Author Topic: 125v Refrigeration Operated from a 12v/125v Inverter  (Read 3498 times)

wsmurdoch

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125v Refrigeration Operated from a 12v/125v Inverter
« on: December 18, 2012, 09:14:47 am »
I have a Kollmann Marine refrigeration system on my 1988 Pacific Seacraft sailboat that you have helped me within the past.  It has both engine drive and 125v systems sharing a common holding plate.  We use the 125v condensing unit (Aspera MA1111A ?) in the marina to avoid running the engine.  I thought it might also be used as a backup to the engine drive system should the engine drive system fail while we are away.  I tried to start the 125v condensing unit from our 500w inverter, but the inverter (a Xantrex ProWatt SW) was not up to the task and kicked off immediately.

I was wondering if a capacitor of about 50 microfarad across the 125v supply to the condensing unit would ease its starting without doing any damage to the (now 25 year old) condensing unit.  I remember you talking about "hot shot units" or something like that in the old forum, but did not see anything about them in this new forum or in your 'Do-It-Yourself Boat Refrigeration' book.

Thanks for your previous help, frozen food, cold beer, and ice.

Bill Murdoch

Richard

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Re: 125v Refrigeration Operated from a 12v/125v Inverter
« Reply #1 on: December 19, 2012, 10:15:26 am »
I no longer have specs on Aspera 1/6 HP compressors but their starting amps should not exceed 300 watts. Because this compressor has an inductance start motor it does not have a start capacitor so I do not know how to add a kick start capacitor to compressor.

If a 500 watt inverter will not start compressor I would first question 12 volt wiring to inverter wire gauge and length. Do not forget ground wire is just as important as power wire. Also 300 watts is 25 amps at 12 volts.
Is inverter connected direct to battery buss with large enough wire? 

wsmurdoch

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Re: 125v Refrigeration Operated from a 12v/125v Inverter
« Reply #2 on: December 19, 2012, 06:06:24 pm »
Good point.  I would have thought the wiring was adequate.  The house bank is three group 29 batteries tied together with 1/0 cable on both the positive and negative sides.  The inverter ties to the batteries at the negative current shunt (total current to/from the batteries) and to the alternator current shunt.  These are the points where the cables from the batteries come together.  The 12v wiring to and from the inverter is No 4 with an inline 50 amp fuse.  My guess is that the total length (total out and back) of the 1/0 cables is 20 ft to the most distant battery and the No 4 to and from the inverter is 15 ft.  I have no record of the grounding wire size or length; it is not on the wiring diagram, but I know it is present. 

However, one never knows about bad connections or bad wires, so I will put a voltmeter on the inverter terminals next time when I try it.  I think mine will latch on both a minimum and a maximum value.  If not, I'll need to be quick.  We will be back on the boat in mid January and give it a try then.

I was guessing the capacitor value as a power factor correction capacitor in case that was the problem.  After a fail to start, the inverter shows code E03 which is "overload shutdown".

Bill Murdoch


wsmurdoch

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Re: 125v Refrigeration Operated from a 12v/125v Inverter
« Reply #3 on: January 16, 2015, 08:39:11 pm »
I thought I'd let you know how this turned out. 

Short story from a lot of work... 

I bought a Chinese plug-in wattmeter on Amazon which will report max watts.  When starting the 125v Aspera condensing unit, it draws a maximum of 1250W before falling to ~250W.  I can't imagine it lasts for more than a few cycles, but it's enough time for the Xantrex PROwatt 600 SW to shut down with an "over load shutdown" fault.  I took out the PROwatt 600 SW inverter and put back in its place the next larger model, the Xantrex PROwatt 1000 SW.  That increased the nominal ratings from 540W continuous to 900W continuous and from 1200W surge to 2000W surge.  The larger inverter starts the little condensing unit without a problem.   I guess the extra surge capacity fixed the problem.  I made no changes in my wiring.  The Aspera motor is the sort without a starting condenser but with the relay that cuts out the starting winding.

Bill Murdoch
who is still enjoying ice and cold beer with a 1988(?) Kollmann Marine Products engine drive and 125v refrigeration system