Norcold vs. regular refrigerator

[FF]

In DC the amps would be ,,,

"My apartment sized fridge 10.7 cu ft uses anywhere from 0.9 to 1.1 amp 120 ( 90a to 110A plus inverter loss 10% at 12v DC) vac while running the compressor.

The defrost heater kicks on, not very often and maybe 4 to 6 amps (40 to 60A )for a short time."


To discharge at 100A would require a large house bank .

 

[BobMc]

Someone wrote:
So with the above 12v appliance you can get 10 hours of use.
With the 120v appliance you can get 1 hour of use, less the efficiency loss.

Does this sound right?
------------------------------

That's basically correct ONLY if the 120V appliance runs continually; most reefers don't!

We've had a 9.5 CuFt Haer reefer/freezer combo onboard for our 11 years of ownership - don't know when the PO bought it to replace a "marine" unit. Works just fine, but certainly is an energy hog. We have a 1100 amp battery bank with a Magnum inverter/charger (wouldn't leave home without it) and have no problems at anchor for up to about 3 days before needing to run the genset to recharge. If we're underway, the bank recharges after one night at anchor in about 3-4 hours.

You've gotta decide how you're going to use your boat, as others have said!

 

[traveller]

Bought trawler 2 yrs. Ago. It had a Kenmore apartment sized a.c. fridge in it. Was going to be one of the first things I replaced. Discovered I liked it better than the Norcold I had on previous boat. My usage is much like what you describe yours as.

 

[seattleboatguy]

I'd love to be able to consider a regular AC refrigerator, since I'm usually plugged in or on my way to be plugged in somewhere. First question please: Has anyone else done this?

For what it's worth, I have a Norcold #0061 AC/DC frig/freezer. Just returned from a 10 week cruise to Lake Champlain, and I spent more time at anchor than I did in marinas. I like the frig, but I want to give you a heads-up if you decide to go with an ac/dc frig. Those things are very power hungry, especially in hot weather. If you go with an ac/dc frig, make very sure your dc wiring is big enough to carry the load. My wiring was not, and resulted in an almost 2 volt drop between the battery and the frig when the frig was working hard. The result was that the voltage quickly got too low, and the frig would shut down (as it is designed to do). Right after it shut down, it would start back up, run for a minute or so, and shut down again. I assume that when I upgrade my wiring to larger diameter wire (as is recommended in the Norcold installation manual), much of this problem will go away. Good luck.

 

[Papa Charlie]

We have been full timers for 8 years now here in the PNW. This is what we have found and why we went the way we did.

There are a couple of issues with traditional boat refrigerators, first they tend to trap a lot of moisture which causes food to go bad very quickly. Second, they have limited space inside so you are going to the store a lot. But they have the advantage of running off the batteries when away from the dock and seem to run a lot to maintain the temperature.

The standard AC units have the disadvantage of needing an inverter to run when away from the dock, but they generally have more room for goods, don't build up moisture in them as much and they have an auto defrost which doesn't really pull that much energy.
Hence we went with an apartment size frig, stainless front with 8.1 cuft of space, lighted interior and frost free. We had an inverter but it was old and replaced it with a Magnum 2850 pure sine wave which provides perfect energy to protect the electronics in the modern refrigerators, our flat screen TV's and other electronics. It also replaced our battery charger which is preserving my house batteries very well for the last 7 years and going.

 

[markajh]

Greetings! Thes is my first post, although I've been searching the forums for a little while now. Bought my 45' Hershine about a year and a half ago--my first boat.

It's a 1987, and the appliances could use replacing--#1 is the Norcold refrigerator/freezer (model 461). Boy are they expensive...I know...I'd been warned about the whole BOAT acronym.

I'd love to be able to consider a regular AC refrigerator, since I'm usually plugged in or on my way to be plugged in somewhere. First question please: Has anyone else done this?

The drawback of course is that it doesn't work as long as I'm out on the water. Made me wonder about the possibility of an inverter for this. Would an inverter work on something like a big fridge/freezer? Additional info: I have an Onan 8KW generator.

I appreciate any kind assistance that is offered! Thanks,

Deb

M/Y Quijotesca

Well - Norcold are widely used in RVs. They do not operate the way a normal refrigerator does. They don't refrigerate the compartment - they remove heat. They don't do well the door being open and closed all the time. Secondly, the system relies on coils that if not kept mostly level when still will damage the fridge. With good invertors and battery banks normal refrigeration, to me, I would not install a Norcold. I find the price ridiculous, repair part costs ridiculous and if you're spending the bucks - be nice to get something that doesn't look like it's from a travel trailer (no insult to those who have one).

