External Garage - Charging

[NastyNick83]

I have an EO Pro Mini, connected with a DC leakage box of tricks all working perfectly at 32A.

However I have bought a new house (~20years old), which has a separate double garage approx. 10metres away from the main house. The garage does have power. I have not moved in yet and therefore unable to thoroughly examine the electrics but do know it is fed by a 20A fuse in the main consumer unit from the house. It has a separate fuse box in the garage with a ring main and lights.

If I was a betting man I'd say it was 2.5mm SWA cable feeding the garage - why would they install anything thicker 20yrs ago?

Anyone had similar?

Thoughts so far:
1) Run a new cable to the garage, which means digging up a driveway
2) Use granny charger at 10A
3) I think I can switch the EO Pro Mini down to 16A - may be able to run that off the ring main from garage (with the 20A fuse) and charge at 3.7kW instead. Would have to reduce fuse in DC leakage box down from 32A to 20A.
4) Install a 16A commando and use the granny charger
5) May be able to install charger on the house instead of the garage and connect direct to consumer unit in house - but think that will mean a fairly long cable to the car. Preference is to charge from the garage.

Missed anything? Naturally I would use an electrician to install anything - but thinking ahead of my options

Nick

 

[Glan gluaisne]

My guess would be the same, that the garage has a radial run of 2.5mm², as that's pretty standard. OK to run at 16 A from that, so either change the garage over to TT (add an earth electrode and Type B RCD) or fit an O-PEN device, plus an interlocked 16 A commando and use the UMC, or install a charge point in the garage wound down to 16 A.

FWIW, I'm in the process of building a charge point that includes a open PEN protection, and DC residual current protection (so needs no expensive Type B RCD or earth electrode/open PEN device) using off-the-shelf parts. It also has an off-the-shelf time switch and variable charge current settings.

Should be finished by tomorrow, with luck, at a total cost of perhaps around £300. I'm doing it partly for fun, and partly as a part of a programme I have of replacing all the custom built electronics in this house to off-the-shelf stuff, as I've accepted that as I get older writing code for obscure bit of kit based around old microcontrollers, or just trying to work out why I wrote code the way I did ten years ago, probably isn't going to get any easier.

 

[LukeUK]

I was in a similar situation, 6 mm² existing supply to the garage, but it already has a ring main, a couple of 16A sockets and some other loads on it, so the EO charger is on its own 6 mm² supply, taken from henley blocks in the meter box. Yes it was a faff digging up the path between the house and the garage, but it was worth it for 7kW with Octopus Go's 4 hour window.

 

[LukeUK]

Should be finished by tomorrow, with luck, at a total cost of perhaps around £300. I'm doing it partly for fun, and partly as a part of a programme I have of replacing all the custom built electronics in this house to off-the-shelf stuff, as I've accepted that as I get older writing code for obscure bit of kit based around old microcontrollers, or just trying to work out why I wrote code the way I did ten years ago, probably isn't going to get any easier.

I've found a couple of open source projects. Have you seen these, or any others?

OpenEVSE - Electric Vehicle Charging Solutions
Smart EVSE | Open Source EV charging

I know there's a difference between tinkering with your own software, rather than someone else's...

Luke

 

[Jason71]

I guess the real question is does your pattern of driving require 32amps or will 10-16 suffice?

 

[NastyNick83]

I guess the real question is does your pattern of driving require 32amps or will 10-16 suffice?

I should have mentioned that in my post.

Current trends aside (nursery runs and the occasional longer journey at weekends) I can't think of any examples where I depleted the battery and needed a full charge the next day in the 10months of ownership. Certainly not likely to be a regular thing.

So the only downside I see from 10/16A is not maximising Agile rates.

 

[Glan gluaisne]

You could push up to about 20 A through 2.5mm² SWA, perhaps even 25 A if the run's not too long, and doesn't pass through any insulation. Main thing to watch will be the terminations each end, as at 25 A the cable's could get a bit warm, so making sure that the terminations are OK at 90°C rather than 70°C might make sense.

At 10m, the voltage drop at 20 A is only going to be ~3.2 V, so a power loss of only about 64 W or so, which is probably not going to make things too warm, and is still well inside the cable rating.

 

[dakaix]

FWIW, I'm in the process of building a charge point that includes a open PEN protection, and DC residual current protection (so needs no expensive Type B RCD or earth electrode/open PEN device) using off-the-shelf parts. It also has an off-the-shelf time switch and variable charge current settings.

Be interested to know what you're using for DC protection. I built my own OpenEVSE charger (in a QUBEV box) during the summer but haven't installed it yet as I haven't sorted DC protection out, all the spark's I've spoken to so far were only interested in installing MATT:E units which I don't have space for.

