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gyrex avatar image

MultiPlus II AC bypass switch help

I've just read the Wiring Unlimited guide - what an amazing and educational resource! Thank you so much to Victron and Margreet Leeftink for writing this, I've really learnt so much about some basic electrical theory.

There's an interesting section in the guide where it suggests running a bypass switch.


This makes complete sense in order to isolate the inverter from the grid and loads in order to be able to do maintenance etc. but I have a couple of questions:

  1. Is a "bypass switch" the same thing as a "changeover switch" such as the Hager SF463? https://www.hagerelectro.com.au/e-catalogue/energy-distribution/control-indication/manual-changeover-switches/changeover-switches/sf463/18978.htm
  2. If it's the same as a changeover switch, how would the switch be wired logically? I've tried working this out but it's not making sense to me and I'm hoping someone might be able to help me understand how this should work?

I've got a diagram below which is how I think it should be wired but I'm trying to understand where the AC-In would be wired to.

I thought maybe that AC-In would be wired into the changeover switch in parallel with the AC-out but I thought this might introduce a loop and this would be a bad idea?

Then I thought maybe it should be wired into the output of the MCB but then I'd have to add an isolator and this didn't make sense and doesn't follow the schematic depicted in the wiring unlimited guide.

Would really appreciate some help here from some experts :)

Multiplus-IIwiring diagram
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1 Answer
daryl avatar image
daryl answered ·

back to between the MCB & changeover switch

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Thanks again for your help Daryl! Like this?

If I do this, even if I switch the changeover switch to mains power, I'm still supplying power to the AC-In of the MP2 which doesn't conform to the diagram set out in the Wiring Unlimited Guide which, when switched, bridges AC-In and AC-Out.

Also, isn't there some danger in that if someone does flick the changeover switch to grid that they'd assume that there's no power being supplied to the 'generator' (that it's isolated) and that it's potentially safe to work on?

Are you able to help me please @Rob Duthie?

Hi

Yes you need to install proper AC transfer change over switch which has break before make contacts and lockout.

Which totally isolates the inverter from the grid, as in above diagram 6.6 AC bypass switch.

Regards

Rob D

NZ

Does he? My installer is installing a Hager SF463 generator changeover switch to change the feed for the protected circuits from the output of the Victrons back to the grid.

What is the reason behind needing to also isolate the inputs into the victron at the same time?

So to have complete isolation when disconnected for service etc.

Sure, you need to be able to remove power from the victrons for service, but that doesn't have to be part of the same switch that moves the protected circuits from inverter-out to grid.

Hi

For electrical wiring you should be using a electrician to do this for you if you are not qualified to do so. As they should understand what the requirements are for wiring in and isolating inverters to the grid etc.

As this type of work is classified a high risk electrical work in the electrical regulations. and has to be inspected etc.

Regards

Rob D

NZ


I understand and agree. The qualified company designing & installing my system provided a different design to the advice you gave gyrex in this thread, so I am trying to understand the difference. Whilst I may not be a qualified electrician I do have significant data centre operation and electrical design exposure so I am taking an interest in understanding the design of my system.

Effectively I am trying to confirm if your "you need" statement above is more a "I would" rather than a "you must" as I interpret it.


Hi

You know that the Mulitplus has a change over bypass relay inside it for critical loads AC2 output AC 1 for non critical loads.

You need to advise what model you are using etc.

Regards
Rob D

NZ

Hi Daryl,

With your design, where has your designer/installer installed the SF463's in relation to the MCB and RCD's (upstream or downstream of these)? I noticed on Hager's website that there's some information relating to having the changeover switch upstream of MEN connections - how does this relate to the location of RCD's?

If you were to wire the AC-in directly to the MCB (per my diagram further up) and bypass the the changeover switch, would this compromise the safety of this circuit because there's no earth path to MEN?

@Rob Duthie

Hi Rob,

Thanks for your response. Are you saying that the Hager SF463 isn't a suitable switch for this design?

Is there a transfer/change-over switch which can achieve the following:

When switched to generator/inverter

  • load disconnects from grid
  • load connects to the AC-out on the inverter
  • grid is passed through the switch to AC-in of the inverter

When switched to grid

  • load disconnects from AC-out on the inverter
  • load connects to grid
  • inverter AC-in/out is completely isolated

I'm struggling to figure out how to achieve these goals through a single switch and really appreciate someone knowledgeable such as yourself helping me understand this. I would have thought this would be an easy task but I can't figure out logically how something like this would work.

I'm not an electrician and I will be getting a sparky to install the AC part of the install but I'd really love to learn as much as possible so that I can plan this design and gain some idea of how the design should work.

Hi

You need to supply me what the main objective is, and all the equipment being proposed so i have a general idea what is required to wire it up to suit your situation.

Regards

Rob D

NZ


My objective is to achieve the following switching illustrated in the diagram below.

The more you post gyrex, the more I suspect we are buying the same system from the same installer.

I haven't bought mine yet mate - I'm just planning the design and putting together an inventory :) I don't know if you're aware but there's a post I made further up where I asked you questions about where your designer/installer planned to install the SF463. Where do you live mate?

Hi

You know that the Multiplus has a built in transfer relay on AC2 output

that can handle 32 amps of load current for the 3kw unit and 50Amps for the 5kw unit.

So why the change over switch? all you need is bypass switch for the inverter.

https://www.victronenergy.com/live/ess:design-installation-manual

My motivation for the changeover switch is to flip the house loads (that normally live behind AC-Out 1) back to the mains if the Victron/Battery system has a failure that it can't self bypass. In a 3-phase configuration I believe a fault in one inverter could cause all 3 to shut down until a repair is completed.

@gryex Essentially my inverters & mains-in on the changeover switch will feed from a switchboard behind the MCB. The AC-out1 on the Victrons will also connect into the change over switch (in the generator port) and the majority of my loads including Solaredge inverters into the load side of the changeover switch.

I think you're mistaking AC-Out-2 and AC-Out-1 Rob. There's no UPS function (no inverter power) supplied to devices connected to AC-Out-2 in the event of grid failure.

I'd like to implement a changeover switch as part of the design in case I need to do work on the inverters or if one of them fails. It means I can easily flick a switch and move my loads to the grid.

From the MP2 manual:

Hi

Yes there is, as this is how my system works as i have Mulitplus 2 wired this way as a UPS backup and grid feed back etc.

I had no power bills for about 5 months now and in credit with power company.

After i reconfigured my system to use lithium batteries and inserted the current CT into main incomer.

Have as lool at the below document

Victron MultiPlus-II-to-MultiGrid-and-MultiPlus-comparison-EN wiring.pdf