# Terminating an electric cooker



## DTR (22 Feb 2015)

Afternoon all,

We're changing over from gas to electric and our cooker has just been delivered. Here is a photo of the terminating panel:







In my usual line of work, I'd crimp those terminations (the screws are M6). But as domestic is a bit of change of scenery, I though I'd double check with you guys. 

For what it's worth, the cooker circuit isn't live yet. It's all run in but not terminated at the CU. I've got a qualified sparky coming next week to do that and sign it off. 

Thanks


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## lurker (22 Feb 2015)

Assume you are going to use a flexible cable between there and the fused wall "box"
When I did mine I put in a longish length of heat resistant sheathed cable so I could slide the oven in and out of the housing cabinet without disconnecting which has been useful later
It's quite expensive I think, although I "borrowed"a length from work
What is the oven wattage?


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## DTR (22 Feb 2015)

Does it have to be flex? The likes of Screwfix etc don't sell heat resistant flex in a heavy enough gauge. I don't know what the wattage is off hand bit I think it's in the region of 11kW. The specs ask for 6mm cable. The fused box is about 2' from the cooker.


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## lurker (22 Feb 2015)

Flat cable is usually 6mm but you can't use it unsupported 
Could you check the wattage as 11sounds a but high


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## DTR (22 Feb 2015)

The retailer says it's 11.3kW, which is a bit high when you run it past Ohms Law. Zanussi's website does specify a 30A breaker though:

http://m.zanussi.co.uk/Products/Cooking ... ZCV68310XA


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## HarryJ (22 Feb 2015)

A bit off topic, but I think I have this oven and unless it's just mine, the grill pan expands when used due to the heat and gets wedged in... so much so that the oven moves before it comes free

Just something to check I guess...

Edited to add; I didn't see it being wired, so unfortunately can't help with that...

Harry


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## Silas Gull (22 Feb 2015)

A 10 kw electric shower requires a 10mm cable because it is drawing close to 45 amps on start up.
Your cooker might come close to this,but only with every ring, hot plate, grill and oven combination going at full chat -
which is where the manufacturers 11.5 kw figure comes from.


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## Phil Pascoe (22 Feb 2015)

I've never seen 6mm flex. Is there such a thing?


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## bugbear (22 Feb 2015)

phil.p":1ab7zsww said:


> I've never seen 6mm flex. Is there such a thing?



I thought it was always this stuff:

http://www.wickes.co.uk/Wickes-Twin-and ... H/p/156183

Not at all flexible. I worked with some recently. Not easy.

BugBear


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## n0legs (22 Feb 2015)

phil.p":14s750z8 said:


> I've never seen 6mm flex. Is there such a thing?



Used regularly on bigger machines.
http://www.industrialextensionleads.co. ... 9868-p.asp


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## Boatfixer (23 Feb 2015)

I bought 6mm flex from a proper electrical factors with no problem. It is readily available but the guy behind the counter reckoned most electricians use twin and earth because they cant be bothered to carry 2 sorts of cable on the van......

Graham


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## DTR (23 Feb 2015)

n0legs":2vpokl9p said:


> phil.p":2vpokl9p said:
> 
> 
> > I've never seen 6mm flex. Is there such a thing?
> ...



That's the kiddie. It's very tempting just to use a T&E offcut but if a job's worth doing....



So back to the original question.... can I crimp the terminations at the cooker-end?


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## mjcann (23 Feb 2015)

Crimp is probably best job, no loose strands, as long as you use decent lugs and a good crimper, not one of those that just puts a dent in it.


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## n0legs (23 Feb 2015)

DTR":1a9d7xco said:


> So back to the original question.... can I crimp the terminations at the cooker-end?



I would say yes to crimp on lugs. 
But it would have to be the quality ones like the ones in the link below:-
http://www.neweysonline.co.uk/cembre-tu ... on.raction.

Nice bit of heatshrink up and over the barrel for some insulation.

If not those then a twist of the conductor, in the direction of the lay :wink: (do you like that ?) and a 'U' loop around the termination screw.


