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UMC charging - naughty idea, or deadly?

Avendit

Active Member
Apr 18, 2019
1,168
791
EDI
We use the UMC to charge at both set of parents, and despite a couple of years of hinting, nether have installed a 16a commando for me. They both have well wired double sockets on ring mains which work fine at 10A, but I'd like to go faster. So the question:

Where on the scale of a bit naughty through to death, flames and blown up cars would be making a 2 plug to 16A commando adaptor be?

If I replaced their double sockets with a commando, that would be fine as the ring would be happy at 16A, so what would go wrong with this idea? I kind of assume something, but don't know enough to know what. Definitely not splitting phases or anything, talking about a 6" adaptor to tap both half's of a double UK socket.

Knowledge electricians of the forum: go!
 

MrT3

Active Member
Jun 26, 2021
1,647
1,082
UK
No one can say it’s a good idea, totally at your own risk and doesn’t conform to current regulations. Sockets are meant to be tested at 20 Amps across both sockets to pass the BS standard but personally I’d only trust an MK socket with that load and you need to make sure the other wiring at all the other sockets in the ring is good.

You also need to think about the load on the ring. If other appliances are in use you could trip the 32 Amp breaker.
 

Adopado

Well-Known Member
Aug 19, 2019
6,318
4,830
Scotland
We use the UMC to charge at both set of parents, and despite a couple of years of hinting, nether have installed a 16a commando for me. They both have well wired double sockets on ring mains which work fine at 10A, but I'd like to go faster. So the question:

Where on the scale of a bit naughty through to death, flames and blown up cars would be making a 2 plug to 16A commando adaptor be?

If I replaced their double sockets with a commando, that would be fine as the ring would be happy at 16A, so what would go wrong with this idea? I kind of assume something, but don't know enough to know what. Definitely not splitting phases or anything, talking about a 6" adaptor to tap both half's of a double UK socket.

Knowledge electricians of the forum: go!
I would be concerned about the other sockets on the ring. The ring isn’t really a loop with the sockets attached … rather the connections on each socket form an integral part of the ring. This means that a loose connection on any of the other sockets introduces a weak point (heat point) in the ring and therefore your supply. If you remove every socket on the ring and redo all the connections I suppose you could reduce that risk but it’s always an issue not having an uninterrupted single cable supply. Thou it would work I think I would be looking for another way to achieve your aim. (Disclaimer: I am not an electrician. )
 

pgkevet

Active Member
Jul 1, 2019
1,886
1,695
mid wales
So much easier just to wire in a commando socket than pratt around with two 13A plugs especially if they are outdoor sockets where visual appearance will hardly matter - don't forget to add a sticker to the 13A cover with 'do not use if commando in use'. A committed Tesla owner is bound to carry drills, wire and command sockets in the frunk...
 
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Apart from the concerns already raised, you can't plug in both sockets simultaneously, so when one plug is connected the other is live.

Switched sockets don't really help that much as you may forget to switch it off before plugging in/unplugging or leave one switched off and therefore overload the other.

I think its an incredibly bad idea, especially as it's targeted for use in other people's homes.
 
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Drew57

Active ember
Apr 4, 2020
1,438
1,717
Chester UK
Where on the scale of a bit naughty through to death, flames and blown up cars would be making a 2 plug to 16A commando adaptor be?
I think its an incredibly bad idea, especially as it's targeted for use in other people's homes.

I agree... trickle charging your granny is preferable to eviscerating your parents

(& receiving both family inheritances early is probably not the prime reason @Avendit is considering this )
 
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Adopado

Well-Known Member
Aug 19, 2019
6,318
4,830
Scotland
It may be feasible to have a general purpose commando wired to the board directly on its own circuit at small cost depending on the existing layout. Done properly even without the EV safety “extras” it would be as safe or safer than plugging the UMC into a 13amp socket.
 

Avendit

Active Member
Apr 18, 2019
1,168
791
EDI
I would be concerned about the other sockets on the ring. The ring isn’t really a loop with the sockets attached … rather the connections on each socket form an integral part of the ring. This means that a loose connection on any of the other sockets introduces a weak point (heat point) in the ring and therefore your supply. If you remove every socket on the ring and redo all the connections I suppose you could reduce that risk but it’s always an issue not having an uninterrupted single cable supply. Thou it would work I think I would be looking for another way to achieve your aim. (Disclaimer: I am not an electrician. )
And while the UMC monitors the temp of the socket it's attached to, there is no way to do this with the ring main.

