Immersion Heater in 1.5mm flex

[tomodo]

Hi guys rewiring an immersion heater from a double pole 20amp switch, circuit is wired in 2.5mm t+e up to DP switch. What are peoples thoughts on using 1.5mm flex the regs state that this is capable of carrying u to 16 amps ,would prefer to use 2.5mm flex but can not find a 20amp dp switch with a flex outlet to take a 2.5mm flex ...

circuit is on 16amp breaker and flex run is about 1 metre.

Thanks

 

[davesparks]

1.5 is the normal size to use, 2.5 is normally too big for both the 20A DP switch and the immersion heater.

 

[Simonslimline]

Cant you use a Double pole switched fuse connection unit instead of the 20A double pole?

 

[davesparks]

Cant you use a Double pole switched fuse connection unit instead of the 20A double pole?

Why? That wouldn't achieve anything other than inconvenience when the fuse becomes tired from running at its rating for long periods of time.

 

[andyb]

1.5 butyl, always used it.

 

[Simonslimline]

Why? That wouldn't achieve anything other than inconvenience when the fuse becomes tired from running at its rating for long periods of time.

Ok fair point.

Regarding the 2.5mm2 & flex, would 433.3.1 (ii) not come in to play here?

 

[7029 dave]

1.5m butyl is plenty big enough.

 

[Darkwood]

Yep the butyl 1.5mm is the best choice as has been stated, it has a greater heat tolerance and won't break down at the Imm' heater terminals due to the heat.

 

[tomodo]

What is reg 433.3.1? haven't got Reg book on me atm ...

Thanks for the replys

 

[Richard Burns]

What is reg 433.3.1? haven't got Reg book on me atm ...

Thanks for the replys

It is whether you need to have overload protection.
In this case the immersion can be normal operation or full fault current, nothing in between, so overload does not happen and does not need to be protected against.

 

[GEOFF S]

Hi


1.5 is pushing it if its a 3kw element, best to use 2.5mm cable.

Cheers

 

[Leesparkykent]

Hi


1.5 is pushing it if its a 3kw element, best to use 2.5mm cable.

Cheers

Why's it pushing it?

 

[davesparks]

Hi


1.5 is pushing it if its a 3kw element, best to use 2.5mm cable.

Cheers

How on earth is that pushing it? 13A through a cable rated for a constant current of 16A is not pushing it.

 

[7029 dave]

Hi


1.5 is pushing it if its a 3kw element, best to use 2.5mm cable.

Cheers

Which most are,why's that then.?

 

[Amp David]

Which reg relates to 'pushing it'?