Residential fridge draw on inverter.

[SDTugs]

Good morning,

I have a "vintage" Amana 19 on my 1976 Hatteras 48' LRC. I have been noticing that while on inverter it draws about 55 amps while running. That seems very high to me. I realize that the 20-25 year old fridge is of an older less efficient technology.

I am wondering what experience people are having with amperage draw with their residential units while on inverter, what units they have upgraded to, and what the new draw is with a modern energy star unit.

I can fit a 17-19 cubic foot fridge in the space I have.

I am also well aware that my boat is rather AC dependent and won't be getting away from running a generator especially as we get farther south.

Any advice is welcomed.

Thank you,

 

[jgwinks]

I answered your other post as well. My household fridge draws 11 or 12 amps on inverter, 1A on 120VAC. 55 on 12V would be 5.5A on 120V, that is pretty high. Running on shore or generator it probably doesn't matter much but on inverter your batteries aren't going to last long. I'd be looking to replace it. A marine type 12V or combo 12V / 120V unit would be more efficient power wise but they're probably 5 times the cost of a cheaper household unit. When measuring for fit remember the newer ones dissipate heat through thier outer skin, so leave a couple inches all around for that.

 

[SDTugs]

I answered your other post as well. My household fridge draws 11 or 12 amps on inverter, 1A on 120VAC. 55 on 12V would be 5.5A on 120V, that is pretty high. Running on generator it probably doesn't matter much but on inverter your batteries aren't going to last long. I'd be looking to replace it. A marine type 12V or combo 12V / 120V unit would be more efficient power wise but they're probably 5 times the cost of a cheaper household unit.

Thank you for the information. My battery doesn't last long like that. I plan to change it out.

I have done a little looking around and haven't encountered many from the normal manufacturers that make a 17-19 cubic foot unit in native 12v It seems like sticking with a household might be the best bet short of having a custom made with a remote compressor.

It also seems that the big names are doing some seriously low draw energy star stuff like Samsung, LG, GE, ETC.

Thanks again,

B

 

[DavidM]

55 amps DC or a bit less than 5 amps AC is about what I would expect from an older residential fridge. New Energy Star rated residential fridges draw about half of that and DC RV or marine fridges even less.

David

 

[jgwinks]

12 volt just isn't a thing for the regular appliance makers, that's just the marine and RV markets. But the household stuff does keep getting more and more efficient. Being able to run on 12 volts directly doesn't outweigh the initial cost IMO.

 

[SDTugs]

Has anyone found a residential brand that they are particularly impressed with in the amperage draw area? I have worked the math on some of the main brands based on their KW/year, but I feel like gives a misleading result. Maybe I am not looking in the right places for the door stamp where the actual draw information lives.

 

[rslifkin]

In my mind, actual draw while running isn't all that important and is only part of the picture. It's the total power usage per day that matters. If a fridge draws 40 amps and runs 25% of the time, total power usage would be the same as a fridge that draws 20 amps but runs 50% of the time.

 

[Moonfish]

We've had a 110V household fridge/freeze for 11 years. It's a constant "battle" between my wife and I about when and how often to run on the inverter. She usually wins...

Ours usually uses 2-5 amps on inverter. However, there are times when I turn on the inverter and the fridge kicks on at 70+ amps. The first time it happened, I immediately turned off the inverter thinking it will kill the batts in short order. Turned the inverter back on, and the fridge went back to 5 amps.

Sometimes, I have to turn off and on thee inverter multiple times in order to get the fridge to not use 70 amps. But I always am able to do so.

 

[SDTugs]

We've had a 110V household fridge/freeze for 11 years. It's a constant "battle" between my wife and I about when and how often to run on the inverter. She usually wins...

Ours usually uses 2-5 amps on inverter. However, there are times when I turn on the inverter and the fridge kicks on at 70+ amps. The first time it happened, I immediately turned off the inverter thinking it will kill the batts in short order. Turned the inverter back on, and the fridge went back to 5 amps.

Sometimes, I have to turn off and on thee inverter multiple times in order to get the fridge to not use 70 amps. But I always am able to do so.

That is about exactly what I see with mine. But since I can't leave it alone I will sit and watch the inverter display. Mine seems to kick on 2-3 times an hour at that heavy draw, and runs like that for 5-10 minutes depending on use.

That being said, I think if my fridge were a child it would probably have a family of its own.

While she runs well, and while on generator or shore power not an issue, she does leave the batteries in rough shape by morning after being on inverter all night.

