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  1. #1
    Join Date
    Oct 2014
    Location
    Rutland Vt
    Posts
    1
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    Mistsubishi Mini Split Comm Error Off Grid

    Hi Guys, Dan here. We just installed an Outback 8kW VFX7248 fully off grid system for a client who also purchased and installed three Mitsubishi mini split heat pumps. The Power System is performing flawlessly. The heating systems.. not so much. The customer can light up each unit individually, but when she attempts to light up more than one, the each consecutive unit trips out on comm error. If she shuts down everything (From the breaker box) she gets the same results starting from which ever unit she first started. The HVAC guys would love to blame the solar guys (as would the lawn care guys), All my guys blame the HVAC guys. I've heard of adding caps to the 240vac input, but each unit is on its own circuit, there should not be Power Factor/ harmonic distortion issue. I'm blaming bad Sushi. Advise? Thanks db

  2. #2
    Join Date
    May 2011
    Location
    Ottawa Ontario
    Posts
    13
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    Quote Originally Posted by Foxfire Energy View Post
    Hi Guys, Dan here. We just installed an Outback 8kW VFX7248 fully off grid system for a client who also purchased and installed three Mitsubishi mini split heat pumps. The Power System is performing flawlessly. The heating systems.. not so much. The customer can light up each unit individually, but when she attempts to light up more than one, the each consecutive unit trips out on comm error. If she shuts down everything (From the breaker box) she gets the same results starting from which ever unit she first started. The HVAC guys would love to blame the solar guys (as would the lawn care guys), All my guys blame the HVAC guys. I've heard of adding caps to the 240vac input, but each unit is on its own circuit, there should not be Power Factor/ harmonic distortion issue. I'm blaming bad Sushi. Advise? Thanks db
    The Off-grid inverter has a generator power input? If so have you tried starting the heat pumps while the backup generator is assisting the inverter.
    8 kw inverter should have a peak power of at leat 16 kw momentarily. This should be sufficient.
    Power factor may be at fault. Some inverters can be programmed for powerfactor corection. Inductive loads will cause the powerfactor to be less than one.
    Capacitor banks could help.
    Good luck

    Sent from my SM-G900W8 using Tapatalk

  3. #3
    Join Date
    Jul 2017
    Posts
    4
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    Old Thread...

    Good Answer...but also thought to add, being as this is "off-grid" there is a battery bank behind all this current draw.

    When considering the mini splits startup there needs to no "bottlenecks" at the battery circuit and all it's associated wiring, and every battery post terminal...low resistance connections in the whole series. And at even 48 volts DC that's still a lot of amps draw across a battery.

    Battery Bank needs to be of large enough amp-hours as does all the wiring sizes capable of the amperage needed for any compressor motor start up surge(s)


    If these were not the inverter type heat pumps start up issues would be many times worse even with a perfect battery bank.

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