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Old 15-06-2016, 17:57   #1
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Convert 110v refrigerator to 12v?

I currently have a 12v chest fridge (one of those cold plate retrofitted ones), but I need a stand up refrigerator.

I'm not going to buy a $1,000+ "marine" 12v refrigerator... too much!

Can I just buy a 110v compact "dorm room" refrigerator, and use my current 12v compressor? Would I just run the discharge / return lines from my current 12v compressor into the new fridge?
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Old 15-06-2016, 19:03   #2
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Re: Convert 110v refrigerator to 12v?

It would be easier to take the dorm-room refrigerator and add an inverter to convert the 12v to 120 AC. The only problem is that compressors demand a lot on startup, so either a larger inverter than you expected may be needed, or you may need a soft start capacitor.
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Old 15-06-2016, 19:12   #3
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Re: Convert 110v refrigerator to 12v?

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Originally Posted by tkeithlu View Post
It would be easier to take the dorm-room refrigerator and add an inverter to convert the 12v to 120 AC. The only problem is that compressors demand a lot on startup, so either a larger inverter than you expected may be needed, or you may need a soft start capacitor.
I do have another problem, and that is that I have to remove and relocate the dorm-room fridge's compressor ANYWAY since it gets in the way of the hull.

If I am doing this already, I figure why not just hook up my current "marine" 12v compressor instead...

How do I know if the compressor will be powerful enough... I guess is my question...
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Old 15-06-2016, 20:37   #4
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Re: Convert 110v refrigerator to 12v?

Convert it to 12V. Why not.

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Old 15-06-2016, 22:37   #5
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Re: Convert 110v refrigerator to 12v?

It's a piece of cake and we do 4-5 of these a month.
Just buy a 120v dorm style refrigerator you like under 7CF.
Rip out the 120v AC compressor set up and
Then Buy a 12v compressor solder it in, vacuum it down, charge it and boom...you are off and running.

Sure we sell them...but if you have some solder skills and access to a vacuum pump and gauge set, I can walk you through how to do it lickedity split. You will use MUCH less power than running a 120v AC unit through an inverter for two big reasons:
1. The 120v AC compressors they put on these units are DOGS when it comes to energy efficiency.
2. You won't lose the inverter 120v to 12v conversion efficiency.

You can see some of the standard units we have been doing:
EcoFridge Marine Refrigerators for Boats | Cruise RO Water & Power
This isn't rocket science, you just have to know how to do it.
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Old 16-06-2016, 10:26   #6
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Re: Convert 110v refrigerator to 12v?

Rich,
Who’s compressor would you suggest? I see these Chinese ones for $50 to $85 but I am leery of them.

Also, (forgive my ignorance) what gas? You can get R20 cans in Mexico pretty cheap.

Thanks in Advance,

Michael
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Old 16-06-2016, 10:32   #7
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Re: Convert 110v refrigerator to 12v?

You can use a Danfoss BD35 or BD50 (Made in China..what most poeple use due to price)

We use Cubigel brand (Made in Spain..a little more expensive, but better quality and less electronic controller failures)

Or
You can use Tecumseh (Made in USA..cheap price, great unit, but more noisy than the other two)

Just Google these three brands and find a cheap deal online for a 12v unit.

The Refrigerant Gas would be R134a, which you can get at any Autozone in Mexico.
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Old 16-06-2016, 10:40   #8
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Re: Convert 110v refrigerator to 12v?

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Originally Posted by SV THIRD DAY View Post
You can use a Danfoss BD35 or BD50 (Made in China..what most poeple use due to price)

We use Cubigel brand (Made in Spain..a little more expensive, but better quality and less electronic controller failures)

Or
You can use Tecumseh (Made in USA..cheap price, great unit, but more noisy than the other two)

Just Google these three brands and find a cheap deal online for a 12v unit.

The Refrigerant Gas would be R134a, which you can get at any Autozone in Mexico.
Thought Tecumseh products were now made in China. At least their engines are.
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Old 16-06-2016, 15:20   #9
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Re: Convert 110v refrigerator to 12v?

My Waeco 12V unit is just a Danfoss 35 with a Waeco inverter slammed on to it. Modern Inverters can be pretty efficient. Mine needs a little over 3 amps (@12V). The inrush current is about 7 Amp so it needs a 10 amp fuse. With a 1:3 on/off time by the thermostat it averages to about 1 Amp for a perfect beer temp on a hot summers day.
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Old 17-06-2016, 06:34   #10
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Re: Convert 110v refrigerator to 12v?

