Electrical Vehicle Chargers - No Diversity?

Pretty much. That's my understanding at least.
Load management is key in larger installations.
If communal/public, a separate DNO supply to an EV feeder pillar is probably better than trying to serve from a building.

Apostolos said:

So, assuming we have a TPN 32A EVC, this means you cant apply diversity and feed it with a 20A MCB. It should always be a 32A MCB

That's not diversity.

Apostolos said:

Assuming you do not have a load management facility between the 5 chargers, does the 'no diversity' mean I have to assume a DB charged with 5 x 32 = 160A load????

Correct. No diversity means that you assume full load rather than only 3 in use at any one time (96 A) or 5 in use, but drawing less than the full 32 A load.

Note that not all EVs can use all 3 phases, and some which can use 3 phases cannot draw as much as 32 A per phase.

As we start to consume more electricity I can't see how a EV charging point supplied from a existing building supply can be installed without load management  - i think it will become a  minimum standard. Some charging points have internal dip switches that allow you set the max current -a crude way of reducing the max demand - and extending charge times.

I would definitely agree with your comment. But this is a different discussion. My experience from small scale buildings like hotels says that the clients do not want to pay extra for an overall load management system. So this cames back to me as a designer to make sure that the boards are big enough to feed the number of EVC chargers without any diversity as per BS7671

Well if the alternative is paying the DNO to lay in a larger supply ,and perhaps a new substation,  or arranging coordinated load management, I suspect that the latter will be back on the table again, certainly when you get above two chargers, and in many cases even for one large one. Charger manufacturers have by and large already woken up to this and can advise how to do it.

In effect the only time any car gets charged at full rate is when no-one else is plugged in. If you do not do  it like this, then there is a very credible risk that 5 cars will one day all be plugged in and all drawing the full current for a few hours together. It is not like electric showers where the use time is short compared to the heating of the cables and the substation transformer.

Mike.

A bigger board is not going to help you.

You need a bigger supply or a smaller load (or load management).

I'm not sure that 722 still explicitly says no diversity, but certainly there won't be much to be had between a relatively small number of constant power long duration loads.

Assuming you do not have a load management facility between the 5 chargers, does the 'no diversity' mean I have to assume a DB charged with 5 x 32 = 160A load????

If you're supplying loads to total of 37kW loads you're probably not going to be using a single phase supply - a more likely arrangement would be a 3-phase supply with up to 2 single phase (32A) charge points on each - so a perhaps more manageable 64A/phase.

   - Andy.

In my view, in the absence of any form of load control, then no diversity should be applied. 

If it says 32 amps, then it means 32 amps, and that in turn means 160 amps in total for five such chargers.

It might be possible to allow a little diversity on a large number of chargers. With say 5 chargers it is reasonable to expect that all 5 will be used at the same time. With say 100 chargers it MIGHT be reasonable to assume that only 90 will be used at the same time. A lot depends on the expected pattern of use.

100 charging points at a large office building might all be used at the same time if everyone starts work at about the same time.

100 charging points in say a supermarket car park are less likely to be all used at the same time. Customers arrive largely at random and then leave largely at random. A supply sufficient for say 60 chargers might in practice be adequate. By the time customer 61 arrives, it is likely that one or more of the first 60 will either be fully charged, nearly full, or be unplugged preparatory to driving away.

In practice some form of automatic load control is very desirable, many types exist. Some even allow for on site solar generation, limiting the total load to say 100 kw from the mains, but allowing a total charging demand of say 150 kw if 50 kw of on site solar generation is available.

Apostolos said:

Its clearly stated in BS7671 that no diversity should be applied to an EVC

This is not the case ... it was in 2018, but in 2020 (Amendment 1) it was updated:

722.311 Maximum demand and diversity
722.311.201 Load curtailment, including load reduction or disconnection, either automatically or manually, may be taken into account when determining maximum demand of the installation or part thereof.

Yes, but in the absence of a load management system it's still zero diversity.