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Old 01-16-2014, 04:13 PM   #21
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Originally Posted by timjet View Post
Well the ice test is out. I'm not going to buy all 4 units and keep only the one that wins the ice test.

Tundra and Vitriofrig are the same and made by Dometic, at 8.5 cuft the largest of the bunch drawing 4.5 amps. Since it's the largest it may have the thinnest insulation??

Isotherm is the smallest at 6.8 cuft drawing about 3 amps with a Danfoss / Secop compressor type BD35F X 2.

NovaKool at 7.3 cuft is right in the middle and draws 5.2 amps

Norcold at 7.0 is next to the smallest and draws 3.2 amps and would appear to be the most efficient along with the Isotherm.

The amp draw as I understand it is per hour and must be multiplied by how often the compressor runs in a 24 hour period to get total amp draw per day.

So based on the figures above the Norcold and Isotherm are the most efficient when the compressor runs.

The Norcold retails for $1359
The Isotherm retails for $2182.

There's got to be more than just a name for that difference in price.
I'm curious too as I may be in that market come next summer...
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Old 01-16-2014, 04:16 PM   #22
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A great danger to fridge efficiency is the guest who holds the door open, gazing at the fridge contents as if at home, with no idea of how carefully we manage the energy to keep the thing cold. Once you explain, most get the idea. But only most.
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Old 01-16-2014, 04:57 PM   #23
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So based on the figures above the Norcold and Isotherm are the most efficient when the compressor runs.
No no no ... the only thing that tells you is how many amps the machine draws at some undefined voltage.

Until you know the capacity of the compressor and evaporator you don't know squat about the unit other than what some marketing guy thinks you want to know.

The 3 Ampere unit might only remove 500 BTUs per hour and needs to run 4 times longer than the unit that draws 5 Amperes.

Find out the capacity then start comparing machines.
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Old 01-16-2014, 05:05 PM   #24
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A great danger to fridge efficiency is the guest who holds the door open, gazing at the fridge contents as if at home, with no idea of how carefully we manage the energy to keep the thing cold. Once you explain, most get the idea. But only most.
Very true but in trying to determine efficiency this variable is the same for all the units.

I'm leaning toward the Norcold because it seems more efficient than the rest (except Isotherm) at least when the compressor runs. There is apparently no way to tell the insulation each unit has.

I know Norcold does not have a good reputation among boaters but my experience has been very positive with no problems with my 15 yo Norcold.

My old Norcold DE 461 according to the manual consumes 1.3 amps at 120 volts. and 5 amps at 12 volts. If Volts * Amps = Watts then using the figures for 120 volts, this would be 156 Watts (1.3 amps * 120 volts). Converting that back to DC volts (156 Watts / 12 Volts) gives 13 amps at 12 volts. However the manual says 5 amps at 12 volts. How can that be??
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Old 01-16-2014, 05:13 PM   #25
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No no no ... the only thing that tells you is how many amps the machine draws at some undefined voltage.

Until you know the capacity of the compressor and evaporator you don't know squat about the unit other than what some marketing guy thinks you want to know.

The 3 Ampere unit might only remove 500 BTUs per hour and needs to run 4 times longer than the unit that draws 5 Amperes.

Find out the capacity then start comparing machines.
Well the voltage is either 12 or 120. But I do understand what you're saying. The efficiency is based on the compressors ability to remove heat not how many amps it uses when running. Is their any practical way of determining this, or is the difference between all these units in their heat removing capability close enough to the same so as to be disregarded.
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Old 01-16-2014, 05:21 PM   #26
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I should probably just give up nagging about it but the above is meaningless.

How much power does it consume?
OK sorry for assuming

5 kW in 24 hours
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Old 01-16-2014, 05:47 PM   #27
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The same fridge in a different boat will not necessarily perform identically. Heat dissipation being the key. My new build Tundra lasted 4 years before it quit. The reason being very bad air flow design. The new unit, Novakool, has front mounted grills top and bottom and is ever so much better from the heat dissipation standpoint.

By the way, the power draw for the Novakool is a lot less because it is more efficient with the compressor running less hours per day. Until run cycles are compared, amps used when the motor is running is just a number.

I also chose the Novakool because it FIT THROUGH THE DOOR, I almost forgot to mention this oft overlooked issue.
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Old 01-16-2014, 09:44 PM   #28
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I get the idea that Norcold has a less than stellar reputation. That is why we have been looking into replacing the original 1984 fridge for the 15 years we have owned her.

Never have gotten around to deciding which way to go. So I get a cold one and sit and ponder every year.