 

[rolomart3]

Greetings! Thes is my first post, although I've been searching the forums for a little while now. Bought my 45' Hershine about a year and a half ago--my first boat.

It's a 1987, and the appliances could use replacing--#1 is the Norcold refrigerator/freezer (model 461). Boy are they expensive...I know...I'd been warned about the whole BOAT acronym.

I'd love to be able to consider a regular AC refrigerator, since I'm usually plugged in or on my way to be plugged in somewhere. First question please: Has anyone else done this?

The drawback of course is that it doesn't work as long as I'm out on the water. Made me wonder about the possibility of an inverter for this. Would an inverter work on something like a big fridge/freezer? Additional info: I have an Onan 8KW generator.

I appreciate any kind assistance that is offered! Thanks,

Deb

M/Y Quijotesca

You can get a boat size refrigerator for less than $300 at home depot. To be sure, get a 2000 watt inverter for less than $150 at Harbor Freight Tools. Yes, it works and since home refrigerators have been hammered to be energy efficient, it will work fine from the batteries.
Just so you know, I did an experiment with my regular full size home refrigerator using the 2000 watt inverter from just 2 group 27 batteries. I got about 8 hours of operation in a hot day. There was still %70 percent charge left in the batteries as measured with the hydrometer. So I estimate that the big home refrigerator could be easily handled by six group 27 batteries.



Now, the refrigerator from Home Depot is much smaller and uses about one third of the energy used by the big home refrigerator.


So in my opinion, you are in the right track and by buying the 2000 watt inverter it becomes possible to use a toaster, a microwave oven, an electric cook top, a TV and a hair dryer. All these items I power in my boat (not necessarily simultaneously) from a bank of 6 group 24 batteries with a total capacity of 480 amp-hours. I recharge them every two days with the generator at the same time I power the water heater and do one event of cooking (the others are done on inverter power).


I hope this helps.

 

[O C Diver]

For those of you who have installed an apartment refrigerator, did you follow the manufacturer's guidelines on clearance? Once again I'm viewing different models and readings manuals, specifically installation requirements. It seems most of the apartment refrigerators now want 4 to 6" clearances on the sides. While I have back and top clearance, it would be going in the space where the old one came out with maybe 1/4 to 1" of clearance on the sides. Wondering if any of you had that situation and how you dealt with it.

Ted

 

[Rossland]

Sounds like the fridges you have been looking at expel heat thru the sides. We have a little bar fridge in our home that does that. If side clearance is tight, you should have no trouble finding a fridge that expels heat thru the back.
Our boat fridge (fridgidaire) has no clearance at all on the sides, and about 6" at the back. Our house fridge is not as tight, but the sides stay cool.

But you do need clearance at the top. Most fridges are designed to draw air in at the bottom next to the floor, and by convection the warm air rises up the back and is expelled at the top.

 

[Al]

Just a general question....
I've heard house refrigerators don't like the motion on boats. Something about needing to be level to work properly.... I guess 'marine' units might be made differently ??
I do know we used a "dorm" fridge one time. Lasted about 1 season. But it was a cheap one too..
Ideas ??

With a 28 foot boat and a failed ac/dc fridge, we purchased a very inexpensive small 2 cubic foot (I recall) fridge from Walmart, We have a 1800 Watt inverter and 2000 Honda gen set. When we drop shore power, we transfer to the inverter. when we anchor we shut the fridge off. The overnight use is nil and the unit holds overnight (Not the freezer part although we find the frozen stuff is still that in the AM.
We use the gen set in the AM as we breakfast, and prepare for movement. The fridge is then on shore power (gen set). We repeat the process as we proceed to get underway. All works fine for our multiply day voyages.

Al-Ketchikan

 

[FF]

"The overnight use is nil and the unit holds overnight (Not the freezer part although we find the frozen stuff is still that in the AM."

If there is room in the freezer , fulling with packages of blue goo will help the box stay cool till next powering up.

You can store the blue goo in a drawer and fill the freezer as you eat your way to empty.

 

[O C Diver]

Sounds like the fridges you have been looking at expel heat thru the sides. We have a little bar fridge in our home that does that. If side clearance is tight, you should have no trouble finding a fridge that expels heat thru the back.
Our boat fridge (fridgidaire) has no clearance at all on the sides, and about 6" at the back. Our house fridge is not as tight, but the sides stay cool.

But you do need clearance at the top. Most fridges are designed to draw air in at the bottom next to the floor, and by convection the warm air rises up the back and is expelled at the top.

