Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

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Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

May 26, 2016, 11:10:17 am

Ours (RF197ACRS) has "twin cooling" meaning it has two ~~condensors~~ evaporators one for the refrig and one for the freezer.

The RF197ACRS energy guide say it uses 445 KWhrs per year.

It is easy to figure out what your refrigerator choice migh need for power. Look at the energy guide label. (An example is shown). Take the KWhrs x 1000, divide by 365 days, divide by 24 hrs. This gets average watts per hour. Divide by 12 to get average amp load on the batteries assuming 100% efficiency. Add 10-20% for the inefficiency of the inverter.

594x1000 / 365 / 24 = 67.8
67.8 / 12 = 5.7 x 1.2 = 6.8 amps average battery load.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #1 – May 26, 2016, 12:55:15 pm

Been doing some quick research on the Samsungs. What is interesting is the specs are all about the Energy Guide, and average yearly consumption. The standard specs say nothing about compressor startup current draw (which your inverter will need to successfully handle - possibly both compressors starting at the same time), and running current draw (which your alternator will need to intermittently handle).

Has this stuff been posted before - or can someone shed some light...

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #2 – May 26, 2016, 04:08:54 pm

I don't see an defrost on/off but there is an energy saver setting. Even though I think it says an annual average usage of about 60 watts it seems like it uses more than that.

Time to get the meters out.

Jim C.'s 6 8Ds have about 750 amp hrs to 50%. 16% of that (84% left) is about 145 watts per hr for 10 hrs. Samsung says 22 cuft refrigerators are around 700 KWhrs per yr or on average 80 watts. The inverter is probably eating the rest at a 5 amp idle load. Lots of other stuff on all the time as well. I think I did the math right.

All of this energy stuff is interesting but you will be very hard pressed to find anyone who has done the switch to either a marine type or residential refrigerator who wants to go back. We don't have any problem staying anywhere over night on the inverter. In the middle of the winter heading south when it is cold and the Aqua Hot is on and night starts at 4:30 and it is not light until almost 8 we will run the Gen in the AM for coffee and toast.

Power management changes a bit. That is why I want to add 2 more 8Ds and a very high efficiency pure sine wave inverter just for the refrigerator. (Separates the age cycles in the battery banks as well). And a smaller pure sine wave inverter just for the TV etc. then I can shut off the big inverter and it's high idle load. There are other strategies towards this goal as well.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #3 – May 26, 2016, 04:30:41 pm

Peter's questions (above) piqued my curiosity, so I decided to conduct a totally unscientific experiment. We have a Samsung RF197, a Magnum MS2812, 6 solar panels, and 2 AGM8D house batteries.

Initial conditions: Everything in equilibrium. Coach plugged into 50amp shore power, both battery chargers (solar and Magnum) in "Float" mode, house bank reading 13.2 volts, and zero amps in or out. Refrigerator holding steady at normal set temps (38 degrees fridge, -2 degrees freezer), Ice Maker off, Energy Saver on, compressor off. Coach interior temp 97 degrees (it is SUMMER in Texas).

What I did. First I disconnected the solar panels using the controller switches under the bed. Then I disconnected from shore power using the manual transfer switch at the base of the bed. The inverter instantly took up the AC load. Result: house battery bank voltage fell to 12.7 volts, and battery amps ( on both the Magnum remote and the Blue Sky IPN remote) showed -5.2 amps. I have observed this reading on a number of occasions under the same conditions. I consider around -5.2 to -5.5 amps to be the normal "baseline" power draw on our coach. Everything is off in the coach except the fridge and the clock on the microwave, and the inverter itself, of course. Edit: also HWH panel, smoke detector and propane detector.

Next, I opened both fridge doors and the freezer drawer. The indicated temps in the fridge started to climb. I went back and watched the remote panels for compressor start-up. After about 5 minutes, the battery volts suddenly fell to 12.5 volts, and the amps jumped up to roughly -23.0 (hard to catch the instantaneous peak reading). Then, for the next several minutes, the voltage held steady at 12.4 to 12.5, while the amps started gradually declining from -23, to -18, to -15 and finally to -14 where they stabilized. After 10 minutes, the battery voltage was still at 12.5, and the amps were steady at -13.8 to -14.0, with the fridge compressor still running. Battery charge was showing 98%.

Not wanting to jeopardize our stash of frozen pizza, I shut the doors to the fridge and freezer. I then went back to the bedroom, raised the bed, and reconnected the solar panels. The Blue Sky remote immediately went into bulk charge mode, battery voltage jumped to 13.2 and amps jumped to +31.5. The Magnum remote, at the same time, was still showing the battery bank at +17 amps, which is roughly the numerical sum of solar panel input (+31) and inverter draw (-14).

