re-wiring a shower

[paulturner1974]

the cross section is 6mm which is rated up to 38amp, there is a rcd, the fuse box unit has been replaced recentley the old one was a 32 amp fuse and so is the new one (so two different sparkys have installed them) the run is appox 15m from fusebox to iisolation switch then approx 3m from switch to shower
the shower has been installed about 2 years the wiring about 8 hope this helps

 

[ban-all-sheds]

the cross section is 6mm which is rated up to 38amp

35A if in an insulated wall but with one side touching a thermally conductive surface.

32A if installed in conduit in an insulated wall but with one side of the conduit touching a thermally conductive surface.

23.5A if completely surrounded by insulation.

the run is appox 15m from fusebox to iisolation switch then approx 3m from switch to shower

OK for voltage drop.

 

[paulturner1974]

so how can i extend the wires by a foot without ripping the entire bathroom to bits if 30amp connectors arent any good

 

[SeanT]

Get someone to crimp it.

 

[paulturner1974]

maplins do crimping stuff will that work?
http://www.maplin.co.uk/Module.aspx?ModuleNo=44094&C=Maplin&U=SearchTop&T=crimping&doy=28m3

using the 6mm connectors?

just asked and they said no way help

 

[ban-all-sheds]

That's the wrong sort of crimp tool.

You need one like this:



But 30A is not the end of the line for choc-block, it goes up to 60A at least. Gets a bit big though....

 

[paulturner1974]

just been on the blower with a local sparky he said the best way to go is to extent the wire at the switch end using a 30amp juction box and pull some wire thru at shower end if i cant do that to use 30amp connectors at the shower end and tape them up to make sure no water can get in can any of you give me your thoughts and recomendations on this please

 

[Chivers7]

Back to basics on this:

Co-Ordination between conductor & protective device

In = current setting of device - circuit breaker

Ib = design current of circuit (shower rating divided by voltage)

Iz = current carrying capacity of conductors

Ib < In < Iz

The shower is 8.5 kw which gives 35.4 to 37 amps so the fuse needs to be above this or at worst equal to this not below, at present it is 32 amps so the fuse is being overloaded.
It won't trip as the current isn't high enough to trip it but it is being overloaded.

The fuse needs to be 40 amps IMO the cable supplying the cable is below this so needs upgrading to 10mm that's what I'd do personally.

I'm not sure why any sparky is advising you to use a 30amp junction box for a shower that uses more current than it's rating.

At least there is an RCD present but when was this last checked, Pablo it should be tested quarterly at worst for mechanical operation

Shoot me down any of you that are more experienced