12v vs 120v Refrigerator

[Bud]

I converted my 115v grunerts frig and freezer to a Isotherm bendable evaporators and variable speed compressors. it comes as a kit. Very pleased, air cooled no water 12vdc. The compressor has three speeds. The units do need a good exchange of air for the equipment/compressor to stay at proper operating temp, that is the substitute for not having to run a pump.
Bud

 

[jclays]

I'm looking for testimony regarding performance of 12v fridge/freezer combos (7-10 cu ft range) in hot climates. Mine needs to be replaced and I am debating paying $$$ for an exact replacement vs a 120v apartment fridge.

My boat came with Tundra T80 (8 cu ft) 12v fridge/freezer. It appears a brand named Vitrifrigo sells the identical model now for $1800

My fridge has always struggled to be cool outside of winter (and forget about truly cold ever). The old non-replacable gaskets are surely part of the problem. I do have computer fans for ventillation. Anyway, I'm not really looking for ways to improve the one I have, moreso wondering if it's actually worth paying $1800 for a new one.

My fridge compressor runs 24/7 most of the year & draws 5.35a. 10 cu ft apartment combos are rated 115-125watts. So basically twice the draw of my 12v, especially after accounting for inverter loss. But i'm just wondering if they draw double the current for nothing, or if they utilize the power to cool faster and thus run notably less than a 12v model.

I have the original Norcold 12/120v fridge freezer combo but for some reason the PO has it running on 12v too hard to get to the AC plug to plug it in to 120v. I run 12v 24/7 no issues. When in port I'm on shore power.

 

[foggysail]

Fifteen years ago our Norcold degenerated and could not chill anything. Replacements back then were in the $1500+ range and no way would I spend that much for another piece of $h!t. Instead, I purchased a Simmons 120VAC fridge from an online distributor delivered for just over $500. Next I ordered a 5KW inverter from Ebay for another few bucks.

Yes, that fridge keeps our ice cream rock hard. Inverters--- be careful selecting inverters if you elect to purchase one. Avoid those for automotive use. They cannot be grounded to your boat's grounding system making them dangerous. They can be safely used if you install an isolation transformer between it and the AC loads. You can find many isolation transformers on Ebay.

I should mention that I have 4 solar panels mounted on top of the boat that keeps my batteries fully charged when away from the dock.

 

[tpbrady]

I have been looking at some 12v appliances sold in the off grid solar market and while they are pricey, they get pretty good energy efficiency for their size mainly because of using 4.5 inches of foam insulation. I was looking at an 8 cubic foot freezer, SunStar 8CU Solar/DC Chest FreezerDefault Title

It is twice the size of my current freezer but consumes less energy when running (55w) and with the much improved insulation should have a much lower duty cycle. I don't need twice the size, but I figure we will fill it up when provisioning for the summer and replace consumption with frozen fish.

Tom

 

[SteveK]

I have the original 120/12 fridge and run it on 12V 24/7 to allow inverter power 120v for other items.
There was a recent discussion on 120/12v v. only 120v AC due to cost and newer have lower power needs and also offer frost free.
From that thread I plan to replace when needed with a straight 120v version due to purchase cost of 60% of 120/12

So, I could not find a good fit in the 120V version. Right now the old Norcold is keeping temp 35-40 but appears to be running twice normal as we remember. Anyway, searched for 120V, found none to fit the space, found a Novacool that fits the spot and is 2 cubic larger and runs only on 12V as I prefer. Ouch the cost! BUT it uses 40W AVG per hour while running. Should be a noticible improvement, time will tell.
Will install in coming months and retire the Norcold to the garage maybe.

 

[foggysail]

Yes, sizes can be a problem. The one I purchased worked out fine without me having to do cabinet work. I have noticed that size is no longer available.

 

[luna]

SteveK.

Before you retire the old Norcold have you given any thought to cleaning the dust bunnies from the condenser coil? Do you know where it is? Is it accessible?

I do this yearly and my full size residential unit runs a lot less when it's clean as it can put the heat into the air (the condenser's job) much easier and quicker.

If the new Nova Kool has the same size of a cabinet as the old Norcold, but has 2 cubic feet more conditioned volume, where do you think Nova Kool got this increase in volume from? Could it be from the insulation's thickness?

Nova Kool lists the current consumption on most of their units as 2.4A or 4.4A, all at 12V. Neither of those compute to 40 Watts.
Nova Kool does not say that their units consume 40 watts, rather they say that most of their refrigerators consume less power than a 40 watt light bulb. If they make mostly the small refers, then they are likely right.

Do any of these small, ouch expensive, 12V refrigerators have a defrost cycle where they run a heating element to melt the ice on the evaporator?

 

[foggysail]

The Simmons that replaced my Norcold 15 years ago has an automatic defrost cycle. No, I have never taken the time to clean the condenser with it or the many refrigerators I have had in my home. It retains the cooling capacity needed to keep the freezer temperature around -3F where I have set it to keep ice cream rock hard.

