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Do I need RCD protection on AC-In on Multiplus-II (UK based)


I'm planning my installation of a Multiplus-II 5000/70/50 in my home in the UK along with ESS and later solar. I will be splitting my existing consumer unit into essential and non-essential loads to enable UPS mode in the event of a grid outage.

My question is whether the circuit protection device fitted inside the non-essential loads consumer unit which feeds the Multiplus-II AC-In input needs to have RCD protection or if an MCB can be used. Of course I will have a full set of RCBOs on the various other circuits on both essential and non-essential consumer units but I'm concerned about discrimination if I was to also use an RCBO to feed the Multiplus-II input. I could probably get a time-delayed RCBO but I wonder if this is really needed.

The Multiplus-II installation manual simply states that

The AC input must be protected by a fuse or magnetic circuit breaker rated at 32 A (for 3 kVA model), 50 A (for 5 kVA model) and 100 A (for 8 kVA and 10 kVA model) or less, and cable cross-section must be sized accordingly.

so my guess is that this might not be so much an inverter product question but more of a UK wiring regs question.

I have the regs and on-site guide so can read up on that but just wondering what others have done? The cable feeding Ac-In will be 10mm2 (singles ideally but T&E possibly) and will be running a short distance through 75x75mm trunking to the AC isolator and then again in the same trunking to the Multiplus-II so risk of damage to the cable is minimal. I could use SWA but that would be cumbersome and probably overkill.

Any thoughts? My feeling is that using a 50A MCB is the pragmatic choice but I'll need to check the regs to see if the short run of non RCD protected cables in trunking is a problem.

Thanks, Craig.

Update: Checked the OSG in section 7.2.5 and as far as understand it, as long as the cables are not “installed in walls or partitions”, which surface mounted trunking isn’t, there is no requirement for RCD protection. The prospective fault current in a fault condition inside the Multiplus would easily cause disconnection of the 50A MCB inside the allowed time so I think an MCB is appropriate. Anyone aware of any other regs which contradict this or am I misunderstanding anything?

craigc asked
sharpener edited ·

1 Answer

Earthing and power feed on this system...?


My plan is to have a solar system with pylon Li batteries supplying 6 lower powered circuits in the house - lights and some socket ring circuits - with the grid charging batteries when needed. The grid will also permanently supply my higher-powered circuits such as the shower and electric cooker (the solar system will not be involved here).


I have 3x 3.5kW pylon batteries, Multiplus II 5kw, 9 x 455W panels in 3 paralleled strings of 3 panels, 250/100 smart soar MPPT , lynx distributer and cerbo gx.

I have attached my wiring diagWiring plus poss consumer unit layout 2.pdfram for the solar system (p1) and for the consumer unit (p2). I need to get an electrician to check and wire this but just have a few questions for you guys if you can help…


1.Is the grounding/earthing safe and correct?

2.With this set up is there any way in which I might be putting power back into the grid or is it just one way? If I am not putting anything into the grid do I still need to fill out the G98/99 applications?

3.How long could my cable runs be consumer unit to the inverter charger? I am still unsure as to whether to have the solar gear in the garage or a different room in the house or even in the loft…

Apologies if some of these questions are very basic!

taddy asked
ponzoa commented ·

2 Answers

Transfer Switch for Victron Multiplus 12/3000

Hi all,

I'm currently planning out my wiring for a van conversion and looking at getting a Multiplus 12/3000. As a newbie to wiring and someone who's British tendencies tend to make me quite modest, I'm damn proud at how confident I feel about electrics after the amount of research I've done. (Main thanks to the author of Wiring Unlimited.)

That being said, I can't for the life of me figure out how this transfer switch relates to van conversions. Most of the info I've read online seems to relate to fitting into buildings rather than vans. But even then I'm struggling to understand it as there seems to be a variety of uses.

What's more, after zooming in on other peoples videos and guides I can see there's roughly a 50/50 split between those who use the 50a and those who use the 16a. But frustratingly, they mention all the reasons and specs as to why they purchased the unit, other than talk about the transfer switch rating.


