Shower

[wba123]

I have just replaced a like for like shower and when i turn the shower on the neutral is becoming live....please help as i have had the shower manufactuer's engineer in and he said that the cable was not the correct size...however i can't see how the size of the cable would make the neutral become live

 

[xAlex]

...does the neutral become live when you turn the shower on?, or when it's off?

 

[wba123]

only when you switch it on

 

[Steve]

How are you testing it?

 

[wba123]

i've tested the neutral with a tester screwdriver

 

[Steve]

i've tested the neutral with a tester screwdriver

Throw it away and stop panicing. Go out and buy a multimeter. I cant believe they sent an engineer on the basis of a test done with a neon screwdriver. They are notoriously unreliable


Though if the ngineer said the cable is undersized, this really should be fixed. Provide more detail. Wattage of shower, distance, any insulation around cable, MCB size?

 

[xAlex]

...All neutral wires are live when you switch the appliance on.

 

[wba123]

10mm twin & earth / 40amp cb about a 20 foot (max) from the C/U....any ideas ? 8.5KW

 

[Steve]

10mm twin & earth / 40amp cb about a 20 foot (max) from the C/U....any ideas ?

Thats fine. 10mm is the biggest cable you'll need for the average shower install.

Neutral is carrying current when the shower is on. Thats why it lights your neon screwdriver, though I once held my neon to the electric meter's plastic casing and it lit up. Very unreliable. Only good at tightening screws (even then they struggle)

 

[wba123]

Alex should the bulb come on in the tester screwdriver when you touch the nuetral ?

 

[Steve]

Alex should the bulb come on in the tester screwdriver when you touch the nuetral ?

The bulb in the tester can come on whenever it wants. I told you, they are VERY unreliable! Throw it away and buy a multimeter. Oh, and stop playing with live wires!!!

 

[xAlex]

...yep, the bulb should come on when the shower is switched on. But as Steve said, it could also come on when the cable is not live and the shower is switched off, due to the test instrument being very unreliable. If the neutral was live with the shower off (which you could not say for sure with your screwdriver), then there would be a problem (a short circuit), in which case the MCB should trip, or if not the wire would probably melt.