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roblamo asked

Multiplus 24/3000 disconnects Onan 4k generator

Hello,

Similar to several other customers, I am having trouble getting my Multiplus to accept AC input from my generator.

I have the 24/3000 w/ a single AC input. No problem when connected to Mains/Grid, but when I am off grid, and power up the Onan 4k generator, the Multiplus continuously connects the input and then disables it (over and over).

Reading the AC input data (thru Venus GX or Mk3-USB), it would appear that both voltage and frequency are well within limits. When I bypass the Multiplus, the generator comfortably supplies sufficient power to the Forest River motorhome.


In accordance with available guidance, I have attempted to:

-disable UPS mode

-enable DCC

-enable Weak AC

-lower maximum input current (generator should be capable of 30a continuous on 120V)


Thank you in advance for any advice you could offer.

--Rob

Multiplus-II
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2 Answers
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jwfrary answered ·

Hi,

dynamic current control is for inverter type generators so if you have a fixed speed one don’t turn it on.

You will need to set the current limit at around 26 amps probably a touch less I would wager on 24 - nowhere near the 4K written on the side due to power factors.


most common cause is the voltage disconnect threshold being set a little high. Voltage dips when the genny connects and then the multi drops out. And so it continues in a vicious loop.

Suggest you try dropping that down and see if it works

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roblamo answered ·

@jwfrary, Thank you for your quick response.

I went out to go disable DCC and troubleshoot some more, based on your input, and here's what I learned.

- First of all, the upper and lower voltage limits were already at their least-restrictive settings (94v-143v).

- While I was on the grid page, I found the NS protection log, and I discovered that it kept tripping for "RoCoF too high". A quick search reveals that RoCoF has to do with LOM detection (safety to prevent back-feeding the grid). Interesting...

--I realized that instead of grid code standard setting="none, feeding energy from DC to grid not allowed" I had "Other" set.

-- I initially thought that must have caused by an inadvertent mouse click, but realized I must have set it that way, at some point, because I was experimenting with the ESS assistant (which apparently cannot function at all w/o a grid code standard).


So...I deleted the ESS assistant, set the grid code standard to "None", and everything started working perfectly. I was even able to disable weak ac, reset the max input current and re-enable UPS mode, while everything continued to function.

The reason I was using ESS is because I also have solar on the roof of the RV (DC-coupled Victron MPPT), and I wanted it to prioritize Solar over shore power while the sun was shining.

- Question: w/o ESS, is there another intelligent way for all the Victron products to talk to each other and serve that function? I believe I already set charging voltages for solar slightly higher than that of the Multiplus.


Thank you so much.

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jwfrary avatar image jwfrary commented ·

Glad you got up and do that. - disregarded the ESS as you can’t use it safely on pluggable installations!

there are a few ways to prioritise dc coupled solar. One is play with the voltages so that the mppt are slightly higher than the multi.

I prefer, the ignore AC assistant. You can use lots of different configurations with this, if you search the forum there tons of ideas.

I generally use the ccgx to tell the multi if it’s day or night using the generator start function of the ccgx.

Then let the multi gen start assistant control our generator.

The thresholds for the generator to start can then be different/night to day.

The Ignore ac input assistant then is set to drop ac using that same input, so when the generator isn’t running then it ignores the ac.

Works with the shorepower, we just throw the shorepower transfer switch across and whenever the gx demands generator starting the shorepower will connect. This way the thresholds are easily Tunable with the CCGX.

The system is on a commercial boat, and uses the battery bank as a UPS back up.

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