So definitely heading towards the flames end of the scale then. Certainly discount doing it at my parents then. (jk).

Thanks all for warnings and thoughts. I knew it would be bad, I just couldn't see why...
 
A commando socket connected to a 13amp plug would give the exact same results as a commando socket connected to two 13amp plugs! It would make absolutely no difference.

Your load would all be from the same double socket - actually, wiring two 13amp plug tops into one commando would be much more dangerous as described by a previous poster (potential one live plug when unplugged) with absolutely zero gain.

If you have a commando connected to a 13amp plug, and say in theory you put a 20amp fuse in the plug top- it would still charge at the 10amp as i believe the restriction is in the charging cable/connector..
 

Avendit

Active Member
Apr 18, 2019
1,168
791
EDI
It may be feasible to have a general purpose commando wired to the board directly on its own circuit at small cost depending on the existing layout. Done properly even without the EV safety “extras” it would be as safe or safer than plugging the UMC into a 13amp socket.
This is what I had at home for almost a year - but it was a garage spur that I re used while knowing there was pretty much sod all else on the circuit. Hadn't thought of the problems of relying the rest of a ring. Stupid post war metal scarcity ideas (on the continent they just use spurs for everything, but at double the cable sizes).
 

Adopado

Well-Known Member
Aug 19, 2019
6,318
4,830
Scotland
A commando socket connected to a 13amp plug would give the exact same results as a commando socket connected to two 13amp plugs! It would make absolutely no difference.

Your load would all be from the same double socket - actually, wiring two 13amp plug tops into one commando would be much more dangerous as described by a previous poster (potential one live plug when unplugged) with absolutely zero gain.

If you have a commando connected to a 13amp plug, and say in theory you put a 20amp fuse in the plug top- it would still charge at the 10amp as i believe the restriction is in the charging cable/connector..
the assumption is that you use the commando attachment for the UMC which automatically sets the amps
 
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WannabeOwner

Well-Known Member
Nov 2, 2015
6,933
3,690
Suffolk, UK
Presume you've tried the "thoughtless" approach on the Inlaws? If they can afford it they should be doing it so that their grandchildren have a planet to grow up on, and should be getting an EV & PV for themselves too. If elderly and/or rural location then not going to the smelly filling station forecourt will be a bonus for them, even if they don't know that yet.

If they can't afford it then get your own wallet out and treat them :cool:

Then its down to reducing the cost of the install. Charger off eBay maybe? I think Commando is a compromise, in the sense that at some future point a wall charger will be a better choice for the incumbents (even if at present its only the occasional need for a visitor).

13AMP (realistically, say, 2.4kW). 5PM arrival to 9AM departure = 15 hours. x 7MPH = 100 miles

16AMP, assuming a straight 16/13 = 23% improvement would be 123 miles. Maybe the actual benefit is more than that? Otherwise doesn't seem very worthwhile (but I may well be missing the bleeding-obvious)

OTOH 32AMP Commando (or wall charger) is going to be a lot better ...
 
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Adopado

Well-Known Member
Aug 19, 2019
6,318
4,830
Scotland
This is what I had at home for almost a year - but it was a garage spur that I re used while knowing there was pretty much sod all else on the circuit. Hadn't thought of the problems of relying the rest of a ring. Stupid post war metal scarcity ideas (on the continent they just use spurs for everything, but at double the cable sizes).
Yes, same here… I have a garage spur with my emergency backup commando. I know exactly what’s on the circuit and the commando is cabled direct to the mini consumer unit.
 
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Adopado

Well-Known Member
Aug 19, 2019
6,318
4,830
Scotland
Presume you've tried the "thoughtless" approach on the Inlaws? If they can afford it they should be doing it so that their grandchildren have a planet to grow up on, and should be getting an EV & PV for themselves too. If elderly and/or rural location then not going to the smelly filling station forecourt will be a bonus for them, even if they don't know that yet.

If they can't afford it then get your own wallet out and treat them :cool:

Then its down to reducing the cost of the install. Charger off eBay maybe? I think Commando is a compromise, in the sense that at some future point a wall charger will be a better choice for the incumbents (even if at present its only the occasional need for a visitor).

