EV Charger Garage Supply

[deejay]

I'm looking at installing a 7kW EV charger on an outbuilding with the following characteristics:

• EV charger will be 60 metres from the main fuse where there is an initial small consumer unit in the meter cupboard.
• Currently there are 2 extra small consumer units for each outbuilding, each with an RCD as a main switch.
• EV charger will be at the furthest point beyond the third CU.
• The SWA to the first outbuilding is 6mm.
• The SWA between the buildings is also 6mm.
• There is a solar array on the outbuildings.

Having done the cable calculations for the 7kW charger, it looks like at least 10mm will be required. Am I correct in therefore assuming that I will have to run a completely separate supply cable to the outbuildings or replace the current one?

I just want to make sure that the current installation is not appropriate for the charger before digging a very large trench!

Any guidance would be appreciated. Thanks.

 

[buzzlightyear]

Having done the cable calculations for the 7kW charger, it looks like at least 10mm will be required. Am I correct in therefore assuming that I will have to run a completely separate supply cable to the outbuildings or replace the current one?

Looks like you need a bigger supply to out buildings

 

[Spoon]

Or change the EV you are getting. Some can use the solar power and the mains at the same time.
What EV are you thinking of getting?

 

[deejay]

Or change the EV you are getting. Some can use the solar power and the mains at the same time.
What EV are you thinking of getting?

It's a Zappi which can utilise the solar but my concern is if the charger is pulling 32A at night with a couple of electric heaters in the outbuildings. I don't think 6mm will be big enough?

 

[buzzlightyear]

It's a Zappi which can utilise the solar but my concern is if the charger is pulling 32A at night with a couple of electric heaters in the outbuildings. I don't think 6mm will be big enough

Bigger feed.

 

[Wilko]

Buzz is flying today !

My starting point is a 50A distribution circuit to accommodate the charger and two 2 kW heaters. 6mm buried is good for 46A (close ...) but for 5% voltage drop the run is 34m max at 46A. Even 10mm is only good for 52m at 50A, while 16mm is good for 82m.

If you stick with 6mm SWA on a 60m run with 32A load (only) the voltage drop will likely be about 15V. This is normally considered too much drop, as the installation supply might be as low as 217V and there would only be 202V at the charger after cable voltage drop. Looking at Zappi specs it seems to say 230V +/- 10%. If I’ve understood them correctly the minimum Zappi supply would be 207V and so this would likely not be ok.

On the other hand, it’s quite likely you will have 240V to start with, giving 225V at the charger and so be within Manufacturer specs.

Another way to look at this is from cost efficiency. 1000 charges of 40kWh at 15p per kWh will cost £6,000 . But you will lose about 15/240 of this in heating the cable, another effect of the cable voltage drop. That comes to £375, I think .

 

[deejay]

Thanks for the input guys. As suspected, it looks like it'll need a separate supply to be safe. I will suggest running another larger cable for the EV ?.

 

[pc1966]

It might be best to put in duct (if not already in) as then you can decide on power and any data cables at the time of install and pull it through.

 

[Gavin John Hyde]

with the correct use of CT clamps and harvi devices the existing supply may well be enough you can set the CT clamp settings to measure the load in the outbuilding(s) and the charger will use the spare capacity.
When the heaters are off the charger will speed up, when the heaters are on the charger will slow the charge.
If you read the instruciton booklet the settings will explain the application fo CT Clamps.
I have installed a Zappi in a similar situation, during the day the use of the other devices would overload the distribution circuit if the car was charging even with his solar pv, so installed 3 CT clamps one to monitor to main incoming supply, the other the Distribution circuit. another monitors the PV
Customer can use any excess capacity in the day to charge the car, - usually a mix of pv and grid at night the charger permits the full 7kw charge rate.
The zappi is by far and abode the best for grid monitoring and load management as some chargers can not process groups of circuits or distribution circuits, The myenergi tech team will talk you through the settings if required. they can even dial into the charger/hub to help you if needed.

 

[deejay]

with the correct use of CT clamps and harvi devices the existing supply may well be enough you can set the CT clamp settings to measure the load in the outbuilding(s) and the charger will use the spare capacity.
When the heaters are off the charger will speed up, when the heaters are on the charger will slow the charge.
If you read the instruciton booklet the settings will explain the application fo CT Clamps.
I have installed a Zappi in a similar situation, during the day the use of the other devices would overload the distribution circuit if the car was charging even with his solar pv, so installed 3 CT clamps one to monitor to main incoming supply, the other the Distribution circuit. another monitors the PV
Customer can use any excess capacity in the day to charge the car, - usually a mix of pv and grid at night the charger permits the full 7kw charge rate.
The zappi is by far and abode the best for grid monitoring and load management as some chargers can not process groups of circuits or distribution circuits, The myenergi tech team will talk you through the settings if required. they can even dial into the charger/hub to help you if needed.

Thanks for that. If the cable distance is 60 metres using 6mm, I would have to limit the Zappi to a max output of approximately 5.8kW (25 Amps) so as to avoid an excessive voltage drop. This would be the max output without anything else running in the outbuildings. Is this correct?

Any other tips/suggestions? It would make life a lot easier if I could utilise the 6mm cable that is already there but I think the cable just isn't big enough.