Wiring the motorhome properly.

[TheMobileWanderer]

OK, so after reading a supposedly complete guide to motorhome wiring, I have discovered I have more questions now than previously. lol (It was far from complete and, for clarity, it wasn't in MHF).

My system will be 48V with much running at 230V on 2.5mm T&E wiring.

1. Where can I find out reliably, which is more efficient; conversion from 48V to 12V or inversion to 230V. That might help me determine whether to run USBs/lighting on 12v or 230V.

2. I have gleaned the 12V wiring should be direct from the 12V fuse box to each 12V outlet. No leapfrogging from one outlet to another. Is that correct?

3. I also glean that the 230V circuitry should be like a ring main, feeding each socket from the previous one, as if in a loop, but not actually being a complete ring, which means there's no last section to run back to the consumer unit. So, it's not a ring. Maybe that means it's linear like good quality Christmas lights? (I mean the ones that don't all go out when one bulb has blown). Anyway, which method is correct and best in terms of least potential for issues later?

4. I wonder; for troubleshooting and to find breakages due, perhaps, to vibration, should the 230V circuits be individual, like the 12V system, with each being fed on its own wiring from the consumer unit?

5. Also, should the wiring be in trunking or conduits or should it be secured tightly? I imagine securing tightly may still enable friction or fatigue from vehicle vibration but, I don't know.

I need to know.

I neither object if more wiring may be required nor if the system would require additional fuses or RCBOs.

Any advice welcome.

Ooops; Jim , would you mind please moving this to the wiring forum. Accidentally put it in the solar forum. Apologies.

 

[Bobby-gg]

When you state the 240v wiring is 2.5mm T&E, do you mean this?

Or do you mean this?

 

[TheMobileWanderer]

Well I was thinking flex (2nd photo) rather than (stiffer) cable (1st photo?).

Whichever is correct, though.

Possibly H07RNF rubber flex.

 

[Lenny HB]

You must use 3 core flex for the 230v wiring as rigid T&E can break under vibration where it's terminated.

For 230v mains you normally use a radial circuit not a ring, so each socket is wired back to the consumer unit.

You can have more than one low voltage socket on the same cable run providing the cable and fusing is suitable.

If running cables under a double floor no need for trunking but advisable to clip it in place and try to keep low voltage and mains wiring seperate (most manufacturers don't bother).

 

[MisterB]

2nd photo, needs to be stranded wire ....

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[BillyBear]

Here a few answers to your questions
1 Motorhome manufacturers and van converters have been using 12v systems for a long time why would you want to change that?
2 see question 1 you said 48v and then further on you say the 12v will have individual circuits ?
3 You are correct the 230v circuit is not a ring but known as a radial. Sockets on one radial heater on another circuit etc.
4 Is a bit it like 3.
5 If like my motorhome,the wiring is in flexi conduit but not very well secured
All the mains cable on my motorhome are 1.5mm and not 2.5 and it is known as 3 core flex not twin and earth. If you go to a wholesaler and ask for twin and earth you will get the flat grey one.

 

[scotjimland]

You will find this useful ..

Caravan Installations Regulations

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[scotjimland]

MAINS ELECTRICAL INSTALLATIONS IN TRAILER CARAVANS AND MOTOR CA

INFORMATION LEAFLET: MAINS ELECTRICAL INSTALLATIONS (NOMINAL VOLTAGE 230V + 10% - 6% AC) IN TRAILER CARAVANS AND MOTOR CARAVANS The contents are based on the British Standard 7671, 2001 (I E E Wiring Regulations, sixteenth edition) incorporating...

www.motorhomefun.co.uk

 

[Bobby-gg]

Well I was thinking flex (2nd photo) rather than (stiffer) cable (1st photo?).

Whichever is correct, though.

Possibly H07RNF rubber flex.

Phew, just making sure after you described it as using T&E

 

[MisterB]

In reality 1.5mm flex can carry 16A, so you could wire up your 240v system using 1.5mm BUT you need to work out what it will be 'feeding' at any one time, as you don't want to be pulling too much current along one cable at any one time, so a few radial circuits, running straight back to your consumer unit might be the best option.

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[meanders]

I hope you are also aware that 48v DC is capable of significant arcing when compared with 12v so you need to ensure any bare terminals are somehow isolated or insulated from any metal or any other terminal. Last thing you need is a fire.

 

[TheMobileWanderer]

Here a few answers to your questions
1 Motorhome manufacturers and van converters have been using 12v systems for a long time why would you want to change that?

1. Because, I think, 48V is better for storage and the wiring should be thinner and cheaper because the amperage is lower than if it were 12V. I'll be running a 5kVA+ inverter which, I understand, means 12V isn't adequate/appropriate.
2. Because I've an aversion to doing things 'just because that's the way we've always done it'.

2 see question 1 you said 48v and then further on you say the 12v will have individual circuits ?