I agree that keeping condenser coiles clean will improve efficiency if efficiency matters.

 

[Shrew]

The problem with calculating energy usage of a 12VDC vs 120VAC fridge is you also have to calculate the 10% - 25% loss in inverting from vdc battery to 120VAC.

 

[CaptTom]

Cleaning the condenser will not make the Norcold fridge freeze the ice cream as hard as a residential freezer. There just isn't a setting for that. If you turn the knob up to "5" it'll freeze everything in the fridge section, and your ice cream still won't be firm.

I'm not sure why they're designed that way. Other than that, they generally work pretty well, despite the "N'ercold" nickname. It's that freezer temperature weakness which would have me considering other options. Most frozen foods are designed and packaged to be stored at 0F. Any less and they don't last long. Frozen "Bubba" burgers, for example, will stick together so tight you can't separate them.

 

[luna]

I agree that keeping condenser coiles clean will improve efficiency if efficiency matters.

Understanding that when you are away from the dock you are likely sourcing your electricity from a box full of chemicals, I would think that the efficiency and therefore the duty cycle, does matter.

 

[SteveK]

SteveK.

Before you retire the old Norcold have you given any thought to cleaning the dust bunnies from the condenser coil? Do you know where it is? Is it accessible?

I do this yearly and my full size residential unit runs a lot less when it's clean as it can put the heat into the air (the condenser's job) much easier and quicker.

If the new Nova Kool has the same size of a cabinet as the old Norcold, but has 2 cubic feet more conditioned volume, where do you think Nova Kool got this increase in volume from? Could it be from the insulation's thickness?

Nova Kool lists the current consumption on most of their units as 2.4A or 4.4A, all at 12V. Neither of those compute to 40 Watts.
Nova Kool does not say that their units consume 40 watts, rather they say that most of their refrigerators consume less power than a 40 watt light bulb. If they make mostly the small refers, then they are likely right.

Do any of these small, ouch expensive, 12V refrigerators have a defrost cycle where they run a heating element to melt the ice on the evaporator?

Luna, I will let you know when you say something I do not already know. Stop being so condescending in your replies.
I have cleaned the dust bunnies and added a cooling fan, no change. It is likely in need of freon or whatever is used now. But it is 33 yeas old, still within temp range but running too often drawing around 10 amps, time to retire it.
The Novakool fridge uses 5.2 amps when running. If it runs for an hour straight that is 62.4 Watts. If it runs for continuously I will be returning it. So I expect 40W.

 

[CharlieO.]

My cheap 120v dorm sized fridge from Home Depot + inverter pull just over 5 amps when running.

 

[luna]

Ok, got it. I will try to be less helpful to you in the future.

BUT it uses 40W whilw running.

BTW, your new Nova Kool will never (unless it malfunctions) consume 40 Watts while running.

Good luck with the new fridge.

I'll chill now.

 

[SteveK]

My cheap 120v dorm sized fridge from Home Depot + inverter pull just over 5 amps when running.

Is the 5A from the 12V battery inverted to 120V?
5A @ 120V= 600Watts which seems high
5A @ 12V= 60W which seems right.

Another reason I went 12V is my inverter is 90% efficient so 10% is wasted when I can go direct with 100% DC

 

[SteveK]

Ok, got it. I will try to be less helpful to you in the future.


BTW, your new Nova Kool will never (unless it malfunctions) consume 40 Watts while running.

Good luck with the new fridge.

I'll chill now.

BUT it uses 40W AVG per hour while running.

 

[luna]

BUT it uses 40W AVG per hour while running.

Units matter.
If it does what you say, then it uses 40 Watt-Hours for each hour of use.

If the new beer in the fridge is warm you can expect it to use the 5.2 X 12 = 62 Watt-Hours per hour, until things get cool.

 

[CharlieO.]

Is the 5A from the 12V battery inverted to 120V?
5A @ 120V= 600Watts which seems high
5A @ 12V= 60W which seems right.

Another reason I went 12V is my inverter is 90% efficient so 10% is wasted when I can go direct with 100% DC

Yes, 5 amps from the battery.

 

[O C Diver]

The problem with calculating energy usage of a 12VDC vs 120VAC fridge is you also have to calculate the 10% - 25% loss in inverting from vdc battery to 120VAC.

Please link one with a 25% loss, doubt it exists.

Here's a Victron 800 watt 12 VDC inverter with a 90% efficiency. The standby consumption is <7 watts. It can be purchased online for <$230.

