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cc5084 asked

Mulitplus 3000W Inverter Overload

I have a multiplus 3000W inverter hooked up to an auxiliary battery bank (500Ah and 13.5V at time of test). On the AC out of the inverter, I have wired in a coleman mach 15000 btu air conditioner. When I turn the air conditioner on, it acts as normal (low fan and high fan). When I turn it to its higher settings, the inverter seems to not be able to handle it (low cool and high cool). The monitored AC output voltage drops to between 50 and 60V and the DC input from the battery bank drops from mid 13's to mid 12's. When this happens, the inverter buzzes and goes into overload and shuts itself off. Any idea as to why this would be occurring?

Lithium Batteryinverter current drawaircondition
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snoobler avatar image
snoobler answered ·

Did you use DC cabling equivalent to the manual's recommendation?

You likely need a soft start on the A/C.

At max output, that A/C unit uses 1700W of power continuously. It needs about 4-5X that to start the compressor, probably > 7000W.


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cc5084 avatar image cc5084 commented ·

We are using 2/0 cabling for the DC batteries.

So the most likely thing that's happening here is that the start up current is too high for the inverter to operate not go into overload. If by some chance it does get past this surge current, it does run just fine after the fact at its continuous power of 1700W like you mentioned.

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nickdb avatar image nickdb ♦♦ cc5084 commented ·
This is why its best to use an inverter based AC unit. It soft starts and provides a stable, consistent load to the multi.
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derrick thomas avatar image
derrick thomas answered ·

Highly recommend one of these

https://www.microair.net/collections/easystart-soft-starters/products/easystart-364-3-ton-single-phase-soft-starter-for-air-conditioners

Much easier on the equipment, and I can start and run my 15k on my Honda 1600.

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snoobler avatar image snoobler commented ·

Agree. These tend to cut the surge current by as much as 70% and will bring the surge to well within the MP surge capabilities.


They do require a 5 start "learning" process, and this would need to be done on shore power.


https://www.micro-air.com/kb-easystart/articles_troubleshooting/easystart_Relearning_an_EasyStart_Soft_Starter.htm

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