There are two dimensions that have to be considered for when purchasing a battery backup for a refrigerator which are; the refrigerator’s power consumption rating and the size of its startup amps. Not obtaining this data and only using the refrigerators nameplate amp rating to calculate the required battery bank will result in a purchase that will be either too big or too small.
How long will a 12 Volt Battery Run a Refrigerator?
A typical Energy Star Refrigerator that consumes less than 300kwh per year, may be able to run on a fully charged 12 volt 100 amp hour storage battery for 30 – 35 hours. This varies with the ambient temperature surrounding the refrigerator and the efficiency of the DC to AC power inverter that is being used.
1) Find out the Refrigerators Power Consumption Rating:
The power consumption rating is a measurement of the amount of power the refrigerator uses over time. Refrigerators contain compressors that cool. However, they do not run constantly, instead cycle on and off, thus the amount of power a refrigerator consumes over a period of time is significantly less than the nameplate wattage or amperage. The nameplate amperage or wattage will specify the amount of power the compressor draws when it is on. For example; if the compressor only runs 30% of the time when a refrigerator is powered on then the overall power consumption would be only 30% of the running (nameplate) amperage.
The power consumption can vary with high or low ambient temperatures or insulation values that will cause the compressor to run more or less. Many conventional household refrigerators are rated for efficiency by energy star, but most commercial and pharmacy refrigerators often do not comply to the criteria that energy star uses to endorse a product.
How Many Watts Does a Refrigerator Use?
An energy star refrigerator that consumes 300 kwh per year can draw up to 150 watts while the compressor runs. The amount of watts a refrigerator uses depends on how many amps it draws. Check the nameplate, power information on your refrigerator. Finding its amp rating and times that by the running voltage (usually 120 volts) is the rated watts.
Refrigerator manufactures usually have the power consumption rating data for their products. This is listed in BTUs (British Thermal Unit) per hour, average WH (watt hours), or KWH (kilowatt hours) per day or per year. Knowing this information is extremely important, for buying a battery backup for a refrigerator, so you do not end up purchasing too much or too little battery capacity. If the manufacturer of your refrigerator does not have these power consumption numbers, there are other ways of getting it, such as buying a power KNH meter and measuring it yourself. Medi-Products might be able to even lend you one.
2) Know the Refrigerators Startup Amps:
The startup amps usually referred to as the LRA (Locked Rotor Amps). The locked rotor amps is the amount of power/amperage it takes to start the fridges compressor/motor from being completely stopped. This usually required about 5 times the nameplate or running amperage, but can even be as much as 10 times. An example: if you had a refrigerator who's nameplate amperage is rated for 3.5 (420watts) you will need a ups with an output of 2100 - 4200 watts. If the UPS surge watts output is not high enough, it will never get the motor started and not be able to run the refrigerator once the power is lost.
So Why is Knowing These Two Factors so Important When You Size a Battery Backup for a Refrigerator?
Our conclusion is, before you buy a battery backup for your refrigerator or freezer do a little homework. If you are planing on buying a refrigerator or freezer and you plan on backing them up with battery, be sure to pick one with lower power consumption rating. This will save you by lowering the size and cost of the battery backup that will be needed to support it.
So often the tendency is to opt for a cheaper UPS system, something small that you can carry for under $500.00, only to find that it will not run the refrigerator, and even if it was able to, it would only run it for a very short time. Calculating the size needed to the battery-bank often gets specified over-sized or under-sized if it is not calculated off of the right data.
Mediproducts can help size, design, engineer and build a suitable system that will be just right for your needs.