2 consumer units 1 ring

[Bumblewing]

hi all, im working on a horse lorry to camper conversion and i have 3 power sources
1. Solar
2. Electric hookup (shore power)
3. Generator.

Explanation:
I have one consumer unit that is used for the shore power and generator and i have a switch which i can switch between the two, so i can either use the generator (if electric hookup/shore power not available) or if im on a campsite i can flip the switch to shore power. i think you get what im saying.

The second consumer unit is connected from my 3000w inverter, i would also like to add that i also have a switch which i use to switch between the two consumer units depending where i am getting power from.

What I'd like to do:
I'd like to add 1 ring to the two consumer units.

Question:
How can I add 1 ring to 2 consumer units and have the ring supplied with power depending where the power is coming from eg, Inverter, Generator or Shore Power? can I add a 2 way switch and connect the two consumer units to ring via the switch.

Sorry if this sounds complicated.

 

[Bumblewing]

 

[yorkspark]

Thats wrong and cannot be done, should only have 1x cu with the genny plugging into the 16a shore power socket, and 10a radials for the sockets.
The max power is only 16a, less in eu countries so a ring would be pointless

the changeover switch should be wired before the cu with the shore/genny to 1 input and inverter (with a remote on/off) to the other input and the outgoing to the double pole rcd protected cu.
The socket earths should be connected straight through and not be switched by the changeover
The battery black is negative not earth and if you have an isolated dc to dc charger, should not have a connection to the chassis negative

 

[securespark]

Why bother with a ring final at all?

 

[ericmark]

My house has battery, solar and grid all synchronised together, so I am sure it could be done with a boat, however the size and cost means not really something one would want to do if there is another option.

The narrow boats often only had a 5 amp shore supply and again there are special inverters that can combine the shore and battery supply, but again not cheap.

With a narrow boat weight is not a problem, you just remove more ballast, but with a road vehicle even if it can carry the weight, it means more fuel is used.

The easy was is run all off an inverter, and turn all power in to DC to maintain/charge the batteries. Then no synchronising required.

My solar panels work on around 54 volt, the solar panels around 250 volt, and AC 230 volt. The higher the battery voltage the less amps, a 230 volt outlet at 13 A needs 130 amp 24 volt and 260 amp at 12 volt, so the higher the battery voltage the better.

Inverter generators can have a DC link to a second generator, not looked into voltage.

But I would think a simple plug and socket arrangement would work better, plug the consumer unit into which supply you want to use, automated syncnised change overs are expensive and I would avoid them.

 

[ebee]

Why bother with a ring final at all?

Well both radials and rings have advantages and disadvantages too.
So there is no harm in doing a ring if you want to.
Can reduce volt drop.
Gives a chance that a break in the earthwire still leaves all points effectively earthed.
In short, you could have say a 16A ring final circuit if that is what you want to do.

 

[securespark]

I could imagine the first may be valid in a large house but not a horsebox.

Re the second point: for all points to still be effectively earthed, there would have to be only one break in the CPC ring.

 

[ebee]

Yes I know ref volt drop but it doesn`t hurt though does it?

But yes second point, you are absolutely correct but if you consider the two (ring v radial) one break in a ring = still effectively earthed but one break in a radial could leave a number of points unearthed. If a group of say 2 or 3 or 4 are so unearthed and an earth fault on one could cause not just that one chassis to become live but a few of them to also become live.

As I said, there are advantages/disadvantages with both methods

 

[EFLImpudence]

In short, you could have say a 16A ring final circuit if that is what you want to do

Not with conductors of CCC less than 16A, you can't so it wouldn't be a UK ring final circuit.

 

[ebee]

Not with conductors of CCC less than 16A, you can't so it wouldn't be a UK ring final circuit.

ELFI are you putting words in my mouth? anyway if all other things are correct then what prevents you putting in a ring of 1.0 or 1.5 0n a circuit - example - a lighting circuit or such.

 

[EFLImpudence]

Nothing - but it wouldn't be what people mean by a (UK) ring final circuit as per 433.1.204.

It would just be a compliant radial final circuit with the end also connected to the OPD - which could be split anywhere along its length to leave two compliant radial final circuits.

 

[ericmark]

I can see point in a ring, but not a ring final, whole idea of the ring final is a 32 amp supply using 20 amp cable, a bit pointless in a horse box. Wiring should be flex so really need pin crimps to ensure no stray filaments, basic following rules used in a caravan. There are special consumer units for caravans with things like push buttons to reverse line and neutral, and all MCB's are often twin pole.

I note with my inverter instructions say

so one has to be very careful, it is clearly not a DIY job, and from the days when I was involved with narrow boats and caravans things have moved on. Even the wagon electrics have moved on, some now use a version of probus for the rear lights etc.

I would still go for the all turned into DC and feeds battery, then an inverter on the battery, far easier than grid tie. But there may be a off the shelf inverter which does it all, I would say post on a narrow boat forum, they are more into this multi-supply use.

 

[SUNRAY]

I can see point in a ring, but not a ring final, whole idea of the ring final is a 32 amp supply using 20 amp cable, a bit pointless in a horse box. Wiring should be flex so really need pin crimps to ensure no stray filaments, basic following rules used in a caravan. There are special consumer units for caravans with things like push buttons to reverse line and neutral, and all MCB's are often twin pole.

I note with my inverter instructions say View attachment 319651
so one has to be very careful, it is clearly not a DIY job, and from the days when I was involved with narrow boats and caravans things have moved on. Even the wagon electrics have moved on, some now use a version of probus for the rear lights etc.

I would still go for the all turned into DC and feeds battery, then an inverter on the battery, far easier than grid tie. But there may be a off the shelf inverter which does it all, I would say post on a narrow boat forum, they are more into this multi-supply use.

And with respect probably not for a lot of the qualified electricians either.