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Old 30-07-2009, 17:11   #1
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120vac Refrigeration Questions

I'm interested in learning the negatives of installing 120v fridge and freezer vs 12v.

Other than incurring a power loss running from an inverter (10-15%, from what I've read) what other nasty things would someone be living with?

I already have an inverter that would power both a small fridge and a freezer. My limited research shows 120v units to be approx 20% the cost of 12v.

I should also say thanks for the extensive information and entertainment this site has provided me for the last year or so, before registering. Kudos, and all that...truly great.
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Old 30-07-2009, 17:35   #2
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I have a small 4.5cf 120v fridge, when running the inverter show a power usege of 9amps a small 12 volt unit should less then 4amps you decide Refigeration is the largest power user on a boat. if you spend any time away from the dock it will pay to have the 12 volt unit..But if you want a 110v Mine is only 4months old for cheap
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Old 30-07-2009, 20:56   #3
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You can get a 3.2 cu ft refer at Sams for $139 that uses 1.2 amps at 40% and a 7.2 cu ft freezer for $189 that uses 1.4 amps. Most 12v units are much smaller and as you know much more expensive, only because fewer are made. I'm going with 120v, but space and weight are not an issue with me. I plan a two 8D battery bank for inverters that will charge two hours a day. That's the plan, we'll see how it works out.
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Old 30-07-2009, 21:14   #4
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Originally Posted by lorenzo b View Post
You can get a 3.2 cu ft refer at Sams for $139 that uses 1.2 amps at 40% and a 7.2 cu ft freezer for $189 that uses 1.4 amps. Most 12v units are much smaller and as you know much more expensive, only because fewer are made. I'm going with 120v, but space and weight are not an issue with me. I plan a two 8D battery bank for inverters that will charge two hours a day. That's the plan, we'll see how it works out.
those ratings are for 120 volts, thu and inverter and 12 volts.. more. If you only are on the hook for short time it will work fine, you will charge at least twice a day with 500amp bank Maybe check ebay for a good price on a 12v unit
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Old 31-07-2009, 05:50   #5
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Refrigeration

You are right that 1.4 amps @ 120v will need something like 18 v @ 12v through an inverter, or so I'm assuming. As I said, I'm in the process of putting a system together and have not actually run it yet, so my comments are more of a question than a statement. I'm hoping two 8Ds will give me 200 amphrs usable power which should run my refrigerator and freezer 5 hrs and that in addition to running two hrs while charging that will be enough.
The reason I'm attracted to 120v is that they are manufactured by the millions and are reliable, as contrasted to 12v systems made only for the RV market.
I think the more important issue for nine lufts is what kind of boat he/she has and how much space for appliances and batteries. 12v systems are specifically designed for small tight spaces on sailboats and RVs, though why anyone would choose to live in a small box is beyond me.
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Old 31-07-2009, 06:08   #6
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IMHO, 120V refrigeration on a typical 35-45' cruising boat is very likely to wind up being much more costly and much more trouble than it would seem.

A couple of things have already been mentioned, e.g., the less-efficient use of battery power thru an inverter, and the commensurate costs of putting those amps back into the batteries.

Another problem is the power factor (PF) of electric motors (compressors) and their in-rush current demands, especially on 120V frig/freezers which are designed to work off the grid....i.e., off of shore power. These two factors mean that you must have available a MUCH larger inverter than you think, in order to accommodate the losses due to less than 1.0PF and to provide enough capacity to start the compressors.

EXAMPLE: on a boat I recently worked on with a sizeable 120V frig/freezer setup, the owner was experiencing severe difficulties even though he had a 3000 watt inverter and a 6.5KW generator. Startup was a particular problem. Compressor motors have two ratings to watch for:

RLA - Run Load Amps. This is the generally cited amps drawn when the compressor is actually running; and

LRA - Lock Rotor Amps. This is the in-rush or maximum current drawn with the rotor in locked position (or, sometimes, starting).

In the case I mentioned above, the RLA was only about 9 amps @ 120V AC, but the LRA rating was 60 amps @ 120V. Now, how're you going to pull 60 amps thru an inverter/charger with a transfer switch rated at 30A?

Bottom line: avoid 120V refrigeration if you can. Go with a well-designed 12V system which will be very gentle on your battery system. And, after all, they're really not all that expensive. You can find a basic AB system for around $1,000 and, if previous experience is any guide, you won't have to touch it for the next 20 years.

