Just how bad a small 'frige is

Cariboocoot

There are many people who post here expecting to save power in an off-grid situation by using a "small" refrigerator, as opposed to a large one. Having an unused Danby "cube" refrigerator and my UPM meter at hand, I decided to see just what the thing would use.

Initial start-up surge: 4.99 Amps (@ 118 Volts = 588 Watts). Running average (so far) 100 Watts.
With the thermostat set "half way" we'll see how many kW hours it consumes in 24 hours.

Considering that my full size refrigerator only uses 130 Watts running, it doesn't look good for the "cube". :cool:

waynefromnscanada

Re: Just how bad a small 'frige is

Every one I've ever seen and checked out, SUCKS!!!!!! No other way to put it. Most have perhaps half an inch of some kind of insulation and that's it. They're built to be super cheap to build and still make a profit for sales. Another thing to watch with those little things are the ones without compressors. If you think the compressor type are hard on tricity, wait till you try one of those! Instead of 100 watts whenever the pressor runs, these suck back 60 or 70 watts non stop, 24/7.

dhsola

Re: Just how bad a small 'frige is

I checked the usage on a Dometic refer/freezer from a camper (circa 1986); from warm, with only a case of water inside of it, I think it burned 375w all night.

I have an unused, 20 year old, 19 cu in refer/freezer that burns 275w (self defrost).

And believe-it-or-not, I have a (in use) circa 1950's Westinghouse refer that burns 160w - 180w. Kinda like this one:

Attachment not found.

Attachment not found.

The little freezer hangs down from the refer ceiling. The compartment on the bottom is where the huge compressor sits. Walls/door are 3" thick. I added EPS foam to back and bottom and layed reflectix over the rounded top/sides and an additional piece inside the refer door. This old refer, combined with a 7.5 cu in chest freezer burns less juice than the 19 cu in self defrost refer (1-1/8" thick walls).

I've had this old Westinghouse for 30 years. When I acquired it, it was sitting outside in the snow - still working. I haven't done anything to this refer but paint it! It's truly amazing how things used to be built to last.

System2

Re: Just how bad a small 'frige is

your not giving everyone a true picture of what the refrig consumes .Its start up is probably in the range your talking about ,but the refridge needs to run 24 hrs just to cool down ,afterwards take another 24hr reading and that is really what your consumptions is going to be.
I"ve been off the grid for nearly 4 years and the technology for off grid to live improves every years.

petertearai

Re: Just how bad a small 'frige is

Good point , I tested my 5 star fridge rated 239kw per year.
It used .9kw in the first 24hours, but i didn't check it for the next 24 hours.
For interest will do a 48 hour check when I can.

Cariboocoot

Re: Just how bad a small 'frige is

For those who seem to think I don't know what I'm doing:

Cariboocoot wrote: »

Initial start-up surge: 4.99 Amps (@ 118 Volts = 588 Watts). Running average (so far) 100 Watts.
With the thermostat set "half way" we'll see how many kW hours it consumes in 24 hours.

For those who don't understand about the vagaries of refrigeration:
The start-up surge will vary depending on how much work the motor needs to do to start running. This will change with the temperature of the refrigerant. If it is allowed to heat up more (as in post defrost cycle) more power will be required and will continue to be required until the refrigerant is back to operating levels (thermal differential inside/outside).
In terms of kW hours used, a 'frige with low running Watts use may consume more Watt hours daily for having to run longer to achieve the same results.
Lack of content in the 'frige will mean higher energy consumption because there is no cold mass to keep it cold. I discounted putting anything inside because that will vary the numbers. By the same token I am not opening the door because that will vary the numbers. This may not resemble "real world" conditions but it does fit for test purposes. The "energy star" ratings aren't exactly real-world either.

There are two other refrigerators that will be tested: one full-size (14 cubic foot) "non energy star" unit and one full-size (14 cubic foot) "energy star" unit.

Even so, the running Watts for the 1.1 cubic foot "cube" are very high compared to known numbers for full-size units on a per cubic foot basis. That is the point of this testing: to show people that the smaller refrigeration units do not use a proportionately smaller amount of electricity. And yes I do already know this so don't tell me I'm skewing the test that way either.

If you don't like the way my research is conducted, by all means do your own! It can be educational and fun!

