Ohme charger - directly to the consumer unit or connection blocks

[4rchibald]

I'm getting conflicting information on installation of an EV charger.
Some electricians require direct connection to tails through connection blocks and a separate, £150 JB while others state that it can be wired directly to the consumer unit on a 32A MCB (CU is 100A with spare MCBs).
Ohme doesn't require an earthing rod so I think that the JB might be an overkill, but wanted to ask for your opinion.


Also tails between the 100A fuse and a new smart meter installed in 2020 look like 16mm² (no markings but are thinner than 25mm) while those going to the CU are the correct, 25mm².
Most electricians told me it's correct as those are only 30cm long, they obviously don't not swap them anyway and they are hesitant to ask DNO due to lead times it takes them.
Shouldn't the meter installer upgrade those to 25mm² as a "new connection" and are those sufficient for a 100A fuse?

 

[EFLImpudence]

The DNO have different rules and use 16mm² for 100A.

Are you sure it is 100A fuse? The label only refers to the maximum rating of the carrier; not necessarily the actual fuse used inside.

 

[4rchibald]

I'm 95% sure as this is what the BG engineer told me, but is there any other way to determine this?
I guess DNO should know when the electrician will make the application for EV charger.

 

[ericmark]

I think EV charges need notifying to DNO, but there are a few diffrent designs, some monitor total use and turn down charge rate if rest of house using a lot of power, some monitor DC and auto turn off if it exceeds 6 mA, some monitor voltage and if not between 207 - 253 turn off, nearly all now have to connect to DNO so they can turn it off to shed load, and those who fit them need special training.

There is therefore no one size fits all. And it seems electricians can't pull DNO fuse, well at least can't replace it, this it seems is a new ruling, I am sure those who are authorised to fit EV charging points will be told what is required, but I have never done an EV installers course so can't say how changes are related to installers.

However it is specialist work, and clearly not DIY.

 

[SUNRAY]

I'm 95% sure as this is what the BG engineer told me, but is there any other way to determine this?
I guess DNO should know when the electrician will make the application for EV charger.

The DNO are highly UNlikely to know for certain the size of your fuse. IF they have records they may well be decades out of date and several meter changes in the meantime. The only thing which is likely to be accurate is a brown paper label showing the test figures, earthing arrangement and fuse size if it's attatched to the fuseholder by the seal.

 

[4rchibald]

I think EV charges need notifying to DNO, but there are a few diffrent designs, some monitor total use and turn down charge rate if rest of house using a lot of power, some monitor DC and auto turn off if it exceeds 6 mA, some monitor voltage and if not between 207 - 253 turn off, nearly all now have to connect to DNO so they can turn it off to shed load, and those who fit them need special training.

There is therefore no one size fits all. And it seems electricians can't pull DNO fuse, well at least can't replace it, this it seems is a new ruling, I am sure those who are authorised to fit EV charging points will be told what is required, but I have never done an EV installers course so can't say how changes are related to installers.

However it is specialist work, and clearly not DIY.

Ohme doesn't need earthing rod as it cuts all supply via integrated RCD.
It has load balancing CT clamp which will be installed but my question is about the requirement to connect via connection blocks and external switch unit which increase the cost.


It's the electricians that have opposing views so while I get that belts and braces is the best option for many, I would prefer to not pay extra £200 if direct connection to the consumer unit is allowed, which I think it is, considering 7kW device

 

[4rchibald]

The DNO are highly UNlikely to know for certain the size of your fuse. IF they have records they may well be decades out of date and several meter changes in the meantime. The only thing which is likely to be accurate is a brown paper label showing the test figures, earthing arrangement and fuse size if it's attatched to the fuseholder by the seal.

I have nothing attached so have to rely on the information provided by the electrician, but how is an installer going to know if the fuse is 100A or maybe just 60A if they can't remove it (yes, I know they many do)

 

[Adam_151]

I'm getting conflicting information on installation of an EV charger.
Some electricians require direct connection to tails through connection blocks and a separate, £150 JB while others state that it can be wired directly to the consumer unit on a 32A MCB (CU is 100A with spare MCBs).
Ohme doesn't require an earthing rod so I think that the JB might be an overkill, but wanted to ask for your opinion.

There is nothing to say it cant be wired to the existing board, a couple of things are to be considered though:

1) Is the right MCB available for the board, normally this will be a 40A for a 7.2kwh charger, its perfered not to have a 32A breaker loaded to capacity for the charge duration

2) Is it via an RCD aslready, having an type AC upstream of the EVSE is not allowed, and while if it is a type A RCD, then while allowed providing the EVSE has protection against dc leakage currents esceeding 6ma, then its best to avoid this, the EVSE does require its own RCD (usually built into it, but always) and to install down stream of the same device is poor design and somwhat defeats the purpose of the dedicated RCD.

If the board is in good condition, has sufficenct capacity and offers a free none rcd way and you can get an mcb, then there no issue using the existing board. With some firms that want to install a separate unit, there is probably a little bit of "This is house standard, do it this way" going on when it might not always be the best solution

 

[ericmark]

There is nothing wrong using an existing 32 amp socket and plugging in a charging lead normal cost around £250 if supplied from a appropriate type of RCD when charging within the building.

Be it 3, 7, or 22 kW (latter 3 phase) if the supply is ample you can connect an EV to be charged.

The problem is when charging outside where visitors can access the car.