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## DTR (23 Feb 2015)

n0legs":9s0v88tp said:


> DTR":9s0v88tp said:
> 
> 
> > So back to the original question.... can I crimp the terminations at the cooker-end?
> ...



I'm all for heavy duty, but are the coloured crimps not ok? They're rated high enough. I have easy access to a ratchet crimper, but I can't borrow a heavy duty crimper or the crimps without some agro....


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## Deejay (23 Feb 2015)

Afternoon Dave

If you can't get a crimper, have you thought about soldering them?

Cheers

Dave


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## n0legs (23 Feb 2015)

DTR":vcn1438k said:


> I'm all for heavy duty, but are the coloured crimps not ok? They're rated high enough. I have easy access to a ratchet crimper, but I can't borrow a heavy duty crimper or the crimps without some agro....



I know which ones you mean but to me they always look a bit flimsy when crimped onto the larger conductors.
I think of it like this--
If I squashed that type of lug/crimp and made into a cylinder would it's cross sectional area be equal to that of the conductor being terminated in it. Also the bit where it goes from the barrel to the ring/fork/spade always looks a little 'skinny' to me, if you know what I mean. 
But although I've just said all of that, if the manufacturer has given them a set of ratings then they must be okay. My trouble is I'm used to dealing with mahooosssive cables and terminations, so everything else looks small :lol: 





Deejay":vcn1438k said:


> Afternoon Dave
> 
> If you can't get a crimper, have you thought about soldering them?
> 
> ...



Ah ! =D> 
Now you're talking, I frigging love soldered on lugs. It's just done, fitted, soldered and done. There's always a place for some solder :lol: 

Though seriously. 
Very little chance of or no vibration at all and a good cable clamp for a nice rigid hold on the outer sheath, and yes solder the lugs on. Job's a good 'un


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## jolly1 (23 Feb 2015)

Regarding calculating the load (amps) cable sizing should include the diversity factor, ie not likely all the load shall be in use at the same time. Should be 10 amps plus 5 amps if the cooker unit has socket plus 30% of the total load.


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## DTR (24 Feb 2015)

n0legs":4nny6vpy said:


> Also the bit where it goes from the barrel to the ring/fork/spade always looks a little 'skinny' to me, if you know what I mean.



I do know what you mean, but then I've seen far too many heavy-duty crimps fail at that location! (admittedly they were all subject to vibration...)




n0legs":4nny6vpy said:


> Deejay":4nny6vpy said:
> 
> 
> > Afternoon Dave
> ...



Soldering, of course! #-o I really like that idea, I think I'll do that!


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## DTR (24 Feb 2015)

jolly1":25abc2ih said:


> Regarding calculating the load (amps) cable sizing should include the diversity factor, ie not likely all the load shall be in use at the same time. Should be 10 amps plus 5 amps if the cooker unit has socket plus 30% of the total load.



Interesting to know, thanks.

So... 11.3kW @ 240V = 47A

10A + 5A + (47A x 30%) = 29.125A


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## gav (24 Feb 2015)

I believe soldering is not recommended for flex terminals as the soft solder can creep/cold flow and become loose on its own. 

Gav


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## DTR (24 Feb 2015)

gav":1fli0pdd said:


> I believe soldering is not recommended for flex terminals as the soft solder can creep/cold flow and become loose on its own.
> 
> Gav



Sigh. Ok. So first I'm going to crimp it. After that I'm going to solder it. Then I'm going to drill a hole through it and pin it. Following that I'll superglue it. Then wrap some sellotape around it. As this is a woodwork forum, maybe I could squeeze a dovetail in there somewhere?

Actually stuff it, I'll just go back to a gas cooker.



Being serious though, we use several thousand soldered crimp connections where I work, all subject to vibration. I've seen untold of broken crimps and snapped cables through fatigue, but I've never once seen a failed solder joint.


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## Deejay (24 Feb 2015)

Afternoon Gav

Is 'cold flow' what used to be known as 'dry'?

