Adding additional Consumer unit for EV Charging

[Scottland]

Hi,

** First of all let me state that a professional will be doing the work I just want a sanity check on what I think I need... **


So, we're getting an EV and need to install a 7.5KW charger.

We currently have a 60A main fuse going into a CU with 100A RCD. We know we need to get the main fuse upgraded, as well as the tails from the main fuse to the CU. Ok with this, unless anyone thinks I'm wrong?

In the CU I have a 32A MCB then running in an underground duct to the garage where there a smaller CU with a current 16A (I think) MCB and a free MCB. However the cable is only 6mm2. The EV chargepoint is wanted in or near the garage, so it seems logical to add the capability to the garage for the EV chargpoint in addition to what I already have in the garage (16A MCB I think).

So what I'm proposing is:
- Upgrade tails and main fuse for 100A
- Break out the feed before the current CU and add a 60A(?) switched main, which then feeds the submain in the garage
- Upgrade underground cable to 16mm2 (total length <20m)
- Update the CU in the garage with an additional 32A MCG for the EV point, plus I think a single 16A MCB I already have feeding the garage.


Have I missed anything? As stated at the top of the page I just want to sanity check what I think I need, a pro will be doing the work.

 

[peige]

I had a Pod-point installed yesterday, the actual install being done by EDF. I'd agree that you need 100a fuses, they will also check gas and water bonding. They actually attached mine to a separate unit straight off the meter so not touching my CU at all. He said this was the preferred method of doing it.

 

[sparkymark75]

If your EV charger doesn’t have O-PEN fault detection built-in, then you’ll need an Earth rod or a O-PEN fault detection device installed.

 

[K.C. Leblanc]

If your EV charger doesn’t have O-PEN fault detection built-in, then you’ll need an Earth rod or a O-PEN fault detection device installed.

Maybe not, the op mentions a 100 mA RCD which would suggests his whole house might be on an earth rod instead of having an earth provided by the network.

 

[Scottland]

If your EV charger doesn’t have O-PEN fault detection built-in, then you’ll need an Earth rod or a O-PEN fault detection device installed.

Haven’t even begun starting to see which chargepoint we want yet, so I’ll keep that in mind.

Maybe not, the op mentions a 100 mA RCD which would suggests his whole house might be on an earth rod instead of having an earth provided by the network.

Looks that way to my untrained eye.

 

[b0rn2sk8]

You are probably already aware but for the benefit of others who may read this. It's not a given that the DNO will upgrade the fuse to 100A, they may refuse. It's wholly dependent on how your house is supplied and capacity. If you have not already, I would check with them first before making any other plans.

If you use a charger like the Anderson or Zappi which can do supply monitoring then its possible (but not ideal) to get away with not upgrading the fuse and tails should it be a problem. Those chargers can ramp down what they are supplying to the car if you are drawing lots of power elsewhere and EV charging tends to be done at night when you are not using high draw appliances. But it really depends on what else you have going on in the house and when you expect to use electricity. That said I would recommend getting it done if you can but its not a deal breaker if cost or the DNO is an issue.

Do you need to replace the supply to the garage? It will may be cheaper to run a separate cable to run the charger on its own supply.

I think the two chargers above also have the earth fault detection that @sparkymark75 mentioned is required. That functionality varies by charger and can negate the need for an earth rod if you don't have one already.

I'm in a similar position to you, fortunately I have a 100A main fuse but I only have 13A out to my detached garage. I am weighing up whether I have the existing circuit ripped out and have a big supply installed to the garage or just run an EV charger on its own feed. The latter is obviously a lot cheaper! I'll be interested to hear how much you are being quoted for the garage supply upgrade.

 

[theone8181]

Just on a bit of a tangent, is 7.5kw the biggest you get for domestic. There's a guy I work with who's a bit full of it (I'm sure you've met the type) and he's convinced you need 3 phase so you can get a 100kw charger (for the house). Why someone would need to charge a car faster than the average mobile phone is a bit beyond me (again from a plugged in at home pov).

 

[sovietspybob]

Just on a bit of a tangent, is 7.5kw the biggest you get for domestic. There's a guy I work with who's a bit full of it (I'm sure you've met the type) and he's convinced you need 3 phase so you can get a 100kw charger (for the house). Why someone would need to charge a car faster than the average mobile phone is a bit beyond me (again from a plugged in at home pov).

That's a load of rubbish, the most you can get on a 3phase supply is 22Kw AC and that's mental for a home user. A lot of cars can't take advantage of that anyway, only a handful can take more than 7kw on AC. To go higher like all public rapid chargers it's all DC and that's silly money.

At home 7kw is more than fine for almost everyone. If you get home and plug in at 7pm and leave at 7am it'll still give you 84Kwh of juice overnight, which is more than 0-100% on all but the very highest end cars. You'd need to be doing over 300 miles a day, every day and being at home less than 12 hours for it to be an issue.

The reality is most people will do less than 100 miles in a day and plug in to a 7kw charger which will take maybe 5 hours to replenish that range?

