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theswitch avatar image
theswitch asked

Will the AC-in of the multiplus transfer straight to the AC out in the event of a total failure of the inverter/charger?

Will the AC in of the multiplus transfer straight to the AC out in the event of a total failure of the inverter/charger.

I know the transfer switch is normally open and the multiplus performs some voltage and frequency tests before closing the transfer switch and allowing power through.

I also tested and know this will happen when there is no battery power to the multiplus. There was still a delay in the transfer switch operating which suggests it still performs tests even without the battery input.

I would like to know whether it is a good idea to install a manual bypass switch in case of a total inverter failure so the loads can still be supplied directly from the generator.



Multiplus-II
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Rob Duthie avatar image Rob Duthie commented ·

Hi


Yes it is a good idea to install the manual bypass switch. do that.

Regards

Rob D

NZ

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13 Answers
Kevin Windrem avatar image
Kevin Windrem answered ·

To be clear, the Multi (and Quatro) do not have an internal transfer switch. They have an AC input ISOLATION relay that disconnects the AC input(s) from the inverter core and therefore the AC outputs.

There is no path from the AC input to the AC output without closing the isolation relay and therefore energizing the inverter/charger core.

As others have said, it is a good idea to install an EXTERNAL transfer switch to bypass the Multi/Quatro in the event of a failure, or for maintenance. I have a manual transfer switch in my system but it could also be done with a relay: no AC output from Multi/Quatro routes grid power to the loads.

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theswitch avatar image
theswitch answered ·

Hi Rob,

It would definitely be a good idea if the multiplus only passes power after doing its checks. However, I know with the selectronic it isn't really necessary. Reason being, even if there is no battery power and the selectronic has failed and can't do the Voltage and frequency check, the transfer switch will go into bypass mode and operate like an automatic changeover contactor. It would be very unlikely that the unit would fail and the transfer switch would fail at the same time.

What I really want to know is, will the multiplus transfer switch operate the same way?

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Rob Duthie avatar image Rob Duthie commented ·

Hi

Not completely sure on that, but i have put them in if i have to remove the inverter for service of breakdown on mission critical applications.

Rob D

NZ

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mt-geek avatar image mt-geek Rob Duthie commented ·

I have a manual switch because if the inverter goes into an error state it drops the relay out

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bonie-wanda avatar image
bonie-wanda answered ·

I believe it’s a good idea, should the Multi/other components go for service or have issues after a software update.

I have it.

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piraya avatar image
piraya answered ·

1. Is the bypass switch connected to OUT-1 or OUT-2 or both?

2. Have anyone tried to use the bypass switch when the Quattro is still connected (which may happen, anyone can unintentionally press a switch)? No problems for Quattro when receiving voltage supply at the "out" terminals?

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iand avatar image
iand answered ·

There's an obvious problem with a Quattro where the two AC inputs are grid/shoreline power and a generator -- which one do you use when bypassing the Quattro?

Also I guess you need to disconnect both inputs and output in case the Quattro fails short instead of open?

And you need to prevent any case where the two AC inputs could get shorted together...

Sounds like a *lot* of switches are needed. Any suggestions?

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piraya avatar image
piraya answered ·

I would not feel sure that the output side is designed to withstand AC input, so I guess switches would be needed.
So yes, a lot of switches, in the right order, controlled by one button. So I agree, it is not realistic, at least not with quattro.

My reason to want such a solution is to be able to stop charging without cutting AC electricity. I.e. for ordinary use, not for emergency. But so far I see no easy-to-install and easy-to-use solution.
How did bonie-wanda set up his solution?

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addy avatar image
addy answered ·

One more question here: since there is an outage during firmware upgrades - could this be solved by shortening AC-in with AC-out (before the upgrade and removing that right after)? Or is there a risk of damaging the Multiplus?

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nickdb avatar image nickdb ♦♦ commented ·
It is only solved with a changeover switch.
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addy avatar image addy nickdb ♦♦ commented ·
...which results in a short outage (which is too much for computers). I know it is not the "usual way of doing" - but does it risk to harm anything?
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kevgermany avatar image kevgermany ♦♦ addy commented ·
Victron say only upgrade the firmware when you need new features. So the upgrade is generally unnecessary.

