Oven Wiring

[VicParticipant @vic]

Our oven went bang the other day and I found this:

The oven was installed by an electrician. I’ve fitted a new oven outlet and trimmed off the damaged wires as you can see. I’ve doubled the ends of the flex over for now to get the oven working but I guess I need these? I ask as they didn’t seem to do much good the first time round? The oven was installed about 4 years ago. Bit of a blow to spend over £20 for three ferrules but needs must I suppose. Unless anyone knows of a cheaper alternative? TIA.

[JasonBModerator @jasonb]

Turn and drill holes to make 3 tubes and crimp them onto the ends of your wires.

[John Doe 2Participant @johndoe2]

If you live anywhere near Hereford, I have a ferrule kit and crimper and would be happy to help.

[VicParticipant @vic]

Thanks for the offer but I’m in Dorset.

[EmgeeParticipant @emgee]

Vic, if you confirm the conductor csa (size) by PM with your address I will post you some crimping ferrules providing I have a size to suit, the terminal clamp or screw will do the job of the crimping.

Emgee

[VicParticipant @vic]

This is a piece of the cable for size. Conductor is around 1.45 and outer diameter 2.82 so I’m guessing it’s 1.5mm.

[derek hall 1Participant @derekhall1]

Seems small cable conductors for an oven….maybe I have misunderstood.

Is it an all electric oven or a gas oven?

[Robert Atkinson 2Participant @robertatkinson2]

What power rating is the oven? Is there a electric hob? Unless it is a small single oven the supply wiring looks too small.
That said the original fault looks like the terminal with the live conductor of flex was not tightened properly. The ferrule may not have helped. They are not essential. The conductors twisted and then folded over on itself should be enough and better than a ferrule that is too small for the terminal.

Robert.

[David George 1Participant @davidgeorge1]

Amazon £15.00
Ferrule Crimping Tool Kit, Hibisaws 0.25-10mm² Self-Adjustable Ratchet Bootlace Crimper Plier Set with 1250 Wire End Ferrule Connectors, Ideal for DIY Electrical Repair and Cable Crimping
Brand: Hibisaws

[VicParticipant @vic]

It’s a NEFF fan assisted single oven. I believe it’s 16A and fitted with the original cable that came with the oven. Yes, it does seem rather small but the cable supplied by NEFF seems to have a proprietary plug on the back of the oven so nothing I can do about it. The cable looks like this:

[EmgeeParticipant @emgee]

Vic

Count the number of strands in the conductor and measure the diameter of 3 to give an average diameter, the number of strands and the diameter of each strand can be used to determine the csa.

What size fuse or mcb protects the circuit ?

Emgee

[Sonic EscapeParticipant @sonicescape38234]

I never use ferrules. Instead I add normal lead solder to the wire. I like this because the alloy is soft and the screw makes it flat increasing the contact area. So a soldering iron could also be an option.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

What power rating is the oven? Is there a electric hob? Unless it is a small single oven the supply wiring looks too small.
That said the original fault looks like the terminal with the live conductor of flex was not tightened properly. The ferrule may not have helped. They are not essential. The conductors twisted and then folded over on itself should be enough and better than a ferrule that is too small for the terminal.

Robert.

16A single oven, Gas Hob. The cooker socket the electrician fitted had separate holes for the supply and oven cables, you can see these in my first photo. The replacement I bought made by MK just has one hole for live, neutral and earth for both supply (twin & earth) and the ovens flex. The holes are rather large. I have indeed stripped off extra insulation, twisted the conductor and folded it back on itself. I’ve done this in the past for thin cables and plug tops.

 

[VicParticipant @vic]

There are 32 strands in the cable, each one is .22mm.

I have, on many occasions tinned thin cables for use in plug tops to get a better grip. I’ve even doubled them over and tinned a couple of times. I wasn’t sure tinning was appropriate in this situation though. This is the breaker, 20A.

[Sonic Escape]

On Sonic Escape Said:

I never use ferrules. Instead I add normal lead solder to the wire. I like this because the alloy is soft and the screw makes it flat increasing the contact area. So a soldering iron could also be an option.

Bad practice!

Over time the solder creeps and the original tightening pressure reduces leading to a high resistance joint.

Many years ago I used to do the same as in your picture but stopped after a ‘nearly a fire’ event.

