Understanding In addition, how to determine the power of a compressor on a refrigeratorbecomes critically important if the main part of the unit breaks down. The owner of the equipment is faced with the need to find a replacement when the old motor stops starting or works intermittently. Incorrect selection of an element according to technical characteristics can lead to rapid failure of a new part or even damage to the cooling system as a whole.
Electric motor power is not just a number in the passport, but a key parameter that determines the performance and energy consumption of the device. Inverter and linear models have their own calculation features that differ from classic asynchronous motors. In this article we will analyze all the available ways to calculate this parameter, from simply examining the label to using measuring instruments.
Why do you need to know the power of the motor
The main reason why users look for information about power is selection of an analogue to replace an exhausted building a node. The spare parts market is overflowing with offers, but not all compressors are interchangeable even if the seats match. If you install a motor with less performance, the refrigerator will work at its limit, constantly overheat and eventually burn out.
In addition, knowledge of the exact parameters is necessary for assessing energy consumption household appliances. Older models can consume significantly more electricity than their modern counterparts. Understanding power consumption helps to calculate approximate electricity costs and decide whether to repair an old unit or buy a new one.
This parameter is also important when diagnosing wiring faults. If you plan to connect the refrigerator through an extension cord or voltage stabilizer, you need to make sure that their capacity matches the current consumption of the motor. Exceeding the permissible load on the network often causes melting of sockets and fire hazards.
⚠️ Attention: Never rely only on the overall dimensions of the compressor when purchasing a replacement. Two outwardly identical motors may have different power and type of refrigerant, which will make them incompatible.
Studying factory markings and labels
The easiest and safest way to find out the technical characteristics is to carefully examine the compressor itself. On the metal body of each motor there is a factory seal (sticker or metal plate) containing all the necessary information. However, manufacturers often use specific codes that are not always clear to the average person. nameplate (sticker or metal plate) containing all the necessary information. However, manufacturers often use specific codes that are not always understandable to the average person.
First of all, look for the model designation, which usually begins with letters indicating the manufacturer (for example, Secop, Embraco, LG, Danfoss). Knowing the exact name of the model, you can use correspondence tables or search on the Internet. Often, next to the model number, the rated power in watts (W) or horsepower (HP) is indicated.
Pay attention to the following parameters indicated on the nameplate:
- 🏷️ Model — full alphanumeric designation of the device.
- ⚡ V/Hz — mains voltage and frequency (for example, 220-240V 50Hz).
- 🌡️ Refrigerant — type of refrigerant used (R134a, R600a, R404a).
- 🔌 Amp — current consumed by the motor (an important parameter for calculations).
- 🔄 LRA — starting current (locked rotor current), critical for choosing a starting relay.
If the sticker does not have a direct power number in watts, do not despair. Having data on current and voltage makes it easy to calculate the desired value mathematically, which will be discussed in the following sections. The main thing is not to erase the information when cleaning the case from dirt and oil before taking measurements.
Calculation of power by current and voltage
When the marking is unreadable or missing, Ohm's law comes into effect for a section of the circuit. This is the most accurate method for classic asynchronous motors. To carry out measurements, you will need a multimeter with the function of measuring current (ammeter) or a current clamp, as well as access to the electrical circuit of the compressor.
The measurement process requires caution, as it involves working with high voltage. It is necessary to connect an ammeter to the gap in one of the compressor supply wires. When the engine starts, the instrument needle will sharply deviate (starting current), and then stabilize at the operating value. We are interested precisely operating current, which is set after the motor reaches the operating mode.
The formula for calculating active power is as follows:
P = U × I × cos φ
Where:
- ⚡ P is the required power in Wattah
- 🔌 U —mains voltage (in Russia the standard is 220-230 Volts).
- 📏 I —measured current strength in Amperes.
- 📐 cos φ —power factor (for household compressors is usually taken equal to 0.6–0.8).
☑️ Check before measurements
Done: 0 / 4
Calculation example: if your ammeter shows 0.8 A, the mains voltage is 220 V, and we take the cosine phi to be 0.7, then the power will be: 220 × 0.8 × 0.7 = 123.2 W. Rounding up, we get a standard motor with a power of about 120-130 W. This method allows you to get a real picture of consumption, which may differ from the passport one due to wear of the windings.
Use of model correspondence tables
For those who do not want to take measurements under voltage, there are detailed technical catalogs manufacturers. Large factories such as Secop (formerly Danfoss) or Embraco publish documentation where each model is assigned a performance code. This data is often used by repairmen for quick identification.
Below is a table of correspondence between popular series of compressors and their approximate power. Please note that the values may vary depending on the boiling point and type of refrigerant.
Series / Model
Refrigerant type
Power (approx.)