Watching with interest.
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Old 01-16-2014, 10:09 PM   #29
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Rob, we replaced the old Norcold on our Krogen Manatee with a Summit FF874SS 8.1 cuft top freezer. Stainless steel door fronts and black trim. Specs 50.25"H-23.63"W27"D, 158 lbs, 370 KWH@year, 1.2amps, $619 free delivery. Had it three months and no complaints, very quiet, has auto defrost which first mate loves, I have a 900 watt inverter to use at anchor but we generally run the generator when underway or anchored.
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Bill,

It sounds like that reefer is perfect for the way you boat. Our unit with shipping back then was around $2,000. To us it was worth it because we had removed the genny (whole nother story) and were concerned about daily amp use. As noted above it fit our needs.

I think that is the bottom line. We all have a different mission and way of getting there.

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Old 01-17-2014, 05:49 AM   #30
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Insulation , and box size are the key differences with most using the same compressor.

The winner is always Sun Frost , that actually has inches of great insulation instead of paper thin , in an attempt to get impressive box size numbers.


Big to fit , and expensive to purchase , but way cheaper than an extra 1000lb of batts for quiet cruising.

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Sunfrost RF16 AC or DC refr...
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Old 01-19-2014, 12:57 PM   #31
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I went the cheap route. Domestic cheapo 120Vac bar fridge, about $150. Cheap 1000w inverter. When cruising, gennie is off and inverter powers the fridge. Drinks are kept in ice cooler to minimize opening the fridge door. Mostly food in fridge. 2 gp 31 batts keep fridge going all night on anchorage without going flat. This rig has worked for 5yrs and 10,000miles.

Only problem with this rig is on multiple days at an anchorage. It takes a few hours for gennie and charger to top up the batteries. I have to do that once or twice a day. Fix is to increase batt bank and charger amperage, but I'll accept this minimal hassle over adding weight and cost. When cruising between anchorages, main engine alt takes care of topping up batts.

Considering toting a domestic top loading freezer for drinks, and only put it on the boat for cruising. Top loading keeps cold inside with hatch open (sort of). Finding ice is a major PITA. Maybe better coolers are needed.
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Old 01-19-2014, 07:29 PM   #32
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There are unpowered coolboxes here claimed to keep ice frozen for days. The cynic in me says that might only be if they are filled with ice, never opened, and kept in a freezer, but probably not.
For me, short of fitting massive batteries or running the genset a lot, the solution is not having the refrigeration on the batteries. Eutectics, propane/LPG, solar, combinations thereof, whole or part supply, sure to be other ways.
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Old 01-19-2014, 07:59 PM   #33
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There are unpowered coolboxes here claimed to keep ice frozen for days. The cynic in me says that might only be if they are filled with ice, never opened, and kept in a freezer, but probably not.
For me, short of fitting massive batteries or running the genset a lot, the solution is not having the refrigeration on the batteries. Eutectics, propane/LPG, solar, combinations thereof, whole or part supply, sure to be other ways.
I have to say that my cheapo $100 Walmart or wherever my son's grandmother in law got a basic 120V small freezer with 1/2 saltwater jugs and 1/2 frozen foods...stays frozen for 18 hours in mild climates with no power what-so-ever. If I applied 4 hrs per day power (2 am, 2 pm) by any means...I think it would keep frozen food indefinitely. I think solar or wind could do that..if not when I exceed the 18 hrs or so...I run my 1000 Honda for a couple hrs to top everything off (batteries) and it keeps the freezer cold.

If I hadn't gotten the freezer for free...I would never had bought one...but I needed it during the summer for a spell, put it on the flybridge and just kept it. On this 3000 mile trip (1200 so far) from Jersey to Florida (while never quite "hot" yet...it has paid itself it's weight in gold as far as keeping extra groceries on board.
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Old 01-19-2014, 08:01 PM   #34
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Drinking Scotch instead of beer. 50% reduction in energy loss due to opening the door. 50% reduction in the use of the head.

Those Yeti coolers are $$$$. They look well built. Anyone actually used one?
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Old 01-19-2014, 08:12 PM   #35
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My uncle has a Frigid Rigid, it's a beast. It could stay cool for 3+ days. But the first day you'll have to add ice as you go to get it to "cool down", once "cooled down" is when it's efficient for days.
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Old 01-20-2014, 02:05 AM   #36
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Richard,

Tossed the SubZeros overboard 2 years ago and installed Isotherm units. The power usage reduction was significant. Currently using less than half of the amp hours per day that I did with the SubZeros.
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