Is anyone able to explain in simple terms what a transfer switch is and what it will do for me in relation to a van conversion? Main things I'm worried about are blowing shore feeds when hooked up at campsites, or over/underpowering my systems.

That being said, my main source of power will be the 525w solar array I plan on installing as well as the Orion DC-DC charger feeding into 2x200ah Victron Lithium Smart Batteries.

Also while I'm here, in Wiring Unlimited it mentions creating a bypass switch for the inverter. (Section 6.6)


I can understand the reasons behind this. But firstly, it looks like a lot of people doing van conversions don't seem to bother with it. Secondly, how do you actually go about wiring this to connect to a comsumer unit?


mattestlea asked
gyzko answered ·

1 Answer

Voltage difference between Smart Solar and Multiplus

I have a Smart Solar 250/60 connected to a Multiplus 800/24/16 and a 24V LiFePo battery using a bus bar.

While charging there is a ~0.3V difference between the voltage reported by the Smart Solar and the voltage reported by the Multiplus. As an example, at the moment the SmartSolar is reading 27.16V and the Multiplus is reading 26.86V.

I know there will be a slight voltage difference, I'm just not sure if 0.3V is expected or if it points to wiring losses. The system is remote (set up for my parents) so don't want to trouble Dad with redoing the wiring if there's not an obvious problem.

Edit: Forgot to mention, the Multiplus is in an ESS system and the load is fluctuating between 100 and 300W while it's charging.

najab asked
najab commented ·

1 Answer

How to wire BMV712 shunt with a DC-DC charger

Hi All, hope someone can set me straight. What is the proper way to wire the Smart Shunt when using a DC to DC charger in my van? Is it Option A or B or some unknown C? I am running two batteries in parallel for my house bank. I would charge on one set of +/- and draw load from the other +/-. Or does it even matter? Will I be able to use the app to monitor total capacity of the batteries or will it always just reset to zero consumed AH every time the DC to DC charger kicks in?


larspawn asked
klim8skeptic answered ·

1 Answer

Maximum length for VE. Can

I don't know if any of the engineers actually read this forum, but I'm hoping to find out the maximum allowable cable length for the VE. Can interface cables. I intend to build my own cables using high-quality shielded cable (probably Cat7) so the attenuation and interference should not be a problem. I only wonder what the maximum latency is...

I can find information on the maximum cable length on the VE. Bus. People on the forums are saying that they're having trouble with longer cables, but the literature seems to indicate that you should be fine as long as the total cable length doesn't exceed 100 meters. Therefore, I believe that these people would do better with larger shielded cables since the literature seems to indicate that they shouldn't have latency problems, but I have found no such literature for the VE. Can.

I'm trying to mount the GX 70 upstairs quite a ways from the battery room. I figured I'd just locate the Cerbo GX up next to the GX 70 location.

If anyone can help, or if anyone can tell me who to contact, I'd really appreciate it!


kienan-maxfield asked
john-r-1 answered ·

3 Answers

Lynx Dist with 2 strings of batteries

I currently have a single string of AGM batteries wired for 48 V. 4x12 200ah. Runs to the Lynx dist in the usual fashion with a Smart Shunt at the batteries before the Lynx. I want to add a second string of identical bats for 400ah. I have an extra connection in the Lynx. Should I run the second string to the Lynx and make my parallel connection for the two strings there? Also, would I need a second Smart Shunt for the second string since its an ESS system? What is best way to do this?


duswami asked
Jeff Jensen answered ·

4 Answers

DC consumer fuses/breaker

The Wiring Unlimited guide says that all DC consumers (load) need an individual fuse. I have about 10 DC consumers that I was planning on splitting into 3 groups and have an appropriate sized breaker for each of the 3 groups. Is this sufficient, or do I still need fuses on all 10 individual consumers? Also, is there any disadvantage to have the individual fuse right after the positive comes off the positive bus bar than directly before the load (consideration for changing blown fuses)?

adrianp105 asked
christern answered ·

2 Answers

Smart Shunt - Specs for longer Aux voltage monitor wire?

