Join Samurai Appliance Repair Man on a trek into the sealed system bowels of a warm refrigerator. Watch with amazement as I show you how to make a definitive diagnosis of a sealed system failure in this fridge using common, inexpensive tools that every appliance tech (who’s worth their salt) and most DIYers already own: a clamp-on ammeter and an IR temperature gun.
Howl, o ye nations! Clap your hands, o ye peoples! No need for line piercing valves and pressure gauges IF you understand how sealed systems work, which we teach in stunning multimedia detail in the Refrigerator Repair Training Course here at the Samurai Tech Academy.
So let’s look at where that current draw comes from and apply that to the compressor in the video.
Compressors are rated by horsepower. Horsepower is a measure of mechanical work. Watts are also a measure of work but the work in this case is electrical. The nameplate rating on compressors and motors gives the horsepower of the motor because you’re usually interested in how much torque that motor can produce at a given voltage.
Horsepower is a measure of mechanical work just like watts is a measure of electrical work. You can convert horsepower to watts using the following conversion:
1 horsepower (hp) = 746 watts
The compressor in the video is an Embraco EGZ80HLP, a typical 1/3 hp compressor. 1/3 hp = 246 watts. Let’s ignore mechanical inefficiencies in converting electrical work (watts) into mechanical work (horsepower) and run the numbers:
P= I * E => I = P / E = 246 watts / 120 vac = 2 amps
So that’s where the “2 amps or maybe a little less” statement comes from in the video.
Not sure how/why I did those calculations? Ohm’s law is something we teach in detail in our Core training course.
Let’s compare this calculated current draw with a measured draw from the exact same compressor model (1/3 hp) in a different refrigerator, different service call, shown in the video below starting at 3:05 in, go ahead and fast forward:
I measured 1.6 amps in the video above but calculated 2 amps. Some of that difference is due to the run capacitor installed on the compressor. The purpose of the run cap is to smooth out the pulses in the motor and help it draw less current while running. But I’d say that qualifies as “2 amps or maybe a little less.”
Here’s another trick for diagnosing sealed systems without having to read system pressures. If you’re working on a model that has a thermistor strapped to the evaporator coil (as many modern models do), then it’s even easier: measure the voltage drop on the evaporator thermistor and compare with the specs in the tech sheet. Knowing that the evaporator operating temperature of a healthy sealed system is -20 to -15F, you can quickly and non-invasively tell if the sealed system is operating correctly with this one simple, electrical measurement.
See a different technique for troubleshooting sealed system problems using just your IR temperature gun in this other post.
You can learn more about troubleshooting and repairing refrigerators in our Refrigerator repair course.