The refrigerator I was specifically looking at, has it's condenser as a grid mounted on the back. I can find a couple that aren't frost free, that can be built in. Wondering if the zero clearance interferes with the frost free function?

Ted

 

[TomandJeri]

The refrigerator I was specifically looking at, has it's condenser as a grid mounted on the back. I can find a couple that aren't frost free, that can be built in. Wondering if the zero clearance interferes with the frost free function?

Ted

"Frost-free" means the evaporator coil, which is inside the space but hidden from view behind a panel (and probably has a fan to move air through the space), is heated for a short time to melt off the frost when the system decides to thaw it out. So I would think that as long as the required rear or bottom clearance is maintained, there should be no problem with functionality.

If it's build into cabinetry but not designed to be 'built-in', you may need to put a vent with grill in whatever makes the 'top' or counter so convection (forced or gravity) can allow air to exit freely. Or just a space between the unit and whatever is above it. In the case of our big cabinet-depth unit at home, there almost no clearance anywhere, but a fan pulls air in through a grate in the front at the floor on one side, and expels air on the other side of the front. But it was designed for essentially no clearance around the sides and top. Just something to consider when shopping.

 

[Tator]

One thing I've noticed about our 10cuft household fridge is that the defrost seems to work all the time as evidenced by warmth around the freezer door while operating on our mod-waved inverter. I have always assumed that this was because of problems with the defrost timer/inverter. I disconnected it once and had such problems with frost build up that I reconnected it.

We use about 225 12v amp/hrs during a 10 hr period to primarily power this fridge and a 110v small chest freezer in the summer Alaskan climate. I keep toying with the idea of replacing our inverter with a pure sine wave but the advertising pitch of "plugs and plays for your existing inverter" seem far from the truth.

Tator

 

[O C Diver]

"Frost-free" means the evaporator coil, which is inside the space but hidden from view behind a panel (and probably has a fan to move air through the space), is heated for a short time to melt off the frost when the system decides to thaw it out. So I would think that as long as the required rear or bottom clearance is maintained, there should be no problem with functionality.

If it's build into cabinetry but not designed to be 'built-in', you may need to put a vent with grill in whatever makes the 'top' or counter so convection (forced or gravity) can allow air to exit freely. Or just a space between the unit and whatever is above it. In the case of our big cabinet-depth unit at home, there almost no clearance anywhere, but a fan pulls air in through a grate in the front at the floor on one side, and expels air on the other side of the front. But it was designed for essentially no clearance around the sides and top. Just something to consider when shopping.

Thank you!

I was looking for a more complicated answer. Couldn't understand why the sides need to be exposed with a back mounted condenser. Guess the manufacturer assumes you won't vent the back and top if you have it built in. My back and top are well vented.

Ted

 

[O C Diver]

One thing I've noticed about our 10cuft household fridge is that the defrost seems to work all the time as evidenced by warmth around the freezer door while operating on our mod-waved inverter. I have always assumed that this was because of problems with the defrost timer/inverter. I disconnected it once and had such problems with frost build up that I reconnected it.

We use about 225 12v amp/hrs during a 10 hr period to primarily power this fridge and a 110v small chest freezer in the summer Alaskan climate. I keep toying with the idea of replacing our inverter with a pure sine wave but the advertising pitch of "plugs and plays for your existing inverter" seem far from the truth.

Tator

That's 2.7 killowatts in 10 hours or 6.5 killowatts in 24 hours! I would have thought half of that was about average.

Ted

 

[Bay Pelican]

That's 2.7 killowatts in 10 hours or 6.5 killowatts in 24 hours! I would have thought half of that was about average.

Ted

I ran a test over several days using a Kill-a-Watt meter for an undercounter Subzero freezer and an undercounter refrigerator. On separate days the two units used approximately 440 DC 12v amp hours per day.

For the same refrigeration space using two Isotherm units (operating on AC so I could use the Kill-a-Watt meter) the average daily usage was 140 DC 12v Amp Hours.

At anchor life was better with the Isotherm AC/DC units with the Danfoss condensers. We cut generator use substantially and were able to leave the boat for long days ashore.

 

[boating rich]

Getting back to the OP, I strongly urge you to get a copy of Nigel Calder's "Boat Owner's Mechanical and Electrical Manual". It will walk you through this whole topic. in detail, and in easy to understand language. Plus a wealth of other things. Much better place to start than random opinions of strangers on the internet. Then you can come back here better educated and understand and evaluate our responses much better.

