Consumer Unit upgrade for EVCP

[canigetsomehelp]

Hi looking for some professional advice please.

I am considering getting a dedicate EV charging point fitted to the house. However from my research I'm trying to mitigate a a problem where the fuse box is not suitable by getting it upgraded prior to adding.

It currently has 8 way fitted with MCBs and main supply 100A fuse.
40A (twin oven)
32A (sockets)
32A (sockets)
16A (Old immersion repurposed for single socket in Bed3)
6A (lights)
6A (lights)
6A (lights)
6A (unused door bell only)

I would like to initially add a 7KW 32A EVCP circuit and a spare way for future solar or outbuilding supply. One issue seems to be that just adding the EVCP would take above the 100A main fuse, so how would that be done? Although we are generally low power users.

My assumption is I need a modern CU with SPD, RCBO's (not seen 40A mini versions) for all circuits bar the EV charger?. (likely Zappi or Ohme home pro).

I would like advice on why type of CU spec I should be expecting to be quoted for. eg RCCB or RCBO, type A,B, or AC etc. I'd like one thats shallow depth as located in middle of wall in reception room. Also this is no where near the kitchen, so would bonding still need upgrading to 10mm and how? Sure it has 6mm currently.

What sort of cost should I be expecting?

Thanks.

 

[Murdochcat]

Eyes on site always trumps internet advice so your best option would be to get local prices

Anywhere from £600 to £1000 if you want to budget AND this would exclude any issues identified during the change

 

[flameport]

One issue seems to be that just adding the EVCP would take above the 100A main fuse

Not relevant, maximum load is based on what's actually connected, not the ratings and quantity of the circuits.

so how would that be done?

Most EVSEs have load monitoring so will reduce the charge power temporarily if an excessive amount is being used in the house.
Most also have a similar arrangement for solar, so you can use any surplus solar generation for the vehicle charging.

My assumption is I need a modern CU with SPD, RCBO's (not seen 40A mini versions) for all circuits bar the EV charger?.

RCBOs for all circuits including the EVSE.
40A exist, depends on the manufacturer of the consumer unit as to what is available.
RCBOs with switched neutrals would be desirable. Some manufacturers have these, others not.

I would like advice on why type of CU spec I should be expecting to be quoted for. eg RCCB or RCBO, type A,B, or AC etc. I'

Metal enclosure, main switch, RCBOs for all circuits, surge protection. Possibly AFDDs for some circuits such as socket outlets.
As many spare ways as can be had - the main cost is what's inside the consumer unit. A larger enclosure is next to nothing extra.
RCBOs Type A as a minimum. AC are basically useless as they are not permitted for most circuits.
Some devices may require F or B, however such things are still relatively unavailable and expensive.

I'd like one thats shallow depth

They are all very similar in depth. Flush mount versions are available.

What sort of cost should I be expecting?

~£1000 would be a start. Could be less, could be more.
All of the existing circuits will need to be inspected and tested. There may well be minor problems which require repair.
May be worthwhile to consider if the existing circuit arrangement would benefit from alterations.
Bonding to water, gas and others will need to be 10mm² minimum - assuming that it's actually required, as many incoming services are plastic now.

 

[plugwash]

I am considering getting a dedicate EV charging point fitted to the house. However from my research I'm trying to mitigate a a problem where the fuse box is not suitable by getting it upgraded prior to adding.

Personally, I would look to have all the work done as one job rather than two separate ones.

I would like to initially add a 7KW 32A EVCP circuit and a spare way for future solar or outbuilding supply. One issue seems to be that just adding the EVCP would take above the 100A main fuse, so how would that be done? Although we are generally low power users.

In electrical installation design, there is a concept called "diversity", basically the idea is that in most installations it is highly unlikely that all circuits will be fully loaded at the same time, if at all. If we built our installations on the principle that everything might be fully loaded at the same time, they would end up ludicrously overbuilt.

There are some diversity guidelines in an appendix of BS7671, but they are just guidelines, installers are allowed to apply their judgement. Suffice it to say, if you really do have a 100A fuse, heat your house with gas and the cooker is your only "large" electrical appliance you are almost certainly fine. Heck even if you had an 80A fuse you would probablly be fine, 60A may be pushing it a bit.

