30A JB's and 32A ring final circuits

[ExArmy]

JB under floorboards covered by carpet is inaccessible, simple.
Using JB's in this day and age when we have Wagos and lineproducts....Inexcusable. Why even argue the point when we have quick and easy MF kits available.

why indeed, wagos are much quicker and easier to install! and i don't pay for them, the customer does, not that it matters as the labour saving evens it out

 

[jamesBoater]

a also if 30A JB's were not sufficient why do wholesalers not stock a 32A jb?

wholesalers do stock 32 amp Junction boxes we use the Hager MF ones when needed.

 

[MDJ]

ive been having a dispute with another electrician about using 30A JB's on rings

a ring is made up of 2 legs of 2.5mm T+E,
2.5mm T+E ref method C has current carrying capacity of 27A

now surely the JB has to be rated higher than the cable, but using a 30A jb although this is less than the 32A MCB its only joining one half of the circuit and is still higher than the rating of the cable
the arguement is that he thinks i should be using 45A JB's as they are rated above the MCB

whats peoples feeling on this matter as this is the first electrician ive met in 10 years that ever had a problem joining a ring with 30A JB's

i also did a little reasearch and although i couldnt find the correct reference in the regs book wikipedia stated that the cable size in a ring should be rated at no less than 2/3 ( two thirds) of the MCB
meaning that the cable rating has to at least be 21.333A so a 30A jb would be sufficient by 8.66A

a also if 30A JB's were not sufficient why do wholesalers not stock a 32A jb?

You only join one leg though in the JB and that's rated at nowhere near 32amp???

 

[rattlehead85]

under the floor is not accessible. what happens when someone puts down laminate, vinyl or glued down lino??

Then your stuffed if a fault appears. Hammer and Chisel and an angry tenant is the scenario.

 

[elliot123]

Going back since when did metal back boxes not have to be earthed? Only an apprentice but have always been taught earth my back boxes college and onsite

 

[Guitarist]

Going back since when did metal back boxes not have to be earthed? Only an apprentice but have always been taught earth my back boxes college and onsite

If a backbox has at least 1 fixed lug, then it does not need to be earthed. That said, I always do, as do many "old school" electricians.

 

[elliot123]

Spouse you learn something new everyday, only takes a minute extra to put a earth in so won't stop

 

[telectrix]

that came in round about 2004 or a bit before. under 16th. still good practice to fit a fly lead though.

 

[Guitarist]

Spouse you learn something new everyday, only takes a minute extra to put a earth in so won't stop

Not sure that I like being called your spouse.... My wife may have something to say about that....

 

[Guitarist]

that came in round about 2004 or a bit before. under 16th. still good practice to fit a fly lead though.

Indeed.

 

[Brightspark2]

Using JB's in this day and age when we have Wagos and lineproducts....Inexcusable.

The Hager MF JB's are good. I like them...


Also OP under the floor is definitely inaccessible!...

 

[amo]

Yes use crimps or run a new length of cable

 

[Tiny Spark]

I always do, as do many "old school" electricians.

Oiii!!

Who you calling old!?

 

[gazj82]

What are your guys thoughts on in line crimps on steel trunking. Got told by some other sparks, it's not in an acessable enclosure, or an acceptable joint.

I told him he was talking rubbish. It's the same as the lugs you crimp on in your mains incoming cables! And if trunking isn't accesible when it has a lid! Well! I won't even say the words I thought to sum him up

What are your thoughts?

 

[davethsparky]

Well with health and safety considerations you may actually need two people to safely manoeuvre a full length trunking lid so you may need to cut a short length just to cover the joint. Then you'd best put a big yellow sticker on it warning of the maximum voltage present. Then a big label identifying the fact that the joint is there. And install a light near it so that you can see it properly and record its location on the plans. And get the trunking tested to ensure it meets all the current product standards for an enclosure.

Jeez its a big metal box designed specifically to contain electrical wiring, who on earth says you can't have a maintainance free joint in there? Hell a lot of it is accessible so you could use your screw terminals of choice, everyone loves to pop the lid off of a trunking and get attacked by sprawling connector blocks!

 

[Lucien Nunes]

The trick is to put the choc block inside a trunking tee or other junction so that when it burns out, you can get at it without taking off a full length of lid. There was a long story behind the pic below but it reminded me why I don't like even MF connections in trunking except for very special situations.

Going back to the OP, what makes a 30A JB a 30A JB? That's the number moulded into the plastic but what does it mean? Under some conditions it's no good for even 15A (Slightly corroded 2.5 lying badly in the terminals, slack screws, installation method pushing cable near max permissible temp) and others its OK for 40 (clean 6.0 meshed together, tight but not overtight screws, low ambient). Even if the whole 32A was on the one JB you could argue the ----, on an RFC you have a comfortable margin.

 

[davethsparky]

Tut tut, trunking lids missing! that's got to be a C2 sir, but what I can do for you is sell you a nice shiny new consumer unit!

 

[SplitJugular]

But in your example you were saying under the floor boards, under the carpet - which is INACCESSIBLE.

Accessible is within reach without having to lift a floor board or moving a 120KG American Fridge Freezer

ok so what you are saying is that the socket behind a 120KG fridge is inaccessible, if that fridge has a 13a plug top then its a portable appliance.


in reply to many other posters on this matter, surely under the floor is inaccessible full stop then, if under boards is ok without carpet, can i tell the customer that they can NEVER put carpet\lamanate down as there are joints under the floor

with enough determination you can get anywhere you need and the level of expected damage when carrying out work is a matter that needs to be discussed with the customer, as i stated earlier if a plasterer re plastered a room and plastered round all the light switches and sockets then you could only remove said sockets or switches by 'scoring' round the edge with a knife and do your best to minimalise damage, these facts did not make the sockets or switches inaccessable its no different to puling up a carpet, i feel that an electrician that doesnt want to pull up a carpet for fear of damage is either imcomputent or lazy.

 

[SplitJugular]

JB under floorboards covered by carpet is inaccessible, simple.
Using JB's in this day and age when we have Wagos and lineproducts....Inexcusable. Why even argue the point when we have quick and easy MF kits available.

dont get me started with this, basically the bloke is the one guy from the council that dishes out a bit of work to us self employed, so i like the work but not this guy, sticky situation,
im all for wagos and push in connectors but he wont let me use the push in connectors i prefer, even though on the box it says suitable for 2.5mm cores and aits rated to 27A (which as i found out is more than enough for RFC) he tells me that i should use a 45A JB, he wont even let me use crimps. recently had to move some dis-boards down to accessible levels and when joining all my cables he wants to use din-rail connectors, nothing wrong with crimps in my experience except when you get those sily crimpers that only work one way??
ultimatly this guy is a complete tool

 

[7029 dave]

an electrician that doesnt want to pull up a carpet for fear of damage is either imcomputent or lazy. Its all part of the job isn't it?