Cheers

Dave


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## Dee J (24 Feb 2015)

The terminals are designed for flex, there is no need for crimp/solder/whatever. Not many places stock 6sq flex as 4 sq heat resistant is rated to 35Amps so is suitable for most domestic cooker situations. But there's plenty of cable on the internet http://essentialsupplies.co.uk/acatalog ... AhLG8P8HAQ

Of course you could do the usual bodge of T&E. See loads of cookers with this and haven't found any failed yet. But YMMV applies.
Dee


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## n0legs (24 Feb 2015)

Dee J":27f66ucr said:


> See loads of cookers with this and haven't found any failed yet.
> Dee



Me too, totally agree.


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## woodchip (24 Feb 2015)

DTR":ezyw419f said:


> jolly1":ezyw419f said:
> 
> 
> > Regarding calculating the load (amps) cable sizing should include the diversity factor, ie not likely all the load shall be in use at the same time. Should be 10 amps plus 5 amps if the cooker unit has socket plus 30% of the total load.
> ...




I think we should be using 220v not 240v which gives 30.4 a


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## Phil Pascoe (24 Feb 2015)

230v surely?


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## Eric The Viking (24 Feb 2015)

You could save the whole crimping thing - strip back enough to keep the lay and bend the bared strands into a Q shape, and tin that properly with solder. Voila! instant terminated end. Used to do it all the time when I wanted a tidy finish on big speaker connectors, etc..


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## Lons (24 Feb 2015)

I've never seen flexi cable used for a cooker and see absolutely no need for it unless you're going to pull the cooker in and out every day. I've fitted well over a hundred kitchens some of which I've wired and some by an electrician where other work has involved him.
Mine is on 10mm T&E flat cable (commonly sold as cooker cable), it's a slot in full cooker comes out about once a month to clean behind and as good as the day it was put in. Was removed and re-installed a few years ago when I did the kitchen. Previous cookers for the past 40 years have been the same as are my kids appliances and pretty much everyone I know. Sounds way OTT to me.

Unless they've changed recently, cookers are intended to be wired under the supplied screws / serrated washers.
and I've yet to see an electrician crimp or solder the connections to one.

Just my two pennerth and could be wrong of course.

Bob


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## n0legs (24 Feb 2015)

Now this gentlemen is one of the finest types of terminations.
A blast from my past for sure.


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## DTR (25 Feb 2015)

n0legs":1lme1k0y said:


> Now this gentlemen is one of the finest types of terminations.
> A blast from my past for sure.



Funny you should post that, I keep a few Ross Courtney's in my tool bag at work for when I have to do an temporary fix on a broken crimp! They're probably more reliable than the crimps are!


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## misterfish (25 Feb 2015)

One thing to also consider is warranty. We had a hob unit that included an extended warranty for 5 years cover that failed twice within the warranty period. After the second failure they replaced the hob with a new version and the repair engimeer told us to make sure we installed the new kit with the cable specified by the manufacturer (heat resistant 4mm flexible) as the warranty company were rejecting claims where installations were not fully compliant with the manufacturer requirements.

Mind you - the office staff of the warranty provider that AEG used initially were planning to replace our 60 cm electric hob with a much wider gas hob and it only took a couple of attempts to get them to supply a suitable bit of kit!

Misterfish


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## Sheffield Tony (27 Feb 2015)

DTR":8hmz08nv said:


> jolly1":8hmz08nv said:
> 
> 
> > Regarding calculating the load (amps) cable sizing should include the diversity factor, ie not likely all the load shall be in use at the same time. Should be 10 amps plus 5 amps if the cooker unit has socket plus 30% of the total load.
> ...



Is this really what the regs say ? Amazing - makes no sense to me at all. It is not like intermittent duty or something like that - it is saying that if you turn all the rings on, the cable _will_ be overloaded, but hey, you don't do that very often :shock: 

This is rather like Fukushima logic. That sort of tsunami was a 1 in 1000 year event, so not worth worrying about. But wait a minute - the plant had been operating for 40 years, so the chance of a disaster having happened already was about 1 in 25. Unlikely things still happen.


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## jolly1 (27 Feb 2015)

Sheffield Tony":257i1uo2 said:


> DTR":257i1uo2 said:
> 
> 
> > jolly1":257i1uo2 said:
> ...



