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Author Topic: AC Refrigerators  (Read 4073 times)
Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #15 on: November 12, 2007, 06:39:40 AM »

David,
     First off you'll want to look at http://http://www.energystar.gov/index.cfm?fuseaction=find_a_product.
And shop for lowest kwh/year.    I have an Avanti 651 with a SS front.  It's 6.3 cu. ft.  Manual defrost of freezer rated at 254KWH/yr.    The Summit model you mention may a good choice also, check it's energy star rating, I think it is 285 KWH/yr.  Also, try to get one that has the condenser coils on the back, if it does you can add insulation to reduce power use.  I added 1" of R7 foam round the sides,bottom and back of mine and 1.5" on the top.  I also relocated the compressor about 2" further to the rear.   These changes reduced my measured power usage to 19 W average over 24 hours or in the energy star units 166kwh/yr, but my initial measurement was 223kwh/yr.  BTW The peak wattage with the compressor running is 150 watts or about 1.25 amps, far less than the 4.3 mentioned above. 
Regards
Jerry 4107 1120


Hi Jerry,
Your refrig is quite efficient but almost 4 times smaller then my 22 cf side-by-side.
If you do the math, the amp draw per qubic ft. works out to be the same!
I have a family of 5 and always 1 or 2 extra friends along, it's the most efficient refrig
for the size we need.
Nick-
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« Reply #16 on: November 12, 2007, 07:38:34 AM »

 Many refrigerators today come without the rear coil, utilizing the outside of the box to dissipate heat. If you build one of these in too tightly, it ain't gonna work!!! Check the manufacturers recommendation for clearances needed around unit.
 I have the rear coil type built in. I wired a small fan into the circuit so fan comes on with the compressor, helping to dissipate heat.
                                                                 HTH
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« Reply #17 on: November 12, 2007, 07:44:56 AM »

Quoting Stone:       ? if your fridge is wired the way you say and if I understand it correctly. when the temp drops [raises] in the fridge and kicks on, the inverter is then turned on by the temp switch...instead of the compressor....
If this is correct then the compressor in the fridge and the inverter starts at the very same time.  If so the inverter would be trying to start while under load from the compressor....Am I correct....
And when you say your compressor is wired to the inverter ' do you mean the fridge plug is plugged into the inverter ac socket ?   
I am not questioning your wiring or your  idea....I think is it an idea I might try...I just want to see if I understand what it is you are doing.....thanks.....Stone.....


I wired a plug directly to the compressor and plugged that into the inverter. Then I disconnected the two wires from the inverter's on/off switch and hooked them to the fridg's temperature control switch terminals (which are no longer hooked to the compressor)
So when the inverter comes on, yes- it sees the load of the compressor that's hooked to it, and they both start up at the same time.  It (the inverter) doesn't care at all. Inverters are designed to be turned on under load.   But that's why it takes a 1000W inverter.  Running, my Summit fridge draws 1.7 amps@ 120 volts, which is only 200 watts or so.  But when the compressor is starting up, it draws almost 12 amps for a fraction of a second, which send any lesser inverter straight into fault mode.  A 500W trace wouldn't work to save it's life.  The 1000W/2000w surge inverter squeals for a moment but it's fine.  Been running flawlessly for almost a year now...
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« Reply #18 on: November 12, 2007, 11:11:49 AM »

Ok I am looking for a ac fridge currently . So I am considering doing what you did...My Diometic went poof..
No more RV fridge for me ' the prices are out of reach...In my bus ' I like to keep it so if it needs something repaired I can replace it with Lowes or Home Depot items ..I do not like to depend on RV equipment any more that I have to....IT"S A BUS NOT A Grin Roll Eyes S/S......

thanks for the reply.......
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« Reply #19 on: November 12, 2007, 11:46:48 AM »

Thanks for all the ideas and info, guys.  There are a couple of points I'll mention, though.  I don't want a single-door model with the freezer inside.  I also want one with the coils in the back, like Jerry mentioned.  I'm also planning on adding 1" of pink Styrofoam to the sides and back (leaving enough space for the coils), wiring a disconnect for the defrost (if it's frost-free), and switching the cabinet heaters (that keep it from sweating).  I like some of the cycle defrost (manual freezer defrost) models, but their elec. usage is not a whole lot less than a comparably sized frost-free model.  Some of the smaller (less than 10 cu. ft. or so) models don't list their energy usage.  TomC, what size is your DC Norclold?

Another thing I don't understand is why some 'fridges are on the energy star list but use more kW's in a year than other similarly sized models that aren't on the list.  I guess I'll keep my eyes out for one that has the right dimensions, will allow additional insulation, has low energy usage, and is on sale.  I do love a good scratch-and-dent item... especially when the scratch or dents are where I won't see 'em!

David
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« Reply #20 on: November 12, 2007, 01:23:51 PM »

I was up at Southern Orygun Diesel a couple years ago and met "a couple" with a Eagle conversion that was 95% done.  He pulled a panel and showed me three refridgerant compressors that ran on 12 volts.  His was a "NO GAS" conversion and he said he wanted to be able to boondock for extended periods.  Those compressors were integrated into his freezer in the bay and his fridge and icemaker.  He said the compressors were very efficient and he was delighted with that arrangement.  I think his household refer had the compressor removed and his system integrated.  Each compressor was the size of a football.  I didn't see any heatexchanger but I assume it was there as he said he recovered that heat for the coach in the winter but ducted it out for summer use.  I guess Nick would know about the compressors.

FWIW

John
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Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #21 on: November 12, 2007, 01:39:45 PM »

Hi John,

Yes, they are made by Sierra. 12v and 24v dc and they are very pricey..... They may even out price the project..

Small refrig's are about all the can handel at the moment..

Nick-
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« Reply #22 on: November 12, 2007, 02:23:19 PM »

Danfoss also makes the efficient 12v compressors used with Tundra and Nova Cool reefers-they work well-they are used in the reefers we put into the Freightliners.   Good Luck, TomC
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« Reply #23 on: November 12, 2007, 04:32:23 PM »

David,
    When you get to adding insulation I think you may want to avoid Styrofoam.  While it's a little less costly it's not near as effective as the urethane based stuff.  Most Styrofoam is about r5/inch while the urethanes and polyiso is r7.  That means less than 3/4" of the r7 will conduct less heat than a full 1" of the Styrofoam.  or it would take more than 1.4" of Styrofoam to be as much insulation as 1" of the r7 material.
Regards
Jerry 4107 1120
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DavidInWilmNC
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« Reply #24 on: November 12, 2007, 05:39:43 PM »

Jerry,

I think what I'm referring to for insulation is urethane (like Kleenex and tissue... just a generic term for me).  It's the pink board from Lowe's or Home Depot.  It's closed-cell and is much sturdier than the standard white Styrofoam.  If I'm not mistaken, the 1" foam board I used in the walls is R7 per inch.  I used a different foam board for some air ducts.  It's kind of beige and has foil on one side.  It's used under siding on houses.  I believe it's polyisocyanurate, though.  Are either of these what you're talking about?

David
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« Reply #25 on: November 12, 2007, 06:38:00 PM »

David,
    The 'stuff' I used is kind of beige with foil on one side and is polyisocyanurate & clearly labled r7/ inch.  The brand is 'RMax' & it's also what I used in all my walls, ceilings etc.  Lowes does sell it but they also sell several other foams that aren't R7/inch.   IMO It's worth the effort to be sure your getting the 'good stuff'.
Regards
Jerry 4107 1120
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