On Board Refrigeration

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belizebill

Senior Member
Joined
Nov 25, 2010
Messages
227
Location
Belize, Central America
Vessel Name
Irish Miss
Vessel Make
36' Marine Trader, D C
I want to replace the 110 V college dorm type fridge on my boat. I have been looking at 12V and 12v/110 V. How do thease dual volt fridgs work? Are there two plugs. How would they be wired if only one plug in ? Im pretty sure my 12 and 110 systems are seperate?? How would the unit switch from the different voltage as needed? BB
 
We have a NovaKool (R4500 I think) with the 12V/110V setup; it does require two plugs, one for each voltage. I kind of forget, but I think the 12V is hardwired while the 110 is an actual plug.

The switching is completely automatic at the fridge, i.e., when shorepower is connected it runs on 110V but once disconnected it switches over to 12V.

I believe there are discussions elsewhere on the forum about whether it's better to have a a straight 12V & use the shorepower to keep the batteries topped up vs straight 110V & use an inverter vs the dual voltage. (Assuming no generator.)

My vote is for the dual voltage.
 
Manufacturers do things differently but I believe the most common way of powering an AC/DC refrigerator is to power the compressor with AC and have a small inverter as part of the refrigerator's mechanism to convert battery power to AC when the refrigerator is "run" on DC.* This, I believe, is how our Norcold works.* However I may have that wrong and it may be that more units use a DC compressor and use a small transformer to convert AC to DC.

Our boat has a Norcold AC/DC unit the previous owner installed the year before we bought the boat (so it's 13 years old now). There is a breaker for the refrigerator on the DC panel and one on the AC panel. We switch over between batteries and groundpower with the breakers, but if one leaves both breakers on, the refrigerator will default to AC power if there is AC power available.

When we thought we had a failing refrigerator about three years ago we went shopping for a replacement. We wanted to retain the AC/DC capability as for us we feel this offers advantages over either a straight DC or straight AC unit..* We also wanted it to fit as closely as possible in the space occupied by the Norcold, and we wanted it to have a Danfoss compressor which everyone I've talked to with knowledge on this subject says is the best compressor for this type of refrigerator out there.

In the end we settled on a stainless steel Isotherm unit. Changing the refrigerator is a big job on our boat--- it has to enter and leave the boat via the front window which has to be disconnected from its fittings. When the Norcold "revived" itself we decided to keep it until it truly died, so we have not yet changed it out. But if or when the day comes that we do, we will go with an Isotherm unit unless by then there is something better out there.


-- Edited by Marin on Tuesday 11th of October 2011 11:50:55 AM
 
Our*AC/DC Norcold went 25 years, and then it was still going.* But, we were heading for a 4 month adventure the next year, and didn't want to have to deal with possible failure.

After installing a custom size box (because Norcold/industry stopped making our size), we went with a 12VDC only*compressor.* Because the compressor was installed in the bilge instead of hanging off the back of the box, we gained 33% reefer space and 100% freezer space in the same physical box dimensions.

As best I can tell, our electrical usage decreased by at least 33% because of a more efficient compressor, and cooler operating location.

These are all good reasons to think about upgrading.
 
As mentioned in previous posts, we went with a 12v DC Isotherm with a remote Danfoss when the Norcold died. We also saw a reduction of at least 33% in amps per day. Would go the same route again.

Rob

37' Sedan

*
 
"As mentioned in previous posts, we went with a 12v DC Isotherm with a remote Danfoss when the Norcold died. We also saw a reduction of at least 33% in amps per day. Would go the same route again."


YES YES YES, the alternate energy folks DO have 12v units that are efficient , better compressor and expensive ,thicker insulation and door seals.

The RV stuff may work in 2 voltages , bur they were never constructed for efficiency.

Look at a Sun Frost IF you need house sized , as well as efficient.
 
belizebill wrote:
I want to replace the 110 V college dorm type fridge on my boat. I have been looking at 12V and 12v/110 V. How do thease dual volt fridgs work? Are there two plugs. How would they be wired if only one plug in ? Im pretty sure my 12 and 110 systems are seperate?? How would the unit switch from the different voltage as needed? BB

With all due respect, from your post, I don't think you're ready to be doing electrical work on a boat.

Yes, your 12 and 110 systems are seperate.* There are not two plugs, there is a plug for 120 volt AC power but the 12 volt DCpower is usually hard wired.* The refrigerator has a circuit that checks for 120 volt AC power If it's there, the refrigerator runs on 120 volts AC.* If it's not, the refrigerator switches to 12 volts DC.. This is all automatic.
*
 
Check the archives, this subject has been BSed to death. The 12V/110V or 12V units from Nova Kool with Danfoss compressor are the same insulated refrigerator and either works just fine. What does most units in is inadequate air circulation - it happened to me 3 years ago.
 