2manytoyz

Re: Just how bad a small 'frige is

Here's how my two refrigerators compare:

Refrigerator in garage: Not running but on: 0 Watts. Compressor running: 114-140 Watts. Total per day: 1.15 KWH, 47.92 Watts per hour average. This is not an Energy Star rated fridge.

Refrigerator in house: Compressor running: 146 Watts. Defrost: 572 Watts. Total per day 2.15 KWH, 89.58 Watts per hour average. This is an Energy Star rated fridge.

Despite the fridge in the garage sitting in a hot environment, compared to the other, and not being Energy Star rated, it uses almost half the energy of the other.

That said, I don't expect much when I see a E.S. label anymore!

ggunn

Re: Just how bad a small 'frige is

Cariboocoot wrote: »

Lack of content in the 'frige will mean higher energy consumption because there is no cold mass to keep it cold.

I'm not sure that will have a net effect. There is thermal inertia, sure, but it works both ways equally. A passive mass is neither a net source nor a net sink of thermal energy. It's kind of like saying that a heavier car will get better gas mileage because when you let off on the gas it will roll farther.

One reason a small refrigerator is less efficient is because of its higher ratio of external surface area to internal volume. But I will give up the beer fridge in my music studio when you pry it from my... well, you know.

Cariboocoot

Re: Just how bad a small 'frige is

The latest numbers:

Unexpectedly, the start-up surge remains at 4.99 Amps despite the refrigerant being cooled down. This is contrary to my experience with larger refrigerators. Perhaps the lesser volume of refrigerant equates to the motor/compressor being the main contributing factor; the change in refrigerant temp (being of such small volume compared to full-size units) not being a significant percentage of the work done.

Running Watts have dropped to less than 100: viewed readings have been as low as 75 and as high as 92. It seems to average around 80 Watts.

Interior temperature is stable at 3C (about 37F).

Kilowatt hours used in the first 24 hours: 0.588 (This number should decrease in the next day as there has been a significant drop in running Watts.)

Note: the refrigerator is running in a cool garage which should help its efficiency. If it were in a hot kitchen it would be logical for it to use more power.

JESSICA

Re: Just how bad a small 'frige is

Cariboocoot wrote: »

The latest numbers:

Unexpectedly, the start-up surge remains at 4.99 Amps despite the refrigerant being cooled down. This is contrary to my experience with larger refrigerators. Perhaps the lesser volume of refrigerant equates to the motor/compressor being the main contributing factor; the change in refrigerant temp (being of such small volume compared to full-size units) not being a significant percentage of the work done.

Cariboocoot:

How do you know the exact start-up surge?
I have read, in this forum, that the kill-a-watt meter is not very good at showing that number. In fact, when I tried with mine, the kill-a-watt reading appeared 1-2 seconds after my fridge started, so I think the number cannot be exact (In my case: New GE fridge, 18 cubic feet: start up: 890 watts !!!, running watts: 96-120; defrost: 390 watts)

2manytoyz

Re: Just how bad a small 'frige is

Not Cariboocoot, but...

You are correct about the Kill-A-Watt meter being too slow to capture the startup current.

I bought a Fluke 334 meter, which has an "In Rush" capture feature. Fluke says it does a "large number of samples in a 100ms time period". No specifics given (proprietary info I'm sure).

For more info on In Rush, good info here: http://www.myflukestore.com/crm_uploads/inrush_current.pdf

I have a 25' travel trailer, with a 13,500 BTU A/C unit. I wanted to be able to run the A/C via a generator. The very popular Honda 2KW generator was too small to do the job. I ended up buying a Yamaha EF2400iS, which does an excellent job.

But if you look at the running current of the A/C unit, either generator could easily handle it. The large current spike on startup was a deal breaker.



Compare that to the running current:



Takes a lot of kick to get the compressor motor spinning.

I've since done a lot of testing with my generator and meter, to determine what I can/can't run. So far, the Yamaha will run everything except the air compressor, which pulls almost 54A on startup. But if you look at the reading on the A/C unit, the generator easily starts a 50A load. So I know the limit is ~52-54A. You won't find this kind of info from the generator manufacturers. Then again, most people don't have such meters, so they don't know what the startup current of their appliances are anyway. Useless info, 'cept for us geeks.