 

[4rchibald]

There is nothing to say it cant be wired to the existing board, a couple of things are to be considered though:

1) Is the right MCB available for the board, normally this will be a 40A for a 7.2kwh charger, its perfered not to have a 32A breaker loaded to capacity for the charge duration

2) Is it via an RCD aslready, having an type AC upstream of the EVSE is not allowed, and while if it is a type A RCD, then while allowed providing the EVSE has protection against dc leakage currents esceeding 6ma, then its best to avoid this, the EVSE does require its own RCD (usually built into it, but always) and to install down stream of the same device is poor design and somwhat defeats the purpose of the dedicated RCD.

If the board is in good condition, has sufficenct capacity and offers a free none rcd way and you can get an mcb, then there no issue using the existing board. With some firms that want to install a separate unit, there is probably a little bit of "This is house standard, do it this way" going on when it might not always be the best solution

We have both 32A and 40A spare MCBs in the CU so this would not be a problem, but looking at two installs at my friend's house they used 32A EV consumer unit.

Ohme has its own RCD built in (Type A 30mA AC and 6mA DC) and their manual contain a suggestion that the upstream RCD should be minimum type A as AC might fail so that contradict your statement about the no RCD downstream

 

[davelx]

If the unit has a built-in RCD and DC protection then an upstream RCD should not be required for the purposes of the unit itself. It may be necessary depending on the type of cable used and the way it is installed, which is why most installations use SWA cable which removes any requirement for an upstream RCD.

 

[ericmark]

heir manual contain a suggestion that the upstream RCD should be minimum type A as AC might fail so that contradict your statement about the no RCD downstream

With the exception of caravans and narrow boats where two 30 mA RCD's are fitted in series, RCD's are selected approx X3 so a 500 mA feeds 100 mA, which feeds 30 mA which feeds 10 mA. In the main with domestic today we only use 30 mA, there may be some old installs with 100 mA, and some 10 mA sockets, but these are rare.

The worry is DC can freeze a type AC RCD, so if the consumer unit RCD feeds multi circuits then clearly don't want it to also feed any device which may inject DC, so solar panels, EV points, storage batteries need dedicated RCD's to ensure under fault conditions they don't remove the protection from other devices.

So with may consumer unit which is all RCBO's having one feed a EV charging point is not a problem, it is where it has been done on the cheap with one RCD feeding many MCB's where the problem arises.

In my property the garage is behind the house, where no tradesmen would go, and if I was to do anything wrong the only person who could get injured as a result are family members, clearly don't want that, but using a TT supply I could install an EV point with very little risk, loss of PEN is not common, but still possible, and sinking earth rods where there may be services is clearly not a good move. The 207 - 253 volt limit is suspect, it may in the main detect loss of PEN, but not that fast, but it will depend on where the vehicle is parked, charging an EV front of my house, Milkman, Post Woman, and others walk past it to knock on my door, so more of a chance with loss of PEN some one touches the car before the auto disconnection.

However today all EV charging points should be registered with the DNO and can be auto disconnected by the DNO to shed load, so although I have the ability to do a risk assessment and install my own 32 amp supply to where I can charge a car, building regulations, etc. Means I can't and I need to employ some one who is registered with the required bodies to do the work at my home.

Oddly I could do it at work, and have installed in my time many EV charging points for forklifts etc. But at my own home, since not paying annual fees to required bodies, although in theory I could pay the LABC etc, in practice even as a time served electrician/electrical engineer I can't fit my own EV charging point. And the forum has DIY in the title, this is simply not a DIY job.

In theory I could fit a commando socket and use one of these they are for sale from UK sites as long as I say the 32 amp socket is for a welding set not an EV charger I can have one fitted by a scheme member. Or use an existing supply in my integral garage, not that I would want an EV parked under my house with the fire risk.

However I would be breaking the rules plugging an EV into the supply, in same way as I can buy a drone or radio transmitter without a licence you can buy EV charging kit, but that does not mean you can use it, be it an electric scooter or EV charging point, being able to buy them, does not mean you can use them within the law.

 

[Adam_151]

Ohme has its own RCD built in (Type A 30mA AC and 6mA DC) and their manual contain a suggestion that the upstream RCD should be minimum type A as AC might fail so that contradict your statement about the no RCD downstream

Thats not contradictory as far as I am concerned, I told you that an type AC upstream of the EVSE is not allowed, and as long as the evse has DC leakage protection then an upstream type A, while allowed, would generally be poor design, as there is is going to be a dedicated RCD for the EVSE (often part of it) as thats a requirement of 722.351.2.101 and having a similar 30ma device upstream is unlikely be in the spirit of what was intended, even though, specifically its not disallowed.

The manual appears to just say that any upostyream RCD must be a mimimum of type A which

a) Appears to confirm the EVSE (like most these says) has 6mA DC leakage protection (Type B RCDs would be required if this was absent)
b) Tells you the absolete mimum requirement - No upstream type AC devices, whereas duplicating the required individual 30mA RCD protetcion upstream with another 30mA device, even if type A is not such a smart thing to do either and not in the spirt of what was intended IMHO

[side tangent: although if you had an upstream 100MA time delayed type A RCD for fault protection then this would be a different situation, a time delayed type AC would obviously have to be upgraded to a type A though - THIS HOWEVER IS NOT YOUR SITUATION]

 

[Risteard]

There must be double pole RCD protection upstream (assuming the device in the EVSE is not to BS EN 61008 or BS EN 61009). This must be a dedicated RCD and not shared with other circuits/equipment.