So, Peter, not sure if this is helpful to your investigation. All I can say is our inverter setup handles the residential fridge without even breathing hard. We leave the fridge on all the time, on the road and at home. Once the temps in the fridge stabilize, the compressor only comes on briefly at long intervals. When parked at the house (even in 100 degree outside temps), most of the time when I go out to the coach it is not running. Of course, on the road when we are opening and closing the fridge doors, it would run more often.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #4 – May 26, 2016, 05:59:47 pm

So that is 8.5 amp when the refrig compressor is running. Chuck says and I agree that is a small portion if the total time, I don't know for sure but maybe 25% at most. There are circulating fans and lights and control circuits that run too. That makes my estimate of average draw of 55-60 watts (using 12.5 volts) or about 5 amps make sense. About 2.1 amps when the compressor is not running.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #5 – May 26, 2016, 09:37:39 pm

Thanks for the calculation and tests guys. So I guess our Samsung 18cf pulls about 8.5 when compressor is running and 2+ when it's not.

I'm not exactly sure what this all means but I guess I shouldn't worry with our 3 8ds and Magnum 2812 about running out of power over an 8 hour time period - of course not using the micro. or my wife's hair dryer not to mention the toaster.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #6 – May 26, 2016, 10:35:11 pm

Well Scott, your experience is not much different from ours. We seem to be pooping out at 10-12 hrs. 3 8Ds should have about 375 amp hrs from full charge to about 50%. That's is about 37 amps per hour for 10 hrs. Inverter eats 5 - 10 amps. Average refrigerator load is about 6 plus 1.2 for inverter inefficiency. That is about maybe 17 amps. So where did the other 20 go? My guess is that there are lots of other loads that go unnoticed and that the batteries are not getting fully charged. They might read 12.7 volts but they aren't fully charged after a day of driving.

I am going to start more testing in the morning.

How do you measure efficiency? Just power consumption? Or is it watts per cu ft? It sounds like the marine refrigerators us about 48 watts. And the 19 cu ft Samsungs us (nominally) 60 watts. How big are the marine refrigerators? About 10 cu ft. So that is 4.8 watts per cu ft. The Samsung is about 3.1. It seems from actual experience that they use more, how much? I will report what I actually measure.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #7 – May 27, 2016, 08:29:49 pm

Report! Residential Refrigerator Power Consumption.

I went out this AM and hooked up stuff to make some power consumption measurements while using the Samsung RF197ACRS residential refrigerator. The Energy Guide for this refrigerator estimates 454 KWhrs per year in normal usage. That works out to an average of 52 watts per hour. A bigger residential refrigerator will use more power. The RF197ACRS is no longer available. The replacement refrigerator's Energy Guide says it uses more energy.

Thanks to Peter Fleming for reminding me that this experiment is possible with the tools I have at hand.

I connected my KillaWatt meter to the refrigerator, my clamp on amp meter to the 12 volt line going into the inverter, and after a couple hours I remembered to check my battery monitor to the house batteries.

I disconnected the coach from power and turned on the inverter. With no inverter loads the inverter draws about 5.7 amps. The draw at the house batteries with no inverter load and no lights or any other 12 volt user controllable loads was about 8.4 amps. These vary a bit over time. That means that all of the other 12v loads consume a steady state 2.7 amps.

Then I turned on the refrigerator. From a warm start the initial power at the refrigerator was 154 watts. Amps at the inverter were as high as 18.8 amps. Amps at the battery were as high as 21.5 amps. The refrigerator reached normal temps (38°/-2°) in just over two hours.

After 10 hours the refrigerator had consumed 780 watts or an average of 78 watts per hour. A three hour moving average watts consumed after 10 hours was 58 watts. This is approaching the Energy Guide Estimate. I will leave everything connected for several days and see where it settles in.

The steady state inverter and parasitic loads at 8.4 amps and 12.5 volts consume another 105 watts.

Three fully charged 8Ds (in good condition) should have about 375-400 amp hrs capacity down to 50%. Or up to 5,000 watts. So an overnight stop of 16 hours has an average of 312 watts per hour. 165 watts goes to the refrigerator and steady state uses. Where does the other 150 watts go? Lights, phone chargers (5-10 watts if they are plugged in even if the phone is not), TV and a DVD player use 60-70 watts if they are newer, your TV antenna booster, your satellite dish, your Bose System (huge power hog), Aqua Hot or furnace, water pump and everything else.