 

[NastyNick83]

My guess would be the same, that the garage has a radial run of 2.5mm², as that's pretty standard. OK to run at 16 A from that, so either change the garage over to TT (add an earth electrode and Type B RCD) or fit an O-PEN device, plus an interlocked 16 A commando and use the UMC, or install a charge point in the garage wound down to 16 A.

FWIW, I'm in the process of building a charge point that includes a open PEN protection, and DC residual current protection (so needs no expensive Type B RCD or earth electrode/open PEN device) using off-the-shelf parts. It also has an off-the-shelf time switch and variable charge current settings.

Should be finished by tomorrow, with luck, at a total cost of perhaps around £300. I'm doing it partly for fun, and partly as a part of a programme I have of replacing all the custom built electronics in this house to off-the-shelf stuff, as I've accepted that as I get older writing code for obscure bit of kit based around old microcontrollers, or just trying to work out why I wrote code the way I did ten years ago, probably isn't going to get any easier.

I fully intend on taking my EO Pro mini and Matte device with me in the move - not sure I'd buy a car charger for 16A charging - but given I already have it, seems like a better option than commando & UMC combo.

The garage is on a 63A 30mA RCD (with a 20A fuse) from the consumer unit. Can I run the Matte device thingy under RCD (i.e. two lots of protection)?

Nick

 

[NastyNick83]

You could push up to about 20 A through 2.5mm² SWA, perhaps even 25 A if the run's not too long, and doesn't pass through any insulation. Main thing to watch will be the terminations each end, as at 25 A the cable's could get a bit warm, so making sure that the terminations are OK at 90°C rather than 70°C might make sense.

At 10m, the voltage drop at 20 A is only going to be ~3.2 V, so a power loss of only about 64 W or so, which is probably not going to make things too warm, and is still well inside the cable rating.

That's good to know. The whole garage is run off that 20A fuse - so anything plugged into the sockets, lights etc. (although wouldn't expect much / any load while the car is charging) does give a bit of wiggle room to run them in parallel to the car at 16A. I hope.

Nick

 

[Glan gluaisne]

I fully intend on taking my EO Pro mini and Matte device with me in the move - not sure I'd buy a car charger for 16A charging - but given I already have it, seems like a better option than commando & UMC combo.

The garage is on a 63A 30mA RCD (with a 20A fuse) from the consumer unit. Can I run the Matte device thingy under RCD (i.e. two lots of protection)?

Nick

Should be fine just moving the matt:e and charge point and re-installing it at the new place. If the matt:e is the version that contains an RCD, then remove the RCD that's already protecting the garage and use the one in the matt:e, or the other way around. It's not good practice to have two RCDs in series, especially if there's a possibility of there being DC leakage that may blind a non-DC tolerant existing RCD.

The cable to the garage only needs over-current protection from the 20 A MCB, if residual current detection is going to be done at the garage end, and before any outlets, charge point, etc, so the CU may need to be re-jigged to remove the garage feed from one of the RCDs (assuming it's a 17th Ed split CU).

 

[NastyNick83]

Photos of the CU, fuse in garage and the DC leakage device I’ve currently got.

Would I need to reduce the fuse in the DC leakage box?

 

[Glan gluaisne]

Best bet would be to rearrange the CU so that the garage is fed from an MCB that isn't fed from the RCD side of the CU, but directly from the main switch. Not hard to do, just needs a bit of shuffling things around, such that the garage MCB is fed directly from the main switch bus on the left. You can then just swap the existing garage CU for the one that has DC leakage and open PEN protection and all will be fine. The 40 A RCBO could ideally be swapped for a 20 A one, but it could be left as it is, as the circuit would be adequately protected from overload by the MCB in the main board, and it will still provide the needed earth fault protection OK.

 

[Fly.guy]

I have a very similar situation with an external garrage and a limited connection to the house. We have been charging the car at 16a for the last 4 years and it’s never once been an issue.
Occasionally if we get home after a long trip it’ll take more than the 7h off peak night to get back to 50%. But by the end of the second night it’s back up to ‘normal’ day to day charge of 70-80%

And if there was a need to head out next day there is always the option of a supercharger 10miles away...

 

[Glan gluaisne]

@LukeUK and @dakaix ,

I've shifted the off-topic stuff on DIY charge points to this new thread: DIY charge point

 

[NastyNick83]

Best bet would be to rearrange the CU so that the garage is fed from an MCB that isn't fed from the RCD side of the CU, but directly from the main switch. Not hard to do, just needs a bit of shuffling things around, such that the garage MCB is fed directly from the main switch bus on the left. You can then just swap the existing garage CU for the one that has DC leakage and open PEN protection and all will be fine. The 40 A RCBO could ideally be swapped for a 20 A one, but it could be left as it is, as the circuit would be adequately protected from overload by the MCB in the main board, and it will still provide the needed earth fault protection OK.

