I want to replace a standard wall socket with a new USB which looks something like this...

enter image description here

The instructions say to turn off the power for the socket. I went to the master house control and took a picture...

enter image description here

I assume that I can turn the power off with the big switch on the right that currently shows "ON". I do not know if this must work in concert with the objects containing white, blue, and red dots (don't know what they are).

Question: If I switch it "OFF" will it turn off the power?

Ancillary questions:

  1. Does anything need to be done prior to switching it off? Are the objects to the left involved in any way?

  2. Does switching it off invite any disastrous consequences that I should be aware of?

  3. Does anything need to be done prior to restoring power? Will the house suffer from thermal shock?

As a final thought, if the picture gives an idea of the date or age, I would be grateful. I have been assuming the house is 1940's British Pebbledash.

  • 2
    My gut reaction? You're risking life and home. You need to have at least some knowledge of electrical systems before you do things like this, or you're likely to get into serious trouble. We can't compensate by per-incident instruction; you need to get your bulk knowledge elsewhere. (Sorry.) Commented Feb 15, 2016 at 12:29
  • 2
    As an aside, it's worthwhile figuring out what each of those fuses cover and writing them on them, so in future you can just take out the specific fuse for the area you want to work on.
    – Rory Alsop
    Commented Feb 15, 2016 at 12:59
  • 1
    If you ever want to sell the house, you may be asked for an "Electrical Installation Certificate" for any works carried out while the property was in your possession - changing electrical sockets is a "non-notifiable work" but in your case you are not carrying out a 1:1 replacement, so the work could indeed become "notifiable" and you may need for it to be signed off by a certified professional.
    – Moo
    Commented Feb 15, 2016 at 13:13
  • 1
    USB-enabled socket is pretty much a regular socket with a usb-charger permanently plugged it. Using regular charger is both more flexible (eg you can use 2A charger for bigger devices) and more eco as you can unplug it when not used to save power.
    – Agent_L
    Commented Feb 15, 2016 at 15:58
  • 1
    Agent_L - these are actually much better than using chargers. They draw no current when nothing is plugged in; they are typically more efficient and produce less heat; they are much safer; and they don't take up space! I just re-did my house with the 2.5A versions, for all of the above reasons.
    – Rory Alsop
    Commented Feb 16, 2016 at 0:10

1 Answer 1


Yes flipping the switch will turn the power off. You will still want to double check at the outlet with a voltage tester.

The objects to the left are fuses and are color coded to the amperage which you can also see embossed on the front (red is 30 amps; blue is 15 amps and I can't read the white one). If one blows then you will probably want to replace the entire panel for one with resetable fuses as I don't think you'll be able to find replacements easily anymore. It's also possible that a previous owner added a bypass wire at the back of a blown fuse. This is not something you want to keep in place.

Remember that the power to everything will be cut including lights and your fridge; freezer and computer. If anything can't handle a sudden power outage well then shut it down before cutting the power.

If you have appliances with an induction motor (like a pump or a blower) then the current may spike when you turn the power back on and blow a fuse. If you have several then disconnect them and after you turn the power back on reconnect them one by one.

  • 2
    Those fuses probably don't need replacement fuses - they are very likely to be rewireable fuses. If one blows, you replace the (blown) wire with another length of fuse wire of the appropriate rating.
    – John
    Commented Feb 15, 2016 at 13:57
  • 1
    white was always 5A lighting circuit
    – Rory Alsop
    Commented Feb 16, 2016 at 0:12
  • 1
    @John assuming the previous owner always used correctly-rated wire when replacing. Commented Feb 21, 2016 at 15:03

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