EV charge point 6mm cable??? Help!

[royhails]

Help please! I need a Tesla Gen 2 EV charger fitted in my garage which is 22m from the consumer unit. My electrician is proposing to route a 6mm cable through pre-existing plastic conduit which has a cable in already and through a void in concrete walls to a sub-consumer unit at the charge point. My very limited knowledge of electrics makes me worry that the cable is not big enough. Also can you site the sub-unit so far from the main consumer unit? The SPD and RCBO will be in that sub-box he says. Advice needed please

 

[MJPD29]

Help please! I need a Tesla Gen 2 EV charger fitted in my garage which is 22m from the consumer unit. My electrician is proposing to route a 6mm cable through pre-existing plastic conduit which has a cable in already and through a void in concrete walls to a sub-consumer unit at the charge point. My very limited knowledge of electrics makes me worry that the cable is not big enough. Also can you site the sub-unit so far from the main consumer unit? The SPD and RCBO will be in that sub-box he says. Advice needed please

Not enough information given here to help. What size is the charger? (Kw)? Is the existing conduit contained in insulation inside the wall? What type of cable is it? Why do you think it’s not big enough?

 

[davesparks]

The second CU can be any distance away from the main one as long as the circuit feeding it is properly designed for the distance.

What size power supply is specified for the charger?

 

[Alan Beard]

In nearly all cases 6mm is a large enough cable, assuming this is a standard domestic tesla EV charger with 7kw output.

Some things to be aware off.
Unlike most EV chargers sold in the UK the tesla unit does not have open pen detection and therefore needs a consumer unit with open pen detection or the supply for the building needs to be on a TT earth, your electrician should know what I am talking about but may not know the Tesla units need to be treated differently.

Any EV charger in the UK needs to be connected to the internet, normally by wifi, make sure you have decent wifi for the charger and car. Many chargers benefit from being able to modulate output to manage overall load on the incoming supply or using excess from solar generation. To do this they need a data connection back to the incoming supply, I don't think the tesla does this but personally I would suggest putting in a supply cable that's combined power and data to be future proof, and or get a data connection to the garage. I would normally do this using EV ultra cable. More expensive but much more future proof.


Also make sure the electrician registers the charger with your DNO, provides an electrical installation certificate and notifies the local authority about the installation.

 

[royhails]

Not enough information given here to help. What size is the charger? (Kw)? Is the existing conduit contained in insulation inside the wall? What type of cable is it? Why do you think it’s not big enough?

The second CU can be any distance away from the main one as long as the circuit feeding it is properly designed for the distance.

What size power supply is specified for the charger?

Thanks for the reply- 7kW

 

[royhails]

Not enough information given here to help. What size is the charger? (Kw)? Is the existing conduit contained in insulation inside the wall? What type of cable is it? Why do you think it’s not big enough?

 

[royhails]

In nearly all cases 6mm is a large enough cable, assuming this is a standard domestic tesla EV charger with 7kw output.

Some things to be aware off.
Unlike most EV chargers sold in the UK the tesla unit does not have open pen detection and therefore needs a consumer unit with open pen detection or the supply for the building needs to be on a TT earth, your electrician should know what I am talking about but may not know the Tesla units need to be treated differently.

Any EV charger in the UK needs to be connected to the internet, normally by wifi, make sure you have decent wifi for the charger and car. Many chargers benefit from being able to modulate output to manage overall load on the incoming supply or using excess from solar generation. To do this they need a data connection back to the incoming supply, I don't think the tesla does this but personally I would suggest putting in a supply cable that's combined power and data to be future proof, and or get a data connection to the garage. I would normally do this using EV ultra cable. More expensive but much more future proof.


Also make sure the electrician registers the charger with your DNO, provides an electrical installation certificate and notifies the local authority about the installation.

 

[royhails]

These are my calculations

 

[timhoward]

While you could arguably tweak the supply voltage and the slightly optimistic ambient temperature, the main thing affecting this is the installation method of 'conduit'.
What cable type are you considering?
Does it actually need to be in conduit?
How long is the conduit?

For example 4 sq mm SWA clipped direct would happily carry 49 amps (before any derating).

 

[royhails]

While you could arguably tweak the supply voltage and the slightly optimistic ambient temperature, the main thing affecting this is the installation method of 'conduit'.
What cable type are you considering?
Does it actually need to be in conduit?
How long is the conduit?

For example 4 sq mm SWA clipped direct would happily carry 49 amps (before any derating).

Thanks for the response, much appreciated. The conduit is probably around 22m long with a cable already in it. All 22m are buried into the concrete walls, floors, ceilings of the house. Temperature here occasionally hits mid 30s. As I’m calculating from the On-Site Guide18th edition what isn’t correct then? I love the maths around cable selection and thought they were accurate