Makes complete sense - thank you!

I assume I could add the existing garage socket ring to the 40 A RCBO and the lighting circuit to the B6 fuse within the new CU (with DC leakage and open PEN protection).

Don't worry - I will get an electrician to do the work

Thanks for your help!

 

[Glan gluaisne]

Yes, no problem with connecting the garage outlets, as the 20 A MCB in the main CU will be protecting that radial OK from overload. Same with connecting to the 6 A MCB for lighting. If you were to accidentally overload the garage supply, the 20 A MCB in the main CU would trip, but as long as you don't use hefty loads in there whilst the car is charging at 16 A everything should be fine.

Very sensible to get someone competent to do the work, but as this would be considered a modification to an existing outdoor circuit there's no need for any Part P chit or additional sign off, so it could be done by anyone that is competent (and competent isn't defined in the regs, so it's OK to DIY it if you know what you're doing).

 

[NastyNick83]

Yes, no problem with connecting the garage outlets, as the 20 A MCB in the main CU will be protecting that radial OK from overload. Same with connecting to the 6 A MCB for lighting. If you were to accidentally overload the garage supply, the 20 A MCB in the main CU would trip, but as long as you don't use hefty loads in there whilst the car is charging at 16 A everything should be fine.

Very sensible to get someone competent to do the work, but as this would be considered a modification to an existing outdoor circuit there's no need for any Part P chit or additional sign off, so it could be done by anyone that is competent (and competent isn't defined in the regs, so it's OK to DIY it if you know what you're doing).

Interesting re: Part P etc. Given I'm installing the EO Pro mini car charger, does that not need sign off from someone? Or does the DC leakage box void the need for that?

Nick

 

[Glan gluaisne]

Interesting re: Part P etc. Given I'm installing the EO Pro mini car charger, does that not need sign off from someone? Or does the DC leakage box void the need for that?

Nick

Because this is an existing circuit, and all you're doing is changing things at the ends of it, then there's no legal requirement for another Part P EIC to be lodged. The same applies to any changes to existing circuits, and is worth knowing, as it can make things a lot easier with a bit of careful planning.

I'm not Part P registered, only because none of the Part P cartels will accept someone that's competent, but retired, as a member any more (which pretty much proves they are really about protectionism and making money!). When we built our house I had to get a Part P chap to sign it off, because of that. In theory building control are supposed to be able to sign off third party work, but in practice the Part P cartels are reluctant to grant third party sign off rights to members, so it's rare to find a BC dept that can do it. The way I future proofed things, was to add several cable runs, mostly ducted runs of SWA, terminated in wiska boxes, with nothing connected to them. They were all on the EIC and duly tested and signed off against Part P, so I've then been able to add stuff outdoors, like CCTV supplies, garden lights, power to a shed, etc, without breaching any regs, as I've only been changing the ends of existing approved circuits.

 

[Alistairuk]

I have an EO Pro Mini, connected with a DC leakage box of tricks all working perfectly at 32A.

However I have bought a new house (~20years old), which has a separate double garage approx. 10metres away from the main house. The garage does have power. I have not moved in yet and therefore unable to thoroughly examine the electrics but do know it is fed by a 20A fuse in the main consumer unit from the house. It has a separate fuse box in the garage with a ring main and lights.

If I was a betting man I'd say it was 2.5mm SWA cable feeding the garage - why would they install anything thicker 20yrs ago?

Anyone had similar?

Thoughts so far:
1) Run a new cable to the garage, which means digging up a driveway
2) Use granny charger at 10A
3) I think I can switch the EO Pro Mini down to 16A - may be able to run that off the ring main from garage (with the 20A fuse) and charge at 3.7kW instead. Would have to reduce fuse in DC leakage box down from 32A to 20A.
4) Install a 16A commando and use the granny charger
5) May be able to install charger on the house instead of the garage and connect direct to consumer unit in house - but think that will mean a fairly long cable to the car. Preference is to charge from the garage.

Missed anything? Naturally I would use an electrician to install anything - but thinking ahead of my options

Nick

Don't be surprised if it's just a normal ring main cable in a plastic pipe - what I found installed between our house and garage!! (No idea who installed that 35 years ago!)

Worse of all it wasn't even a single plastic pipe, it was in sections and ended up having to dig a trench to find the damn thing which of course took a random, non-direct path across the garden - since it proved impossible to just pull the new cable through with the old!

The end result is I have new cable running from house box to garage where it terminates in a fuse box (breakers) and then on to the lights, sockets and car chargers.