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I think the question title says it all:

Given a distribution board in the house (220 VAC), is it enough to shut off only the room's fuses, or must one shut off the main switch for the board before safely touching wires?

Does the answer depend in any way on the fuse type?

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  • you should double check that the power is off with a tester Dec 14 '14 at 21:24
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And here is why you check it before hand, even though you have turned off that room. People get into Junction boxes and re-wire - joining two separate circuits into one - in that case one circuit in the house can be fed from two breakers (as long as they are on the same phase). Always check with testor - and NOT JUST a proximity induction testor - but an actual touch the wires testor. OK. Be safe.

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    WHY in the world would someone combine two breakers to one circuit??? The only time I have seen this was when someone who didn't know what they were doing did some wiring. Dec 15 '14 at 11:52
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    @SpeedyPetey: I think you've answered your own question. Someone did something that they thought was "clever"....
    – keshlam
    Dec 15 '14 at 17:50
  • I have come across this situation more than once. Originally there were two different circuits in a J box in an attic. At some later time someone must have opened it up and then connected all the blacks together and all the whites etc. Being that they were on the same phase they did not realize their mistake - I only found it when trying to isolate the breaker for a particular outlet. It required both fuses to be turned off. Dec 16 '14 at 4:00
  • @SpeedyPetey: I've seen the following case with my own eyes: Several circuits correctly wired to several breakers were mounted into a common conduit and run across a whole building. Due to another failure a hidden cable fire took place destroying the insulation of the cables in the conduit. Different circuits mated and created a crossed wiring without being noticed by either user and electrician. circuits were under power by either of the two breakers. Only thorough testing before work prevents accidents in such cases.
    – Ariser
    Aug 19 '15 at 9:09
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You say "that room". Circuits are not nearly always designated to one room or area. Many, many times a room will have some devices on one circuit while others on another circuit. It is pretty rare that rooms are strictly wired so that one circuit distinctly feeds one room.

Also, panel directories are not always extremely accurate. So something that says the breaker is for one room might also have other things one it.

Again, a tester is the ONLY way to be sure what you are working on is dead. IMO you should not even pick up a tool or open a box until you are in possession of a decent tester.

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Yes. Once you shut off the room fuse, no electricity will be going to that room.

However it is important to test all connections before working on them so you are positive that they are not powered.

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