Yep. 48V storage and adjust to the usable voltage as determined by each appliance voltage, such as lighting/USBs: 12V, macerator WC: 24V, aircon (potentially): 48V or kitchen equipment: 230V (No diesel heating or gas)

3 You are correct the 230v circuit is not a ring but known as a radial. Sockets on one radial heater on another circuit etc.
4 Is a bit it like 3.
5 If like my motorhome,the wiring is in flexi conduit but not very well secured.

All the mains cable on my motorhome are 1.5mm and not 2.5 and it is known as 3 core flex not twin and earth. If you go to a wholesaler and ask for twin and earth you will get the flat grey one.

 

[TheMobileWanderer]

Thank you all.

In reality 1.5mm flex can carry 16A, so you could wire up your 240v system using 1.5mm BUT you need to work out what it will be 'feeding' at any one time, as you don't want to be pulling too much current along one cable at any one time, so a few radial circuits, running straight back to your consumer unit might be the best option.

Good points there though I think I'll use a standardised thickness (2.5mm) to try to reduce any errors with maintenance later on. Trying to keep it simple for any future owner, if there is one.

I hope you are also aware that 48v DC is capable of significant arcing when compared with 12v so you need to ensure any bare terminals are somehow isolated or insulated from any metal or any other terminal. Last thing you need is a fire.

Yep, thanks for that.
I think I'll be using Lynx distributors. Are you thinking of any other places specifically, where arcing may occur? (I'm used to working with 230V domestically).

 

[68c]

A quick Google has just taught me 48vDC is the normal battery storage for house solar systems. Perhaps you are on to a good thing, I imagine there are a lot more house systems than motorhomes so it may be you can buy the kit cheaper without mentioning the 'motorhome' word which always seems to push the price higher. Perhaps have your solar array at 48v as well.

 

[meanders]

Thank you all.

Good points there though I think I'll use a standardised thickness (2.5mm) to try to reduce any errors with maintenance later on. Trying to keep it simple for any future owner, if there is one.

Yep, thanks for that.
I think I'll be using Lynx distributors. Are you thinking of any other places specifically, where arcing may occur? (I'm used to working with 230V domestically).

any switches or relays need to be suitably specc'd.

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[pappajohn]

My system will be 48V with much running at 230V on 2.5mm T&E wiring.

Do NOT use T&E domestic cable.
It's designed for a static installation, not one subject to movement and vibration.
Multi strand copper cable is more suitable.

 

[TheMobileWanderer]

A quick Google has just taught me 48vDC is the normal battery storage for house solar systems. Perhaps you are on to a good thing, I imagine there are a lot more house systems than motorhomes so it may be you can buy the kit cheaper without mentioning the 'motorhome' word which always seems to push the price higher. Perhaps have your solar array at 48v as well.

Yes, three arrays at 48V. (subject to finding space for aircon, which may site beneath a panel). I priced what I need at 12v. It was scary thousands, 12k-15k (GBP) if I recall. Read about solar and watched a guy 'cleversolarpower' and his youtube tutorials and book. I carried on learning and reading, from there. Priced 48V and with more power and cheaper wiring, the components were all cheaper. Total at 48V - £6k incl VAT. Haven't considered 12V since. This isn't just a project for the Motorhome though. It's a test-bed for if/when I put the house off-grid.

 

[TheMobileWanderer]

Do NOT use T&E domestic cable.
It's designed for a static installation, not one subject to movement and vibration.
Multi strand copper cable is more suitable.

Thanks pappajohn.
I'm considering either/both 2.5mm flex (multi-strand) and H07RNF rubber flex. When I wrote 2.5mm T&E, I hadn't realised it meant stiff cable, distinctly/specifically.

 

[autorouter]

Many points have already been covered, but here's a few more. I'm sure you're aware of this already, but the 230V breakers need to be double-pole types. The MCB and RCBO breakers available in DIY stores in UK are all single-pole and are not suitable. Get double-pole breakers from specialist electrics suppliers like CEF, or maybe caravan accessories shops.

The consumer unit boxes are also not quite right, because they usually have a 'common neutral busbar', which is not required for double pole circuits. However these consumer units can be used if you ignore the neutral bar.

In a motorhome you will have sheathed twin or 3-core cables for 230V wiring and 12V wiring. Maybe even for 48V. You could adopt a colour code such as white for 230V and black for 12V.

12V wiring in the presence of 230V wiring needs to have the same insulating layers as 230V wiring. That means no 'thin wall' 12V wiring, use full thickness insulation. And maybe use 230V-grade sheathed 2.5mm² twin cable for cable runs to 12V sockets and appliances.

 

[TheMobileWanderer]

Many points have already been covered, but here's a few more. I'm sure you're aware of this already, but the 230V breakers need to be double-pole types. The MCB and RCBO breakers available in DIY stores in UK are all single-pole and are not suitable. Get double-pole breakers from specialist electrics suppliers like CEF, or maybe caravan accessories shops.

The consumer unit boxes are also not quite right, because they usually have a 'common neutral busbar', which is not required for double pole circuits. However these consumer units can be used if you ignore the neutral bar.

In a motorhome you will have sheathed twin or 3-core cables for 230V wiring and 12V wiring. Maybe even for 48V. You could adopt a colour code such as white for 230V and black for 12V.

12V wiring in the presence of 230V wiring needs to have the same insulating layers as 230V wiring. That means no 'thin wall' 12V wiring, use full thickness insulation.

Thanks autorouter Yep, I've read your previous posts about double pole breakers.
Good tip about insulation, I think.
As I read it, the principle should be that the minimum insulation used, should be the maximum needed by any specific voltage. So with 230V potentially beside 12V, the minimum insulation, on both wirings, should be that (thicker) needed for 230V cabling.

The handbook I am writing for the electrical system is challenging too.
Indexed and summarised because I want as much as possible to be easily accessible rather than making someone wade through a huge manual for one 'little' piece of info.

And maybe use 230V-grade sheathed 2.5mm² twin cable for cable runs to 12V sockets and appliances.

?? You mean the stiff 2.5mm single thread wires in grey sheath?

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[autorouter]

My motorhome set up is similar to what you are proposing. I have a Multiplus 3000 and 7kWh of 48V batteries (equivalent to about 600Ah at 12V). I run electric appliances like microwave, kettle, airfryer and rice cooker. A Sterling 12V-48V B2B charges the 48V directly while driving. It takes 70A from the 12V alternator.

My original idea was to run the 12V hab circuits from a 48V DC-DC converter. I bought a 20A (240W) converter to do this. However I decided to leave the original 12V 100Ah leisure battery in place, powered by the split charge relay through the EBL. Mostly because if there's ever an issue with the 48V side, I have a fully charged and functioning leisure battery as a backup for basic motorhome facilities.

I also have an LPG tank, which runs the Truma heater/water heater, fridge, hob and oven.

I don't have any solar (yet). We tend to stop in one place for two or three days, then move on. I often use aires with (low-amps) hookup, so keeping topped up isn't a problem. I have fitted an EV inlet socket on the side of the motorhome, so I can stop at an EV charger point for a couple of hours to top up if required.

 

[autorouter]

?? You mean the stiff 2.5mm single thread wires in grey sheath?

No, definitely not. I got a reel of stranded 2.5mm² twin cable with black sheath, that I use for runs to 12V sockets and appliances. Twin pos/neg cable is used a lot in motorhomes. In metal cars, and even panel vans, there is usually an easy negative return path through the bodywork and chassis to save running a negative wire to every device. However in a coachbuilt motorhome it's not easy to find a metal return path, so twin wires are more common.

 

[Raul]

Regarding breakers MCB's next time you go abroad, or ask a funster on return from France, pop in Leroy Merlin or Brico Depo, and get some proper breakers, single module double pole. Makes the installation much simpler, and takes half the space in CU. Uk double pole are double module so you loose allot of ways in the CU.
And remove the neutral bar completely, you don't need it.

Like this ones

 

[scotjimland]

Regarding breakers MCB's next time you go abroad, or ask a funster on return from France, pop in Leroy Merlin or Brico Depo, and get some proper breakers, single module double pole. Makes the installation much simpler, and takes half the space in CU. Uk double pole are double module so you loose allot of ways in the CU.
And remove the neutral bar completely, you don't need it.

Like this ones

good tip, and double pole, one module MCBs are also available in the UK

 

[Raul]

good tip, and double pole, one module MCBs are also available in the UK

Thanks for the heads up, , can you give us an example/ link please?

Edit, just found some £40 for a schneider
Wow.

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[BillyBear]

I am very much looking forward to reading the handbook you are writing. It will be very interesting

 

[TheMobileWanderer]

I am very much looking forward to reading the handbook you are writing. It will be very interesting

I guess that's referencing my post.
l'll certainly publish it but unless the electrical system is that which I've designed/created, it'll only be of use to other electrical people in terms of improving their handbooks.

 

[BillyBear]

I guess that's referencing my post.
l'll certainly publish it but unless the electrical system is that which I've designed/created, it'll only be of use to other electrical people in terms of improving their handbooks.

Yes it was. I was going to ask how you would charge those batteries with a 12v alternator but Autorouter answered that one for me in one of his posts. How much solar will you use to keep them charged and what amps per battery will they be. A 5Kva inverter would pack a decent wallop and it makes me wonder what you are trying to power with all that.

 

[TheMobileWanderer]

I'm contemplating a 48V alternator but a converter to 48V might suffice.
Solar is currently planned to be 2380W in total. 300W, 195W and 100W, 4 of each in series and either joined in parallel or each using its own MPPT.
I'm building it to power similarly to the house - a test-bed for making the house off-grid as much as never needing grid or ehu in moho. And at 48V, its much cheaper than a 12V set-up

 

[scotjimland]

Thanks for the heads up, , can you give us an example/ link please?

Edit, just found some £40 for a schneider
Wow.

WCED 6kA MCB’s 2 pole Single mod. WKN106B – UK EV Installers Shop

WCED 6kA MCB’s 2 pole Single mod. WKN106B 6A B Curve 2P 1 Module 6KA MCB Dimensions (W x H x D mm) - 17.8 x 82.4 x 78.5 Rated current In (A): 6,10,16,20,25,32,4

shop.ukevinstallers.co.uk

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