So the conclusion is that an efficient residential refrigerator adds a new, manageable load to your power supply. It will reduce your dry camping time compared to an LP refrigerator by several hours without a boost from the generator or solar panels. Compared to the 12v marine style refrigerators the difference in power use will reduce your dry camping time by a few hours. The residential refrigerators have twice the capacity or more than the marine refrigerators.

Your batteries need to be in good condition. Older inverters have a pretty high steady state idle load. Newer inverters are much more efficient. The difference between an older inverter and a newer more efficient inverter can be almost the entire refrigerator consumption.

I am interested in your comments and experience. I am not an expert in this area by any means but just trying to follow the logic and math.

More later after a couple more days of testing.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #8 – May 27, 2016, 09:28:37 pm

Roger - You are amazing.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #9 – May 28, 2016, 09:41:52 am

Quote from: Roger & Susan in Home2 – May 27, 2016, 08:29:49 pm

Report! Residential Refrigerator Power Consumption.

... After 10 hours the refrigerator had consumed 780 watts or an average of 78 watts per hour. A three hour moving average watts consumed after 10 hours was 58 watts. This is approaching the Energy Guide Estimate. I will leave everything connected for several days and see where it settles in.

More later after a couple more days of testing.

I ran out to the barn this morning in the rain and my jimjams to check on my science experiment. At 24 hrs and 9 minutes the Samsung RF197ACRS refrigerator has consumed 1550 watts including a start from ambient temperature (74°). This is an average of 64.2 watts/hr. Over the past 14 hours it consumed 770 watts or 55 watts per hour. This is close to a steady state condition. If the outside temps were much warmer and we were in and out of the refrigerator all day the power consumption would increase. Your results will depend on your refrigerator model and how you use it.

The test refrigerator uses about 100 watts when the compressor is running and less than 10 when it is not once it got to a steady state. To get an average of 55 watts per hour it looks like the compressor/evaporators/fans must be running a bit under 50% of the time. Without spending several hours sitting in the coach specifically listening I can't say for sure but that is what it seems like from the power numbers. While you can hear the refrigerator in the coach in actual use almost any other inside noise is greater and the refrigerator running just becomes background noise.

More later.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #10 – May 28, 2016, 11:50:48 am

Roger:

Very excellent testing and analysis!

When dry camping and using your typical load on the 12 V system each night, to recover each day for the next night, the generator will need to run enough to replace the 375 amp-hrs consumed. For example with a 125 amp charger this would take 3 hours of run time (solar-on-the-roof would help to reduce generator time). An 80 amp charger would take almost 5 hours. A high amp charger would be another consideration when going to an electric-only fridge.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #11 – May 28, 2016, 12:08:05 pm

Quote from: prfleming – May 28, 2016, 11:50:48 am

Roger:

Very excellent testing and analysis!

When dry camping and using your typical load on the 12 V system each night, to recover each day for the next night, the generator will need to run enough to replace the 375 amp-hrs consumed. For example with a 125 amp charger this would take 3 hours of run time (solar-on-the-roof would help to reduce generator time). An 80 amp charger would take almost 5 hours. A high amp charger would be another consideration when going to an electric-only fridge.

That just about matches our system with the electric fridge. We have the Xantrex 3012 which will charge a max of 150 amps, however it only stays there for a few minutes then starts dropping until absorption is reached . We run the generator 2 hours in the morning and 2 hours in the evening. My DW times her microwave use for the evening and the coffee maker during the morning run.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #12 – May 28, 2016, 01:01:42 pm

If you consume 375 amp hours in a day that works out to be 15.6 amp avg for the 24 hrs. My refrigerator uses about 65 watts (after inefficiencies) per hour or about 5.4 amps per hour on average. The old refrigerator used some 12v while on LP but not much so before the residential refrigerator that 375 amp hours would have lasted about 36 hours. In a perfect world.

Our experience is that a six or seven hour drive day is not enough to fully recharge the batteries. So that after a few days you are starting nowhere near 100% and get to pooped out faster. CraneMan's generator use is much like ours, a couple hours in the morning to make coffee or toast and a couple hours in the evening often to run AC. And while the gen is running the big charger is pushing in 100+ amps into the batteries for a few minutes and tapers off quite quickly. And a two hour charge doesn't restore the batteries to 100% either.

The IH45's with 6 8D batteries are charged with a 435 amp alternator, almost three times the capacity of my current 160 amp alternator.

