The situation when the refrigerator stops turning on or starts making clicks without starting the compressor often makes owners think about self-diagnosis. The first element that technicians pay attention to is the start-up relay, located at the bottom of the unit next to the motor. It is on this small plastic or carbolite block that various numbers, letters and abbreviations are usually printed, which to an untrained person look like a random set of symbols.
Understanding this what do the numbers on the refrigerator relay meanis critically important when selecting a replacement for a failed component. An incorrectly selected device can lead to burnout of the motor windings or constant knocking out of plugs. In this article, we will analyze the structure of the marking in detail, explain the meaning of the numeric codes and help you understand the technical nuances without unnecessary complexity.
The main purpose of the starting relay and its marking
The starting relay is a key element of the asynchronous starting circuit compressor motor. Its task is to briefly connect the starting winding to create torque, after which it must turn off this winding, leaving only the main winding to work. The numbers on the device body are not a batch serial number in the usual sense, but serve as a compatibility code with specific compressor models.
The most common designations, such as PTC or RKT, indicate the type of element used inside. In posistor relays (PTC), the role of a switch is performed by a ceramic element, the resistance of which increases sharply when heated by current, breaking the starting winding circuit. The numbers next to these designations often indicate the rated resistance or permissible operating current.
It is important to note that the markings may be located on different sides of the case. Sometimes the main technical parameters are stamped on the inside of the cover, which can only be seen after removing the part from the compressor. Visual inspection must be careful: look for inscriptions lasered or embossed in plastic, as stickers can fade or peel off over time.
⚠️ Attention: Never install a relay with a resistance marking different from the original, even if the mounting dimensions are the same. The difference in the actuation current may result in the motor not starting or the winding burning out.
Deciphering manufacturers' numerical codes
Worldwide component manufacturers, such as Danfoss, Secop or Indesituse their own coding systems. The most popular system is three-digit or four-digit codes that directly correlate with the power and type of freon that the compressor is designed for. For example, a series of 100s or 200s often indicates compatibility with a certain range of cooling capacity.
Let's look at commonly used designations using popular series as an example. The numbers can indicate not only power, but also the type of refrigerant. For old models operating on R12, and modern ones using R600a or R134a, different protection response characteristics are required. An error in selection can lead to incorrect operation of the thermal protection.
Below is a table of correspondence between the most common relay codes and compressor types, which will help you navigate the range of spare parts:
| Relay code (Example) | Compressor type | Power (W) | Compatibility |
|---|---|---|---|
| 100 CLR / R600a | Low temperature | up to 100 | Small refrigerators |
| 103 CLR / R134a | Medium temperature | 100-150 | Standard models |
| 105 CLS / R600a | Low temperature | 150-200 | Two-chamber refrigerators |
| RKT (RKT) | Universal (USSR) | up to 250 | Old models Atlant, Biryusa |
When searching for spare parts in online stores, use these codes to filter the results. If you see a relay labeled 10-12N or similar, this may indicate the maximum current in amps that the thermal protection inside the housing is rated for. Such parameters cannot be ignored when replacing.
Differences between posistor and induction relays
Numerical marking also helps to distinguish the type of device. PTC relays, which are installed in 90% of modern refrigerators today, are usually marked with the letter combination PTC (Positive Temperature Coefficient). This means that there is a ceramic disk inside, which, when voltage is applied, heats up and changes its resistance, opening the circuit.
Older models used inductive (electromagnetic) relays, often designated as CSR or simply having a coil inside. The numbers on them may indicate the coil voltage or cutoff current. Visually, they are often heavier and have a different method of attachment to the compressor. Replacing an induction relay with a posistor relay (and vice versa) is only possible with special adapters and recalculation of the circuit parameters.
Modern universal replacement kits often contain several replaceable inserts with different resistances. These inserts also contain numbers, for example 22 Ohm or 47 Ohm. The choice of the correct insert is determined by the power of your compressor, information about which is on the motor nameplate.
⚠️ Attention: If you change the induction relay to a universal posistor relay, be sure to check the installation direction. PTC resistors are sensitive to orientation in space and must be installed strictly in the position indicated by the arrow UP.
How to read the technical specifications on the case
In addition to the model code, on the relay case you can often find lines with technical parameters written in small print. The limit values of currents and voltages are indicated here. For example, the inscription 250V~ means the maximum operating voltage of the network, and 50/60Hz the current frequency.
Particular attention should be paid to the marking of currents. Often there are designations like FLA (Full Load Amps) and LRA (Locked Rotor Amps). The first value indicates the current during normal operation, the second indicates the current that occurs at the moment of starting, when the motor rotor is still stationary. The relay must withstand short-term surges up to the LRA value without destroying the contacts.
For correct decoding it is useful to know the following abbreviations:
- 🔌 VAC — Volts AC (maximum voltage).
