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Old 10-09-2015, 04:07 PM
OPCHARGE Male OPCHARGE is offline
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Default SOLAR REFRIGERATION

This is a long one and may require someone like Jeffrey Yago to crack, but will gladly listen to anyone who has help.
After 15 years of using a propane refrigerator/freezer on our homestead we are ready to move to a A/C unit. (The 18 cu.ft. propane unit struggles here in the south during the summer, and the freezer never really gets as cold as we would like for storing meat).
We have a full solar array that feeds our 24VDC battery bank ( 20, 6VDC golf cart batteries in series/parallel) with a wind turbine to help out during the winter and diesel generator backup. So while we can always have power if needed, we do still tend to be stingy with it. We have a dedicated building that is our pump house/ battery storage/ and all inverters, charge controllers and transformer. We use all 120 A/C in the home.
The "Solar" refrigerators out on the market, as in those for people living off the grid, i.e. Sundanze and Sunfrost are not only quite costly, but with the cost of shipping them out this way, well forgetaboutit.
So..... enough with background info, here we go with the problem. The 18 - 21 cu.ft. refrigerator/freezers on the the market all have a automatic defroster in them. It is the electronically controlled heating element in the defroster that is my concern. It drains power that I don't want to use, and with my luck it will always do it at night when my panels are sleeping. No manufacturer has been able or at least not willing to tell me how to disconnect it. Time was one could just "cut the red wire" and all was good to go, but now with the invention of the circuit board, cutting said wire puts an error single to the system.
Next I thought that I would put my new fridge on a timer, cutting if off/on every nine hours as most the defrosters work on about a 10 hour cycle. This way each time my fridge "restarted" I would have 10 more hours to go before the defroster would want to kick on. But no....... it seems, according to the manufacturers that the internal timers know when there has been a power loss and keep the defroster working on it schedule. It is an accumulative timer, so no go there.
Also there is this problem, and I promise not to list anymore after this because if you have gotten this far into my epistle, you are also aware of the many other problems we have to overcome to have an A/C fridge/freezer. The control unit on these newer fridges draw very little in terms of watts. So little that I would be unable to run my inverter in search mode, rather I would have to leave it on 24/7. And leaving the inverter on 24/7 is another way to use up that power that I do not want to "spend". The only way I have figured out to beat this problem is as follows. Next to the fridge, at the A/C receptacle plug in a battery charger that works only when the batteries ( 2, 12 VDC batteries ) drop to a specified voltage. The batteries power a 120 inverter that powers the fridge. (yeah, I know, I am making DC from the sun, sending it to my batteries, making A/C sending that into the house, turning that into DC for the fridge batteries which is being turned into A/C to power the 120 Fridge, OMG)
If any of you out there have beat the refrigerator Rubicon, please let us know how you did it or if you have ideas on how to do it, please post those as well.
Thank you in advance - OPCHARGE
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Old 10-10-2015, 05:15 PM
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Re: Defroster -- instead of shopping for a brand new fridge, go to a used appliance dealer that does their own repairs. Tell them what you want to do, they will probably unplug the "red wire" for you and you can see if it works. Don't forget to set the "energy saver" switch to OFF.

RE: Inverter sensing the fridge. You may be over analyzing but . . .

I assume you have periods of time when there are NO energy draws on your system. How long are those periods? If the fridge is only off for a couple of hours at a time you may be OK.

Or -- plug in a night light to the same outlet so that the inverter can sense the current draw. That would probably waste less energy and cost FAR less than using a separate inverter for the job.

Be sure to remove all or most of the courtesy lights if they're incandescent. I found that the lights in our fridge drew more power than the compressor did!

Once you find the right box, consider gluing foam board to the shell where appropriate . . . just a bit more insulation.
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Old 10-10-2015, 05:45 PM
OPCHARGE Male OPCHARGE is offline
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Mr. Randall,
Thanks for your helpful ideas. I think we will go out looking for a used appliance
dealer and see what they can do for us.
And yes, what would it hurt to have the fridge off for a couple of hours here and there. I have considered the "night light" earlier, but withdrew the idea because that would require my inverter to be running 24/7.
Gluing foam board, adding additional insulation is the best thing a person can do to help out their refrigerator. Take a look at those high dollar "solar" refrigerators and one sees 4 inches of insulation. It make a HUGE difference.
Take care down there - OP
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Old 10-18-2015, 01:46 PM
OPCHARGE Male OPCHARGE is offline
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Update to looking for a "solar refrigerator" and needing help on same.

