5a juction boxes, good idear?

[green121]

Hello,
I had a plasterer come round my house and skim my walls after a sparky had re-wired my house.
He went through two cables with his trowel. One was 3core and earth going to the light switch in the upstairs hall and one was supplying the upstairs smoke alarm. As it was a sunday i had no choice but to go to a shed and get two junction boxes to connect each cable back together. i used 5A junction boxes. i have since been told i should have use 20a boxes. Are the 5amp safe? The mcb is on the consumer unit is 6a.

As you can guess i have limited electrical experience so please go easy if the above was a stupid question!

Thanks

 

[davy_owen_88]

5A junction boxes are fine on a 6A MCB. Where these junction boxes now located?

 

[RobFurn]

For a start the Spark should have capped the cable when he rewired your house to prevent such problems with the plasterers trowel

http://www.tlc-direct.co.uk/Main_Index/Cable_Accessories_Index/Capping/index.html

anyhow your JBs are only good for 5A so if your lighting load exceeds 5A then I suppose they are potentially dangerous, but TBH I would think they would be ok

BTW how have you positioned the JBs i.e. are they visible or buried....?

personally I would have repaired the cable with a through crimp (butt splice) crimp terminal like these:
http://www.tlc-direct.co.uk/Products/CTBUTTslashB.html

then after the repair cover the lot in heatshrink.

 

[green121]

Thanks for your help.
The jb's are not in the best of places (i will probably be told off for this). They are behind the skirting board in the cavity wall. Access is not easy but you can get to them if you really had to.

 

[CallEdsFirst]

Thanks for your help.
The jb's are not in the best of places (i will probably be told off for this). They are behind the skirting board in the cavity wall. Access is not easy but you can get to them if you really had to.

Not really accessible then. Not in the "can gain access to them without wrecking the place" sense of the word!

And surely if a circuit can run to 6a before being overcurrent, then 5a JB's are not allowed.

 

[davy_owen_88]

I've compared a 5A JB and a 6A JB and the terminals are identical. Plus a 6A lighting circuit is very rarely going to be carrying 6A and in this case is only going to carry the load of the 2-way lighting and a smoke alarm.

On another note, 20A junction boxes are far nicer to work with than 5/6A ones. Even with small fingers they get very irritating - especially when you start losing the grub screws within loft insulation

And back to the OP, if you knew where you were putting them was a bad idea why did you still do it? Why didn't you tell your heavy handed plasterer that you were going to bill him for an electrician to carry out the remedial work. At least then when your lights go out you won't have to rip apart your house to find some JB's stuffed inside a wall cavity.

 

[green121]

Thanks for your help davey_owen.
I should have billed him. At the time i thought i was doing right. hindsight is a wonderful thing! To be honest being a Sunday i panicked, i just wanted to sort the problem. Then after thinking about it, i started to worry.

 

[CallEdsFirst]

I've compared a 5A JB and a 6A JB and the terminals are identical. Plus a 6A lighting circuit is very rarely going to be carrying 6A and in this case is only going to carry the load of the 2-way lighting and a smoke alarm.

I'm not predicting a problem, merely being technical! It just screams of a failure to arse cover yourself if you install items not rated (identical or not, they are 5a rated) higher than the overcurrent device protecting the circuit. You wouldn't install cable capable of only 31a on a circuit with a 32a MCB because the cable then becomes the weakest link/fuse (fuselink?)

Rarely or not, it could run at 5.99 amps all year, melting the terminals in the JBs and still not tripping the MCB.

This coupled to the fact that the JBs are not accessible means its a bodge. No matter how fine a line there is dividing bodge from professional install, its still the wrong side of it.

I agree that the plasterer caused the actual issue, but the electrician also failed to protect his installation adequately too. Perhaps they should go halves!!!!!

 

[green121]

I have another question/point. Sheds sell 5amp jb's but the lowest mcb I have seen (in my very limited experience) is 6amp. Why would they ever sell 5amp jb's?

 

[CallEdsFirst]

There are OCPD devices lower than 6a, just not as common.

Mem for instance go to 1a as do most, certainly those in industrial markets. Hager do a 0.5a type C!!!

http://www.memonline.com/f05.html


WARNING PDF Link!
http://download.hager.com/hagergrou...ger_Product_Information/4 HagerProtection.pdf

Not that this truly answers the question, but it gives you an idea that what is a available in sheds is not the sum total of the product range available, but you knew this already!

 

[davy_owen_88]

My point is that a 1A overload is not going to destroy a 5A JB. Simply consider the size of the terminals compared to the cables that you are joining. If you get a good connection between the cables then the junction box will be fine. On the same note, if you fitted a 60A JB and made a ****-poor connection, the jb is going to be toast.

P.S I don't know why I'm arguing my point, I don't fit lower than 20A JB's anyway, due to them being far easier to work on

I have another question/point. Sheds sell 5amp jb's but the lowest mcb I have seen (in my very limited experience) is 6amp. Why would they ever sell 5amp jb's?

Because standard 3036 fuses came in 5A/15A/30A sizes and then when MCB's become the norm the standard sizes became 6A/16A/32A. They still sell 5A JB's because people still have 5A circuits.

 

[CallEdsFirst]

My point is that a 1A overload is not going to destroy a 5A JB. Simply consider the size of the terminals compared to the cables that you are joining. If you get a good connection between the cables then the junction box will be fine. On the same note, if you fitted a 60A JB and made a p**s-poor connection, the jb is going to be toast in no time.

P.S I don't know why I'm arguing my point, I don't fit lower than 20A JB's anyway, due to them being far easier to work on

And my point is we're not talking practicality, but regs! Nobody ever said they made sense! Underrated components not sufficiently protected could theoretically get you in bother.

And none of us want that!

 

[davy_owen_88]

Agreed!

 

[CallEdsFirst]

You're just giving in so I shut up!!!!

You and your 20a JBs! "I overrate everything, look at me!" Come on! Fight me!

 

[green121]

Calm down people! I only wanted some FRIENDLY advise. Thankyou both for your time.