I always see people reference this book which I agree is a wealth of knowledge. I have a copy from twenty years ago. Has it been updated and is it worthwhile getting a new copy?

 

[sunchaser]

I ran a test over several days using a Kill-a-Watt meter for an undercounter Subzero freezer and an undercounter refrigerator. On separate days the two units used approximately 440 DC 12v amp hours per day.

For the same refrigeration space using two Isotherm units (operating on AC so I could use the Kill-a-Watt meter) the average daily usage was 140 DC 12v Amp Hours.

At anchor life was better with the Isotherm AC/DC units with the Danfoss condensers. We cut generator use substantially and were able to leave the boat for long days ashore.

Similar power usage to our Novakool 110/12V unit. The NK is not frost free but defrosting is no more than a monthly 1 1/2 hour chore. Plus a chance to get rid of the yucky leftovers and old veggies that tend to accumulate.

It is interesting to note on TF the expensive and complicated lengths people go to for keeping a cheap household fridge going.

 

[danderer]

I always see people reference this book which I agree is a wealth of knowledge. I have a copy from twenty years ago. Has it been updated and is it worthwhile getting a new copy?

I think so. Each edition has added information on new technologies and standards. He also corrects previous versions e.g. "In the previous edition I recommended X. I've now come to the conclusion that Y is the better answer because..."

 

[Tator]

I ran a test over several days using a Kill-a-Watt meter for an undercounter Subzero freezer and an undercounter refrigerator. On separate days the two units used approximately 440 DC 12v amp hours per day.

For the same refrigeration space using two Isotherm units (operating on AC so I could use the Kill-a-Watt meter) the average daily usage was 140 DC 12v Amp Hours.

At anchor life was better with the Isotherm AC/DC units with the Danfoss condensers. We cut generator use substantially and were able to leave the boat for long days ashore.

Will the Kill-a Watt read accurately on a modified sine wave inverter?

Tator

 

[diver dave]

Good question and i wish i knew the answer. I do have the test equipment on hand to get us the answer. But... modified sine wave inverters have a large amount of harmonic content. Those harmonics cause undesirable heating in motors and transformers. Mostly due to iron losses. That then means lower reliability and efficiency. Dont have a specific metric without testing though.

 

[TomandJeri]

Good question and i wish i knew the answer. I do have the test equipment on hand to get us the answer. But... modified sine wave inverters have a large amount of harmonic content. Those harmonics cause undesirable heating in motors and transformers. Mostly due to iron losses. That then means lower reliability and efficiency. Dont have a specific metric without testing though.

I would also add voltage spikes to the list of phenomena that an inverter driven motor must handle. Spikes are higher with VFD's and inverters (sort of the same thing anyway) than with utility power, and motors designed for such duty have insulation rated for both higher temperatures (usually) and higher voltage spikes (always, per the NEMA MG-1 standard).

I would not run anything with an integrated induction motor, like hermetic refrigeration equipment, on an inexpensive inverter, which will generate nasty harmonics and voltage spikes.

 

[Tator]

The inverter, in my case , is a Heart 3000. The fridge compressor has now been running for 14 years and a lot of hours on it with no apparent harm. My concern is with the defrost timer and that I may be running the fridge longer and harder due to always having the defrost cycle activated.

Tator

 

[diver dave]

I would also add voltage spikes to the list of phenomena that an inverter driven motor must handle. Spikes are higher with VFD's and inverters (sort of the same thing anyway) than with utility power, and motors designed for such duty have insulation rated for both higher temperatures (usually) and higher voltage spikes (always, per the NEMA MG-1 standard).

I would not run anything with an integrated induction motor, like hermetic refrigeration equipment, on an inexpensive inverter, which will generate nasty harmonics and voltage spikes.

Agree. And, even one more. Radio interference on boats, where distances are short from culprit to antenna, are made more severe by radiating devices with sharp wavefronts and heavy currents. True SINE waves have no sharp edges.

 

[O C Diver]

Similar power usage to our Novakool 110/12V unit. The NK is not frost free but defrosting is no more than a monthly 1 1/2 hour chore. Plus a chance to get rid of the yucky leftovers and old veggies that tend to accumulate.

It is interesting to note on TF the expensive and complicated lengths people go to for keeping a cheap household fridge going.

As travel trailer / RV refrigerators go, the Novakool seems to be a step up from Norcold (not much of a challenge). If I decide to spend roughly 3 times the price of what it's worth (an apartment refrigerator with two 12 volt compressors), Novakool would likely be my choice. Here's the problems I have with them:

The 7.3 cuft model (size replacement for what I have now) has 2 compressors. This isn't redundancy, this is twice the failure points.