Cariboocoot

Re: Just how bad a small 'frige is

I'm not using a Kill-A-Watt meter.
The unit I am using has a higher sampling rate (but probably not as good as the Fluke).
Unfortunately you can't buy them anymore: I tried.

JESSICA

Re: Just how bad a small 'frige is

Cariboocoot wrote: »

I'm not using a Kill-A-Watt meter.
The unit I am using has a higher sampling rate (but probably not as good as the Fluke).
Unfortunately you can't buy them anymore: I tried.

If you are talking about the Fluke, it seems you can buy it here:
http://www.myflukestore.com/p1249/fluke_334.php

Cariboocoot

Re: Just how bad a small 'frige is

JESSICA wrote: »

If you are talking about the Fluke, it seems you can buy it here:
http://www.myflukestore.com/p1249/fluke_334.php

No, I was referring to the UPM meter I'm using.

Fluke is still in business and selling high-quality products, rest assured.

ggunn

Re: Just how bad a small 'frige is

Cariboocoot wrote: »

No, I was referring to the UPM meter I'm using.

Fluke is still in business and selling high-quality products, rest assured.

If it works, it's a Fluke.

2manytoyz

Re: Just how bad a small 'frige is

FWIW, I bought the Fluke 334 on Ebay, gently used. Still had the original box, carry case, leads, and even the disposable clear cover placed on the LCD during shipping. Owner said he had it for a month, needed one with different specs. I got it for $100. YMMV.

Cariboocoot

Re: Just how bad a small 'frige is

Today's power use figure: 0.540 kW hours.
Not quite the big improvement I was expecting, since the running Watts have gone down almost 25%.

Time to start the next stage of the experiment!

solar_dave

Re: Just how bad a small 'frige is

Cariboocoot wrote: »

Today's power use figure: 0.540 kW hours.
Not quite the big improvement I was expecting, since the running Watts have gone down almost 25%.

Time to start the next stage of the experiment!

Adding thermal mass in the form of beer every day for a month?

Cariboocoot

Re: Just how bad a small 'frige is

solar_dave wrote: »

Adding thermal mass in the form of beer every day for a month?

Beer? In Canada? Where would we get that?

Cariboocoot

Re: Just how bad a small 'frige is

Preliminary results on the Whirlpool 14 cu. ft. "non-energy star" 'frige (about 30 years old):

Initial start-up surge: 4.19 Amps
Running Watts settled down to 275 (at first it was over 350)
It's been on for two hours and has already used half a kilowatt hour.

That's not good. :roll:

solar_dave

Re: Just how bad a small 'frige is

Cariboocoot wrote: »

Beer? In Canada? Where would we get that?

I know it is a challenge, think of all the work required to rotate it in and out of the fridge and the restocking runs required to prevent staleness!

techntrek

Re: Just how bad a small 'frige is

solar_dave wrote: »

I know it is a challenge, think of all the work required to rotate it in and out of the fridge and the restocking runs required to prevent staleness!

Far better than rotating out gasoline every 6 months!

Cariboocoot

Re: Just how bad a small 'frige is

Results for the "non-energy star" 14 cu. ft. Whirlpool:
Running Watts settled down to 270-285
Start-up surge 3.48 Amps after initial cooling
Unexpected power use: 15 Watts while doing nothing
Total for 24 Hours: 3.38 kW hours!

I guess we mark that one down as "energy hog" as its usage is nearly 3X what the cabin 'frige (16 cu. ft.) uses.

First numbers from the 14 cu. ft. "energy star" are somewhat confusing:
Start-up surge 7.27 Amps
Running Watts 25 "fan only" 145 -165 with compressor running
The Energy Star label says it should use 61 kW hours per month (probably that month is February)
That would be 2 kW hours per day
We'll see

waynefromnscanada

Re: Just how bad a small 'frige is

Interesting thing I've found with two different freezers. Both of them I added (converted to) capacitor start, so they would instantly start, even after just running a second ago, therefore with full back pressure on the compressor. A state in which it would never start as it was wired as it came from the factory.
Now to what I found. Start it after not having ran for 10 or more minutes and initially, after the start surge, they would draw around 120 watts, but within 2 or 3 minutes the draw would ease down to perhaps 85 or 90 watts and stay there till it shuts off. BUT - - - if while running, I shut it off for a second or two, then restart it, the after start draw hangs around 120 watts and stays there for whatever time it continues to runs. To me, very strange and makes no sense.
Would love to understand what's behind it.