So like Peter Flemming I am changing out my alternator to a 240 amp Delco Remy and making other changes to improve the charge side of things and the capacity part as well. It would be nice to add solar as well but a new alternator and all of the other parts to this are far cheaper than solar and we are very low time boondockers. All of this needs to be in another thread.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #13 – May 28, 2016, 06:28:18 pm

Excess space / lines removed.

Quote from: Caflashbob – May 28, 2016, 05:29:40 pm

Not related to the exact question posted but the heart interface manual mentions running the batteries between 50% to 90% as the gen run time is prohibitively expensive and noisy for most to get from 90% to 100%. For the longer cycle life I opted for mk gels. I think the agms are ten percent roughly higher capacity than the gels with a bit less low temp power and 1/2 the cycle life. As the batteries age the extra initial capacity should match the gels in a few years? The gels would seem to be able to stay closer to their new specs in hard use for longer. Mk's engineer mentioned the latest gels might have double the cycle life shown.
Choose the batteries you want. AGMs out sell Gel by 100 to 1.
...
Minimum of four 8d's and/or a lot of solar for any electric refer.
Certainly not the case for most users.
And a more effecient inverter?
Of course! The operating load at idle for an older inverter is about what it takes to run an efficient res refrigerator. My 1000 watt Magnum inverter uses enough less watts at idle to almost (80%) run the refrigerator on the savings alone compared to our original Xantrex.
Original systems were not designed for this much draw and to be able to dry camp for a few days on internal capacities without running the gen.
Sure they were. Take out the 25 or so 10 watt halogen bulbs and replace them with 2 watt LEDs. The 200 watt savings in one hour of lighting is enough to run a res refrig for almost four hours. I don't think very many expect to dry camp for two days without some additional power.
All changes with double the electrical draw.
I have no idea what this means
Unless like a lot you do not mind the gen or camp pole to pole.
Each of us gets to choose what we want to do even if it is not your choice.

Thanks for the input.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #14 – May 29, 2016, 01:38:38 am

All the unicoaches came with gels. Did everyone have problems with them? The mk engineer said he regularly fielded calls from Foretravel owners with original gels that were 10-12 years old.

100 to 1?

Flooded cell and agms have similar chemistry.

Why I hesitate to run a residential refer is the crowded camp sites along the pacific coast. Booked six months ahead everywhere.

Rv biz has record sales. Where are they going? Same campgrounds. Full.

So we dry camp in overflow areas or wilderness areas within campgrounds like San Simeon state beach hundreds of nights.

Versus hwve to have a power pedestal.

DW dislikes the parallel parking campsites with a bunch of greys gathered in the early afternoon in a group with an adult beverage in their hands.

Versus spread out non powered sites in the trees like in New Mexico above Los Alamos.

Different ideas for different folks.

Lots of customers bought Rvs for the social life.

Built many coaches for readers long ago who would drive to a pretty spot and enjoy books.

Quietly. Remote. No gen.

It's not what you want to do but what you can do if the mood or circumstances arise.

God bless you if you have an inaudible gen like my old prevosts I sold with the Martin 20k turbo diesel four cylinder thick block engines on air feet in a sonus sound insulated stainless bus door compartment opposite the entry door.

Standing next to it you could barely hear them run.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #15 – May 29, 2016, 09:44:36 am

Refrigerator Power Use Science Project
Sunday Morning, 48 hrs, 4 minutes into this test.
2.68 KWhr total, 55.76 watts per hour including the warm start.
Over the past 24 hrs, 1.13 KWhrs, 47.2 watts per hour at steady state conditions. (About 100 amp-hrs including inverter inefficiency)

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #16 – May 29, 2016, 10:37:22 am

Quote from: Roger & Susan in Home2 – May 29, 2016, 09:44:36 am

Refrigerator Power Use Science Project
Sunday Morning, 48 hrs, 4 minutes into this test.
2.68 KWhr total, 55.76 watts per hour including the warm start.
Over the past 24 hrs, 1.13 KWhrs, 47.2 watts per hour at steady state conditions. (About 100 amp-hrs including inverter inefficiency)

For 2 days use fairly insignificant for 3 AGM 8D's we must be using 3 times that on other items. DW likes the TV and I use the laptop. Aquahot and the heat exchangers might use a lot also.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #17 – May 29, 2016, 11:09:51 am

Everything adds up. I was surprised by how much power was being consumed when I thought everything was turned off.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #18 – May 29, 2016, 11:24:15 am

Quote from: craneman – May 29, 2016, 10:37:22 am

For 2 days use fairly insignificant for 3 AGM 8D's we must be using 3 times that on other items. DW likes the TV and I use the laptop. Aquahot and the heat exchangers might use a lot also.