Chamber volume (l)
Secop NL10F
R134a
1/5 HP (~100-110 W)
up to 150 l
Secop TL45G
R134a
1/3 HP (~160-180 W)
200-300 l
Embraco EMT6140
R600a
1/4 HP (~120-130 W)
up to 200 l
LG MA100NAE
R134a
1/3 HP (~150 W)
250-350 l
When searching in tables, pay attention to abbreviations. For example, HP means horsepower. To convert them to watts, use the ratio: 1 hp. ≈ 735-750 W. However, in refrigeration technology, “refrigeration” horsepower is often used, so it is easier to focus on fractional values: 1/5, 1/4, 1/3.
What does LRA mean on the nameplate?
LRA (Locked Rotor Amps) is the current that the engine consumes at the moment of start, when the rotor is still stationary. This value is 5-7 times the operating current. It is critical for selecting a starting relay and diagnosing the condition of the windings. If the actual starting current is very different from the LRA, problems with starting are possible.
Features of inverter and linear compressors
Modern refrigerators are increasingly equipped with inverter motors, the operating principle of which is radically different from the classic ones. In such systems there is no strict connection to a constant speed. The power of the inverter constantly changes depending on the load, so determining its “nominal” is more difficult.
For inverter models, the power consumption range or maximum value is often indicated on the nameplate. For example, the inscription 100-350W says that the motor can operate both at minimum speed to maintain temperature and at maximum speed for rapid cooling. Average consumption is usually in the middle of this range.
Linear compressors, popular in technology LG and Samsung, have a direct drive piston system without a crank mechanism. Their power also varies. To diagnose such components, conventional current measurement methods can give a distorted picture due to the complex shape of the current sinusoid created by the inverter control board.
To accurately determine the parameters of inverter systems, it is recommended:
- 📱 Use the refrigerator service menu, which displays the current speed and current.
- 🛠️ Use special clamps that can measure alternating and direct current at high frequencies.
- 📄 Focus exclusively on the model code in the official service manual.
⚠️ Attention: Technical characteristics and service menu interfaces may vary depending on the specific model and year of manufacture. Always check the manufacturer's official documentation for your device, as details may change.
The influence of power on the operation of the refrigeration system
The power of the compressor directly affects cooling capacity the entire unit. A motor that is too weak will not be able to provide the necessary circulation of refrigerant, especially in a hot room or when the chambers are fully loaded with food. As a result, the temperature inside will be higher than normal, and the engine operating cycle will become continuous.
On the contrary, installing an overly powerful compressor is also dangerous. The piping system, evaporator and condenser are designed for a certain volume of pumped freon. Excessive power will lead to the fact that the liquid refrigerant may not have time to evaporate and will enter the engine cylinder, causing water hammer.
In addition, consistency with the thermostatic expansion valve (TEV) or capillary tube is important. These elements throttle the freon flow. If the motor power does not match the capacity of the capillary, the pressure balance in the system will be disrupted, which will lead to ineffective operation or freezing.
Diagnosing faults through current consumption
Measuring current strength is not only a way to find out power, but also an excellent method diagnostics. If you measure the current and it differs significantly from the nameplate values, this is a signal of a problem. For example, increased current may indicate an interturn short circuit in the windings or mechanical jamming.
Reduced current often indicates a loss of valve group performance. The pistons pump “idle”, without creating the required pressure, although the electrical part consumes less energy. In this case, replacing the motor with one of similar power will not solve the problem if the reason is in the compressor itself, and not in its power.
Be sure to compare the data obtained with the reference values for your model. If the operating current exceeds the norm by more than 15-20%, operation of the refrigerator should be stopped until the reasons are clarified. This will help avoid a fire or complete failure of the equipment.
Is it possible to install a compressor more powerful than it was?
Theoretically, it is possible if the seats and pipelines match, but this is risky. A more powerful motor will create excess pressure in the system, which the condenser and evaporator of the old refrigerator are not designed for. This may lead to depressurization of the circuit. It is better to look for an exact analogue.
Why does the compressor hum but does not start?
Most often this indicates that the starting current (LRA) is too high for the starting relay or winding, or a mechanical jamming of the piston group has occurred. Also, the reason may be a drop in voltage in the network, due to which the motor does not have enough power to start.
How to convert Amps to Watts without a calculator?
For a quick estimate in a 220V network, you can multiply the current value in Amperes by 200 (taking into account the approximate power factor). For example, 0.5 A × 200 = 100 W. This will give an approximate value sufficient for the initial selection of an analogue.
Does the type of freon affect the power of the compressor?
Yes, indirectly. Compressors designed for R600a (isobutane) often have lower operating power and cylinder volume compared to their R134a counterparts, since isobutane has different thermodynamic properties and requires less quantity to operate effectively.