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Old 06-03-2012, 19:13   #1
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Refrigeration While Cruising

I debating whether to buy an inverter for my regular size fridge or buy a small dc cooler. Which would be more cost efficient?
I saw an inverter at WM for a hundred bucks that would produce 100 watts, would that be enough for a fridge?
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Old 06-03-2012, 19:16   #2
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Re: Refridgeration while cruising

One thing to realize is that the DC systems actually have their own inverters. That said, I much prefer a 12v system. While many larger motor yachts use 110 systems, these tend to be boats that run the generator pretty much around the clock. I can't see where running one off an inverter would be energy efficient.
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Old 06-03-2012, 19:26   #3
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Re: Refridgeration while cruising

Quote:
Originally Posted by edbulmer View Post
I debating whether to buy an inverter for my regular size fridge or buy a small dc cooler. Which would be more cost efficient?
I saw an inverter at WM for a hundred bucks that would produce 100 watts, would that be enough for a fridge?

I have an inexpensive very small fridge that uses 65 watts on 110v AC. A regular size fridge would be more. However, when it first kicks on it can use 90-110 watts for a few minutes.

As to the inverter, this fridge would not kick on using a 700 watt modified sign wave inverter. It would just hum so I only tried it for a second or two.

It works fine on a 1000 watt true sign wave inverter that was intended for computers and other stuff, but use it for the fridge on overnighters on the hook, too.
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Old 06-03-2012, 19:33   #4
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Re: Refridgeration while cruising

So it look like the best thing would be to buy a small dc cooler as I don't want to run my generator all night long, I will be travelling for 2 months up the intercoastal.
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Old 06-03-2012, 21:13   #5
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Re: Refridgeration while cruising

I cut out my old built in freezer after the cost of a new or used compressor was going to be in the $1000 plus range. When I took the bottom out there was only 1 inch styrofoam barely glued to a plywood bottom. AND an unused void that could have held a 50 gallon san tank or something. Initial test was to put a bucket of ice (cold ice not warm ice) in both the original freezer and chest freezer I got from HD and see what happened overnight. Built in melted and about 60 degrees overight. HD 1/2 gone and about 48 over same time frame. SO I set up the HD freezer and put in the kilowatt (pro tip: they only like that for a few seconds) the freezer pulled about 70 watts in cool down. And it got cold. I was getting to about 5 degrees in a few hours. So I set it up on a timer for 30 minutes every 6 hours and it keeps it at just below freezing. With enough cold mass in the freezer I can use less time. I also did the same for one of my marine a/c units that needed ac to run anyhow. This runs at about 900 watts but can cycle better and gives me way more btu's than I had from the built in. Also keep in mind I was replacing 1974 technology so your mileage may vary In setting up both I had to come up with a way to remove the heat from both of them. One is a new louvered vent on the outboard of a storage locker - or just leave the locker open while a/c in use. The freezer just ducts in to an internal locker that goes to a bilge. no moisture from that so im not worried about mold or mildew it may actually keep the bilge dryer than normal. My neighbors use their a/c hot exhaust to dry clothes with or they can turn theirs around and heat the cabin if needed. We are looking at a way to see if the condensate can be used as a potable water source. Since during the summer we pull a few gallons an hour out of the air.
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Old 06-03-2012, 21:57   #6
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Re: Refridgeration while cruising

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I cut out my old built in freezer after the cost of a new or used compressor was going to be in the $1000 plus range. When I took the bottom out there was only 1 inch styrofoam barely glued to a plywood bottom. AND an unused void that could have held a 50 gallon san tank or something. Initial test was to put a bucket of ice (cold ice not warm ice) in both the original freezer and chest freezer I got from HD and see what happened overnight. Built in melted and about 60 degrees overight. HD 1/2 gone and about 48 over same time frame. SO I set up the HD freezer and put in the kilowatt (pro tip: they only like that for a few seconds) the freezer pulled about 70 watts in cool down. And it got cold. I was getting to about 5 degrees in a few hours. So I set it up on a timer for 30 minutes every 6 hours and it keeps it at just below freezing. With enough cold mass in the freezer I can use less time. I also did the same for one of my marine a/c units that needed ac to run anyhow. This runs at about 900 watts but can cycle better and gives me way more btu's than I had from the built in. Also keep in mind I was replacing 1974 technology so your mileage may vary In setting up both I had to come up with a way to remove the heat from both of them. One is a new louvered vent on the outboard of a storage locker - or just leave the locker open while a/c in use. The freezer just ducts in to an internal locker that goes to a bilge. no moisture from that so im not worried about mold or mildew it may actually keep the bilge dryer than normal. My neighbors use their a/c hot exhaust to dry clothes with or they can turn theirs around and heat the cabin if needed. We are looking at a way to see if the condensate can be used as a potable water source. Since during the summer we pull a few gallons an hour out of the air.
Sorry for the thread drift, but a former employer told me that the cruise ships that he had worked on harvested the condensate from the A/C and refrigeration systems as a fresh water source.
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Old 06-03-2012, 22:17   #7
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Re: Refridgeration while cruising

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Originally Posted by edbulmer View Post
I debating whether to buy an inverter for my regular size fridge or buy a small dc cooler. Which would be more cost efficient? I saw an inverter at WM for a hundred bucks that would produce 100 watts, would that be enough for a fridge?
This is a fairly huge subject. Efficient refrigeration depends on good insulation more than anything else. Most pre-built fridges have poor insulation, because they want to advertise bigger interior capacity. They don't usually shout about energy consumption. When we pulled the built-in fridge off Ocelot, it had barely 1" of insulation. Our new one has 4" all around, 5" on the side facing the entryway (where the sun can come in) & 8" on the bottom.