 

[jgwinks]

In my mind, actual draw while running isn't all that important and is only part of the picture. It's the total power usage per day that matters. If a fridge draws 40 amps and runs 25% of the time, total power usage would be the same as a fridge that draws 20 amps but runs 50% of the time.

Right. The smaller the fridge generally the thinner the insulation, they try to capitalize on interior volume. The little dorm fridges are terrible in that regard, they'll run constantly on a warm day. I'm not sure if the efficiency labels estimate the annual cost and should reflect that. Also the more it runs the quicker it will die.

 

[O C Diver]

Before you make any decisions, buy a kilowatt consumption gauge. They plug into the outlet and the appliance plugs into it. Run it for a week to get an average. Multiple that number by 52 weeks to find annual consumption. That number will give you a comparison point against other new refrigerators based on their energy guide numbers. The killowatt consumption meter costs around $25.

I'm very happy with my residential apartment refrigerator from Summit.

Ted

 

[luna]

rslifkin has the right idea in that it's the total power used that is important. Insulation amount, gasket effectiveness and the think first, then open, adjust the contents, then quickly close procedure are the most important things to keep the duty cycle and therefore the power consumption low.

For those that have a residential refer. that consumes multiple times the normal amount of running current when first energized, it's likely the resistive defrost element that is right next to the evaporator that is powered. Its automated.
This heater usually turns on when first powered up and then again at some timed interval (about every 5 hours) while the refer. remains powered. Its job is to keep the evaporator free of ice, so it can cool the refer.

 

[SDTugs]

Before you make any decisions, buy a kilowatt consumption gauge. They plug into the outlet and the appliance plugs into it. Run it for a week to get an average. Multiple that number by 52 weeks to find annual consumption. That number will give you a comparison point against other new refrigerators based on their energy guide numbers. The killowatt consumption meter costs around $25.

I'm very happy with my residential apartment refrigerator from Summit.

Ted

That is a great idea. That would definitely give me a solid basis for comparison prior to having to take a fridge out of the boat. I haven't done this one yet, but I have never replaced one that i was excited to do a second time.

Thinking with the door definitely costs electricity. That is something that I will have to train my way out of.

 

[BruceK]

Residential fridges here come with a consumption rating and it`s shown in every advertisement. Varying between 2.5 and 4.5 in retailer adverts I see, higher is better. I`d have assumed USA has it but don`t see it mentioned above so maybe not.

 

[O C Diver]

Residential fridges here come with a consumption rating and it`s shown in every advertisement. Varying between 2.5 and 4.5 in retailer adverts I see, higher is better. I`d have assumed USA has it but don`t see it mentioned above so maybe not.

In the USA it's called an Energy Guide. There is a scale that rates the model and also a projected electrical consumption for a year based on a standardized test. While the test includes defrost function, it does not include cooling food down, opening the door to remove food, and making ice.

This is the one for my Summit apartment refrigerator in my boat.



Ted

 

[twistedtree]

In the USA it's called an Energy Guide. There is a scale that rates the model and also a projected electrical consumption for a year based on a standardized test. While the test includes defrost function, it does not include cooling food down, opening the door to remove food, and making ice.

This is the one for my Summit apartment refrigerator in my boat.

View attachment 138123

Ted

I have found these to be quite accurate, looking at the annual kWh consumption. Divide that by 365 and you get the daily consumption. The energy star web site let's you compare various models. Any modern fridge running on 120 VAC I think will be as good or better on power consumption vs a multi-voltage model.


And as someone pointed out before, the amp draw is only part of the story and alone can't be used to draw any real conclusions because fridges cycle on and off. The Energy Star sticker (or web site) tells you what the actual energy consumption will be.

 

[tiltrider1]

This is a side note to using residential refrigerators. Most of our refrigerators are stuffed into cabinets with very poor ventilation. I installed a 12v computer fan that constantly draws in outside air and pushes it through the cabinet. This greatly improves the efficiency of the refrigerator.

 

[O C Diver]

This is a side note to using residential refrigerators. Most of our refrigerators are stuffed into cabinets with very poor ventilation. I installed a 12v computer fan that constantly draws in outside air and pushes it through the cabinet. This greatly improves the efficiency of the refrigerator.

I would go a step further and say that with a little pre-installation engineering, you can likely improve a little on efficiency by insuring an improved air flow over the condenser coils. Mine enjoys a nice draft through the cabinet.