Bill
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Old 31-07-2009, 13:09   #7
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refrigeration

I went back to the boat to meet the guy who sold me the 5 ton air conditioner to talk about hooking it up and running the vents and while there I checked the specs on the freezer and refrigerator. The freezer runs at 1.7 amps 60% at 90 degrees and the refer at 1.2 @ 40% at 90 degrees. I understand what you mean by lock rotor amps and we all have heard the rumble as motors kick in, but for some reason these units are noiseless even when you first plug them in. The compressors are the size of a softball and the energy saving stickers claim these units are efficient. I'm going to try running them on a 1000 watt inverter for 4 hrs a day and see what happens.
I turned over my 20kw Northernlights genset for the first time today and instantly fell in love. It just sort of quietly purrs. Very happy.
Still no word back from nine lufts on the size of the boat.
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Old 31-07-2009, 13:21   #8
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We cruised MX for three years with most time at anchor. We had a 120v apt size no frost refer with ice maker. It used lots of power thru our inverter especially when the in the defrost cycle and just before it dumped ice (the ice tray heats first). We had to run the genset 2 hours in the morning and 2 in the evening, a pain. But during those run times we also made water. Evenso, if I were to do it again. I would go with a chest type 12 v refer/freezer. Not as much room. Ice trays, not ice maker. Solar panels. Hope this helps. Opps. Not in our Newport. We had a trawler then.
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Old 31-07-2009, 13:56   #9
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At this time there is no boat, but once it appears (this fall), I suspect it will be a monohull in the 27-29' range, and primarliy outfitted for one person's needs.

IMO, cooler/ice boxes are virtually useless for extended cruising. Twenty years ago I remember paying $7 for a bag of ice on Cat Cay, something that's not a part of my future plans.

While $1000 may not cause some people to blink, that figure prompts my gag reflex. If the 120v appliiances can be used, both a decent sized fridge and separate freezer is <$400. Adding a wind genny, plus a few batteries, and I figure you could be setup well for less than $2000.

I don't know the answer to this, obviously, and do appreciate all thoughts.
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Old 31-07-2009, 14:09   #10
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Egad, man, $1,000 prompts your "gag reflex", but $2,000 doesn't???

Build yourself a spreadsheet and calculate ALL the costs involved with 120V AC refrigeration, not just the initial acquisition cost.

For a boat your size there's only one cost-efficient and trouble-free solution: 12VDC refrigeration. Every other alternative is gonna eat up the bucks, now or later, and will have you laying over in port awaiting parts when you want to be cruising.

B.
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Old 31-07-2009, 14:10   #11
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I've been trying to figure this out also for a little trawler I have now. I think you re going to find the 120V wont work out. It's just too much draw through an invertor and at the high amperage conversion to 12V. (A small 12v cold machine took 1.25 hours avg. per day with a 100 amp alternator and 4 winds wind gen to keep going on my last boat). I was enticed by the small refrig's at the hardware store showing 1.2 or 1.4 amp draw, but I suspect even that is too much. Right now there are a bunch of 12v/120v Nor cold units on the market as low as $400 brand new due to store bankruptcys, a couple were advertised on this web. Pick one up quick...
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Old 31-07-2009, 14:19   #12
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If you want to keep costs down these work very well and draw very little.


It's an Engel. Quite a few cruisers are carrying these in addition to their fridge. Excellent fridge or freezer.
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Old 31-07-2009, 14:22   #13
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I looked closely at that..The engels are reputed to be great. They are quite small though and quite expensive! To get decent room, you might as well buy a cold machine type for the $ if you have a box. Also, they are either a freezer OR a refrigerator, they dont have separate sections....
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Old 31-07-2009, 15:30   #14
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refrigeration

the units I've got both specify that they need 2 to 3 inches clearance on all sides, so that's not really going to work with tight spaces. I also thought I could add insulation panels to the sides and top to increase the R factor but that's not an option.
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Old 31-07-2009, 18:11   #15
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.....To get decent room, you might as well buy a cold machine type for the $ if you have a box. Also, they are either a freezer OR a refrigerator, they dont have separate sections....
The biggest problem I'm causing myself is the desire for a separate fridge and freezer, and the more dollars needed to satisfy this desire.

I'm currently living in a truck camper and well understand spacial requirements of various comforts. Both a frdge and freezer (3.5-4.5 cf each) would not take up too much personal space in a boat, and would probably feel luxurious.

The small 3-way fridge I have in the camper has been hardly used, as I need to drive the vehicle daily. Living out of a large cooler, buying ice every couple of days, gets old quickly.

Most all problems can be solved with money...and compromise. I may run some tests on a 120v 4.0cf beer fridge I have.

I did double check, and yes, $2000 is more than $1000... I'm a spreadsheet nut. Knowing that I'll probably want some type of auxiliary method for charging (no matter the voltage), I chose a wind genny, for the sake of...just making a choice, projecting forward. Please understand that I'm trying to plan ahead, have little prior experience with same, and will learn as I go.

The intellect and knowledge on this forum is high.
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