Multiplus ii Install UK

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pauldunn asked Dec 15, '22

Multiplus ii Install UK

Hello

I am trying to explain to my electrician how I would like the AC side of my Multiplus ii installed but he doesn't have any experience of Victron gear and I am by no means an electrician so I am probably not explaining things well. My electrician has experience of installing inverter systems such as Growatt etc but not (I assume) a truly on/off grid system like the MP can provide.

What I want to do is have the MP supply power on AC OUT 1 to the existing consumer unit. I know I will be limited to 72A or less from the MP but this is totally fine for my house usage and in the event of grid failure I will just be careful what I turn on. If this becomes a problem then I will have some of the loads moved to AC OUT 2 or even just get another MP to run in parallel.

In order to avoid any issues from the MP, or if for someone reason I need more power on a particular day than the MP can provide, I would also like a changeover switch added to switch between powering the existing consumer unit from the inverter or the grid.

After reading up as much as I can this is what I have in my head:

Basically I would like the electrician to install the new consumer unit and the changeover switch.

Does this make sense and/or is reasonable or am I getting this totally wrong hence why my electrician in not following what I want to achieve very well?

Incase its relevant I have 4x US5000 Pylontech batteries connected to the MP.

I have further questions about ESS configuration with these batteries but I will start a separate thread about that so not to confuse this one.

Thanks in advance for any and all advise on this.

Multiplus-II

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Answer 1 · 2022-12-15T13:08:39Z

johnone answered · Dec 15, 2022 at 01:08 PM

Your diagram makes sense to me - it's very similar to a system I've installed. The difference being, no ET112 meter (ESS works fine without the meter) and a Type S time delay RCD (instead of the 50A MCB) supplying inverter AC in. There will be an issue with discrimination with the RCD's in the existing consumer unit if you use a regular RCD in the new consumer unit - sparky should know all about RCD discrimination. Example of a changeover switch (which seems essential, e.g. for maintenance):
https://www.fusebox.shop/products/125a-changeover-switch-and-busbar

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pauldunn commented · Dec 15, 2022 at 03:21 PM

Brilliant, thanks for validating the diagram. I will now pass this to the electrician and the comments on this thread. If he has any further questions I will post them back.

I was thinking about using a changeover switch like this:

https://www.tradesparky.com/circuit-protection/switch-and-fusegear/changeover-switches/lewden-cs1004p-4p-changeover-switch

But maybe the one you have suggested is a better solution. Does it switch over without loss of power?

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johnone pauldunn commented · Dec 15, 2022 at 06:59 PM

Re 'switch over without loss of power', with a mechanical switch there will always be a period with no power, the issue is how long. As the Lewden switch has an 'off' position, that probably means way too long a delay for appliances. Whereas, the Fusebox switch, in practice, is quite quick - things like microwave and oven clocks don't need resetting. But, it wont be anything like as quick, or reliable, as the Multiplus 'less than 20 milliseconds' UPS functionality - presumably that is done electronically. Another attraction, for me (given not much space where the existing consumer unit is), with the Fusebox switch is that it fits in a regular din rail enclosure, whereas the Lewden is much bigger, especially depth-wise.

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Answer 2 · 2022-12-15T13:26:34Z

Yeah, similar to my system as well although both of my consumer units are new and are RCBO based rather than split RCD boards. That said I do use a 50A MCB from primary CU to MP-II rather than a time delayed RCD/RCBO because I couldn't find such a device which was type tested for my Fusebox CUs. As far as I can tell a 50A MCB is perfectly fine in this context because any earth fault will cause disconnection of the MCB within 0.4 seconds given the PFC involved. I do of course have RCD protection to all sockets, lights and other consumer facing loads.

I also have a Fusebox SCO125 changeover switch arriving today and it will be installed in such a way as to select between the AC-Out1 MP output or the 50A MCB which supplies AC-In albeit upstream of the AC isolator so that I can isolate the MP-II while still supplying 50A to the changeover switch and secondary CU. I didn't feel any need to have a separate MCB for the changeover switch mains input since most of my heavy loads (EV, Cooker, Shower) come directly from my primary CU.