The frige has a built in Inverter. I know because I tried to repair* my old frige.

When you plug in you have 110 when you un plug it automaticly turns on the inverter.

SD
 
The most efficient fridges will use pulsed DC with a brain that attempts to slow the unit \to extend the run time as the brain learns.

The "most efficient" (in terms of cold vs amps used) would be operating , slowly , 24/7.

But too many owners would panic , so the mfg will only allow a 50 min run time.

Vacume plate insulation is great , but really expensive.

Even high quality insulation needs to be 2 fridge ,3 freezer inches thick , which cuts down on interior volume.
 
OK, I bought the Isotherm 12volt with the ASU system with enternal cold plate. Also a Isotherm Freezer 110 volt for the long trips. BB
 
superdiver wrote:rwidman wrote:belizebill wrote:
I want to replace the 110 V college dorm type fridge on my boat. I have been looking at 12V and 12v/110 V. How do thease dual volt fridgs work? Are there two plugs. How would they be wired if only one plug in ? Im pretty sure my 12 and 110 systems are seperate?? How would the unit switch from the different voltage as needed? BB

With all due respect, from your post, I don't think you're ready to be doing electrical work on a boat.

Yes, your 12 and 110 systems are seperate.* There are not two plugs, there is a plug for 120 volt AC power but the 12 volt DCpower is usually hard wired.* The refrigerator has a circuit that checks for 120 volt AC power If it's there, the refrigerator runs on 120 volts AC.* If it's not, the refrigerator switches to 12 volts DC.. This is all automatic.
*

*I disagree, i think he needs to do it himself for sure, and learn.* I would have asked almost the exact same question 2 years ago.* After redoing the electrical on my boat I now have enough knowledge to be truly dangerous, but at least I have learned....* if he is anything like me us answering his question might only soak in a bit, having to figure it out as he goes with guidence from others teaches him for LIFE!

Here's part of the OP's post:

"Im pretty sure my 12 and 110 systems are seperate?? "

Think back to when you went to school.* They made you finish the first grade, then you were prepared for the second grade.*Only when you passed the second grade did they allow you into the third grade.* It continued like this until you graduated and were deemed "educated".

The OP needs to know a lot more about boat electrical wiring before he starts doing it himself.* Learning by making mistakes is not efficient and it could be deadly.

There are books available if he wants to learn but it's best to know what you're doing before you tackle and actual boat.

*

*
 
Actually The Question about the two systems was rhetorical. Of course they are separate.I have never dealt with a AC/DC unit and did not know how they will be wired. Granted electrical is on the bottom of all my expertise and I too,know enough to be dangerous. Everybody off the boat, Im changing a bulb! BB****** Live like you are going to die tomorrow, LEARN like you will live forever-Gandhi


-- Edited by belizebill on Friday 14th of October 2011 03:22:27 PM
 
Sunchaser's comment about air circulation is dead on.

If the compressor can't efficiently get rid of the heat it has removed from the fridge box then it can't cool and will run and run and run. Won't matter that the Danfoss unit is more efficient than the Novacool (oops Norcold) unit.

The Novacools have or can have a 12vdc output to run a muffin or computer fan and it will make a big difference to the cyle time and overall operation of the fridge when used to run the fan to exhaust the fridge cavity.




-- Edited by C lectric on Tuesday 8th of November 2011 07:58:59 PM
 
Ive ordered some SS louvered vents and a small fan. It should help. Going to redo the gally,so while everything is apart, it should be an easier job. Thanks for the inputs. BB
 
Does any one still use the Eutectic systems that came standard with a lot of the boats. They were wired up to engine.

When we bought our present boat the PO had kept the eutectic system and ran it soley from the new generator he had installed.*The boat is set up with a traditional underbench fridge*with*a large underseat*(saloon) freezer.Both have big Eutectic plates. The compresser*lives in the engine room and is raw water cooled.

It works well, however with the unit *siting in that enviorment in summer, with the long refridgerent*runs from the compressor to the eutectic plates, all runing through the engine room, must be very inefficient.
 
Eutetic plated are usually sized for the number of hours that power will not be aviliable.

On power boats that's 12 -14 hours between noisemaker operation to sleep at night.

Sailors will usually prefer 1 to 4 days of eutetic operation , but that required a LARGE (usually engine driven) compressor and the plate volume takes away lots of room from inside the fridge or freezer.

Hundreds of pounds of batteries today make DC possible for days , and do not require room in the fridge.

BUT seldom can the be recharged in the low time (usually under 2 hours) of a mechanical system.

