question

overtaxed avatar image
overtaxed asked

Multiplus II AC Out 2 - What happens in overload?

If there's an issue with the Multiplus II's output on L1 (let's say an overload that causes it to stop inverting), what happens to L2 output? I'm thinking of using L2 as a generator autostart (start when the grid fails) but I want to make sure it would also drop L2 if there's an issue/overload on L1 while on battery. Is there any situation where L2 would be up but L1 would not on a multi, or is that condition not possible (which is what I'm hoping, I want the generator to start if there's not shore power available, even if the Multi in inverting correctly, I still want the generator to kick in).


Thank you!

Multiplus-II
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

8 Answers
nickdb avatar image
nickdb answered ·

Inverters switch as a group. So if one cuts out, they all will. Though this can be deselected in setup, but haven’t tested results myself.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

overtaxed avatar image
overtaxed answered ·

Only one multiplus, just wondering if an overload cuts ac2 in addition to ac1 or if ac2, because it's not being run through the inverter stays live during a an overload shutdown. Is there any situation where interved power would be down but ac2 would be up?

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

overtaxed avatar image
overtaxed answered ·

OK, doing some more reading on this, appears that AC Out 2's default behavior will work for my application:


1) Main power present, 120/240 volts available on AC Out 2

2) Main power not present, no voltage on AC Out 2

3) Multi off/overloaded/shutdown, no voltage on AC Out 2


Do I have that right?


Also, looking at the other relays, seems like I could program this behavior on several of them. One important detail is missing though, AC Out 2 relay, when closed, passes 120/240 volts. What do the other relays pass (for example, the K1/K2 relays), 120/240V or 12V? I don't need much amperage, but my autostart works on 120 voltage sense, so a relay that passes 12V when closed won't work for my application.

1 comment
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

nickdb avatar image nickdb ♦♦ commented ·

Yes. AC2 is an offshoot of AC1 via its own relay. The relay can be overridden with the general relay assistant but is open without grid or when the inverter shuts down during overload.

0 Likes 0 ·
img-0649.jpeg (227.7 KiB)
overtaxed avatar image
overtaxed answered ·

Perfect, that's a great place to do my voltage sense for the generator autostart. Thank you very much!!

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

overtaxed avatar image
overtaxed answered ·

One quick question, what's the min wire size that the push in terminal on AC2 out will accept? I need about .1 amp, so, whatever the smallest wire size the terminal will grab will be what I use; I'll fuse it right at the Multi (probably a 5A fuse). Again, only using this for voltage sense, not to actually power a load.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

overtaxed avatar image
overtaxed answered ·

For anyone else with this question, I did find it in the manual, AC2 takes 10AWG as the minimum wire gauge. I'm not sure if that's a mechanical minimum for the spring terminal or the sizing for the fuse (Victron recommends 35A max, which would be 10 gauge), but I'll use 10G out of the terminal block over to my voltage sense lines.


Pretty sure this is the best way to do what I'm trying to do; with the Victron directly in path (pre-transfer switch), I want to make sure I catch 2 different power failure situations for generator autostart, "Power failed, invertering" and "Power failed, inverter not functioning". My use case for this is kind of strange, so I doubt others would wire this way, I'm trying to drive the absolute maximum uptime possible for the power; I don't care if the generator runs more than it needs to, I just want to protect the power feed into the RV (we travel with animals and need to be sure that the AC can stay running if something happens to shore power or the Victron).


Thank you for the help!!

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

overtaxed avatar image
overtaxed answered ·

Just wanted to provide final update, I moved my "voltage sense" line over to AC2 today on the Multiplus, seems to work exactly as expected. Shore power disconnected, no voltage on AC2 (as expected). Multiplus off, no power on AC2. I didn't intentionally overload the inverter, but if it does overload, I'll report back; everything seems to indicate that would also trip AC2 to off as well.


Thank you for the help!


2 comments
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

nickdb avatar image nickdb ♦♦ commented ·
Glad you’re making progress
0 Likes 0 ·
overtaxed avatar image overtaxed nickdb ♦♦ commented ·
Thanks again for the help!


Progress? I just spent the last hour rounding up and putting tools away. My first Victron project is complete! Very happy with the outcome, and, as expected, everything from Victron was top notch and worked exactly as it should!

0 Likes 0 ·
overtaxed avatar image
overtaxed answered ·

One more question. If I set an assistant on the AC2 output (for example, telling it to open the relay if a certain temperature is reached) does that override the default behavior of the AC2 terminal? For example, if I set a generator start/stop assistant on AC2 to start on load conditions, would that then make AC2 stay connected without shore power? Or would it basically have 2 conditions at that point, if no shore power; no power on AC2, AND if the load is high, no power on AC2?

1 comment
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Alexandra avatar image Alexandra ♦ commented ·

@Overtaxed

The multiple assistants depending on how you set them up have an AND OR logic. Mentioned briefly in the manual.

This is where it can get a bit tricky, you will need to test your programmed logic. By creating the overload and grid faliure conditions to test if it is working as expected.

Usually the system prioritizes the on conditions first. So if one on condition is met then it is on.


0 Likes 0 ·