When planning the power supply of a cottage or apartments, the question often arises about what kind of starting current the refrigerator consumes at the moment it is turned on. Many users underestimate this parameter, relying only on the rated power indicated in the device passport. However, it is a short-term voltage surge in the first fractions of a second of starting the compressor that can cause the circuit breakers to trip or the generator to overload.
Understanding the nature of this phenomenon is necessary not only for engineers, but also for ordinary owners of household appliances. Inrush current can exceed the rated value by 3-7 times, which creates a significant load on the wiring. If you plan to connect the freezer via an inverter or UPS, ignoring this data will lead to constant emergency shutdowns of the system.
In this article we will analyze in detail the physical causes of peak loads, provide specific numbers for various types of compressors and discuss methods for protecting electrical wiring. Refrigerator is one of the most energy-intensive devices in the starting mode, and correct calculation of network parameters will avoid fire hazardous situations and extend the life of the equipment.
Physical nature of the starting current
To understand why starting current much higher than the worker, it is necessary to turn to the principles of operation of the electric motor. When voltage is applied, the compressor rotor is stationary. In order to move it from its place and overcome the force of inertia, as well as the refrigerant pressure in the system, an instantaneous transfer of enormous energy to the stator windings is required.
At this initial moment, the resistance of the windings is minimal, since there is no electromotive force of back-EMF, which occurs only when the rotor rotates. This is why the current increases sharply. As soon as the motor shaft begins to rotate, the resistance increases and the current quickly decreases to the nominal values indicated on the device nameplate.
⚠️ Attention: The peak load duration ranges from 0.5 to 3 seconds. If the circuit breaker responds faster than this time, it may trip falsely, even if the wiring can handle the rated current.
It is important to note that compressor does not start in a vacuum. There is already pressure within the system that must be overcome. This is especially true for models that turn on shortly after turning off, when the pressure in the circuits has not yet had time to equalize. This is why modern refrigerators have a restart delay.
Depending on the type of compressor
The magnitude of the starting jump directly depends on the design of the engine. In modern household appliances, two main types of drives are used, each of which has its own characteristics of energy consumption. Conventional (linear) compressor works on the “on-off” principle, which creates regular peak loads on the network.
Unlike them, inverter models equipped with a soft start system. The electronics gradually accelerate the engine, which avoids sudden voltage surges. However, even inverter systems have their limits, although their starting current is much lower and closer to the operating current.
- 🚀 Linear compressors: Characterized by a high starting current, which can reach 30 Amperes or more depending on the power.
- 📉 Inverter systems: Provide a soft start, the starting current exceeds the operating current slightly, usually 1.5-2 times.
- ⚙️ Compressors with PTC relays: Use a thermistor to limit the current at the time of startup, reducing the peak load.
When choosing equipment for autonomous power supply, for example, a generator, it is critical to know the type of your engine. If you have an old one refrigerator with a linear motor, the power reserve of the generator should be doubled. For inverter models, the requirements are less stringent, but you cannot forget about them.
Table of starting current values
For practical calculation of the required power of protective devices and generators, it is convenient to use averaged data. Below is a table showing the relationship between rated power and starting current for various classes of household appliances.
It should be remembered that Starting current is a calculated value and may vary depending on the ambient temperature, network voltage and the condition of the motor windings. The given values are averaged and are suitable for preliminary planning of the electrical network.
| Equipment type | Rated power (W) | Starting coefficient | Starting current (A)* |
|---|---|---|---|
| Single-chamber refrigerator | 150 - 200 | 3.5 - 4.0 | 3.5 - 5.0 |
| Double-chamber refrigerator | 250 - 350 | 4.0 - 5.0 | 6.0 - 9.0 |
| Freezer | 300 - 400 | 5.0 - 6.0 | 8.0 - 12.0 |
| Side-by-Side refrigerator | 400 - 600 | 4.0 - 5.0 | 10.0 - 15.0 |
*Calculation made for 220V network. Actual values may differ depending on the engine efficiency and the load on the shaft at the time of start.
Using these data, you can easily calculate the required generator power. For example, for a two-compartment refrigerator with a rating of 300 W and a factor of 5, the peak power will be 1500 W. The generator must withstand this load without voltage drop.
Calculating the power of the generator and UPS
Selecting an uninterruptible power supply or gasoline generator requires taking into account not only the active, but also the reactive component of power. Starting current creates a reactive load, which is not taken into account when simply summing up watts per devices.
For correct calculation, you must use a formula that takes into account the power factor (cos φ). For refrigeration units this parameter is usually 0.6-0.8. If you ignore this factor, the selected generator may stall every time the compressor starts.
☑️ Calculation of generator power
⚠️ Attention: The total power of all simultaneously switched on devices should not exceed 70-80% of the maximum generator power. Leave a reserve for starting currents.
It is also worth considering that inverter generators copes better with short-term overloads than traditional synchronous models. If you plan to frequently use equipment in the absence of a central network, investing in a high-quality inverter energy source will be justified.
Impact on electrical wiring and machines
Old electrical wiring in houses built last century is often not designed for modern loads. Aluminum wires with a cross-section of 1.5 mm² can heat up during regular starts of a powerful compressor, especially if other devices are connected to the same socket.
Circuit breakers (circuit breakers) have two protections: thermal and electromagnetic. Starting current can activate an electromagnetic release, if selected wrong. For refrigerators, it is recommended to use circuit breakers with characteristic "C", which are designed for short-term overloads, in contrast to characteristic "B".
If the machine knocks out exactly when the refrigerator is turned on, this is a sure sign that the rating of the machine is too low or the wiring has a high resistance. Replacing the machine with a higher rating without checking the condition of the wires can lead to their melting.
Why does the socket get hot?
If the socket gets hot, it means there is a bad connection or oxidation at the contact point. When the inrush current is high, the contact resistance generates heat. This is a fire hazard!
Methods for reducing the starting load
There are technical solutions to minimize the impact of the refrigerator on the network. One of them is the installation of soft starters (SPDs). They limit the current at the moment of start, gradually increasing the voltage on the motor windings.
Another method is to use voltage stabilizers with a starting current limiting function. Such devices are able to “smooth out” peaks, protecting the rest of the equipment in the house from power surges that inevitably occur when starting a powerful motor.
- 🔌 Separate line: Laying a separate cable from the panel directly to the refrigerator socket.
- 🛡️ Soft start devices: Special blocks embedded in the power circuit compressor.
- ⏱️ Delay relay: Eliminate switching on at unstable voltage or immediately after a surge.
It is important to note that interference in the electrical circuit refrigerator installation should only be carried out by qualified specialists. Incorrect installation of additional elements can disrupt the operation of the control system and lead to breakdown of expensive equipment.
Frequently asked questions (FAQ)
Can inrush current damage the electronics refrigerator?
The starting current itself is a normal operating mode and should not harm a working appliance. However, if there are constant power surges in the network or a phase is “broken” at the time of start-up, this can damage the control board or motor windings.
Why does the refrigerator hum more when it is turned on?
The increased hum in the first seconds is associated with the maximum force that the engine develops to start. At this moment the starting current is maximum, and vibration is transmitted to the body and pipelines stronger than in stable operation mode.
Do you need a stabilizer for a new inverter refrigerator?
Inverter models are less sensitive to voltage surges and themselves have built-in protection systems. However, in networks with extremely unstable voltage (from 170V to 260V), installing a stabilizer will extend the life of the compressor.
How can I find out the exact starting current of my model?
Accurate data can only be obtained using a current clamp with a Peak Hold function. In technical documentation, manufacturers often indicate only the rated current, and the starting current has to be calculated by multiplying by a coefficient.