24” energy star fridges

icarus

As a direct physical replacement for a “full size” (24” Dometic LP fridge) I am beginning to see a number of VCC/inverter compressor energy star fridges, made by name grade companies, including LG/Samsung/Whirlpool etc, all claiming ~.8-.9 kwh/day consumption.  They all seem have ~4 amp draw spec.  The question I have, is what would a realistic guess (or real world experience) current draw be with one of these?

as it dials down to maintain might it routinely only draw 2 amps say?  Sizing a 24/7 inverter and battery bank matters in this application.  For example if one would run on a Sursine 300, which will put out ~600 watts for 30 minutes would be nice rather than having to bump up to a bigger inverter.  

Thoughts are welcome,

Tony

BB.

With a 4 amp draw (at 120 VAC?), that would put them at 480 Watts peak draw...

I wonder if that is not the draw of the defrost heater (assuming that this, at least in North America, tend to be frost free models)?

-Bill

mcgivor

BB. said:

With a 4 amp draw (at 120 VAC?), that would put them at 480 Watts peak draw...

I wonder if that is not the draw of the defrost heater (assuming that this, at least in North America, tend to be frost free models)?

-Bill

Most probably is, the compressor should be in the 150W, 1.25A neighborhood .

littleharbor2

My Hotpoint 18 cu.ft. fridge in Baja , according to my Kill-a-watt meter draws .75 amps @ 115 volts when running.

icarus

littleharbor2 said:

My Hotpoint 18 cu.ft. fridge in Baja , according to my Kill-a-watt meter draws .75 amps @ 115 volts when running.

Is this an inverter compressor fridge?  

T

BB.

Littleharbor2, is your fridge "frost free"? Have you caught the defrost cycle on the Kill-a-Watt? I wondered if any of the inverter refrigerators use "heat pump" mode to defrost, or do they still use the electric heating element....

-Bill

Dave Angelini

Guessing Yes and GE does not make inverter compressors at this time. The defrost is about 500 watts on the one a client bought. I have not seen an electric in a long time that you have to defrost excepting freezers

icarus

So, the next question would be (aside from the average running watts of a the LG inverter 11 cu ft fridge) would be what might a good estimate of a duty cycle be.  I know that inverter compressors dial down, but they also shut off eventually.  Might a 50% duty cycle given average Delta temp be sort a a good ball park guess?  How often does a defrost cycle run and is it possible to either disable it, or set it up to go manually?  

I confess to coming to this party a bit late, having been “off the grid” for so long, I haven’t paid any attention.  

Tony

BB.

For frost free systems... The defrost cycle seems to run about once every two hours. Neil, a former member here, found that when he disabled defrost cycle, that at >~24 hours, the refrigerator started to use more energy (on average) as the frost started to restrict airflow on the evaporator.

From my limited experience, frost free refers use a fan to move air over the evaporator and the relatively high wattage heater, Calrod, to quickly melt frost before heating the fridge itself. It was really something to see the Calrod glowing dull red, and a quick burn on my hand, in the upright freezer I was manually defrosting (over filled, poor air flow--A different issue).

-Bill

Dave Angelini

Hey Tony, My experience is with 22 Cu ft or so for an average full time offgrid home. The defrost is once a day and always when the sun is not out. You can shut down the breaker or unplug and this often resets the time of day. You can tweak it. However a home with 3 or 4 people really has to have a large enough battery to make this negligible.  The LG 22 inv is the same defrost as a non inv fridge.

The Inverter type is also variable speed so that is a concept you need to know as to your duty cycle question. To me this size range really is not any more or less power. Both are around 1.8 KWH depending on room temp. I am comparing a Maytag/Frigidaire standard to a LG/Samsung inv. The difference is no surge and really low noise. Both are bottom freezer single door without icemakers. I think you can get lower energy use by making ice in the morning or doing that during winter. I don't like the noise of auto ice making at night anyway. 

The other thing I notice with helping lots of clients learn the offgrid strategies is that your canadian energy star stats are more accurate than the US. Ours seem to be quite a bit higher. Maybe they assume we have warmer house temps than you frost lovers up north. We actually use more fridge power in winter because we cool the house in summer and get it toasty in winter with our canadian osburn wood stove.

You will notice food lasting alot longer in summer with electric reefers over ammonia/propane. Good hunting!

icarus

Dave, Bill et al.  Thanks for your help, as always....