Yes, that's exactly what the regulations state, do a search for cooker diversity factor
If you wish to test being amazed, how long will a 10 amp fuse take to blow, when carrying 20 amps


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## Phil Pascoe (27 Feb 2015)

"This is rather like Fukushima logic. That sort of tsunami was a 1 in 1000 year event, so not worth worrying about. But wait a minute - the plant had been operating for 40 years, so the chance of a disaster having happened already was about 1 in 25. Unlikely things still happen."

No. No. No. The chance of disaster was 40 in a 1000. If the odds on winning the lottery are 14,000,000 to one, you don't make them 7,000,000 to one by buying two tickets. You have two chances in 14,000,000.


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## jolly1 (27 Feb 2015)

phil.p":21616mf1 said:


> "This is rather like Fukushima logic. That sort of tsunami was a 1 in 1000 year event, so not worth worrying about. But wait a minute - the plant had been operating for 40 years, so the chance of a disaster having happened already was about 1 in 25. Unlikely things still happen."
> 
> No. No. No. The chance of disaster was 40 in a 1000. If the odds on winning the lottery are 14,000,000 to one, you don't make them 7,000,000 to one by buying two tickets. You have two chances in 14,000,000.



Diversity is applied in many cases without you realising. For example a ring circuit of sockets has 10 13 amp socket outlets, each capable of supplying 13 amps so by you logic, 10 x 13 amps = 130 (edit did me sum wrong) amps which would require something of the order of 35 mm squared, might be a wee bit difficult to get two of them in the socket terminations.
Current is not the only factor in specifying cable, aim of the calculation is to limit the volt drop , see IEE regulations, (I squared R losses)to 2.5% of the nominal voltage say 240Vac.

Your comment regarding Fukushima logic, is actually risk management. Time elapsing does not change the odds the odds remain the same. A simplistic view of 1 in a 1000 year event, odds of it happening today are 1000 x 365, or another method is to say 0.001% like I say it is a simplistic view
At it simplest level risk can be considered the odds of an event happening. If you wish to have 100% guarantee not to be knocked down by a car, then don't cross the road or walk beside a road. Aim of Risk management is to mitigate risk to an acceptable level, not eliminate them.


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## DTR (27 Feb 2015)

So in the end I crimped then soldered the flex terminations at the cooker, and insulated the crimp shanks(?) with heatshrink. Overkill probably, but rather that than worry about it not being good enough. 





You lot have got me worried about my nuclear reactor now though


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## jolly1 (27 Feb 2015)

I would be more worried about the dreadful wind turbines


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## No skills (27 Feb 2015)

DTR":2d0j3z9v said:


> You lot have got me worried about my nuclear reactor now though



I'd only worry about it if all the neighbours paddling pools burst at the same time in the summer. Haven't got pet lizards as well have you? Hmm... mini tsunami + small nuclear reactor + iguana = mini Godzilla?

Wheres the risk assessment chap gone?


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## n0legs (27 Feb 2015)

DTR":32g58cw3 said:


> So in the end I crimped then soldered the flex terminations at the cooker, and insulated the crimp shanks(?) with heatshrink.




Nice one :wink:


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## owen (28 Feb 2015)

All that fuss and you could have just stripped back the flex and connected straight to those connections. :shock:


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## DTR (28 Feb 2015)

owen":5ssmgbv9 said:


> All that fuss and you could have just stripped back the flex and connected straight to those connections. :shock:



Where I work that kind of termination isn't considered reliable enough, hence the crimps (or a Ross Courtney!). Solid core would have been acceptable formed into a loop around the screw.


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## n0legs (28 Feb 2015)

owen":17781ph2 said:


> All that fuss and you could have just stripped back the flex and connected straight to those connections. :shock:



"If you go above and beyond, you rarely have to return" 
John Roberts
Senior Electrical Installation Lecturer 
S.Wa.E.B


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## owen (2 Mar 2015)

DTR":1geanqw1 said:


> owen":1geanqw1 said:
> 
> 
> > All that fuss and you could have just stripped back the flex and connected straight to those connections. :shock:
> ...



