue-by-four about the significance of Table 1A vs 1B, for all that!
Cheers, Stefek
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Stefek Zaba wrote:

However, this case isn't one where the current is /limited/ to the 'design load' by the nature of the appliance.
So although, as Andy Wade showed, the "diversity" of a 5kW hob may only be 13.6A, if the cable is protected by a 16A or 20A MCB, the design current of the circuit then becomes the rating of the protective device.
IMHO.
Owain
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