My water heater switch is located in the service yard.  It is just beneath the distribution box.  When I unscrew the switch, I found that the wire behind it is very short and is not possible for me to change it.   I tried pulling the wire down a bit but there isn't much to pull.  The wire comes out from the distribution box and it comes out from a hole made in the distribution box.  The hole has a rubber ring around it.

I wonder how is it possible that the wire is so short ?  Does it mean I have to open up the distribution box ?  But it very dangerous to open the distribution box as there's where the main supply comes in.

Could anyone advise me how to change this switch ?  Thanks you very much.

Could be the electrician had wired the switch first before terminating at the distribution box hence the short wiring. 

You can turn off the in coming power supply by flipping the circuit breakers to off before opening the distribution box. Then do what you need to do and close back the DB before turning on the power supply again. 

I suggest you use a test pen as well to check if the power is confirmed cut off before removing the switch.. 

If you have totally zero knowledge, then best is call for an electrician to do it for you. 230V shouldn’t kill you but will still give you a nasty shock. 

I'm trying to picture what you're trying to say, please correct me if i'm wrong:

1. You're trying to change the water heat switch (i presume the switch is faulty?), but the wiring is too short for your liking.

2. The wiring to the switch may have come loose because it is too short? Maybe that's the reason why switch is faulty?

Either way, it seems like you'll need to extend the wiring.

If there's access, why not get yourself some connectors and extend the wires? See below.

Probably the electrician who install it provided just sufficient cable length to get his job done.

I had a similar problem with my hall light switch (also just below the DB). I was able to re-do it myself.

But my take is: for u to ask this question here, best you get a qualified electrician to re-do it.

Edited April 14, 20188 yr by w7_lee