Advice on using existing 32A cooker supply for EV 7kw charger

[coloured]

Even though its not actually over 32A, I would be unhappy with having an connected to a standard / non-uprated way in a wylex standard board (as it appears OP has) because an EVSE will be pulling on the limit for that way and pulling it for hours at a time. Plus the majority of these boards had 60A main switches.

You right it's an 60A CU. So in the first instance will get that changed to a new/current unit

 

[Murdochcat]

Yes but you also need the earthing and bonding checked / updated and the incoming supply too.

You just can’t extend a cable and install an EV charger

And you need to do forms for the DNO too

 

[ericmark]

You right it's an 60A CU. So in the first instance will get that changed to a new/current unit

In that case, it should have been a 60 amp DNO fuse as well. The fuse carrier is likely 100 amp as is mine, but the fuse inside it likely 60 amp, some times there is a sticker to tell you.

The EV has evolved, around 2011 my neighbour got a Renault Kangoo electric van for his milk round, it would only charge at 3 kW, it had a claimed 140 mile range, but he would some times need rescuing due to flat battery and his round was a fixed 68 mile, seem to remember it was 22 kWh battery, which would take about 8 hours to recharge. The battery sizes have since jumped to 33 kWh and then 44 kWh so it has now double the capacity of the old van.

The result is the chargers have also increased in size, and now 7 kW single phase and 22 kW three phase seem to be the standard AC charging units. So your looking at 30 amp for a long time, 4 mm² may be OK for a cooker, when max power is only for a short time, but for an EV charger, 6 mm² when buried in a wall, is more the order of the day, outside where in free air you may get away with 4 mm² but not when buried in a wall.

There does seem to be a problem, it is assumed if one can afford a EV, you can also afford the EV charger, this does not take into account the company car, where the company is concerned about their corporate image, and even if a petrol or diesel would do the job better, they want their staff to use an EV.

I know years ago, I was lucky, both my son and I shared the works van, so neither had to pay extra income tax to take it home, but taking the van home often resulted in paying extra income tax. Not a clue if that is still true? It was a duel edged sword, if you stopped owning your own car, and used the company car for everything, then you could gain, but swap jobs, and you needed a new car fast, having an EV charging point installed to charge a company car, can leave one with a unused charging point so easily. I would not personally want an EV charging point for a car I did not own. But one would want a method to record the power used.

I upgraded my consumer unit, and still I could not have a 100 amp supply without adding an extra fuse. The solar and battery plus the grid do not exceed 100 amp, but that is with a 60 amp DNO fuse, if a 80 amp was fitted, I would exceed the 100 amp total.

With solar an EV can be used as a energy store, not sure how it works, but I know I save a lot of money charging my battery at night at cheap rate, and using it during the day, since most of my trips are short, the EV could even simply standing in the drive, save me money, but even as an electrical engineer not sure how this all works.

So even as an electrical engineer I would not be doing the work myself, it is a specialist job.

 

[JohnW2]

Not if there is already a type AC device upstream

I thought the perceived problem with Type AC RCDs was that, under some circumstances (e.g. non-sinusoidal residual currents and/.or DC components) they might not operate when they should (in response to a residual current), whereas a Type A will operate (in response to a residual current) in some of those situations ?

In what way would the existence of an upstream Type AC compromise the functioning of a 'downstream' Type A one?

 

[JohnW2]

Plus bear in mind that SPD's should be fitted now too

... unless the owner of the installation doesn't want SPD(s).

 

[Murdochcat]

... unless the owner of the installation doesn't want SPD(s).

Not sure I agree with that .

How many sparks know how to do risk assessments and SPDs aren’t exactly expensive either

 

[Adam_151]

In what way would the existence of an upstream Type AC compromise the functioning of a 'downstream' Type A one?

You are looking at it the wrong way around, the upstream type AC does of course not compromise the ability of the downstream type A to function, however the presence of the downstream type A does not shelter the upstream AC from being affected by the load. The type A is guarenteed not to be affected by the upto 6ma of DC leakage the charging of the vehicle could be putting on the mains without the internal RDC-DD of the EVSE cutting it it off from supply*, but the type A doesn't do anything about the DC leakage other than not be affected itself, the type AC will still see the same, and those are not considered suitable for any level of DC leakage, so must not be present in the path to any EVSE

*If the EVSE does not have this protection, then type A rcds are not suitable either and type B must be used

 

[ericmark]

... unless the owner of the installation doesn't want SPD(s).

