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svalvasori avatar image
svalvasori asked

Multiplus switches from grid to inverting under load

I'm using a Multiplus 12/3000/120 in a boat. It's attached to a 920Ah lead acid bank. Settings are stock except for battery type ( Flooded deep discharge flat plate antimony) and shore limit (43A) When disconnected from shore and the generator (Kohler 11kW) running the Cerbo shows grid power available. I wait 2 mins and turn on a water heaters (12A) and everything works as I expect. I then turn on one AC (12A compressor) and the Cerbo shows the grid power disappear and switch to inverting; which then of course overloads the Multiplus. I have boost enabled and have not seen this happen at the dock (50 A shore power, shore limit set to 48A). These loads are all running through the Multiplus (this is a 120V/240V 50A split phase and all L1 loads run through the Multi)

When the above is happening on L1, I also have the following loads on L2 (not through the Multi) - 12A water heater, 10A AC pump and 12A compressor.

I wonder if the generator is dropping out (why else would the, mutli lose grid?) but it's brand new and should support 45A on L1 and 45A on L2. It could be the extra draw on the AC unit's starting, but I thought that the Multiplus would draw from the batteries to help in this situation - it does this perfectly at the dock.

Any thoughts welcome!

Steve.

Multiplus-II
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rstarr avatar image rstarr commented ·
I just posted a very similar question, were you able to resolve this?
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rslifkin answered ·

Do you have UPS mode enabled on the Multi? If so, try disabling it. You also may need to widen the frequency range setting for the Multi. It's possible that the A/C start drops the generator voltage or frequency enough for a second that the Multi decides it's no longer a suitable source and switches to inverting.

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svalvasori avatar image svalvasori commented ·

Here are the graphs from the time period I'm talking about - the input voltage dips very slightly.


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I just had something similar happen at the dock, Since I'm on dual 30A inlets at the moment I have my shore current limit set to 26A (in the above graphs I was on generator so it was set to 48A). Extra power was required and power assist boosted it up to the 33.6A that was required for a time period, but at some point switched to invert with no loss of power and then overloaded. Batteries are at 100% so adding in 7.6A (~75A@12V) should be able to continue for quite some time. While this happens I am also seeing a high DC ripple warning, but to my eyes I don't see anything out of the ordinary - voltage drops ~ 0.5V under a 265A load.

UPS was enabled, I'm not sure why it should not function correctly in my system but have turned it off to see if there is a difference.

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1625764134113.png (220.5 KiB)
1625765641039.png (253.4 KiB)