Turn off the power at the double pole (pull Switch ) or mains if unsure . Inside the cover there should be a data label. telling you the power consumption in killowatts. Because you describe you shower as a 10000, I would guess that it is ten thousand watts or 10kw in new money. Always get a qualified or competant person to do the work. If your thinking of replacing your shower with a new one, say a 10.8kw. You need to determine what load this will exert on your supply cable and fuse expressed in amps. Because you 6mm cable is rated at so many amps I think its 32 amps you may consider upgrading to 10mm cable . A rough formula for working out the demand of you shower is to divide your 10kw (10,000watts) by your voltage which will give you your load expressed in amps so ! 10000 div 240 volts = 42 amps. So it may well be that your cable is not big enough for your current shower, especially if its a long run as this will cause voltage drops which will push up your amps.
Alan, December 2008