Inverter VE.Direct | Victron Energy

Inverters allow you to power domestic equipment - requiring 230V/120V AC - using 'leisure' or 'automotive' batteries rated at 12V, 24V or 48V DC.

www.victronenergy.com

Ted

 

[kthoennes]

Lots of prior discussions on this topic of course, but nearly every time we're on the boat my wife and I still say getting rid of the troublesome, lukewarm Norcold and replacing it with an LG single door (LRONC0605V) 120v fridge was one of the best improvements we've made to the boat. Runs on its own inverter with a built-in auto-switch. Size matched the old Norcold DE-0061 very closely, and the LG draws 210 kWh per year (0.58 kWh per day) according to the specs, but I put a consumption meter on it and got even lower. And it cost us around $300. Even when we've left the boat for a week in mid-summer at 100*F, the ice is still ice and the ice cream never melts.

 

[SteveK]

Lots of prior discussions on this topic of course, but nearly every time we're on the boat my wife and I still say getting rid of the troublesome, lukewarm Norcold and replacing it with an LG single door (LRONC0605V) 120v fridge was one of the best improvements we've made to the boat. Runs on its own inverter with a built-in auto-switch. Size matched the old Norcold DE-0061 very closely, and the LG draws 210 kWh per year (0.58 kWh per day) according to the specs, but I put a consumption meter on it and got even lower. And it cost us around $300. Even when we've left the boat for a week in mid-summer at 100*F, the ice is still ice and the ice cream never melts.

The Norcold I have I think is the same as yours. The LG single door (LRONC0605V) would fit easily into the space as it is smaller by 1 cu foot.
The space I have allows a larger fridge than the current 7 Cu foot and I hope to be as happy with my 9.1 Cu foot choice.
I know my wife is looking forward to a bit more room.

 

[kthoennes]

Same here, could have gone a little bigger in the cabinet space available but I wanted good ventilation all around, and I needed room behind it for the inverter, and I didn't find a 9cf that would quite fit at the time. I did have to fabricate a new frame to make it look pretty and built in since it didn't have cabinet trim like the Norcold or like RV fridges do but that was just molding and a miter saw. And I wanted extremely low power consumption and that LG was so low I didn't believe it until I tested it myself. That Norcold model is 6.3cf, the LG is 6cf, but it feels like there's actually more usable or convenient space in the LG.

I struggled with that Norcold so many times -- including having the rusty racks sandblasted and powder coated, that it was a great relief to take it to the landfill. For all my maintenance and repairs and parts searching, it never worked well.

 

[SteveK]

We are on Day 2 running the new fridge and happy to report the specs are right for power draw, time will tell on the hook. Amazing quite, just the whisper of the built in fan running.
Kudos to Novakool for building a 9.1CF fridge that fits into the unmodified space that a 7CF Norcold occupied,.
The difference is the coils are on the back wall of Norcold and take up about 5 inches, whereas the Novakool is all on the bottom with fan circulated cooling to the front, no need for top venting.

 

[boomerang]

We got tired of running the 3000w inverter continuously refrigerator while cruising just to power the household refrigerator and bought/installed a straight up dc powered one. What we had was a Danby 10cf energy star certified, which meant nothing insofar as the total amps the thing sucked out of our battery bank powering it through the inverter. We have a smallish house bank of around 700 amps and with the inverter and fridge using around 12A a lot of the time, I felt I could do better. I ordered an RV refrigerator that fit in the same hole and it's using way less total AH over a 24 hour period, averaging 5-6 amps while its on. We haven't been out to try it but I could tell it's much more economical. I left the boat unplugged yesterday and last night so the power cord wasn't in the way while we're painting our topsides and I checked this morning before I plugged it back in and the battery SOC meter barely showed any reserve used. The other system would've put a noticeable dent in the SOC bar graph if we overnighted with no shore power. I'm sure we'll be happy with it in the future.

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[rslifkin]

We are on Day 2 running the new fridge and happy to report the specs are right for power draw, time will tell on the hook. Amazing quite, just the whisper of the built in fan running.
Kudos to Novakool for building a 9.1CF fridge that fits into the unmodified space that a 7CF Norcold occupied,.
The difference is the coils are on the back wall of Norcold and take up about 5 inches, whereas the Novakool is all on the bottom with fan circulated cooling to the front, no need for top venting.

The coils being underneath on the big Novakool units means you can also add more insulation to the outside of them if space allows for less power use and better performance in hot weather. Mine has an extra 1/4" layer of foam on the sides and top plus 3/4" on the back and that lower angled part behind the freezer.

 

[SteveK]

I would have added insulation had there been room left. The sides & top are 3/4" space. The back has a lot of cables but could have maybe 1-2" here and there, not worth the effort IMO. The location of fridge is out of sun and salon temp seldom goes above 80*F, that is when air temp may get to 90*F+ outside.

 

[rslifkin]

I would have added insulation had there been room left. The sides & top are 3/4" space. The back has a lot of cables but could have maybe 1-2" here and there, not worth the effort IMO. The location of fridge is out of sun and salon temp seldom goes above 80*F, that is when air temp may get to 90*F+ outside.

For the sides I added insulation right until any more wouldn't fit in the cabinet. And the top was limited by the opening. But I agree, at 80* it'll perform fine, just a small difference in power use.