No frost free. Is there anyone here who doesn't have a frost free refrigerator in their house? This is the year 2018, not the 1950s. They should makes these frost free with a switch to disable the feature if you own a sailboat.

Price is also a factor. While the Novakool is more energy efficient, I can buy a 10 cuft frost free for a third of the price and use the difference to pay for the extra electricity for 20 years.

Finally, there's service. If you're cruising, and your 2 year and one day old (out of warranty) refrigerator quits, do you want to waste some number of days trying to find a repairman for your $2K+ refrigerator or spend $700 and resume your life.

For me, the decision is much easier as all the electrical infrastructure is already in place on my boat, and there may even be a power savings over the Norcold that I'm currently using.

Ted

 

[sunchaser]

Ted

Sounds like you have found what works for you. Fortunately there are many ways to accomplish the simple task of buying and using a refrigerator. Rocket science it is not.

As I sit at a wilderness non powered dock with about 8 other vessels I note none are the same. But they all got here with few similarities except they float. All owners appear bright, chipper and alert as they prepare pot luck using a variety of fridges, stoves and power sources.

So many choices ——

 

[Rossland]

OC Diver, you summarized it well.

I wish someone would test 12V fridges using using the same protocol used by Energy Star. Better still I wish the 12 fridge manufactures would submit their units for testing. The fact that they have chosen not to do so, makes me suspicious that they already know the results.

Our previous boat had a dual voltage NovaKool. It would not keep ice-cream hard, milk lasted about a week, and defrosting every week to ten days was a PITA. We found that by using a hair dryer, we could reduce the defrosting process to less than an hour, but then we would need to factor in the energy used by the hair dryer. If we just left the door open until
all the frost melted, everything else had warmed too, and the tiny compressor would run continuously for a long time to cool everything again.

Our present boat has a much bigger "domestic" fridge, connected to a pure sine wave inverter. While it is now 11 years old, and not as efficient as a new fridge, it works well, actually freezes stuff in the freezer compartment, and has no trouble maintaining the ideal temperature in the refrigerator section. And the fact that we never have to defrost is sooo nice.

But to each their own. I have gone camping using a block of ice in a Coleman cooler. But I don't want to go camping on the boat, which is why I love our domestic fridge.

 

[ranger58sb]

Our previous boat had a dual voltage NovaKool. It would not keep ice-cream hard, milk lasted about a week, and defrosting every week to ten days was a PITA. We found that by using a hair dryer, we could reduce the defrosting process to less than an hour, but then we would need to factor in the energy used by the hair dryer.

Was that a unit with separate freezer? Or with the little sheet metal freezer compartment thingy right there in the fridge?

We have both, and the double door/separate freezer model keeps everything hard. Doesn't ice up too quickly, depending on how often we open the door... and maybe we defrost every couple months...

We don't really use the freezer much in the smaller unit. Maybe for some frozen veg or some such, otherwise not much else fits. That ices up faster, but mostly 'cause it's my beer fridge, and we open that door more often.

A heat gun defrosts fast. We can do both units, all three compartments in less than an hour.

-Chris

 

[Destinees]

Greetings! Thes is my first post, although I've been searching the forums for a little while now. Bought my 45' Hershine about a year and a half ago--my first boat.

It's a 1987, and the appliances could use replacing--#1 is the Norcold refrigerator/freezer (model 461). Boy are they expensive...I know...I'd been warned about the whole BOAT acronym.

I'd love to be able to consider a regular AC refrigerator, since I'm usually plugged in or on my way to be plugged in somewhere. First question please: Has anyone else done this?

The drawback of course is that it doesn't work as long as I'm out on the water. Made me wonder about the possibility of an inverter for this. Would an inverter work on something like a big fridge/freezer? Additional info: I have an Onan 8KW generator.

I appreciate any kind assistance that is offered! Thanks,

Deb

M/Y Quijotesca

Although you can use a regular refrigerator as a "ice box", with it defrosting and no power until you plug in again. However with absolutely no regrets we spent the $1200-$1400 to replace a 20 yr old NorCold ac/dc frig with a new NorCold ac/dc frig. First, you don't want to run a regular refrigerator using an inverter; it would draw too much as "ac" power. The new NorCold automatically switches between 120V when the generator is running and 12V when motoring. It keeps most things frozen and cold by running the generator in the morning for an 1-2 hours and in the evening 2-4 hours for the heat pump a/c, television watching, and recharging everything on board.