12v refrigeration systems are usually a bit more efficient than AC units, because they know you're running off a battery & not just plugging into the wall. Ours draws 4-5 amps (at 12v) when it's on, but it isn't on very much. We spend ~60Ah/day of our electricity budget on our refrigeration.

But I suspect you're also talking about ease-of-implementation efficiency, and it's hard to beat plugging an AC fridge into an inverter. But it'll probably use gobs of power. You'll have to look at the power consumption specs for your fridge to choose an inverter, but probably better to get one that's 2-3 times more powerful than you need. This will not only let it handle the surge-loads of starting the fridge, but will also let you use some power-tools or a blender as well.

But most cheap inverters are only (slightly modified) square waves, & as mentioned above, some fridges don't like them. True sine-wave inverters mimic more exactly what comes out of a domestic wall socket, but they're more expensive to buy & less efficient to run.
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Old 07-03-2012, 05:23   #8
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Re: Refridgeration while cruising

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12v refrigeration systems are usually a bit more efficient than AC units, because they know you're running off a battery & not just plugging into the wall. Ours draws 4-5 amps (at 12v) when it's on, but it isn't on very much. We spend ~60Ah/day of our electricity budget on our refrigeration.
For more efficiency, get a holding plate system (mine uses ~20Ah/day)
Tom
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Old 07-03-2012, 05:54   #9
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Re: Refrigeration While Cruising

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Originally Posted by edbulmer View Post
I debating whether to buy an inverter for my regular size fridge or buy a small dc cooler. Which would be more cost efficient?
I saw an inverter at WM for a hundred bucks that would produce 100 watts, would that be enough for a fridge?
I've been using a 12 volt ENGEL refridgerator for years and really like it:
THE BIANKA LOG BLOG: WHAT WORKS! WHAT'S COOL!
It runs off 12 volts or 120 AC. The good thing about running the Engel off 12 volts compared to using an inverter is you don't need to have an inverter running 24/7. The more you convert energy the bigger are your losses. I have two 75 watt solar panels and they keep my 12 volt bank topped up even with the Engel running 24/7.
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Old 07-03-2012, 07:14   #10
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Re: Refridgeration while cruising

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Originally Posted by teejayevans View Post
For more efficiency, get a holding plate system (mine uses ~20Ah/day). Tom
We have 'em - prefer the evaporators. It has to do with how we use the freezer section. But I don't think there's a significant efficiency difference between evaporator & holding plate systems. Holding plates have to run longer to do the phase change, which isn't always as efficient, especially if you're air cooled, as we are. Water cooling is usually more efficient, especially here in the tropics, but more $$ & complexity. I still say insulation is the biggest factor, which means that if you want the most efficient system, you really need to build it yourself. But that's a whole 'nother can of worms.
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Old 07-03-2012, 13:27   #11
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Re: Refrigeration While Cruising

Note-this is only for a 2 month trip, after that we will be on the dock and only doing day trips-with full 50 amp service. What I need is temporary.
I saw at WM an inverter on sale 1000 watts for $100 bucks. My fridge draws 5.6 amps max-mostly 2.6. Would this inverter do for me. It will be on while running so batteries will always be charging. At night it's cooler so fridge will run much less and I will throw genny on a couple of times during the night. The alternative is to hook up a dc cooler which I think I can wrangle at about $170.
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Old 07-03-2012, 13:34   #12
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Re: Refrigeration While Cruising

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Originally Posted by edbulmer View Post
Note-this is only for a 2 month trip, after that we will be on the dock and only doing day trips-with full 50 amp service. What I need is temporary.
I saw at WM an inverter on sale 1000 watts for $100 bucks. My fridge draws 5.6 amps max-mostly 2.6. Would this inverter do for me. It will be on while running so batteries will always be charging. At night it's cooler so fridge will run much less and I will throw genny on a couple of times during the night. The alternative is to hook up a dc cooler which I think I can wrangle at about $170.
that's the ticket, But if your fridge doesn't like modified sine wave you'll have to spring for a few more bucks to upgrade to the pure sine wave inverter.
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Old 07-03-2012, 19:01   #13
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Re: Refrigeration While Cruising

Ok Live in BC Canada. By Dufour35 has a real crap ice box. Poorest thing on the boat. When I bought it it had an engal Fridge freezer. Worked wonderful for several years then one day notice an ice built up around the plate. Pump works but no cold. I have tried Engel, and stores that sell Engel but no one could point me to a repair shop.

Worked great and keep hearing others sing its praises, so any suggestions on a fix. Please

One question. On refigeration posts here I hear about how important insulation is on a fridge, but waco and engle have so little?
Cheers
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Old 10-03-2012, 13:22   #14
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Re: Refrigeration While Cruising

I don't want to buy one inverter and then have to spring for another one.
I called my manufacturer and they say the fridge draws 2.6 amps (5 max on startup) would this be okay for a 1000 w inverter to handle (modified wave)
Anyone here done this before?
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Old 10-03-2012, 13:30   #15
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Re: Refrigeration While Cruising

My fridge draws about the same as you are looking at and it runs fine on my modified wave inverter. however my inverter is 3500 watts. I run a lot off that...
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