That is as you say permitted, there is a massive difference between protecting equipment and personal, and the SPD protects equipment so the owner is allowed to choose.

In what way would the existence of an upstream Type AC compromise the functioning of a 'downstream' Type A one?

It would not, however we assume the is a reason for the upstream RCD other than protecting the down stream one, so the stuff it was put there to protect would now not be protected, however I do feel 6 mA is rather small, even type B we see 10 mA being quoted, so unless there is some device to auto disconnect when it detects DC then it is all rather pointless.

I don't know if you have tried to measure DC on an AC supply, I have with this clamp on, which I will admit is cheap, the requirement to zero, every time the meter orientation is changed makes it hard to use, may be more expensive meters are better? I can measure 6 mA DC but would not want to rely on it being under 6 mA with a hand held meter.

Now the AC scale is another story, again 1 mA increments, but far more steady, so testing to see a circuit is under 9 mA (30% of RCD rating) that is easy enough. However 543.7.1.1 tells use 3.5 mA so clearly we need a meter which can measure that low, for equipment using a plug and socket and not being to BS EN 60309-2 not sure if the plug and sockets used with EV's are to that standard?

However since the EV charging point has to be installed by some one able the register the work with the authorities it is not a DIY job, and the person doing the work should be able to explain what is required.

I realise a simple no you can't do that, does not work, one does need to explain why one can't do that what ever that is, and I would hope we have explained how it is very unlikely that the cooker supply can be used. It seems likely he has a lot of work which needs doing, including getting the supply upgraded, maybe he can get a gas powered generator to charge the car?

 

[JohnW2]

.....

 

[Murdochcat]

.....

The cost of SPD's now when added with a new CU is negligible now and if the customer doesn't want one, then they can simply switch off the MCB marked SPD.

Its that easy.

I stopped offering not to fit them with the 18th AMD 2 came out ................

And you aren't a registered installer so why comment?

 

[JohnW2]

Not sure I agree with that .

Maybe you don't, but BS7671 appears to ....

443.4.1
Protection against transient overvoltages shall be provided when the consequences caused by the overvoltage could result in
………..
For all other cases , protection against transient overvoltages shall be provided unless the owner of the installation declares it is not required due to any loss or damage being tolerable and they accept the risk of damage to equipment and any consequential loss.

How many sparks know how to do risk assessments and SPDs aren’t exactly expensive either

As above, the decision not to want SPDs has not necessarily got anything to do with any 'sparks'.

 

[JohnW2]

The cost of SPD's now when added with a new CU is negligible now and if the customer doesn't want one, then they can simply switch off the MCB marked SPD. Its that easy.

You may believe so.

I stopped offering not to fit them with the 18th AMD 2 came out ................

That's rather ironic, given that it was AMD 2 which clarified that owners of domestic installations always had the option of declining an SPD. Prior to AMD 2, BS7671 was a bit confusing, since it implied that owners only had that option if a risk assessment had not been undertaken.

And you aren't a registered installer so why comment?

... because I am the owner of a domestic installation and so, per BS7671, could (and would) decline the offer of SPD(s) in that installation.

 

[cdbe]

I laid in a spare length of 10mm cable before I permanently fixed my flooring down - it will go from board to the area where I'd plug in a car - just in case.

My nephew recently got a job fitting EV chargers and I vaguely recall him saying they use "special" cables incorporating additional data cables - but don't quote me on it.

 

[briwire]

You would have to have some work done in the consumer unit so that the old cooker supply has its own RCD protection. If you get that done, I can't see a problem.

 

[JohnW2]

You are looking at it the wrong way around, ...

Well, certainly a different way around. I was thinking/talking only of matters of safety.

However, I admit that, despite many attempts to get better educated, I remain confused about some of the differences between different trypes of RCD. For example, you go on to say ...

The type A is guarenteed not to be affected by the upto 6ma of DC leakage the charging of the vehicle could be putting on the mains ....

As I understand, neither Type A nor Type AC should trip in response to a DC residual current.

If one goes by the BS7671 descriptions, the difference between a Type AC and a Type A is that the Type A should operate in response to an" "alternating sinusoidal residual current OR residual pulsating direct current" even if there is a "superimposed smooth direct current up to 6 mA" - but (by implication) that that is not necessarily true of a Type AC.

If that is true, then I'm not sure that I really understand the problem you perceive of having a Type AC upstream of a Type AC.