Tiny workshop - extension lead?

[Jack Pattenden]

The MCB is sized to protect the wiring, the exact current rating of the wiring will be dependant on the type and size of cable fitted, and how it is installed as there are derating factors to consider depending on whether it is run through insulation or buried in a wall etc.
A double socket is normally rated at 20A, the 13A (or less) comes from the fuse in the plug top.

Key things to note is the assumption that you will not be pulling that load continuously through a socket, they are simply not designed to handle it. Think of a kettle - it runs at 3kw (~13A), but only for a couple of minutes max.
It is also assumed there is some diversity (i.e. you are not going to have two kettles plugged into every double socket in your house).
The 13A fuse does not blow at 13A, it actually takes quite a lot more than that for some time, depending on ambient temperature before it blows.

The problem you have is two fold. Firstly you are intending on pulling large continuous loads - which is why I suggested considering an EV socket as these are designed for continuous charging of an EV
Secondly the compressor will pull a large amount of inrush current on startup - this is what tends to blow the fuses in the plug top.

BS1362 fuses (i.e. the one in the plug) go to a maximum of 13A, because funnily enough that's what the plugs are rated to.
Even if you could find some sort of magic 16A one that would fit, it wouldn't necessarily solve the problem with the inrush current. Its also getting silly and dangerous.

The easiest and safest solution is to install another 16A or 20A breaker into the consumer unit on the RCD side of the board, and feed a 16A commando socket.
It could be mounted next to the consumer unit (if there is space) so there is no chasing of walls etc, and then just run a heavy duty 16A extension lead (2.5mm or 4mm H07 cable would be ideal) out to the balcony.
Then you can revert it should you need to vacate the property.

Alternatively you may just have to realign your expectations, ambitions and your equipment to suit your current situation.

You should also be aware that having the sockets on the non-RCD side of the board is a bad idea, surprised this hasn't been picked up.
At a minimum you will want RCD protection in your workshop.

I think another 16A breaker and a 16A commando socket at the consumer unit is a good shout and simple enough to do. I'll have space for it there.

Thank you!

 

[skotl]

I think another 16A breaker and a 16A commando socket at the consumer unit is a good shout and simple enough to do. I'll have space for it there.

Thank you!

Yep but you really, really should get a qualified spark to do that for you. There are many reasons but, being a rental and not your house, is the one I’ll put front and centre.

On the assumption that a qualified spark is doing it, has the requisite test equipment and is able to measure the earth impedance, then it makes sense to fit a C16 MCB rather than an a B16.