Discuss 16mm tails with 100A fuse ??? in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

which just goes to prove that a well manufactured CU coupled with competent installation, lasts for years with no problems. now we have to fit metal boxes because neither of the above criteria apply today in a lot of cases.
 
Now then Wilko why take all the time to carefully reassemble that old Wylex and take pictures, I reckon you're going to flog and install that somewhere else. :D
It's interesting that the internals had changed to single screw neutral block terminals, I thought that was well after wooden backs had been superceded on those boards. Maybe it's had a transplant in the past. :)
 
which just goes to prove that a well manufactured CU coupled with competent installation, lasts for years with no problems. now we have to fit metal boxes because neither of the above criteria apply today in a lot of cases.

Very true Tel, do you remember the Wylex 'Extenso' units, I've taken a few out. They had no main switch just a couple of fuseways & neutral/earth bars. You'd supply it from the end of the busbar on the original [full] Wylex which had screw terminals on the feed side of the last fuse carrier, I liked how you could also remove the thinned out front of the fuse cover on Wylex boards when retrofitting plug in MCBs due to the increased depth although some didn't realise from the amount I've seen left off in cupboards. :)
 
which just goes to prove that a well manufactured CU coupled with competent installation, lasts for years with no problems. now we have to fit metal boxes because neither of the above criteria apply today in a lot of cases.

I made this point to the Chairman of BEAMA when the metal CU's were forced on us ........... he didn't agree that wrapping carp in metal didn't make them much safer ..
 
I am finding this thread interesting.

In what respect? The difficulty engaging with the DNO's? The contradictory opinions?

What would you do?

Personally I would leave the 16mm tails in place if I was happy the maximum load was well below 87A
 
In what respect? The difficulty engaging with the DNO's? The contradictory opinions?

What would you do?

Personally I would leave the 16mm tails in place if I was happy the maximum load was well below 87A

I can tell you working for a supplier, we see loads of installations with 100amp cutout, 16mm tails on both customers side and at cut, firstly we are not allowed to down grade or even up grade DNO fuses, that is down to them and only them can make that call. If the cut out has 16mm tails on 100amp service fuse, I will replace, can not change customers tails. (just advice them) I will change out any Ali tails. I do agree with your last statement not many domestic properties are going to pull anything like 87 amps.
 
Here's a pic of the lovely fuse box that was taken out for this job. Wylex plastic front and a wooden back box. The internals look like new :)

View attachment 37862
That's just showing off, is the screw driver there for show or did you use it to disconnect? :D
You are too particular! I'm lazy these days, I normally just snip off the cables at the point they terminate or if I'm full of energy, get the battery drill out set on high speed with a flat screw driver bit :D
 
why not just bung in a 60A KMF between meter and CU. this will make up for the short tails and also give a point of isolation independent of the DNO fuse.
Sounds the best Idea!, since I think it was mentioned that the tails ran up the cavity and over a door way?
 
Wylex plastic front and a wooden back box. The internals look like new :)

With an older board,I would say that some oxidisation always take place over time.
The board looks to have a extra shiny busbar and fuse contacts

I could very well be wrong and it may be older but I suspect it has not that long come out of the box :)
 
I've had a few wylex boards like that to change, but majority I get are the old mem ones. Last change was one of the wooden backed ones, and have another one to do in next fortnight the same and thenthis week there is one that's the old porcelain type.
 
Derating was probably the wrong choice of words. What I am saying is if the conductors are not clipped direct throughout the ccc should be based upon them being enclosed even if it is for a short length.

When at college today doing the Periodic course I questioned the tutor on this. He said you were correct
 
Wylex plastic front and a wooden back box. The internals look like new :)

With an older board,I would say that some oxidisation always take place over time.
The board looks to have a extra shiny busbar and fuse contacts

I could very well be wrong and it may be older but I suspect it has not that long come out of the box :)

I know that the fuses can become really tight after years of not being touched Des, loads of people say 'never had a fuse blow' , not surprised really with the overcurrent a rewirable will put up with. :)
 
Well, I did try to move the tails but only got the 20cm I needed for the new CU and they won't budge any more, although there is slack at the meter. So changing the tails will be mission messy. Tails leave the external chest high meterbox in a cavity brick wall, go up and over the front door and drop down from the ceiling. CU mounted high up next to ceiling behind front door. New CU is in the location of the original fuse unit, at Customer's request. But somewhere in that lot the tails go through a beam I reckon and are jamming up. Nothing I can't sort if I rip into the plaster ceiling she's just had done :( .

In terms of load, I am sure a 60A fuse would be fine. 2BR mid terrace, newish combi for CH and HW. Biggest drain will be an induction hob she's got on order.

There's no insulation anywhere near the tails that I can see looking from both ends. The tails will be less than 3m long.
induction hobs do not have as big of a load as you think
 
Thanks Tom - I'm planning on clamping it, just for my own education. I think that having a "high" max current, it will reach temp very quickly and wind back. I will report in a couple of weeks when Mr Kitchen catches up.
 
One would think reading this thread that none of you had ever picked up a cable 6 inches from the end after soldering a lug on. Copper conducts heat well enough that the temperature near the end of a cable is influenced by what it is connected to. If it's screwed into a chunk of brass that doesn't itself generate heat, then it will sink a fair amount of heat from the cable core and the end will run cooler. If the terminal gets hot - not as in a loose connection but something like a 45A switch terminal where the contact heats in normal operation - then heat might flow into the end of the cable. Then there's the bunching where cables enter an enclosure - heat that can't be effectively dissipated there might be mitigated by the section that's completely in free air as it heads towards its terminal.

What I'm getting at is that there are all sorts of thermal flows near the terminations so applying an installation reference method won't yield a useful answer. Those are designed for average conditions on average cables and as has been mentioned somewhere upthread, it has been proven over decades of experience that where those CCCs are adhered to, no damage is likely under the somewhat different conditions encountered at the end.

As for 16mm² tails: {NOTE FOR THE UNINITIATED: DO NOT DO THIS! IT IS A THOUGHT EXPERIMENT ONLY!} One day when no-one (especially your insurer) is looking, try reducing your tails. If you have GCH, gas cooker and no electric shower, try 2.5mm². Electric cooker or heating, make that 4.0. If you have a shower you will have to go up to 6mm. Ensure your connections are well made. Report your findings... {AGAIN DIYers DO NOT TRY THIS AT HOME!}
 

Reply to 16mm tails with 100A fuse ??? in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock