Consumer unit/ B2B help needed (1 Viewer)

[Mr Meenah]

I'm surprised I even got this far as I have no previous experience but it charges and inverts and switches so I must of done something right..inserts smug face.
This is the AC Side of things set up in he workshop before I find a place for it in the van. At the moment the Shore power goes straight into the Charger/inverter without being protected. The Consumer unit ( connected to AC out ) has a red lamp on it that lights up if the polarity is reversed as is the case on some foreign campsites. Logic would tell me I need to connect shore power to the consumer-unit and the consumer-unit to charger/inverter. This however would mean I need another consumer unit between the inverter and the living area. Is this right?
Also which side of the isolator switch does the +ve from the B2B charger go?

 

[Abacist]

Surely the first thing the shore mains must be wired into is Residual Current Device Trip then to the charger/inverter.
On my van I don't have a charger/inverter but I have a separate inverter and the 240 volts produced by it goes to an RCD trip before the consumer unit and the external mains goes first to an RCD trip then to the surge protection device then to the consumer unit.

 

[Mr Meenah]

That's what logical to me too. Do you have a picture of your set-up?

What side of the battery isolator would you put the feed from the B2B feed?

 

[autorouter]

Because the mains is potentially lethal, you have to think carefully about all possible scenarios that might arise in the future, including the possibility that someone else who doesn't know how it's wired will be setting it up and using it.

First, you need two RCDs. Hookup power goes straight to one, and inverter power goes straight to the other.

There will be things you want to never be connected to the inverter, like the charger. Also some things you don't really want to be connected to the inverter, like the mains elements in the water heater and space heater. These can go on an MCB wired to the hookup RCD.

For simplicity, you can just wire some sockets to an MCB from the inverter RCD, and wire some different sockets to an MCB from the hookup RCD. Mark them in some way so there's no confusion. No need for any switches if you do that.

If you want some switching arrangement, you need to be careful that you can never switch on both at the same time. You need a proper changeover switch that switches one source off before the other source is switched on. A 'break-before-make double pole changeover' switch. The switch can be manual, or alternatively a relay (electrically operated switch) that automatically switches over whenever the hookup is connected up.

You then wire an MCB that is switched between hookup and inverter RCDs, and wire the items/sockets you want to be always powered to that.

In my MH I have a big consumer unit box with two RCDs, several MCBs, and a manual changeover switch on one side.

 

[autorouter]

What side of the battery isolator would you put the feed from the B2B feed?

I'm sure there's a variety of opinions. My view is, an isolator is for isolating the battery from everything, so put it on the side away from the battery. In fact I'd be tempted to put it on the far side of the fuse, as long as the fuse is big enough - ie on the positive busbar.

You'll notice that the alternator feed always goes straight to the starter battery. That's because if it's disconnected from the battery while the engine is running, it blows the diodes in the alternator. That's not a problem with a B2B, as far as I know.

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[Mr Meenah]

Great info. The Sterling charger/inverter switches automatically ( seamlessly apparently) from mains/inverter & inverter/mains. There is only one AC out and I'll connect a consumer unit to it. The charger will only be connected to mains and when not on EHU charging will be through the B2B to start with. I have two 132ah LiFePo4 batteries and will see how I get on with them before, and if, fitting solar. I aim to travel as opposed to spend weeks 'boondocking'.

 

[Wissel]

Personally I'd opt for two separate consumer units. One between EHU point and the inverter/charger that powers the charger and a fridge on 240v/water heater on 240v/etc and a second from the inverter.

I'd wire all sockets (apart from ones you never want running from battery power, like a fridge on 240v etc) to the inverters consumer box.

I've done similar for my next conversion. I have a separate 240v charger and inverter, so in my van one consumer unit is connected to EHU point and powers my charger. This unit has polarity protection and double pole MCB's. The second is after the inverter and powers everything else. I don't have any appliances that should only run on mains power, so only have my charger connected to consumer unit one, but the idea is the same.

 

[Mr Meenah]

@Wissel it sounds like we might have the same consumer unit with double pole mcb's although I dont know whether it has polarity protection or just a light that comes on if mains polarity is reversed..
I would need the socket for my fridge to be connected to inverter power as its a domestic fridge, likewise I'll be cooking with a 240v induction hob as I've no gas in ghe Camper.

 

[Wissel]

@Wissel it sounds like we might have the same consumer unit with double pole mcb's although I dont know whether it has polarity protection or just a light that comes on if mains polarity is reversed..
I would need the socket for my fridge to be connected to inverter power as its a domestic fridge, likewise I'll be cooking with a 240v induction hob as I've no gas in ghe Camper.

I use a 240v fridge myself

I built our consumer units, but they work the same as yours (light for polarity test). The probable only difference is a changeover switch that swaps the polarity if needed. I used one of these if interested:
Amazon product ASIN B01CERR130
It was having an inverter on permanently for my fridge that made me see I liked having 240v on tap. So I swapped the small Victron Eco inverter I had out for a much larger one. Amazingly, it uses no more power (itself) than the smaller one, due to a more programmable Eco mode.

My system is very different now to most vans, as I run loads off 240v. I have a PC, a 27" monitor, a 24" monitor, 4G Router, WiFi router (these work together so if WiFi is available it's used, but auto switches to 4G if WiFi is lost), Echo Spot, Steljes active speakers, Type-C USB hub (x2), domestic fridge, Tassimo, probably more. I have most appliances on WiFi switches, so the van can go into "night mode" using a routine on Alexa - one button or voice command and all off/on. I also have WiFi switches on a lot of the 12v bits (electric awning/step/MaxxFan/etc), and have other routines programmed. It makes setting the van up or getting ready to drive away a breeze

Of course, most of the above wouldn't make sense in most vans. But for full-timing and wanting all the convenience of a house, and having 400Ah of LiFePO4 (soon with 750w of solar), it is perfect for us.

 

[Mr Meenah]

@Wissel does that switch change automatically?

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[Wissel]

@Wissel does that switch change automatically?

Nope. It's one of the few things in our van I have to do myself

Tbh it just replaces one of those polarity change leads. I would imagine that most people using one of those leads plugs into EHU and checks a plug in tester. If wrong, fit the lead. Either way, then switch other things on.

I do the same, but instead of plugging in a lead, then going back in the van to check the tester, then going back out to add a lead, I plug in the lead, go back to the van to check if light comes on and if it does, flick the switch. Just a simpler system (IMO).

 

[Mr Meenah]

@Wissel
Can I ask how you wired the changeover switch please?

 

[Wissel]

Can't remember exactly, but the jist was using this switch:

It's made to switch from a generator to mains. I attached the mains to the top left and the inverter to top right, then from the bottom onto whatever needed to be powered.

 

[Mr Meenah]

Can't remember exactly, but the jist was using this switch:
View attachment 303910
It's made to switch from a generator to mains. I attached the mains to the top left and the inverter to top right, then from the bottom onto whatever needed to be powered.

Oh, ok. I thought the idea was to put the switch between consumer unit and, in my case charger/ inverter, and flick the switch if the polarity is reversed (red light on).

 

[Wissel]

Oh, ok. I thought the idea was to put the switch between consumer unit and, in my case charger/ inverter, and flick the switch if the polarity is reversed (red light on).

Ah, sorry, my mistake. I have two of these

The other one does the polarity.

I ran two sets of wires from the RCD to the top of the changeover switch. One wired correctly, the other backwards. I added a polarity checker before the RCD.

So when I connect up, if the light comes on, I flick the switch before turning the RCD on. Here's an old drawing that shows the polarity changer. Just ignore the second changeover:

Thinking about it, I did a video on the finished unit:

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[Mr Meenah]

Brilliant thanks. I'll take a look.

 

[Mr Meenah]

Wissel
do I connect the inverter (outgoing) earth to the same busbar as the shorepower incoming earth?