Ted

 

[jgwinks]

And if there's no condenser coil on the back, it dissipates the heat through the skin on the top and sides. Needs some space all around for that.

 

[Comodave]

And if there's no condenser coil on the back, it dissipates the heat through the skin on the top and sides. Needs some space all around for that.

100% agree. The refer in our boat went out last summer. We had to cut it up to get it out the door. The only one that would fit in the door was an Isotherm that was larger in cubic feet so I had to modify the cabinet to get it to fit. It is a dual voltage refer. And I don’t really monitor the power consumption but it cools extremely well. I added a second 12 volt fan to circulate the hot air out of the cabinet. Also the refer is 2” narrower than the old one so I have 1” on each side for cooling air to get into the cabinet. And I left 2” on top when I modified the cabinet to let hot air out. Venting is critical to helping the refer cool well. And that will help with power consumption too.

 

[SDTugs]

I have found these to be quite accurate, looking at the annual kWh consumption. Divide that by 365 and you get the daily consumption. The energy star web site let's you compare various models. Any modern fridge running on 120 VAC I think will be as good or better on power consumption vs a multi-voltage model.


And as someone pointed out before, the amp draw is only part of the story and alone can't be used to draw any real conclusions because fridges cycle on and off. The Energy Star sticker (or web site) tells you what the actual energy consumption will be.

I will give the Energy Star website a look. I had been researching fridges based on the manufacturers published Energy Star ratings. I tend to take things like that with a grain of salt. It never seems to be very clear what their control really establishes (lab vs. real world use).

 

[twistedtree]

I will give the Energy Star website a look. I had been researching fridges based on the manufacturers published Energy Star ratings. I tend to take things like that with a grain of salt. It never seems to be very clear what their control really establishes (lab vs. real world use).

I would assume that a manufacturer would accurately quote the energy star rating, but it can’t hurt to check. Just be sure you are looking at the annual kWh figure. That’s what your battery impact will be. The big number on the sticker is an annual cost for that power at some random cost per kWh.

The energy star test is based on operation under specified condition that model real work use, and they are quite accurate in my experience. It’s not like old EPA mileage ratings which were always very optimistic. But now even those are pretty accurate.

 

[SDTugs]

I would assume that a manufacturer would accurately quote the energy star rating, but it can’t hurt to check. Just be sure you are looking at the annual kWh figure. That’s what your battery impact will be. The big number on the sticker is an annual cost for that power at some random cost per kWh.

The energy star test is based on operation under specified condition that model real work use, and they are quite accurate in my experience. It’s not like old EPA mileage ratings which were always very optimistic. But now even those are pretty accurate.

Great to hear that they are accurate in your experience. I will continue down that path to enlightenment.

 

[Comodave]

I would assume that a manufacturer would accurately quote the energy star rating, but it can’t hurt to check. Just be sure you are looking at the annual kWh figure. That’s what your battery impact will be. The big number on the sticker is an annual cost for that power at some random cost per kWh.

The energy star test is based on operation under specified condition that model real work use, and they are quite accurate in my experience. It’s not like old EPA mileage ratings which were always very optimistic. But now even those are pretty accurate.

I think they give the cost per KWH on the Energy Star sticker. So you can figure out the annual KWH used.

 

[twistedtree]

I think they give the cost per KWH on the Energy Star sticker. So you can figure out the annual KWH used.

Yes, all the figures are there, with cost and annual kwh in smaller print than the resulting annual cost.

 

[twistedtree]

Great to hear that they are accurate in your experience. I will continue down that path to enlightenment.

I'm not sure you will get to enlightenment, but you hopefully will get cold drinks and less battery draw

 

[Comodave]

Yes, all the figures are there, with cost and annual kwh in smaller print than the resulting annual cost.

I have not looked at an Energy Star sticker in years but I thought the data was there. Glad you can confirm that.

 

[SIBERNUT]

Ditto on the muffin fan, i wired mine to come on with the compressor.

 

[jimL]

OC Diver, I have been following you for years. Looks like you have a different boat!

JimL

 

[BruceK]

I will give the Energy Star website a look. I had been researching fridges based on the manufacturers published Energy Star ratings. I tend to take things like that with a grain of salt. It never seems to be very clear what their control really establishes (lab vs. real world use).

Well yes, one fridge manufacturer/importer here was caught fiddling consumption "VW dieselgate" style, by a consumer magazine doing comparison tests. Afterwards they bought that fridge brand retail rather than mfr supplied. But assuming the same test for all fridges, it does provide a guide which uses more/less.