20A MCB on 32A EV Charger for 6.6kw car

[tim_n]

I've had a 32A charger installed under government funding for a 6.6kw electric car. My understanding is that the Nissan Leaf will pull around 27.5A. I'd want about 20-30% overhead on that to be safe, so a 40A MCB is required.

On the day of install, they only had 20A MCBs so they fitted that and said "Don't worry it'll be safe" - they'd be out in a week to fit the 40A MCB.

I've plugged the car in, no fires. But concerned that the MCB is the weak point and will be running at capacity rather than 20-30% below. Or am I worrying unnecessarily? It's a £2.78 item. Currently I'm running it off the 13A socket which has a specific lead with an inbuilt resistor to work off 13A sockets to be safe. I'm not sure how intelligent the car is when pulling a load of a 32A supply which is restricted to 20A.

 

[omega015]

First off why do you need 20-30% overhead to be safe? are you planning to run other items from this circuit? you already would have about 15% overhead on the stated rating of a 32a MCB if its pulling 27.5a. Also depending on the MCB type the trip current could be anywhere from 3-20 times the max rating.

Also there's some conflicting information here (unless I misread something), you state the lead has inbuilt resistors so it works of a 13a socket, in which case isn't it pulling 13a or less? so the 20a MCB is acceptable in this case. If this isn't the case then what your implying is the car/charger will be trying to pull 32a from a 13a socket and then that 20a MCB is the least of your worries.

A quick bit of google searching leads me to some information that this resistor tells the charger what the maximum current is available, so I assume this is a standard 13a lead with a 13a plug on it (and it hasn't been a diy job) in which case the charger will know to only pull 13a max, so again the 20a MCB is fine for this load.

 

[tim_n]

Perhaps I didn't explain well.

13a lead is for 13a only. It's for charging from places that don't have a fast charger. I'm using it because I do not want to use the 32A on a 20A MCB.

I have a 2nd 32A lead connected to a 32A charger. It has a separate consumer unit directly connected into the meter away from the main consumer unit. It is this consumer unit that has a 20A MCB. It is for faster charging. It is just a lead connected to the circuitry in the charger that plugs into the car. It's entirely possible there is intelligence in the podpoint to stop all these problems.

I thought the point of the MCB was to trip at points over their rating?

 

[EFLImpudence]

If I read it correctly, the 13A socket/plug and lead is an additional item being used instead as he is not sure about the charging circuit.

Other than that, yes, a 32A MCB should be fitted.

As for 3 - 20 times, that is for short-circuit or earth-fault.
Drawing 27.5A through a 20A MCB should cause it to trip in a bit over an hour.

 

[tim_n]

If I read it correctly, the 13A socket/plug and lead is an additional item being used instead as he is not sure about the charging circuit.

Other than that, yes, a 32A MCB should be fitted.

As for 3 - 20 times, that is for short-circuit or earth-fault.
Drawing 27.5A through a 20A MCB should cause it to trip in a bit over an hour.

correct!

 

[ban-all-sheds]

On the day of install, they only had 20A MCBs

Didn't they know what they were going to install? Not having the right parts is inexcusable. You really should complain, both to the CEO of the company who did the work, and to OLEV.

Did they give you an Electrical Installation Certificate?

 

[tim_n]

No EIC as far as I remember... I believe it was supposed to be passed over by the office via email this week. Not had anything as yet though.

 

[Simon35]

No EIC as far as I remember... I believe it was supposed to be passed over by the office via email this week. Not had anything as yet though.

In which case, I hope you haven't yet paid them.

 

[tim_n]

It's paid for by the government - I did have to pay an additional £99 for the upgrade from 16A charger to 32A.

Regardless I'm competent enough to swap MCBs on my own, but I'd really rather have the people contracted to do the work finish it off and certify it. The whole house is being professionally rewired in less than 12 months since it's a rat nest of cables by a previous sparky who lived there, many of which I've decommissioned because they'd physically melted into the walls. If anyone is interested I'll happily post some wonderful pictures... My favourite was finding live bare mains wires behind a telephone socket or the 30 odd sockets in the recording studio, some of which were wired into the lighting circuit.

 

[winston1]

Regardless I'm competent enough to swap MCBs on my own, but I'd really rather have the people contracted to do the work finish it off and certify it.

In that case why don't you wait a week when, according to your first post, it will be?