I have no problem with keeping food cold with good LP fridges winter or summer.I have insulated the boxes with foam board, and have fans on the evaporator and Condensers.  The duty cycle is quite reasonable with this strategy.  The bottom line is that when the fridge fails, chasing to an inverter fridge is a doable move.  That said, my cost for LP is ~$.50/day so changing out the fridge, possible adding PV  etc doesn’t not make economic sense, but knowing real world numbers going forward is helpful.  

Still would like to see a real world KWH report on a 11 cu ft inverter Lg.

Tony

mcgivor

icarus said:

Dave, Bill et al.  Thanks for your help, as always....

I have no problem with keeping food cold with good LP fridges winter or summer.I have insulated the boxes with foam board, and have fans on the evaporator and Condensers.  The duty cycle is quite reasonable with this strategy.  The bottom line is that when the fridge fails, chasing to an inverter fridge is a doable move.  That said, my cost for LP is ~$.50/day so changing out the fridge, possible adding PV  etc doesn’t not make economic sense, but knowing real world numbers going forward is helpful.  

Still would like to see a real world KWH report on a 11 cu ft inverter Lg.

Tony

Here is some collected data for a 14 cf inverter refrigerator in the hottest time of the year.
https://forum.solar-electric.com/discussion/354372/inverter-refrigerator-logging-results#latest

icarus

Thanks Mcgivor for that...Tony

littleharbor2

icarus said:

littleharbor2 said:

My Hotpoint 18 cu.ft. fridge in Baja , according to my Kill-a-watt meter draws .75 amps @ 115 volts when running.

Is this an inverter compressor fridge?  

T

Sorry for the late reply. I was on the road yesterday.

No it's your basic fridge I bought it at Home Depot. Best energy Star rating of models on the floor being my criteria. I don't recall the actual Kwh/year numbers on the label but somewhere around 360 - 385ish.

littleharbor2

BB. said:

Littleharbor2, is your fridge "frost free"? Have you caught the defrost cycle on the Kill-a-Watt? I wondered if any of the inverter refrigerators use "heat pump" mode to defrost, or do they still use the electric heating element....

-Bill

Yes it is. When I first plugged it in, brand new, I got a bit over 1 amp current draw reading on the KAW.
 While running. After a few days I noticed it had dropped to .75 amps. Those are the only numbers I noted with the KAW meter.

BB.

I noticed too on my refrigerators--When "warm" (just plugged in, new food put in fridge/freezer) the compressors used more energy than they did vs when the fridge/freezer was "cold" (i.e., deep freeze below 0F used less power than when cooling below 32F). However--When at 0F or less, the compressor did run longer (less efficient at colder temperatures, and probably more heat loss through cabinet--Under stable conditions).

Adding more things to cool (like making ice), will up your energy usage noticeably (as will kids opening doors looking for snacks, getting an adult beverage a couple times a day, etc.).

-Bill

PS: I should add--The typical cause of battery "failure" is simply sulfation... Which makes the battery look much smaller AH/Capacity wise. Looking for specific open/shorted failures are more like sudden failure events, not the "slow aging/death" of sulfation.

PNW_Steve

I have a 10.8cu.ft. Frigidaire in my RV. 

With the defrost function enabled my inverter screams a low voltage warning when the defrost function runs. Usually between 2:00-400am.

The batteries are at nearly the lowest SOC at that time of day and I may need to upgrade my battery and inverter wiring.  I did not properly account for the current draw when the defrost cycle runs. 

BB.

The "cheap" fridge/freezers of the frost free persuasion, typically have a little clock motor drive and relay pack. You will generally find it around the bottom front or rear of the cooler... You can twist the stub shaft until you hear the contacts first "clunk" and that will be start of defrost cycle... Do that around noon-2pm, and that should repeat every day (assuming constant 120 VAC power and 24 hour timer, mine seemed to have been 12 hour timers).

https://duckduckgo.com/?q=refrigerator+defrost+timer&atb=v122-1__&iar=images&iax=images&ia=images

Hmmm, things keep changing:

http://www.acmehowto.com/howto/appliance/refrigerator/check/defrosttimer.php

A mechanical defrost timer controls the defrost cycle of the freezer. In older models, the timer runs continuously and roughly every six hours, cuts power to the cooling system and sends power to the defrost heater. In newer models the timer advances only while the compressor or defrost cycle is running - an improvement for efficiency. As the timer continues to advance, power to the heating element is cut and power is restored to the cooling system. 
...
To test whether the defrost timer is simply failing to advance, locate the advance screw and turn it clockwise until you hear it click. This advances it to the next mode. If it was cooling before, it is now in defrost mode. Simply wait about 35 minutes and check whether it has left defrost mode and has resumed cooling...

-Bill