Have checked with every used appliance mart within 50 miles ( both of them ) does not look like I will be able to go that route as they were not able to help.

My new idea is I am going to get two electro / mechanical thermo switches. Place one in the refrigerator section, the other in the freezer. I will wire them in parallel to the main power cord for the fridge.

So when either reaches the set point (fridge or freezer to warm) it will allow power to proceed onto the condenser, and the draw will be enough to kick on my inverter. I think this is a way to bypass the electronics and not require my inverters to be running 24/7.

Now...just need to find out a way of taking out the automatic defroster.
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Old 10-18-2015, 05:58 PM
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Excellent advice Randall.

Hi OpCharge
12 volt has lived off grid for years also--he has a wealth of knowledge.

hope you have solved the problem---I started to run my fridge of propane---but propane has increased in price---I have an RV with a 3 way split system---had thought seriously about solar but would be too pricey for the little gain.
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Old 10-18-2015, 11:28 PM
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Quote:
Originally Posted by randallhilton View Post
Be sure to remove all or most of the courtesy lights if they're incandescent. I found that the lights in our fridge drew more power than the compressor did!
That's funny ! That is also the first thing I did. I replaced the 15 watt bulb with a 1 watt LED !
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Old 10-19-2015, 12:38 AM
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Quote:
Originally Posted by OPCHARGE View Post
My new idea is I am going to get two electro / mechanical thermo switches. Place one in the refrigerator section, the other in the freezer. I will wire them in parallel to the main power cord for the fridge.
Re: thermo switch. Set your fridge t-stat to it's lowest setting so that it is always calling for cooling.

I'm not up to date on the newest models but I believe that the cool section temp is controlled by a fan which moves air from the frozen section. I would be concerned (and I could totally be off track) that your cool section t-stat will result in the fridge cycling too often. That might eat up the savings you get from shutting down the inverter. But I don't know for sure.
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Old 10-20-2015, 11:46 PM
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Quote:
Originally Posted by Txanne View Post
Excellent advice Randall.

Hi OpCharge
12 volt has lived off grid for years also--he has a wealth of knowledge.

hope you have solved the problem---I started to run my fridge of propane---but propane has increased in price---I have an RV with a 3 way split system---had thought seriously about solar but would be too pricey for the little gain.
Had a guy on another site that claimed to run his three way on solar 98% of the time. I sent the info to 12v to see if it sounded feasible. This was a couple years ago so do not have the info anymore. He somehow changed the controls to 12volt first then propane.
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Old 10-22-2015, 09:12 AM
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I've ran propane almost fulltime from day one. I had a small 12 volt fridge for a short period but it wasn't big enough. (in area/size)

I never allowed a fridge to become a necessary item for survival. It's just a luxury when it's possible to have it. I can live without it..

Right now propane is a good value for me. I can fill a 100 lb. cylinder for $55 and it will last ~5-6 weeks. I operate 2 fridges (One with a small freezer compartment in the top and a small camper sized unit for drinks and milk) and my cook stove. I never became dependent on a large freezer for food storage by design and purchase whole milk in boxes that will last for over a year on a shelf. Powdered and canned milk works in a pinch..

If one must run a 120 V.A.C. unit in an alternative situation, the only one that makes any sense to me is the freezer to fridge conversion idea. (Add another thermostat to it. We chatted about that, Bones) Could be a PITA to keep it dry inside but it seems to work well and is a good idea if you really think about it. Freezers are always insulated better than the majority of the fridges on the market..
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Old 10-23-2015, 08:34 PM
JeepHammer Male JeepHammer is offline
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I'm New, and I don't want to step on toes here...