Good info. That's not too bad.

The info on the mk website seems to show the gels have the ability to take a quicker recharge on top of their double the cycle life over agms. Plus better power at lower temps.

The 225 amp hour capacity of the gels versus the 250 amp hours of the agms is a consideration of course.

To test actual capacity for a couple of year old agms that have been cycled extensively to see how they held up would be something to add to this thread.

My guru buddy constantly removes other battery banks and installs mk gels only.

Nominally four for most uses.

Interesting that the IH-45 has six and a 435 amp alternator. Seems the later plate construction announced in 2013 by mk/penn has allowed more than the old standard of twenty percent of amp hour capacity when recharging.

Six times 225 equals 1350 so 435 is quite a bit more than 20%.

Losses in cabling and such will reduce this. The dual inverters would not exceed 300 I would think.

To address the posters question my guru buddy mentions some residential refers have the spool type compressor motor mounted so as when you drive the oil internal in the refrigerant goes through the compressor motor and is audible.

In a house the refer does not slosh around unlike the Rv.

He thinks the compressor motors life might be lessened as it was not designed to have the oil go though it.

Some were horizontal mounted. The newer ones may lay down and be more prone to this.

If you hear funny noises while driving a residential install that may be what he has noticed.

Marine refers are made to be moving

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #19 – May 29, 2016, 01:04:17 pm

Quote from: Caflashbob – May 29, 2016, 11:24:15 am

If you hear funny noises while driving a residential install that may be what he has noticed.

Even if our Samsung residential fridge was making gurgling noises while we're driving down the road, I doubt either of us could hear it.
A. Our hearing ain't what it used to be, and B. there would be too much competition from all the other background sounds.

We'll just think positive, and not worry about it.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #20 – May 30, 2016, 09:24:24 am

Refrigerator Power Use Science Project

Monday Morning, 72 hrs, 5 minutes into this test.
3.96 KWhr total, 54.9 watts per hour including the warm start.
Over the past 48 hrs, 2.81 KWhrs, 50.3 watts per hour at steady state conditions. (About 105 amp-hrs/day including inverter inefficiency)

Switched back to inverter, 100% charge. I will report time to 50%.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #21 – May 30, 2016, 11:00:08 pm

Refrigerator Power Use Science Project

Monday Evening, 85 hrs, 8 min into this test.

It has been 13 hrs since I switched to inverter. I thought I might get to 50% after 12-15 hrs. But no! I am still at 12.4 volts, 85% capacity and 17.9 hrs left to 59% based on my trusty Victron Battery Monitor. I am switching back to the land line, I will do this cycle again. Back on land line the charger is pushing 102 amps back into the batteries.

The Victron is telling me that during these 13 hours, 131.7 amp hrs have been withdrawn from my three 5 year old Lifeline batteries. At 12.5 volts that is 126 watts per hour. My KillaWatt meter watching what the refrigerator uses says 0.66 KWhrs in the the 13 hrs or just as expected, 50.8 watts per hour.

The other 75 watts per hour represent a 6 amp draw on the battery. The inverter uses almost 5.7 amps at idle. Part of this power is used to power the cooling fans. The other fraction of an amp powers the radio, the indicator lights, the LP gas detector, the CO detector and other loads that are always there.

Pretty Interesting stuff here at least to me. I hope this has value to some of you.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #22 – May 30, 2016, 11:40:16 pm

Quote from: Roger & Susan in Home2 – May 30, 2016, 11:00:08 pm

I hope this has value to some of you.

Very Interesting! I don't think anyone has ever documented the exact "real world" power demands of a residential fridge. Should be very helpful to anyone planning this upgrade, or to those who wish to modernize and optimize their electrical system.

Only thing that would make it better would be some nice 4-color graphs...but I guess that's asking too much.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #23 – May 31, 2016, 01:02:27 pm

Just for Chuck, well everyone I guess, a four color graph. For a person who never uses Excel or Numbers this represented a real challenge. My world is very large data bases, 2-4 million records, 200,000 transactions a day. So a simple four color graph was a learning experience.

Re: Residential fridge energy use (split from Re: Yacht Fridge VS Residential Fridge)

Reply #24 – May 31, 2016, 01:23:19 pm

Quote from: Roger & Susan in Home2 – May 31, 2016, 01:02:27 pm

Just for Chuck, well everyone I guess, a four color graph.

Very Nice! Thanks, Roger! I am (was) a English major, so lots of numbers make me kinda woozy. BUT, pictures I can understand!

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