I need to run a longer wire for monitoring Aux (starter) battery voltage. I did find a thread linked below saying it's low voltage which I would expect, however there are no specs available anywhere to confirm this. Does anyone know the actual specs on what is going through the Smart Shunt Aux port so I can appropriately size the wire over a ~15 ft total length? Cheers!


adam-martin asked
pwfarnell answered ·

2 Answers

DC Minus Trennung / Verkabelung

Hallo zusammen,

ich habe nochmal eine Frage zu dem leidigen Thema DC Minus Verkabelung.

Man soll ja grundlegend den DC Minus nicht absichern. Ok das absichern wäre das eine.

Was wäre aber wenn man z.B. den Laderegler komplett aus dem Verbund heraus trennen möchte

z.B. weil er defekt ist. Dann wäre meine Idee einen DC ausgelegten NH-Trenner einzubauen.

In dem NH-Trenner wird nur der DC Plus abgesichert, aber der DC Minus wird mit einem NH-Trennmesser Einsatz verbunden, heißt wenn ich den NH-Trenner öffne, weil ich den MPPT wechseln möchte, dann wäre ja sauber auf der Batterieseite der DC Plus/Minus von der Batterie getrennt.

Folglich, die PV Seite wird auch über einen PV Trenner abgeschalten, die Batterie Seite über den NH-Trenner abschalten und somit wäre der MPPT sauber aus dem Verbund ausbaufähig.

Spricht dann in dieser Form was dagegen ?


mactoolz asked
steffen-graap answered ·

4 Answers

Cable for 2008 Compact Multiplus 12v 1200va 50AMP monitoring?

I would like to monitor my inverter; it's around 13 year old Phoenix Compact multiplus 12v 1200va 50AMP. Ideally via a pi; but PC if necessary. What hardware/cable do I need (a little late Christmas present for the boat)?




abroad asked
zentropa answered ·

4 Answers

Wiring: Autotransformer balancing Ecoflow Delta Pro Solar Generators

i am inquiring about balancing the loads for two Ecoflow Delta Pro Solar generators with a Victron 100a Autotransformer. I would like to validate the wiring. The two generators come into a proprietary hub where I will take a modified 30amp L14-30 cord and INPUT the L1, L2 and the ground into the autontransformer and cap the neutral. Then OUTPUT L1, L2, N and G to a 100amp breaker in my main panel with a interlock kit.


cbstive asked
Kevin Windrem commented ·

2 Answers

Can a tank sender be a long distance from a Cerbo GX

My fresh water tank is about 15 metres from the Cerbo GX unit. I'm looking at installing a 0-10V sender unit to monitor the tank levels.

I'm guessing that 15m is too far for a USB connection (eg. if a GX tank 140 were used), so what are my options for connecting my tank senders to the Cerbo GX over this distance? I haven't committed to the aforementioned sender, so if there is a better sender option which doesn't require drilling into the tank to install and can send over this distance, I'd be glad to hear about those, too.

fartkek asked
Andrea answered ·

2 Answers

Et112 wiring

I have a et112 that I want to use as a grid consumption meter. I can see the 3 wires into et112 setup but where does the usb plug in? Is this just a standard usb cable or must it be the specific victron usb with 3 wires that is sold by victron dealers

choicelocks asked
wkirby answered ·

1 Answer

MPPT RS 450/200 Kabelschuh fast an hardware


auf den Bilder konnt ihr sehen das die Kabelschuhe fast das Bauteil daneben wegdruck.

Das sind ganz normale klauke Kabelschuhe fur 70mm2 , ist das noch ok ? Ein kleiner spalt ist da hab aber auch schon was vom Kabelschuhe weggefeilt.

Vielen dank

Best GruSe




donroberto asked
donroberto commented ·

2 Answers

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