Electric Socket Warm

[malagabob]

I’ve installed a electricity supply to a new shed. I’ve taken the supply off the back of an existing power outlet, through the outside wall to an all weather outlet box. From there via a 3 pin fused plug to the shed via 1/2 armoured cable to a double three pin back box and plate which incorporates a trip. This box is, I noticed warm, not hot. I intend to only have power to the shed when needed,switching off at the all weather box. What could be causing the back box to be getting warm tIA.

[Electrochem]

You fall foul of current (no pun intended) regulations:

https://www.electricalsafetyfirst.org.uk/find-an-electrician/building-regulations/england/

I can't answer your question, but it seems a pretty amateur way to do it!

[The Builder]

To answer Electrochem's point, Bob....
Of course it's a good idea to have an electrician carry out this kind of work, but Building Control don't necessarily have to be notified.
New circuits are notifiable, but if this is just an extension to an existing circuit, it's not necessary unless it's somewhere such as a bathroom.

I agree with Electro. I wouldn't have done it that way.
Could you tell me what you mean by 1/2 armoured cable, Bob?
Also, is the circuit protected by an RCD actually in the house, as well as the one in the shed?

As for warming. Normal for high loads such as 3kw. Or even smaller loads for extended periods.
Loose wiring connections can do this.
Even loose contacts within the socket. (Where the pins go in.)

[malagabob]

The socket that is getting warm is of the 2 outlet type. It also incorporates a circuit breaker. I’ve checked the wiring connections twice to make sure they’re tight, and am tightening down on wire not on the insulation.
Armoured cable is for outdoor use. It has insulated copper wire E,L,N. These are also insulated as a group. There is a galvanised wire shroud around this (the armour) Everything is encased in more insulation.
The feed I suppose you could call it a spur which is feeding the shed Is only feeding a wall socket in house into which only a chest freezer is connected. This is the only appliance. I’ve checked this by removing isolating other fuses in consumer box, and checking what other circuit/appliances aren’t working.
Yes there is a RCD in the line in question. In the house consumer box. TIA.

[The Builder]

Ok Bob. That's fine. You have RCD protection on that circuit at the board.
The reason I asked is that if it weren't there, you would have a length of cable (to the shed) which would not be protected in the event of an earth fault. That's what I meant when I said I wouldn't do it that way.

I would have possibly used an exterior waterproof outlet with built-in RCD.
While I'm at it. The armour should also be earthed, even though you have a green earth core. This might sound picky, but it is a requirement of the regs.
The reason is that if you managed to slice into the armoured cable and short out the armour to the live, then the house RCD may possibly not save you since you would have no fault route back to earth. The route must be to earth to operate the RCD.

Back to the plot. And I should have thought of this earlier.
RCD sockets take a little current to operate their mechanism. They are basically two little solenoids (Live & Neutral) that keep a plunger in balance. (If the two sides are not equal because of an earth leak, then the plunger flies over to one side and shuts everything off.)

That's most likely where the bit of warmth is coming from.
As Mr. Sqad would say... no big deal ;o)

[malagabob]

Thanks builder. I have as a way of checking, temporary fitted a good make “MK“ double outlet. All seems ok . Not getting warm. So it proves what you say. The power outlet with integrated breaker gets warm under normal use. Thanks again.