You are talking a fairly small freezer or fridge,
You are talking about somewhere around 15 watts for the defroster to run.
Not a lot of draw there to start with.

Secondly, have a look at the 'Energy Star' rating on the freezers you are looking at, the energy star rating will tell you how well insulated the unit is.

Third, and this one is kind of tricky,
When the defroster runs, it kicks the pump off. No point in having the unit run when while defrosting.
You normally have to take the pump controls back from the defrost circuit, and that is actually pretty easy,
You simply identify the wires to the pump, the power source going into the relay, and cut the relay out,
Then you can disconnect the heater without any issues.

The thermostat in the freezers *Normally* don't connect to the heater unit controls,
The thermostat/switch is usually ahead of defrost circuit, so when you bypass the cut out relay, you still have the thermostat controlling things.

--------------

If you want a LONG LIVED freezer, then consider having a look at the compressor assembly.
Look for COPPER lines from/to the pump.
Not 'Steel', Not 'Aluminum'.

Copper lines allow you to have the unit serviced,
They also allow you to move that pump producing HEAT out from under the freezer box.

In free air, the pump will cool itself better, and it's heat won't warm up what you are trying to cool down.

Remote pumps require a service tech that knows what they are doing,
But getting that pump out and away from the freezer will make the unit MUCH more efficient,

The same can be said about the condenser.
The 'Radiator' that is usually on the back of the unit.
Getting that condenser in free air will increase efficiency, and make it MUCH easier to clean.

Industrial units do this all the time and they work MUCH more efficiency than 'Consumer' units do, and they live a lot longer also.

I'm off grid, I had the compressor and condenser units moved to the 'Utility' room, and it was worth the money for the energy it saved over the last 15 years.
I vent the heat in the summer, and use that heat in the winter.

What the guys are telling you is correct, Insulation is the name of the game.
Built in units are WORK to make the hole, but they respond better to extra insulation than stand alone units do.
No metal between insulation panels wicking in heat, no barriers for the insulation.

Be careful with that spray can expanding foam, you can get it places that need to vent heat and reduce the life & efficiency of your freezer...
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Old 10-31-2015, 08:51 AM
OPCHARGE Male OPCHARGE is offline
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Here is the latest on my Solar fridge trek. I found a HVAC repairman who was some help. Yes, no problem in disconnecting the "auto defroster" from the freezer. However the defroster, which runs every 6-8 hours and pulls between 400 and 600 watts would have to be manually turned on at least twice a day. He says that the ice build up in the freezer compartment is not the issue, it is the build up in and around the internal cooling coils. Once they get frozen over the compressor will have to work harder and will eventually fail. So if I had to manually turn on the defroster twice a day or so, not only would it be a pain but would defeat the whole reason for disconnecting it in the first place, to save energy.
Bottom line - one cannot turn a "auto defrost" fridge/freezer into a "solar fridge" and recognize any savings or benefit.
My new plan or goal is to come up with efficient 120VAC stand alone freezer. Most likely it will be a chest type, I will over insulate it and put my own compressor in it.
I have looked into SunFrost freezers and while they seem to be nice enough, they
just don't have the numbers I am looking for. (Their energy star rating is within a couple of points of a same sized Kenmore )
Thanks everyone for your help and ideas so far, I will keep posting as I fumble along the road to solar refrigeration.
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Old 07-27-2016, 06:35 AM
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I understand that you may have this taken care of but this is what I do. My son got me a outdoor freezer/ fridge that was being thrown out. First of all I did not know they even made them. After looking at it I figured out that it has a freezer on the bottom and fridge on the top. The top just uses a knob that controls the amount of cold air from the freezer. They don't have a defrost cycle and have extra insulation and I think are made for a garage. the only thing wrong with it was the door seal was pulled out and I was able to get it put back in and running. I run it off my solar system with a timer. I do have to run it a hour longer in the summer with no problems. I have 1200 watt 12 volt sun following solar panels. 14-12 volt deep cycle batteries and a 1400 watt pure sine wave inverter. I know that is not the best setup for most people but where I am at that is the best that I can get without driving 70 miles. We really do live in the wilderness.
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