Cheapest and easiest solution is generally buy the much lower priced 120 V appliance and use a small inverter. However, you will use substantially more amps. That could be a real issue for long distance cruisers or living on the hook. I still suspect it is cheaper to increase your house bank than to buy 12 V appliances unless using RV type units which seem to be mostly chest types.
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Old 17-06-2016, 09:13   #11
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Re: Convert 110v refrigerator to 12v?

I have 3 or 4 "scratch-n-dent" Cubigel compressors that we use in our Dorm fridge conversion units that I will sell for $250 including the electronic control module. Brand new in the box, I just can't sell/use them as new since. That is less than a Danfoss Controller for the whole set-up! PM me if interested.
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Old 17-06-2016, 09:53   #12
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Re: Convert 110v refrigerator to 12v?

Generally with a dorm style fridge, the watts required to cool the fridge will be close to the same for 120V or 12V. That is the amount of heat gain is a function of the box design and insulation.

While the 12V compressor uses less amps when running, it will run longer then a 120V compressor.

OK there can be differences in the COP between 12V and 120V compressors. If your not changing the evap or condenser, the difference is not so great. I suspect that the overall energy use between a 12V and 120V dorm fridge will be close to the same.

Yes there are efficiency losses running an inverter, but it's not so bad. Lets not forget that the black box on the danfoss is an inverter (DC to AC) so no free lunches there.

As an example, my cheap $120 magic chef 120V 3.5 CF fridge pulls 15 amps when running off the inverter, which it great gobs tons of load But it only runs 10 minutes ish per hour (4 times 2.5 ish minutes). So while its moving lots O amps when the motor is on, it's duty cycle is much lower then a 12V compressor. Average hourly load is 2.5 amp-hr or 55- 60 amp-hr in a day. A 12v compressor with variable speed, might get that down to 45 amphr. A difference of ~ an amp per hour.. OK it saves energy but at a cost.

My 120V fridge and a cheap inverter combined cost $200. It's been 9 years now and still going strong. BTW I am at anchor and have traveled 200 miles in the last two months or so.
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Old 17-06-2016, 18:49   #13
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Re: Convert 110v refrigerator to 12v?

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Originally Posted by SV THIRD DAY View Post
This isn't rocket science, you just have to know how to do it.
There IS one tiny tiny problem with the mini fridge that I currently have...

The condenser coils seems to be somewhere inside the walls of the mini fridge. My only option would be to take it apart and hope that I can remove those coils (since my current 12v marine compressor has the condenser coils remotely already).

Would that be feasible? Or would I be better off starting with a mini fridge that has external condenser coils?

P.S. I REALLY love this mini fridge because it has racks on the door unlike most other that have soda/beer can holders (which are useless to me since I drink neither on a regular basis...)
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Old 17-06-2016, 18:53   #14
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Re: Convert 110v refrigerator to 12v?

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Originally Posted by TitoSoto View Post
There IS one tiny tiny problem with the mini fridge that I currently have...

The condenser coils seems to be somewhere inside the walls of the mini fridge. My only option would be to take it apart and hope that I can remove those coils (since my current 12v marine compressor has the condenser coils remotely already).

Would that be feasible? Or would I be better off starting with a mini fridge that has external condenser coils?

P.S. I REALLY love this mini fridge because it has racks on the door unlike most other that have soda/beer can holders (which are useless to me since I drink neither on a regular basis...)

No..no no...No problem at ALL.
Almost all of the units these days have the condensing coils under the skin of the exterior wall. But you have access to the copper lines back where the compressor is...so it literally a solder off the old 120v compressor and then solder on the new. easy pleasy....
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Old 17-06-2016, 19:13   #15
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Re: Convert 110v refrigerator to 12v?

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No..no no...No problem at ALL.
Almost all of the units these days have the condensing coils under the skin of the exterior wall. But you have access to the copper lines back where the compressor is...so it literally a solder off the old 120v compressor and then solder on the new. easy pleasy....
Yup I do see that!

I just always thought that it was more efficient to keep the condenser coils in a separate location since their whole purpose is to get heat AWAY from the fridge.
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