If things do look more marginal, many EV chargers offer a "grid limit" feature. A current transformer is placed around the incoming tail from the grid, and if the EV charger detects overloading it will reduce the charge rate to compensate.

I would like advice on why type of CU spec I should be expecting to be quoted for. eg RCCB or RCBO, type A,B, or AC etc.

Generally newly installed RCDs/RCBOs in the UK should be type A.

An all RCBO board is slightly more expensive than a dual RCD configuration, but will mean that any tripping problems are contained to a single circuit.

 

[Murdochcat]

And you should NEVER attach an EV to a shared RCD , despite the fact some ignorant installers do

 

[Risteard]

RCBOs with switched neutrals would be desirable.

Essential (in actual fact mandatory) for the EVSE circuit.

 

[canigetsomehelp]

Not relevant, maximum load is based on what's actually connected, not the ratings and quantity of the circuits.

I was following online diversity guidance of full highest circuit + 40% of others.

40 + (0.4 * (32+32+16+6+6+6) = 79.2
Assuming the EVCP will use 29A as 7kw/240.

this gives a load value of 108.2A

I'm assuming you are saying that should used what connected not fuse ratings. in the case of sockets/lights how do you know as depends what gets plugged in?

 

[flameport]

I was following online diversity guidance of full highest circuit + 40% of others.

Mostly irrelevant, as that was written decades ago when houses only had 3 circuits - lighting, cooker and a ring for the sockets.

 

[Murdochcat]

Essential (in actual fact mandatory) for the EVSE circuit.

Spot on - specifically I'm thinking of 722.531.3.1

which should also include PV circuits too IMHO

 

[Murdochcat]

I was following online diversity guidance of full highest circuit + 40% of others.

Adding up the values of the breakers and multiplying by 0.25 may be more accurate TBH

The "guidance" on diversity for a consumer unit is about 40 years out of date and NOT to be relied on

 

[ericmark]

If memory serves me well, the Wylex fuse box shown, has a 60 amp main switch

so it would need replacing to upgrade the fuse size. Even with a 100 amp main switch, with things like solar panels and batteries we still have a problem upgrading from 60 amp, my own house has a 6 kW solar panel array and a 3 kW battery, so 39 amp plus the 60 amp DNO fuse only just within limits.

I am not sure if both solar and battery can be used together, but noted the smart meter in house display while daughter taking a shower, and the shower is not 2.98 kW, so a far whack was being delivered by solar and battery.

There was a time when we saw 63 amp RCD's being fitted in consumer units (CU) which were supplied by a 100 amp fuse, and had MCB's on each RCD which exceeded the 63 amp, it has now been made clear that is not permitted, clearly since some people still have 60 amp supplies there is nothing wrong in selling CU with 63 amp RCD's, but some one needs to sign that they have designed the installation, and it is up to them how they go about it.

I would think today most EV chargers have the 6 mA DC detection built in, so type A RCBO's are OK. However one can't take this for granted, and not seen a single module width RCBO which is type B, although mine did say type B on the packet, after they were fitted found they were type AC curve B. My fault never opened the packets, the guy just fitted what I had provided, which is a lesson to be learnt, let the electrician doing the work select the materials.

I look at both smart meter and solar panel display and both show the max demand, this is normal rare I use more than 4 kW except for when having a shower, but the peak was at 2 am when one would expect to be charging a car. Had my wife made coffee just ½ hour earlier then likely over 5 kW load. One would hope the EV charger is monitoring the total power being used, and auto reduce charge rate, but this depends what charger is fitted.

As to what is mandatory and what is recommended I am not sure, BS 7671 is not law, but can be used in a court of law, not sure about the CENELEC Harmonisation Documents? It is to comply with these that BS 7671 gets updated so often, and there are laws which are not repeated in BS 7671 like items being supplied with plugs, so we have an array of laws and regulations and it is hard to keep track, so we get loads of Chinese whispers as well.

However one thing I do know is even as a time served electrician I can't fit a CU without getting the LABC to check my work and pay their fee, so I would simply not do it, and would get a scheme member to do the work, and issue a compliance certificate. So putting it simply, I don't need to know, I take an interest of course, but I have no intension at my age of taking any more courses or exams to do electrical work.