If your computers cannot be switched off, you require a different solution, usually a UPS.

Shorting AC in and OUT is not an option.


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Kevin Windrem avatar image Kevin Windrem commented ·
This can not be done as there is no isolation between the inverter/charger core and the AC output. With much of the unit changing state as the control system reboots, this could harm the unit.

As nicked said, you need a hangover switch (either automatic or manual) around the Multi/Quattro. You should have this anyway to route shore/grid power to your loads in case the Multi/Quattro fails.

If you have mission critical electronics that can't tolerate a brief power interruption needed to energize a transfer switch relay then they should be on a UPS. A UPS will also handle low/high voltage which the Multi/Quattro can not do.

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addy avatar image addy Kevin Windrem commented ·

...and the UPS has a internal bypass switch for their firmware upgrades - which IMHO the multi should also have...

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nickdb avatar image nickdb ♦♦ addy commented ·
The multis are not a UPS, they have basic changeover functionality which is fine for home use. They lack many features of a proper UPS and are not intended to replace one for sensitive applications.

If your environment needs this level of protection, then hang a UPS off AC OUT.


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sharpener avatar image
sharpener answered ·

I have got this changeover switch and it is possible to move it by hand sufficiently quickly that the computer and router stay alive and the radio pre-sets are not lost. Even though there is a noticeable short break with the lights.

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nickdb avatar image nickdb ♦♦ commented ·
Same. 20ms is achievable if you’re quick enough.
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addy avatar image addy commented ·

AFAIK those are not allowed here in germany - I have one of these: https://hager.com/de/katalog/produkt/him406-lastumschalter-4p-63a and there is no way to switch in 20ms. :-(

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sharpener avatar image sharpener addy commented ·
If my German isn't too rusty it says those are not suitable for switching between the public supply and a PV or ESS supply. Which is what we want to do. So 20x more expensive and no more suitable.
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Fideri avatar image
Fideri answered ·

I use an external automatic changeover/transfer switch, hooked to the output of the Quattro before my loads. My version has 2 inputs, so Quattro and grid, but it can have multiple inputs, so multi/quattro, grid, shore power, generator, etc. It can be programmable so you assign the order of priority.

The risk of having 2 power sources active at the same time is radically reduced. ATS are basically "make after break" as opposed to "make before break" machines. You get what you need.

F.

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sharpener avatar image sharpener commented ·
Can you post a link?
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Fideri avatar image
Fideri answered ·

@sharpener

I bought mine offline but here is a typical type from Amazon US: https://www.amazon.com/OELFFOW-Automatic-Electrical-Generator-Changeover/dp/B0CGCNG6JZ/

And here's a generic picture.

I forgot that they come in different capacities. Mine is 147A.

F.

61c9xmm7cnl-ac-sl1500.jpg


61c9xmm7cnl-ac-sl1500.jpg (92.6 KiB)
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delf67 avatar image
delf67 answered ·

That only switches your "lives", you have to common the neutrals of all your incoming supplies, not sure that would meet the UK regs? Surely you need to isolate L & N?

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sharpener avatar image
sharpener answered ·

It wouldn't. And in addition doesn't the Multi fail the tests on startup if the neutrals on AC-In and AC-Out are linked together?

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Fideri avatar image Fideri commented ·
That particular version might not. Mine has separate neutrals. A common neutral seems to be an American thing. They come in different flavours.
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Rob Duthie avatar image
Rob Duthie answered ·

In NZ you cant switch the Neutrals

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delf67 avatar image delf67 commented ·

But the MP/ MP2 switches neutrals between grid and inverter, so how does that work?

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Kevin Windrem avatar image Kevin Windrem delf67 commented ·

I asked this question in a slightly different context.

Answer: If you can't switch neutral along with hots, join the AC input and AC output neutrals.

Also disable the internal ground relay and provide the appropriate safety ground to neutral connection externally. This is probably done in the service entrance.

https://community.victronenergy.com/questions/265963/common-neutral-in-and-out-of-a-multiquatro.html

(There are some ESS grid codes that specifically specify connecting in and out neutrals.)

The best approach is to switch the load neutral same as the hots where possible and allowed by local codes.

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