Ah right didn't know that.. nearly every oven I have changed ( I work for a landlord so do bits and bobs of everything) has been connected that way without any crimps. Maybe next time I'll crimp them (probably not).


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## DTR (3 Mar 2015)

owen":2x97g93i said:


> Ah right didn't know that.. nearly every oven I have changed ( I work for a landlord so do bits and bobs of everything) has been connected that way without any crimps. Maybe next time I'll crimp them (probably not).



Ha, my company is a bit anal about these things (admitedly we don't deal with cookers much....). But if it's good enough for them, it's definitely good enough for me


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## Phil Pascoe (3 Mar 2015)

n0legs":890bdepu said:


> owen":890bdepu said:
> 
> 
> > All that fuss and you could have just stripped back the flex and connected straight to those connections. :shock:
> ...


Slightly off tack, but I worked with a mechanic who was meticulous. I commented one day, and he told me he was apprenticed to an old man who used to say if it's meant to move, grease it. If it's ever meant to move again coppaslip it. If it's meant never to move, locktite it. You might be the poor sod who gets the job back.


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## bugbear (3 Mar 2015)

I have a dim memory than you're not meant to use solder on high-current connections, due to galvanic corrosion
and/or thermocouple heating effects, which is why connection blocks (AKA terminal strips) are used, so that everything
is (nearly) the same metal.

Can the more knowledgeable/experienced comment on this?

BugBear


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## DTR (3 Mar 2015)

bugbear":2bu2yzdl said:


> I have a dim memory than you're not meant to use solder on high-current connections, due to galvanic corrosion
> and/or thermocouple heating effects, which is why connection blocks (AKA terminal strips) are used, so that everything
> is (nearly) the same metal.
> 
> ...



Intriguing... we use a very large number of soldered connections on circuits pulling a continuous 20A. What is the definition of high current? In any case, heavy duty crimps are tinned...


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## bugbear (3 Mar 2015)

DTR":gjtc2rs7 said:


> bugbear":gjtc2rs7 said:
> 
> 
> > I have a dim memory than you're not meant to use solder on high-current connections, due to galvanic corrosion
> ...



It may (well) be simply that I'm misremembering what I heard, or that I was listening to someone who was themselves confused.

BugBear


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## n0legs (4 Mar 2015)

bugbear":1nscee64 said:


> I have a dim memory than you're not meant to use solder on high-current connections, due to galvanic corrosion
> and/or thermocouple heating effects, which is why connection blocks (AKA terminal strips) are used, so that everything
> is (nearly) the same metal.
> 
> ...




I've soldered lugs onto cables that run in the 1000s amp range, it's the way it was done before crimps and mechanical connections were invented.
On High Voltage, which is my specialty, we soldered almost everything. The soldering process actually avoided the corrosion issue, we solder aluminium conductor to copper regularly. The solder being the inert barrier between the dissimilar metals.
As for terminal strips, they are the spawn of the devil and for those who cannot terminate cables properly or solder.
The cheap dung type are nothing more than a bright alloy, white/pig metal comes to mind, with steel screws. These steel screws will cause corrosion of a copper conductor.
The tinned brass type are slightly better, but should not be relied upon to be a long term electrical connection at mains/household voltage or higher. I've seen too many with the polythene insulation (insulation, yeah right) melted off. 
The ceramic type are far better and the only ones I could recommend for use. When I used to do house bashing I would change the connections in a shower to this type.
Ideally when making off any mechanical/screw type connection onto copper conductors an anti-corrosion paste should be used, it will protect the copper from the inevitable dissimilar material issue that is usually encountered.
Give me a gas torch, the right solder, the correct flux and I'll join brass, bronze, copper, aluminium, steel, galvanised steel and lead to themselves and each other. 
You can't beat a soldered connection, the only reason we've gone away from them is due to skill shortage.
I've seen our crimps fail and they're done with a 20 ton crimper that takes two guys to use, the same goes for the cr4p mechanical/bolt on lugs and through connections we've used over the years. 
I love solder, I want to marry it :lol:


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