13AMP (realistically, say, 2.4kW). 5PM arrival to 9AM departure = 15 hours. x 7MPH = 100 miles

16AMP, assuming a straight 16/13 = 23% improvement would be 123 miles. Maybe the actual benefit is more than that? Otherwise doesn't seem very worthwhile (but I may well be missing the bleeding-obvious)

OTOH 32AMP Commando (or wall charger) is going to be a lot better ...
13amp via UMC is only 10amps in reality whereas the 16 amp commando is a real16 amps so a very useful extra. Of course32 is even better!
 

Avendit

Active Member
Apr 18, 2019
1,168
791
EDI
If you have a commando connected to a 13amp plug, and say in theory you put a 20amp fuse in the plug top- it would still charge at the 10amp as i believe the restriction is in the charging cable/connector..
The UMC knows which adaptor it has and tells the car to limit appropriately. So with an adaptor to the commando, you could pull 16a through a socket.
 
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Avendit

Active Member
Apr 18, 2019
1,168
791
EDI
Presume you've tried the "thoughtless" approach on the Inlaws? If they can afford it they should be doing it so that their grandchildren have a planet to grow up on, and should be getting an EV & PV for themselves too. If elderly and/or rural location then not going to the smelly filling station forecourt will be a bonus for them, even if they don't know that yet.

If they can't afford it then get your own wallet out and treat them :cool:

Then its down to reducing the cost of the install. Charger off eBay maybe? I think Commando is a compromise, in the sense that at some future point a wall charger will be a better choice for the incumbents (even if at present its only the occasional need for a visitor).

13AMP (realistically, say, 2.4kW). 5PM arrival to 9AM departure = 15 hours. x 7MPH = 100 miles

16AMP, assuming a straight 16/13 = 23% improvement would be 123 miles. Maybe the actual benefit is more than that? Otherwise doesn't seem very worthwhile (but I may well be missing the bleeding-obvious)

OTOH 32AMP Commando (or wall charger) is going to be a lot better ...
The 16a is a hugh step up as you loose almost 2a to running the car systems while charging. So it's really 8a up to 14a going into the battery - almost double.
 

Avendit

Active Member
Apr 18, 2019
1,168
791
EDI
Presume you've tried the "thoughtless" approach on the Inlaws? If they can afford it they should be doing it so that their grandchildren have a planet to grow up on, and should be getting an EV & PV for themselves too. If elderly and/or rural location then not going to the smelly filling station forecourt will be a bonus for them, even if they don't know that yet.

If they can't afford it then get your own wallet out and treat them :cool:

Then its down to reducing the cost of the install. Charger off eBay maybe? I think Commando is a compromise, in the sense that at some future point a wall charger will be a better choice for the incumbents (even if at present its only the occasional need for a visitor).

13AMP (realistically, say, 2.4kW). 5PM arrival to 9AM departure = 15 hours. x 7MPH = 100 miles

16AMP, assuming a straight 16/13 = 23% improvement would be 123 miles. Maybe the actual benefit is more than that? Otherwise doesn't seem very worthwhile (but I may well be missing the bleeding-obvious)

OTOH 32AMP Commando (or wall charger) is going to be a lot better ...
One set of parents are very set on the next car being an EV, just waiting for the right one. Currently outback users, so the newly announced suberu might persuade them (Y is too expensive and doesn't have enough ground clearance for their imaginary uses).

Other side first step is to persuade them to get trvs on the radiators 🙄. Could well treat them, hadn't thought of that, so thanks. I wonder if there are any early Tesla chargers on eBay that are being upgraded to v3's?
 

NewbieT

Active Member
Aug 16, 2019
1,563
1,133
North West
Technically it might work, but I would personally put it in the unsafe category, reasons posted above.

I got Mum & Dad to fit a 16A commando with isolator + RCBO (with DC tripping). It doesn’t have PEN fault detection. If I need to top up because I’m heading onwards 16A vs 10A makes fairly big difference.

Mum & Dad won’t let me pay for electricity but they get help in other ways. They’re now thinking of getting a charge point fitted (because the next car will be electric).
 
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WannabeOwner

Well-Known Member
Nov 2, 2015
6,933
3,690
Suffolk, UK
13amp via UMC is only 10amps in reality whereas the 16 amp commando is a real16 amps so a very useful extra

Thanks.

I recollected an ancient thread and had a search, this one looks useful

 

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