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Old 07-13-2017, 05:55 PM   #1
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Reducing refrigerator start up current

My 1000w Xantrex inverter built in low voltage alarm 'bleeping" when my house batteries got down to ~12.5 volt lever and the refrig turns on. So........not letting not knowing anything about electronics stop me I went back to see if I could reduce the start current that causes the few millisecond noise coming from my inverter every time the refrigerater starts. My refrig is an inexpensive 3.2 cf Igloo that I modified (reduced its power consumption) for boondocking. Not a lot of $$$ risk in screwing around. After some confusing and conflicting recommendations and advice on the internet I took the risk and installed a Supco 3'N 1 Start RCO810 solid state start capacitor. My cheapo refrigerator did not come with a start capacitor. So my refrigerator upgrade pushed its cost from $100 to $115.

Refrigerator as received: 8.42 amps start, 0.62 amps run. Measured with a clamp on amp meter.

Refrigerator after adding the RCO810: 5.32 amps start, 0.62 amps run. Again measured with same clamp on amp meter.

This change worked great this last week while dry camping. The house batteries got down to 12.25 volts and when the refrig was running dropped to 12.05 volts. The Xantrex inverter worked fine did NOT "bleep" when the refrig compressor started up.

Happy camper.

Any comments or insights??
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Old 07-13-2017, 07:05 PM   #2
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Excellent solution.
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Old 07-13-2017, 08:57 PM   #3
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I'm sold. Sounds like a winner!
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Old 07-14-2017, 09:07 AM   #4
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Great implementation.

Just don't forget about the stored charge if you work on something in that area. I've been shocked more than once by caps.


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Old 07-22-2017, 10:58 AM   #5
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Great idea. In light of how hot it's been lately, I started thinking about installing a small window type airconditioner in the rear door (again). The biggest problem seems to be the starting surge that requires a larger generator than needed once the unit is running. I'm hoping a starting cap will allow the use of a smaller gen, and I don't see any reason it wouldn't work (or help) in that application too.
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Old 07-22-2017, 01:03 PM   #6
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I've been through this with a roof top AC. The supco caps really only help move you from marginal to reliable. They are however cheap enough, and simple enough to wire up, to just try.

I ended up with a softstart unit (take a look at hypereng.com) which managed a whole other level of locking current reduction. It's more expensive, and at least on a unit with a multi-speed fan the install is more complex.
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Old 07-22-2017, 04:46 PM   #7
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[QUOTE=MadScience;207972]I've been through this with a roof top AC. The supco caps really only help move you from marginal to reliable.QUOTE]

Do you remember the inrush and running current of the roof unit? I'm guessing it's quite a bit higher than the 5000btu window A/C I'm looking at installing in the rear window. It's only .61hp drawing 450W or 4A. I can't find specs on the inrush, but if I'm running a small 1000W gen and install a big cap, I might stand a chance of getting it going. If not, I guess I'll need a bigger gen, but anything is better than being unable to sleep at night due to the heat.
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Old 07-22-2017, 11:48 PM   #8
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On mine, running is between 10 A and 14 A. Inrush is hard to measure, but was above 50 A. Now it's more like 30 A. But it really depends on how well that start went. My roof top AC has many many hours on it, likely 5k+, and I could probably stand to replace the compressor (in other words the whole thing).

A 1kw generator will be a challenge. I'm working with a 2kw unit, but also a 13.5k btu ac (which will chill an eb van full of gear, and is more than one might spec with just humans in it).

If I was in your situation, I'd honestly just step up to a 2k generator, since those really aren't that different in cost, weight or noise to 1k units. This seems to be the same in both name brand (cough, honda eu) or generic.
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