2 electricity supplies to one building

The main fuse, the meter, the henley block  and the consumer unit all say 100A on them


That may well be, but what does your supplier say? Regulation 132.16 states that no addition or alteration, temporary or permanent, shall be made to an existing installation, unless it has been ascertained that the rating and the condition of any existing equipment, including that of the distributer, will be adequate for the altered circumstances.


The main fuse feeding your "street" may be 400 A so what would happen if four of your neighbours did the same?


Regards


BOD

BOD,

The main fuse, the meter, the henley block  and the consumer unit all say 100A on them.

But I don’t think the supply is the issue here. I think the problem is, as mapj1 said, the earthing and the fact that the charger may need an earth rod while the other circuit in the garage uses the earth from the supply. As he also said the installer is set up to do “standard” installations and don’t seem to know what to do if they get a non standard one. 

I just wanted to understand if the problem was real and if they knew what they were talking about or if it was a case like the proverbial car mechanic sucking in through his teeth while shaking his head. 

Thanks for all the input everyone.

 as there was to be a device fitted to monitor total load at the meter and to throttle back the supply to the charger if it got close to the 100A max available 


How do you know that you have got a supply capable of a 100 A load?


Regards


BOD

"I was often blamed wrongly for things on the basis of “he said” “she said”. Made me all the more keen to listen to all sides in my later life!"

EEEhh Lyle, I know that situation only too well.


I used to get accused of all sorts by people jumping to wrong conclusions. I deliberately never corrected them in detail (I just said no i did not and left it at that.).

If, however, they actually asked if I`d done/said such I would explain to them in more detail.. If someone said "You must have otherwise you`d prove it. I avoided proving it. I can be awkward just for the crack of it.


I have noted people saying things that they have misundertood .

One example a few years back was "The Building inspector said he had used the wrong cable!" wheras I said "no it is not!" When the building inspector turned up later I asked him what he`d said about the way the previous electrician had wired it and he replied "He had used larger cable than he needed to,( which I thought was a good plus thing for future resiliance)"


So the meaning was misunderstood.


Another instance.

A relative was so concerned that he contacted the local council. 

He had split from his partner and the children lived with her.

She had got her brother to build a strong floor in the loft and a ladder via the bathroom..

His main concern was kids falling down from loft to bathroom when using ladder.

The Council inspector replied to him something like 1/ she said the kids are not allowed to go up there (he knew this untrue as kids tell you everything)

. 2/ she said it was just to store as few light things.

The inspector added that the floor that was very much more than strong enough to hold what she had stated.


He was upset that the inspector had accepted her explanation .

I read it. then read it again.


I told him that my initial reading was like his but told him to read it again.

I explained that the inspector was actually pointing out that the floor strength exposed her story as likely to be false.

Bingo the inspector did in course get her to remove it.

It also depends on things like if there is a water supply to the garage, and if things get plugged in there that get used in the garden.

But in any case, even if this is the case, converting the garage sockets and lights to use a local electrode would be easier than a rewire.

I suspect this is a technician working from a play-book of standard solutions,  rather than designing properly for the situation.This is OK, 90% of the time, but

there needs to be a proper process for handling non standard cases.

Mike

As far as I can see, 722.411.4.1 does not apply because the EVCP will be in the garage and the car will have to be in the garage to use it.

I think it is reasonable because "two supplies" has a rather specific technical meaning. If the problem is simple, like the other supply cable is PME then he should report this and convert the whole garage to TT.  It is after all a separate building! It could be that the communication is poor, but lack of competence is no excuse for that. Adding a charge point, with all the known and acknowledged potential difficulties, is not a job for a probably very inexperienced and probably underqualified person. Even fitting an Earth rod is potentially quite difficult, bonding could be, and we are outdoors so safety is particularly important. I wonder what capacity the supply to the property is? Obviously, a 7.2 kW charger could be another unknown problem too.