 

[Jez]

Just on a bit of a tangent, is 7.5kw the biggest you get for domestic. There's a guy I work with who's a bit full of it (I'm sure you've met the type) and he's convinced you need 3 phase so you can get a 100kw charger (for the house). Why someone would need to charge a car faster than the average mobile phone is a bit beyond me (again from a plugged in at home pov).

In the main an upgrade to a residential house only goes as far as 3ph 70KVA under anything like a sensible pricing scheme (<£5k range). The largest widely available 3ph chargers are only 22kw. 100kw is nonsense as sovietspybob mentions, even even if you could find the charger and be prepared to pay for it, you would be into commercial pricing for your 3ph upgrade.

 

[theone8181]

In the main an upgrade to a residential house only goes as far as 3ph 70KVA under anything like a sensible pricing scheme (<£5k range). The largest widely available 3ph chargers are only 22kw. 100kw is nonsense as sovietspybob mentions, even even if you could find the charger and be prepared to pay for it, you would be into commercial pricing for your 3ph upgrade.

Oh I agree with you guys, I just thought you'd find it funny. We have a laugh with this guy as he's so full of it.

 

[Scottland]

You are probably already aware but for the benefit of others who may read this. It's not a given that the DNO will upgrade the fuse to 100A, they may refuse. It's wholly dependent on how your house is supplied and capacity. If you have not already, I would check with them first before making any other plans.

If you use a charger like the Anderson or Zappi which can do supply monitoring then its possible (but not ideal) to get away with not upgrading the fuse and tails should it be a problem. Those chargers can ramp down what they are supplying to the car if you are drawing lots of power elsewhere and EV charging tends to be done at night when you are not using high draw appliances. But it really depends on what else you have going on in the house and when you expect to use electricity. That said I would recommend getting it done if you can but its not a deal breaker if cost or the DNO is an issue.

Do you need to replace the supply to the garage? It will may be cheaper to run a separate cable to run the charger on its own supply.

I think the two chargers above also have the earth fault detection that @sparkymark75 mentioned is required. That functionality varies by charger and can negate the need for an earth rod if you don't have one already.

I'm in a similar position to you, fortunately I have a 100A main fuse but I only have 13A out to my detached garage. I am weighing up whether I have the existing circuit ripped out and have a big supply installed to the garage or just run an EV charger on its own feed. The latter is obviously a lot cheaper! I'll be interested to hear how much you are being quoted for the garage supply upgrade.

Yeah, about to start a conversation with DNO about this. I think we should be ok, but it's good to know about chargers being able to manage without possibly. Zappi was one I was going to look at actually.

Due to the position of the garage, it makes sense to do it this way as the route for a direct cable for the chargepoint might be more/as complicated, it also means I can make the garage supply better as it's currently being fed using an unarmoured cable fed through an MDPE water pipe

Just on a bit of a tangent, is 7.5kw the biggest you get for domestic. There's a guy I work with who's a bit full of it (I'm sure you've met the type) and he's convinced you need 3 phase so you can get a 100kw charger (for the house). Why someone would need to charge a car faster than the average mobile phone is a bit beyond me (again from a plugged in at home pov).

The next step up seems to be 10.5 at the moment. I've seen a few mention it, but I think 7.5 will suffice for most for now.

 

[gazref]

7kw is more than enough for a home user. I did 160mile commutes and shift work so used 70-80% and only had 7-7.5hrs to charge before being off again. The guys at work(massive facility) had access to 21kw chargers simply to aid charge and move behaviour so outside of a commercial setting it's simply overkill.

Personally wouldn't bother with a zappi unless you have solar , you can do timed charging from your car if you want off peak electricity.

ChargedEV installed mine would recommend and use again. He did a great job with wiring and put an earth rod in too

 

[the-evaluator]

Maybe not, the op mentions a 100 mA RCD which would suggests his whole house might be on an earth rod instead of having an earth provided by the network.

I read it as 100A RCD, not 100mA. So an RCD that'll be rated for 100A but will trip at 30mA. Something like this for example.

 

[lookitsjonno]

I did exactly the same as you, branched off current fuse box, underground 28 meters with 16mm SWA, new CU in the garage. I offered to dig the wire in myself but it cost £1k all in. I thought this was a tad on the expensive side but we know the sparky and he did a good job. I'd have expected to pay £7-800 ish.

 

[Scottland]

I did exactly the same as you, branched off current fuse box, underground 28 meters with 16mm SWA, new CU in the garage. I offered to dig the wire in myself but it cost £1k all in. I thought this was a tad on the expensive side but we know the sparky and he did a good job. I'd have expected to pay £7-800 ish.

Thanks that’s really useful. Did you have to uprate the main fuse?

 

[ash_scotland88]

All interesting reading.
Currently planning CU upgrade and allowances for a MCB (?) to garage and allowing 32amps for a potential home charger.

 

[lookitsjonno]

Thanks that’s really useful. Did you have to uprate the main fuse?

I could be wrong but I don't think so, sparky certainly didn't mention it. I think I have 100amp main fuse which is now shared between the house and the garage.

 

[Scottland]

I could be wrong but I don't think so, sparky certainly didn't mention it. I think I have 100amp main fuse which is now shared between the house and the garage.

Would make sense, if you have a 100A main already then that should be sufficient for most houses.