westbranch

Re: Just how bad a small 'frige is

definitely no expert here but could it be like an air compressor, starting at above its 'normal' kick in pressure and as you said , starts instantlt, thus under higher than normal pressure (mid cycle) and thus is having to 'finish off' the cycle, all at higher back pressure???

e

waynefromnscanada

Re: Just how bad a small 'frige is

westbranch wrote: »

definitely no expert here but could it be like an air compressor, starting at above its 'normal' kick in pressure and as you said , starts instantlt, thus under higher than normal pressure (mid cycle) and thus is having to 'finish off' the cycle, all at higher back pressure???

e

That's what I can't figure. If that is what it is, I don't understand why, after a few minutes the pressure doesn't gradually return to normal operating pressure. Got to be something like that, but I just can't get my head around it. Not the end of the world, just that I always like to understand what's going on.

LucMan

Re: Just how bad a small 'frige is

waynefromnscanada wrote: »

Interesting thing I've found with two different freezers. Both of them I added (converted to) capacitor start, so they would instantly start, even after just running a second ago, therefore with full back pressure on the compressor. A state in which it would never start as it was wired as it came from the factory.
Now to what I found. Start it after not having ran for 10 or more minutes and initially, after the start surge, they would draw around 120 watts, but within 2 or 3 minutes the draw would ease down to perhaps 85 or 90 watts and stay there till it shuts off. BUT - - - if while running, I shut it off for a second or two, then restart it, the after start draw hangs around 120 watts and stays there for whatever time it continues to runs. To me, very strange and makes no sense.
Would love to understand what's behind it.

It's all about refrigerant pressures in the system. Most domestic units utilize capillary tubes for refrigerant metering into the evaporator. Cap tube systems normally bleed refrigerant from the high side to the low side during the off cycle, hopefully equalizing the pressures before the next restart. The compressor start winding is designed for low starting torque as the pressures should be equal on start up.
Capacitor start compressors use high torque start windings as they are designed to be used in an expansion valve system where there is little or no equalization during the off cycle. The compressor is called to start with a high pressure on the discharge side and a low pressure on the suction side. In a freezer that may be a a difference in pressure of 100 to 1.
By installing a start cap on your compressor and restarting it immediately after shut down you have bypassed the normal equalization process and the compressor is starting against a much higher head pressure than it is designed for.
Not a good idea to try to restart until pressures are equalized on cap tube systems whether they are refrigerators or A/C units. The old rule of thumb is 5-10 minutes before restart.

Cariboocoot

Re: Just how bad a small 'frige is

Energy Star optimism: the actual results for the "61 kW hours per month" rated unit is an average 2.9 kW hours per day. That's 50% more power than the rating indicates it would use. Most of the time the door wasn't opened either.

It's also far worse than the "non energy star" 'frige I've got running at the cabin.

"You pays your money and you takes your chances." :roll:

waynefromnscanada

Re: Just how bad a small 'frige is

LucMan wrote: »

By installing a start cap on your compressor and restarting it immediately after shut down you have bypassed the normal equalization process and the compressor is starting against a much higher head pressure than it is designed for.

Agreed, but why after being restarted, don't the pressures ever return to their normal operating pressures, for the rest of that cycle, no matter how long it runs? That's the part I can't understand Not being difficult, just weird in always wanting to understand everything.

DavidOH

how bad a small 'frige

My 3.1 cu ft Ref/Frez tested at 78 watts. ( was listed at 84). Not so bad, but compare size/wattage they use to much for the size.

It's an Edgestar this one:
http://www.compactappliance.com/CRF320SS-EdgeStar-Midsize-Compact-Refrigerator-Freezer-Stainless-Steel/CRF320SS,default,pd.html?cgid=Appliances-Refrigerators-Refrigerator_Freezer

TheBackRoads

Re: Just how bad a small 'frige is

Tested our small 'frige that is used for keeping drinks cool. (a waste I know) Over 3 days it used 1.81kW hours or about .59kW a day. The ambient temperature range was 78.8 to 68.4. I can get the exact model if anyone wants but its a small Danby.









Honestly not as bad as I was expecting.:-)

Edit: I also wanted to mention it uses 0.00w doing nothing (manual defrost and thermostat)