Another thing you'll want to have installed is an earth rod to provide a reliable earth connection in the event of grid failure. You MUST NOT rely on the incoming DNO earth when running off grid because it could have been damaged or otherwise disconnected. You must have an independent earth. This "TT" earth can however be attached to your main earthing point along with the DNO earth but your electrician will keep you right on that.

Which Multiplus-II variant are you installing out of interest? And are you aware of the situation with G99 type testing approval for the Multiplus-II at present? Short version is that compliance with G99 was suspended for new installations in September due to some new rules, but that compliance is likely to be reinstated following some technical changes in firmware very soon.

Hope this helps.

Answer 3 · 2022-12-15T15:27:59Z

pauldunn answered · Dec 15, 2022 at 03:27 PM

Thanks for the detailed response, especially about the earth rod.

Maybe I should have the existing consumer unit replaced and use RCBOs while I have the electrician on the job. Just this summer gone I lost an entire freezer load of food while on holiday which would not have happened if RCBOs had been installed.

Those Fusebox units with SPD look nice, is that the brand to use this days?

The MP 2 I will be using is 48/5000/70-50. I was looking at the certs and it seems to have been updated and mentions this variant is now supported for G99 https://www.victronenergy.com/upload/documents/Certificate-ESS-G99-1-2021-Multiplus-II-48V-3K(GX)-48V-5K(GX)-24V-3K(GX).pdf

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johnone commented · Dec 15, 2022 at 04:43 PM

Re G99, that's the document Victron have submitted to the ENA - when they get round to it (snowed under currently) they will assess (well, they farm that out to a 3rd party) and decide whether or not to deem the Multiplus compliant (shouldn't take more than a few weeks).

However, it is ultimately up to the DNO to decide what can be connected to their network. Always best to ask them.

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Craig Chamberlain commented · Dec 16, 2022 at 03:01 AM

You are most welcome, I think we are all on a similar journey.

I would certainly encourage you to consider replacing your existing CU with an RCBO board especially given what you have gone through with your freezer losses. It will possibly bring other safety benefits depending on your existing setup.

I am also using a MP-II 48/5000/70-50 but wasn't expecting to be able to supply 72A from AC-Out1. I know the internal contactor can handle 50A and I know the inverter can produce around 19-21A but I didn't think we could get 70A+ out. If so then great but would appreciate if someone can confirm this. I thought I'd get 50A when grid was active or ~20A when on backup mode. Maybe I'm wrong.

I really like Fusebox units but I'm not a professional electrician. However if you look on YouTube for Artisan Electrics or Nick Bundy who are both well known, they seem to like them a lot. Hager is another good brand but seem to want to price themselves out of the market. I think Fusebox are fantastic value.

As @Johnone has already said, the revised G99 certification is in the process of being assessed by the ENA and my personal opinion, after a few disappointments, is that it will be approved compliant in the next 1-3 weeks.

I'd suggest getting your electrician to do an EICR to assess if there are any pre-existing faults. Then off the back of the test, get a quote to replace the existing CU and add a new one as per your design. You'll probably get surge protection as well as better discrimination in the event of a circuit trip, and will have an overall safer 18th edition setup. Replacing a consumer unit with the knowledge that there aren't any split ring final circuits or other faults should allow the electrician to bring the price right down.

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johnone Craig Chamberlain commented · Dec 16, 2022 at 10:50 AM

Ooops - (as others have noted) the Multiplus G99 docs on the ENA db, the ones dated 29th Nov, have today updated to 'Further information required'. Be interesting to hear what the problem is??

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Craig Chamberlain johnone commented · Dec 17, 2022 at 10:28 PM

yeah, it’s incredibly frustrating isn’t it. Starting to wonder if I’ve backed the wrong horse. Would love to be proven wrong but that has to happen soon because I’m not going to stay in limbo forever.

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Answer 4 · 2022-12-15T23:09:02Z

sharpener answered · Dec 15, 2022 at 11:09 PM

If you are worried about losing a freezer load of food you might want to install a changeover contactor in place of the switch, with the coil wired to the output of the Multi, then if it fails the loads will automatically switch back to grid.

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