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Old 01-28-2014, 10:51 PM
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Default Running a Refrigerator from an Inverter

Sigh...... I'm still looking at a modification to run my refrigerator on an inverter.
This addition of a few parts should help. IF I can figure it out.
It's written in some foreign language called 220 volts !






http://mtbest.net/chest_fridge.html
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Old 01-28-2014, 11:28 PM
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Line Voltage Thermostat.. No power needed to operate.. ~$75..

Cut a heavy extension cord and put this inline between your inverter and the fridge..

"The ET141 remote bulb thermostat incorporates a temperature-sensitive liquid-filled sensing element that actuates precision snap-acting switches through a diaphragm and linkage mechanism. The switches are Single-Pole, Double-Throw (SPDT) snap-acting type, totally enclosed, and are suitable for low or line voltage power switching."

141-0520
Remote Bulb Thermostat Range 30°F to 110°F (-1°C to 43°C)



http://www.kele.com/thermostats-and-...41-series.aspx
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Old 01-28-2014, 11:58 PM
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What I am REALLY trying to figure out is PART 2 :

" Part 2. Reducing the start power surge from the compressor.

The next part of the article deals with reducing the surge current of the compressor at switch on, which is very important for me living on a small 600 watt Inverter. This part is a bit more technical, and mainly aimed at people who are trained at doing this sort of thing. I certainly will help anyone who asks for support here.

First of all a bit of background. Most fridge compressors for the sake of cutting costs do not include a start or run capacitor, as they are really “not” needed as people are living on the grid with “unlimited” power available. The times are now changing and we should start to look at saving as much energy as we can, especially if you are like me and live off Grid.

The first part we need is a Potential Relay, I have included a picture of my relay, which I had to source from the USA. I live remote and could not find a locally available unit, so I searched on the
----------------------- Page 3-----------------------

Internet and came up with this one. Available from http://www.carbonbrush.com/gerelays.html,

search for Mars169 Potential Relay. If any one knows where to
purchase in Australia please let me know. The original Potential relay I
found was made by “Electrica” model number 'RVA 3G3D' which has a
pick up voltage of 180 to 195 and drop out voltage of 40 to 105.

You will also need some Motor Run and Start capacitors. I purchased a selection of run capacitors from 4uF to 12uF and start capacitors from 10uF to 100uF all rated at a working voltage of at least 400 volts, which seems the norm for Australia.

figure 4 The Potential Relay

First remove the original current relay from the compressor and wire up the relay with capacitors as shown in the diagram in figure 5.
Make sure the 'thermal overload device' of the original unit if present is also wired in, as this will protect the compressor if the new relay or capacitor should fail.

Now try various capacitors while keeping an eye on the power factor. Begin with a start capacitor of about 20uF and run capacitor of 6uF. Switch on the fridge, and record the True power, current and voltage. Calculate the power factor and repeat until the power factor just becomes around 0.90.

Don't forget to wait 5 or 10 miutes between starts to allow the refrigerant to drain away from the compressor. I found 6uF for run and 30uF for start were ideal. You will also notice that the start surge power will drop as well once the power factor is correct the surge will nearly be the same as the True run power. Also don't forget to wire a 15k ohm 2 watt resistor across the start capacitor to discharge it, if we don't the, potential relay contacts have to discharge the capacitor after every run cycle. This may result in the contacts welding together and causing possible damage to the compressor.

The power factor should be as close as possible to 1.0. The power factor is the ratio of True power to Apparent power. And gives us an idea of the amount of power demanded from the Inverter or from the power grid to run.

For example my Power Meter reads true 'run' power as 136 watts. But the Voltage and Current measured separately produce an apparent power (VA) of 0.938 amps x 228 volts which equals 214 watts.
Thus the power supply or Inverter has to supply 214 watts and not the True indicated power of 136 watts. The power factor is then 136/214 or
0.64, which is very low.

figure 5 Wiring Scematic

The amount of power we are charged for from the Power Company is actually only 136 watts, when they are supplying 214 watts, so we are getting 78 watts for free. But this also means that my little Inverter has to supply an extra 78 watts, when this is not needed if the Power Factor was reduced to say 0.9 which is the acceptable value for power factor.

