1mm cable on 1.5mm lighting circuit

[scottscott]

My lighting circuit consists of 1.5mm cable, I want to add an extractor fan which would share a switch with the room light but the fan states a maximum 1mm supply cable. Do I have to install the fan on a separate circuit?
Thanks

 

[daytona]

you cant install it on a separate circuit if its going to come on with the light.
the reason it states 1mm max is probably a csa issue.sometimes you will struggle to get a 1.5 in the fan terminals.
personally i been using 1mm for fans for over 20 years and never had an issue.


one more point,dont forget to apply all the regs for a fan install in a special location. zones,bonding,notification etc

 

[scottscott]

Thanks Daytona, the lights and fan are in a new bathroom and so will be inspected by someone from the building regs. Are there any safety issues in putting the 1mm cable within a 1.5mm circuit? I imagine doing this would automatically downgrade the whole circuit.

 

[daytona]

no,not if your adding a fan.
your only going to add a very small load which will be spurred from the bathroom light fitting.1mm can carry 6 amp ok .
sensible question to ask though!

 

[1 interceptor]

Daytona seems to have covered this quite well, and like he said, the reason for the 1mm CSA cable is due to the terminals on the fan and the low consumption of the fan unit..just be careful not to try and overtighten the connectors on the PCB as they are only soldered into place and can break the solder connection on the PCB..

 

[Spark123]

It normally isn't a problem, a 1mm twin and earth cable is rated 16A without any correction factors. Just to check, how is the cable installed? Does it come into contact with thermal insulation? Is it grouped with any other cables? Does the ambient temperature exceed 30deg C? Is the circuit fed from a rewirable fuse? How long a length of 1mm are we talking?

 

[scottscott]

Thanks for all of the replies, to answer all of Spark123's questions:
The cable will be chased into the wall, although in the loft cavity it may come into contact with the thermal insulation (glass fibre). It won't be grouped with any other cable. The ambient temperature is very unlikely to exceed 30C. The circuit is fed from a Hager consumer unit which has mini-circuit breakers but I don't think it has re-wirable fuses (one has never blown so I haven't been inside it). The length of 1mm will not exceed 2m.

 

[daytona]

pukka!

time to get the tools out!