Lived with all them ,and worked for a while for Adler Barbour, and today Propane is my solution
 
I have a Rich*Beers system with two plates in the freezer, run off a 110v compressor. Great system. Once went 48 hours without power or opening, and the temp was 31F when I got the power back.
 
I've seen refrigeration systems that use seawater and a heat exchanger much like the typical boat air conditioning systems. I've seen them in catalogs, not actually installed in boats. It seems that would be more efficient than just dumping hot air into the cabin (or more typically, behind the cabinets).
 

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rwidman wrote:
I've seen refrigeration systems that use seawater and a heat exchanger much like the typical boat air conditioning systems. I've seen them in catalogs, not actually installed in boats. It seems that would be more efficient than just dumping hot air into the cabin (or more typically, behind the cabinets).
*That's the way mine is. It can run with the seawater pump on (normal) cooling the coils and a fan also blows through there, removing heat into the bilge. You an actually run it on the hard by switching the RW pump off and just letting the fan blow through the coils like a window A/C. Have never used it that way but it's possible.
 
Have never used it that way but it's possible.

This is a huge PLUS if you spend time in a boat yard on the hard.

With only water cooled fridges , you have NO fridge.
 
Keith wrote:rwidman wrote:
I've seen refrigeration systems that use seawater and a heat exchanger much like the typical boat air conditioning systems. I've seen them in catalogs, not actually installed in boats. It seems that would be more efficient than just dumping hot air into the cabin (or more typically, behind the cabinets).
*That's the way mine is. It can run with the seawater pump on (normal) cooling the coils and a fan also blows through there, removing heat into the bilge. You an actually run it on the hard by switching the RW pump off and just letting the fan blow through the coils like a window A/C. Have never used it that way but it's possible.

lightbulb.gif


Now that makes me wonder if you could take some soft copper tubing and bend it into a design that would match the coils on the refrigerator, strap it to the coils (without blocking the air flow), and pump seawater through it for more efficient cooling.*

*
 
Have never used it that way but it's possible.

This is a huge PLUS if you spend time in a boat yard on the hard.

With only water cooled fridges , you have NO fridge.

You can always install the thru-hull in the water tank, that way you always have water available for cooling - even when on the hard. This would require a return water hose to the same water tank to circulate the water (for systems with water pumps).
Then you could install a filter in this line, this would then work as a water polishing system...
 
I'm Amazed

Lived with all them ,and worked for a while for Adler Barbour, and today Propane is my solution

I'm amazed that someone didn't pick up on this. My god man don't you realize how dangerous this is. What a RV refrigerator with a burning flame, are you nuts? :flowers:
This frowned upon by most in the industry but Done right this is probably on of the most efficient systems you can use. One of my friends owns a Blue Water 55 and he has made the conversion to what is essentially a RV refrigerator. His insurance company almost dropped him but after examining his system gave him the green light. He has a remote shut off at the tank a continuous line from the tank to the appliance a sniffer and it's vented out the side of the cabin. Dean swears by this system but has had to put up some pretty heated discussions, one of them with Nigle Calder. He's had the refer up and running for several years , No energy draw and silent. What silenced the insurance company was the realization that the flame burned continuously like a pilot light and had a thermal shut off built in, The flame is hardly larger than a candle flame.
 
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I think I'm going with an ice machine and two cold plates. I've got 4x4x2 ice boxes in the aft and if I spend my money on an ice machine that is plumbed into these boxes I could fill them up and use the cold plates to keep the ice cold and have enough for a long time. I think. All speculation now though.
 
You can always install the thru-hull in the water tank, that way you always have water available for cooling - even when on the hard. This would require a return water hose to the same water tank to circulate the water (for systems with water pumps).
Then you could install a filter in this line, this would then work as a water polishing system...

Not a bad idea but it didn't work for us. On our last boat, we had a cold plate system, with two plates in the freezer and one in the refrigerator. The system was water cooled only. The first time we were on the hard, we plumbed a closed loop system into one of the 75 gallon water tanks. Within 48 hours the we had an algae bloom in the tank - sh.t!!! The water temp was in the high 90's and the system was struggling. OK, no problem, we'll clean it up and add ice. The amount of heat that a refrigerator/freezer compressor needs to get rid of to operate efficiently requires a greater mass than any water tank we have and we don't own an ice company.
 
The Eagle had a raw water cold plate freezer but I disconected it. The stern was remodeled with a 120 volt refridge and freezer. They will be replaced with 3 way units, AC/Dc/propane. The stern has scuppers on both sides and the propane tanks are under the stern sink already with alarms and shut off. However I will have approved by insurance before installed.
 
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