- ⚡ HP — Horsepower (motor power, often indicated as 1/4 HP, 1/3 HP).
- 🌡️ TC — Temperature Class, insulation temperature resistance class.
- 🔄 Cycles — Number of permissible on/off cycles per hour (usually 6-10).
If the power marking (HP) on the relay has been erased, but the model code has been preserved, it can be found in the manufacturer’s catalogs. However, if the compressor is non-standard or rewound, it is better to focus on the current consumption, measured with clamps during operation.
What to do if the marking is completely erased?
If the numbers on the relay are not readable at all, the only way to find a replacement is to remove the old element and go with it to the store to compare the seat and pins, or measure the resistance posistor with a multimeter (in a cold state it should be low, about 3-50 Ohms, depending on the model).
Instructions for selecting an analogue for replacement
The process of selecting a new relay begins not with a trip to the store, but with studying the nameplate on the refrigerator compressor itself. The metal sticker on the motor indicates the type of coolant, power and sometimes even the recommended type of starter. This data is primary for the search.
Next you need to remove the faulty relay. To do this, remove the back cover of the refrigerator, disconnect the wires (after photographing the connection diagram) and carefully remove the relay from the compressor legs. Shake the device: if a ringing or knocking sound is heard inside, it means that the posistor or contacts are damaged, and a replacement is definitely needed.
Use the following checklist when purchasing a new part:
☑️ Check before purchasing a relay
If you found a relay with a similar code, but from a different manufacturer (for example, Danfoss instead of Secop), make sure that the power range matches. Universal relays often have a wide range, for example, from 1/8 to 1/3 HP, which allows them to be used on many models.
⚠️ Attention: Technical characteristics of compressors and requirements for relays may change in new modifications of refrigerators. Always check the parameters on the nameplate of a specific unit, and do not rely only on the refrigerator model.
Frequent errors during decoding and installation
One of the most common mistakes is ignoring the type of freon. A relay designed for R12may not work correctly with a compressor for R600a due to differences in starting currents and oil characteristics. Although the relay may physically snap into place, its service life will be measured in minutes.
The purpose of the pins is also often confused. A relay usually has three main contacts: Common, Start and Run. Mixing up the wires when connecting can lead to a short circuit or the engine running in the opposite direction (which is unacceptable for piston refrigerator compressors and leads to valve failure).
Another important point is the condition of the contacts. If you bought a used relay or an analogue that had been in storage for a long time, the contacts may have oxidized. Before installation, it is recommended to check the resistance between the contacts with a multimeter. At rest, the circuit between the common and working contacts should ring (the resistance is close to zero), and the starting winding circuit should open after the posistor warms up.
Diagnostics of faults through relay analysis
The appearance of the relay can tell about the nature of the refrigerator malfunction. If the plastic housing is blackened or melted, this indicates overcurrent or poor contact at the connection to the compressor. In such cases, it is often necessary to check not only the relay, but also the motor itself.
If the relay is intact, but the refrigerator is humming and does not start, the problem may be a jammed compressor. Trying to “revive” it by installing a more powerful relay (“with a higher number”) is a dangerous path. This can lead to burning of the refrigerator wiring or a fire, since the protection will not work in time.
In some cases, cracks may be noticeable on the relay. This is a consequence of thermal expansion or mechanical shock. Moisture can get inside through the crack, which will cause corrosion of the contacts and unstable operation. Such a relay can only be replaced; repair by soldering or gluing is impossible and unsafe.
Questions and answers (FAQ)
Is it possible to use a relay with a higher numeric code if a smaller one is not on sale?
The use of a relay with a higher operating threshold (high power) is acceptable in extreme cases, but is not recommended. The protection will operate later, which increases the risk of overheating of the compressor windings during startup. It is better to find an exact analogue or a universal relay with an adjustable range.
What does the letter "S" or "M" mean at the end of the relay code?
These letters often indicate a series or modification of the housing. "S" can mean standard series, "M" - modified or for certain types of compressors (eg low torque). It is important that the electrical parameters match and the seats fit.
Why are the numbers on the new relay different from the old one?
Manufacturers often update product lines. Old codes (for example, Danfoss 1012) can be replaced by new ones (for example, Secop 101244). The main thing is to check the correspondence table (cross code) and physical dimensions.
Can a relay burn out due to a power surge in the network?
Yes, a strong voltage surge can break through the insulation of a posistor or weld the contacts. However, more often the relay fails due to aging materials or problems with the compressor itself (difficult starting). For protection, it is recommended to use a voltage stabilizer.
How to check a posistor with a multimeter without removing it from the relay?
In a cold state (after 15-20 minutes of inactivity), the resistance between the contacts of the starting winding should be small (from 3 to 50 Ohms). If the multimeter shows infinity or one, the posistor is broken. If zero, a short circuit is possible.