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Thread: Fridge not running on generator, invertors but only on grid

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    Fridge not running on generator, invertors but only on grid

    Maybe someone can shed some light on this one.

    Yesterday the street muni transformer blew (IMHO due to no oil change in 8 years and very hot weather) leaving us with no grid electricity. So after a 6 hours I decided to start the three phase generator (with each phase servicing a specific single phase section of the house) to get the fridge and freezer cold again. The fridge (which is a brand new Bosch KGN36XI32 with power demand of 160W) simply refused to start up on the generator supply. That I could understand as the wave form on the phase is a bit dirty.

    So I switched the fridge supply to the standby 400W Victron sine wave inverter with a 2,5mm2 lead. Now the fridge's internal light came on, the touch control panel worked but the compressor did not start. At full load demand the fridge should start up ... not the case. So I pulled a spare 1,5kW Meanwell sine wave inverter out. Now the fridge's internal light works, but the touch control panel only randomly and the compressor refused to start.

    OK, my logical deduction is the fridge went with the transformer to electrical heaven. A nice way to start Christmas.

    After 12,5 hours a new transformer was installed and grid supply was reinstated. Let me try again I told the Boss, and she just laughed.

    Low and behold, plug Mrs Fridge in and there she starts up and purrs away ....

    Can anyone shed some light on the reason why the grid supply works, but two pure sine inverters do not?

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    Diamond Member AndyD's Avatar
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    Modern day appliances can be very complex devices with internal communications between different control boards and even between control boards and components and sensors. Sometimes the comms systems require a very low neutral earth voltage. The only thing I can think of is maybe a lack of N-E bond caused problems with the comms.
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    Thanks for the reply. That is one thing I have not thought of. Will measure and see if this is the issue!

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    You are spot on. The inverter(s) are V-0-V and there is a 70+V on N-E which the fridge does not like and will refuse to start. I did not realise the inverters were V-0-V so I now have a few decisions to make as I cannot connect these into my household circuits.

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    Get a 600VA 1:1 ratio isolating transformer, primary side to the inverter and secondary side to the fridge. This will isolate the V-0-V issue.
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    It pays to buy quality inverters. Feedback from Meanwell is that it will auto sense V-0-0 downstream of the outlet and adjust the inverter's output to V-0-0. I will try this tomorrow in a controlled way.

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    Diamond Member AndyD's Avatar
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    Glad you're on the right track. If it's any consolation I like all the Meanwell devices I've come across, their power supplies and drivers are well designed, nicely manufactured, functional and they're reliable. I haven't worked with their inverters yet but hopefully they're equally good.
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