Dogbone Blows Shore Power Breaker -- Multiplus?

[howson]

Note: I initially posted the wrong diagrams. See post 22 for current configuration as of 29 Apr 23.

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I know what is causing the issue...I just don't understand why. What's going on (power flow)? My hope is that one of the "real" electricians here can explain so my thick skull can comprehend.

I made up a 30A dogbone today with a SmartPlug female end so I'd have a spare cord with me. Every time the EMS contactor in the camper engaged the shore breaker blew with the new cord.

The problem IS NOT too much power drawn by the RV or a mis-wired dogbone.

Below is the wiring when the breaker blows. What I think is happening is the 120V shore power is being applied simultaneously on the Multiplus' input and output. (Trace the wiring and you'll see what I mean.)

-DIAGRAM REMOVED-

With the manual switch set to NOT 50A the Multiplus' output is isolated from the input power. This config works perfectly.

-DIAGRAM REMOVED-

I couldn't find anything specific on the Victron Community site and my googlefi failed me searching for a clue. Obviously having shore power on the input and output of the Multiplus is no bueno...I just don't understand why the shore breaker popped (except for the obvious that too much current was drawn...but why?)

For the curious, below is the standard 50A configuration.

-DIAGRAM REMOVED-

If you're curious about the switch and the installation, full thread on the topic here: https://gdrvowners.com/forum/operati...-manual-switch

Howard

[Jkwilson]

Typing on a tablet so I’m using “switch 3” to mean terminal 3 of the switch.

Howard, I’m not seeing a path for power to go from shore power to the MP output.

In any switch position, the black hot goes directly and only to the input of the MP.

In 50A position: The red hot goes into the switch via 3 and out via 2 and then directly to the panel. The MP output goes to switch 11 and out of switch 10 directly to the panel.

In NOT 50A position: The red hot is not connected to anything but unused switch 3. MP output goes into the switch on 9 and again out on 10 and to the panel black hot, and into the switch on 1 and out on 2 then onto the panel red hot. In this position, the shore power red hot isn’t doing anything.

[TedS]

The only difference I see between the 50 amp shore that works and the 30 amp that blows the breaker is the dogbone that ties L1 to L2. Is there a short inside the dogbone construction and the NOT 50a switch position breaks the short path?

[Cate&Rob]

Even though the MultiPlus can output to both L1 and L2, it would seem that it does not like L1 and L2 bonded on the input side. I wonder if this has something to do with the Powerboost function on part of the supply current but not all of it (although, I don’t see how it would know this). Seems like a question to ask Victron.

Rob

[howson]

TedS

Using a commercially made, 15A-to-50A dogbone and the original power cord has the same results. Shore breaker pops in the 50A position. As emphatically stated in post 1--the issue is not due to the new power cord.

[Cate&Rob]

A further thought . . . is this because the Multiplus is seeing a different current in the neutral than in the L1 feed ? BTW, why does the neutral go through the switch if it is connected the same in either switch position ?

Rob

[howson]

A further thought . . . is this because the Multiplus is seeing a different current in the neutral than in the L1 feed ? BTW, why does the neutral go through the switch if it is connected the same in either switch position ?

Rob

The Multiplus doesn't throw an error code or give any indication of a fault. Neither does the EMS, so can't answer your first question, Rob. The component that "sees" a problem is the shore power breaker.

Why the neutral wiring through the switch? I didn't give it much thought and was "borrowing" heavily from TucsonJim 's diagram. For my setup the neutral wiring does look like an unnecessary complication.

Jim's diagram is below and was taken from his thread (and excellent PDF) documented here: https://gdrvowners.com/forum/operati...ique-solutions

[TedS]

Is it possible that the Multiplus output is not totally isolated from the red hot somewhere downstream of the switch?

[Cate&Rob]

TucsonJim Jim's diagram shows different paths for neutral depending on switch position. In your diagram you have parallel neutral paths (usually not a good thing) with one direct and one through the MultiPlus . . . but both paths always connected. I admit that I don't see how this would affect the source circuit breaker . . .

Rob

[Scott'n'Wendy]

The problem IS NOT too much power drawn by the RV[/B]

Yes it is.
That is the only way to pop the shore breaker. Too much power draw.
What Rob says is correct. A neutral wire should never go through a switch. In electrical circles the phrase "Never Neutral" is used when taking about neutral wires and switches.
Either L1 and L2 are being shorted together, or L1 or L2 are shorted to neutral causing the high current condition that pops the shore breaker.
Just saw this thread and I gotta go but will come back later and look over. Somewhere...is a short.

[Cate&Rob]

Scott'n'Wendy

When you switch the source of power, you should switch line, neutral and ground. Many get away with a DPDT switch switching just line and neutral.
(at least . . . this is my understanding)

Rob

[howson]

Yes it is.
That is the only way to pop the shore breaker. Too much power draw.
What Rob says is correct. A neutral wire should never go through a switch. In electrical circles the phrase "Never Neutral" is used when taking about neutral wires and switches.
Either L1 and L2 are being shorted together, or L1 or L2 are shorted to neutral causing the high current condition that pops the shore breaker.
Just saw this thread and I gotta go but will come back later and look over. Somewhere...is a short.

OK, let me clarify. What I meant by "RV is not drawing too much power" is having an air conditioner, charging circuit (in the Multiplus) or other high-draw components in the RV that active (of course) will pop the 20A breaker due to too much power draw. All of those "natural" causes were accounted for and are not causing the problem.

I realize that something is causing the power draw or the breaker wouldn't pop.

My ignorance regarding the neutral through the switch...obvious now that it is pointed out.

[TedS]

Note: I initially posted the wrong diagrams. See post 22 for current configuration as of 29 Apr 23, so Ted's response below is "OBE" (overcome by events...aka my error)

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Remove 15 to 13 neutral jumper. Move Multiplus output neutral from 16 to 13 to provide switching from shore power neutral to Multiplus output neutral. You may have created a power loop. The Multiplus output neutral is not electrically the same as shore power neutral.

[howson]

Deleted the content of this post as it was totally and completely wrong...so much so to leave it would just add to the confusion.

[howson]

TedS -- dang it, I don't understand. My knowledge of 120vAC is so limited that I'm stuck in a paradigm that "all neutrals should be tied together".

I'm going to step away for a bit and go do something else for awhile and then come back and look at this some more.