My Power factor finished up being 0.91 with a start capacitor of 20uF and run capacitor of 6uF and the surge dropped from about 800 watts to about 200 watts. I can now safely run my fridge from my 600 watt Inverter.

Installing this on a boat it is very important to have a 12 volt relay which
powers the offshore power with a simple low current simple charger or transformer.. Then when the power on offshore switches off the invertor will automatically switch on ,as with a bad offshore source you can also
damage your compressor and other electronic devices on your boat .

This will keep compressor running without a restart.(Also handy to get the freeze up before departing on a journey ,as huge load in freezer will take a lot of battery power to get up to temperature.

Graeme Brown "
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Old 01-29-2014, 12:07 AM
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I KNEW there was a way to reduce the surge by adding capacitors.
Just figuring out which ones is over my head. His 220 volt set up for South Africa is taken from an article from Australia.

I just need a "translation" into 110 for US in North America.

That quote is from an article :

Converting a freezer to start up on an inverter and saving you power.
www.spiritofjack.co.nr
July 2009

Part 1. Changing the Thermostat.

A lot of people have now realised how efficient an old Chest Freezer is when modified to run as a “Chest Fridge”. It is a little bit awkward to get things in and out of, but
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Old 01-29-2014, 12:11 AM
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I can't find that "Part 2".
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Old 01-29-2014, 12:17 AM
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Part 2 is ALL that I posted. I did not post part one, which was about changing the thermostat of a freezer to a higher temperature of a refrigerator. I have a refrigerator already so I have no need to do part one.
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Old 01-29-2014, 12:40 AM
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I want to see the Diagram/Wiring Schematic..
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Old 01-29-2014, 01:05 AM
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Ya know.. The more that I think about it, I don't believe that you would need to change the values of the caps at all. Those circuits deal with time, not amplitude. The difference between 50 and 60 cycles wouldn't make that much difference and the amplitude would be controlled by the input voltage. If anything, maybe a little smaller value cap to make up the difference between 50 and 60 cycles.. Just an educated guess..

The voltage of the caps that he suggests would be fine. A little overkill but not an issue..
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Last edited by 12vman; 01-29-2014 at 01:38 AM.
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Old 01-29-2014, 05:56 PM
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Yup, I knew there was a way to add caps to it. They tend to have a very wide range of voltage acceptance.
Finally figured out which relay he was referring to MARS169 fixed terminals $25.00 Coil: 375VAC, Pick-Up: 180-195V, Drop-Out: 0-105

Now the diagram:
and
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Old 02-10-2014, 03:12 AM
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Have you thought about something like this?

http://engel-usa.com/
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Old 02-10-2014, 01:39 PM
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Lightbulb

Yes, I have looked at many High Efficiency refrigerators, and the ENORMOUS cost did not make economic sense. For that kind of money I can add another ( or TWO ) solar panel(s) an inverter and a couple more batteries.

I have a mini frig/freezer. I'm just looking a ways to make it run better.
This modification is ~$30 and won't spike my inverter so much.
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Old 02-10-2014, 04:28 PM
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Two schools of thought.

First is taking a 5 or 7cuft chest freezer & attaching something like a Johnson controller to run the temperature in the refrigerator range.

Second is to run same size chest freezer as a freezer freezing water jugs & using those jugs in the frig turning the frig into a cooler. My little 520watt solar system will run a 5cuft chest freezer no problem though my solar panels are adjustable which makes a difference.
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Old 02-10-2014, 09:10 PM
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The posted link addresses the first one.
He changes the thermostat as well as adding the relay and cap.
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Old 03-03-2014, 12:02 AM
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I have used these to replace capacitors and potential and current relays.

"The company has introduced its new E Class Series hard-start devices. Designed to provide reliable operation, these units couple state-of-the-art electronic potential relay technology — to sense starting voltage — with a safety timing circuit, says the company. Other features of these devices include instant restart and simple two-wire connection, the company says. Sealed Unit Parts Co., Inc. (Supco), P.O. Box 21, 2230 Landmark Place, Allenwood, NJ 08720; 732-223-6644; 732-223-1617 (fax); info@supco.com (e-mail), www.supco.com (website)."
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