EV Consumer unit 16mm tails

[SteveSparks]

This is a very random question that doesnt relate to anything I'm doing in the real world - I'm a commercial electrician and I've never istalled an EV charger.

I've noticed on many YouTube videos that 16mm tails are commonly used to supply a seperate designated CU for EV chargers. I'm not questioning the safety, but I am questioning the justification for its selection. As far as I can see, 25mm tails are required when on 100A main fuse - I can't find anything that gives any exception to this rule.

I know (in the real world) 16mm tails are perfectly safe for a CU soley feeding an EV charger - but does it not (theroretically) make the installation non-compliant?

This may well be a really stupid question to many of you - this isn't my field, I'm just curious

 

[happysteve]

Conductors need to be suitable for overload (taking into account installation methods etc), and fault protection.

Assuming there are no issues with insulation, grouping etc, then overload is fine because the nature of the load will mean the current carrying capacity of the cable is never exceeded.

In theory you could use the adiabatic equation to determine whether 16mm tails are sufficient or not... but bear in mind that the earthing conductor is 16mm, so if 16mm is not sufficient then... well... I have questions.

 

[Avo Mk8]

This may well be a really stupid question to many of you - this isn't my field, I'm just curious

You should see at the bottom of this page under "Similar threads" it now shows a similar post to yours from last year - "EV consumer unit tails".
Might be of interest!

(EV consumer unit tails - in - UK Electrical Forum - https://www.electriciansforums.net/threads/ev-consumer-unit-tails.214566/)

 

[SteveSparks]

Thanks Steve,

I get that, I'm maybe overthinking things in this instance. I was under the impression that 25mm tails were required with a 100A main fuse, without exception. Regardless of the adiabatic equation, in my mind I thought this was a requirement we had to adhere to.

I maybe held that belief through heresay, that I have misinturpreted

 

[happysteve]

No worries! It's a useful rule of thumb, in a "paint by numbers" sort of way. You'll not find a Reg saying that, though

 

[SteveSparks]

You should see at the bottom of this page under "Similar threads" it now shows a similar post to yours from last year - "EV consumer unit tails".
Might be of interest!

(EV consumer unit tails - in - UK Electrical Forum - https://www.electriciansforums.net/threads/ev-consumer-unit-tails.214566/)

Apologies, I should have searched for that. I just read through it - it all makes sense, I just thought it was a rule we couldn't deviate from. What I take from this is that we can determine the sizing to long as we can justify it.

 

[oscar21]

I usually get slated on here for saying things like this but - do you always do what you are told? We are capeable of making our own informed descisions every now and then.

 

[SteveSparks]

I usually get slated on here for saying things like this but - do you always do what you are told? We are capeable of making our own informed descisions every now and then.

Yes I am a goody two shoes

I agree, it just seems this is something I had misinturpreted.