Ian P

 

 

 

[VicParticipant @vic]

Ian, I have heard this before. I’ve done this many times though without any problems – so far. I should add that I’ve put a lot of plug tops on cables at various jobs over the years and in very many cases the cables have been tinned by the manufacturers of the equipment ready for a plug to be fitted.
Everything I’ve bought in more recent years though have come with a fitted plug top.

[VicParticipant @vic]

I incorrectly assumed the Electrician supplied and fitted a cooker outlet. The BG branded unit he used though is a 20A flex outlet. This seems better suited to both the T&E supply cables and the flex to the oven than the cooker outlet I’ve used. I’m now thinking to get one of these instead. The oven is 16A and both of these are rated at 20A. As the cabling failed in the BG unit I’m inclined to go for the MK this time!

[VicParticipant @vic]

Then again, I’ve always liked Crabtree stuff and this looks good.

[VicParticipant @vic]

I’ve ordered the Crabtree one from Screwfix, click and collect. I’ll use this and just double the wires over if needed. Thanks for all the suggestions. And yes, I’ll make sure the terminal screws are nice and tight!

[Ian P]

On Ian P Said:

On Sonic Escape Said:

I never use ferrules. Instead I add normal lead solder to the wire. I like this because the alloy is soft and the screw makes it flat increasing the contact area. So a soldering iron could also be an option.

Bad practice!

Over time the solder creeps and the original tightening pressure reduces leading to a high resistance joint.

Many years ago I used to do the same as in your picture but stopped after a ‘nearly a fire’ event.

Ian P

 

 

 

I’ve seen this happen several times, not to be recommended.

[duncan webster 1]

On duncan webster 1 Said:

On Ian P Said:

On Sonic Escape Said:

I never use ferrules. Instead I add normal lead solder to the wire. I like this because the alloy is soft and the screw makes it flat increasing the contact area. So a soldering iron could also be an option.

Bad practice!

Over time the solder creeps and the original tightening pressure reduces leading to a high resistance joint.

Many years ago I used to do the same as in your picture but stopped after a ‘nearly a fire’ event.

Ian P

 

 

 

I’ve seen this happen several times, not to be recommended.

Totally agree, especially with a high current device like an oven where the connections tend to get warm at the best of times; if the  resistance increases the solder will soften loosening the joint and increasing resistance further etc…

edited to add: The soldered ends you used to see on bought items were only for low current devices like lamps, probably to ease putting plugs on them during production – not something you see any more. The junction boxes you buy are designed to work without solder, ferrules, etc.

[VicParticipant @vic]

“Totally agree, especially with a high current device like an oven where the connections tend to get warm at the best of times”

This was my concern.

I think my plan going forward is sound but I’m still somewhat surprised the live wire burnt out the way it did. The Electrician must have tightened up several dozen terminal screws at the time this work was done, installing a new consumer unit etc. Hard to imagine he left this one screw slightly loose, and it’s taken four years to burn out.

[Andy StopfordParticipant @andystopford50521]

Its not uncommon, I suspect thermal cycling over the years gradually loosens the connection if a hurried electrician left it slightly loose to begin with. Plug sockets, where they’ve been mean over the length of cable so the connections are hard to see when the cables are inserted, being particular offenders.

[larry phelan 1Participant @larryphelan1]

Interesting subject. I too am surprised at the size of cable fitted to new ovens these days. Back in the day it was always 6 mm sq, now it is no more than 1,5 ! seems a bit strange, but any new cooker I have seen is the same, some of them even fitted with a three pin plug. Am I missing out on something ??

[SillyOldDufferModerator @sillyoldduffer]

Couple of things going on here, putting Vic into the shadow line where a proper electrician is needed.

A 16A oven exceeds the 13A plug and socket limit, requiring a separate wall-plate etc.  Given the first electrician might have been a bodger, Is the connection from the wall-plate back to the consumer fit for purpose?   Unlike the short cable to the oven, where the wires can safely be on the thin size, a cable buried inside a wall is insulated and may overheat.    Mild overheating won’t instantly burn the house down, but the insulation slowly hardens over time, risking a short?

Root cause I suspect is the electrician failed to properly tighten the terminal screws.   None of the ferrules show any sign of the crushing caused by a tight screw.   Contact was good enough to pass the electrical tests, but the live started to spark later, perhaps after summer/winter temperature changes stressed the wires slightly.   Typical human error: even a trained person who normally does a good job will blunder if distracted or rushed.

Another vote against tinning multi-stranded wire.   Although once considered a good way of keeping the strands together, several problems emerged later, bad enough to avoid doing it today!

Dave

 

 

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