No Frost system, features and varieties

It is probably difficult to find a person in modern society who has not heard about the No Frost technology or function, which translates as “No Ice”. This technology came to the Russian market along with Stinol refrigerators, which many considered “ours.” But when the Italians renamed the plant they built to Indesit and began producing their refrigerators and washing machines there under the Indesit and Ariston brands, doubts began to creep in, where did this No Frost come from and is it really necessary? Many people know that the Italians and the Merloni concern are very competent sellers who produce mass-produced equipment of acceptable quality, competing only with the Koreans and Germans, who were much more expensive. So, in essence, the consumer had no choice but to take what was cheaper without any questions asked. It was not profitable for manufacturers to sell cheap refrigerators, so it was necessary to offer users something “special”, and in order for them to buy, it was necessary to intimidate them with something, focusing their attention on such shortcomings as icicles or constantly frozen doors on single-chamber refrigerators 50 -s.
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Разобранный таймер оттайки системы NOFrost.jpg

Differences and varieties of No Frost

The figure below shows the differences between refrigerators from the 50s and 60s and modern ones. As you can see, a lot has changed. Most importantly, the freezer began to be located in a separate chamber, and it was also possible to separate the main source of moisture by placing shallow frozen products in a separate refrigerator compartment, where the temperature did not drop below 3-5 degrees.

The design of the seals has also changed. They became softer and more elastic and received additional chambers and ebbs for better insulation of the refrigerator from moisture and temperature. The frostiness soon went away, but somehow the equipment needs to be sold, so they continue to come up with Free frost, Full Frost, No Frost and other frosts.
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The device of the system

In order to understand how the system works, you need to look at this diagram, where we see how the voltage along the blue branch goes to the thermostat through a thermal fuse. And if the thermostat is closed (the refrigerator has thawed), then the voltage goes to pin 3 of the timer, and there it goes to either the compressor or the heater using contacts controlled by a motor. In addition, the circuit has a fan that rotates along with the operation of the compressor.

A timer is essentially a regulator that shows where the current goes to the compressor or to the heater. In domestic refrigeration, different types of data systems are used, but the principle is the same for all.

Disadvantages:
- More knowledge and higher professionalism are required from the refrigeration operator;
- Unlike a conventional (compressor + thermostat) system, this system has many additional elements that increase the likelihood of product failure;
- The price of a No Frost refrigerator is higher than that of drip-type refrigerators;

Advantages:
- Higher maintainability due to the more accessible location of the evaporator in contrast to the drip evaporator;
- Heat absorption is more efficient due to the absence of ice crust and the presence of a fan.

As we can see, this system has both pros and cons. And what is more important to you is up to you to choose. But let's look at the main elements of this system in a little more detail.

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Defrost relay

A temperature relay with a thermal switch works like a thermal relay, where:

T - opening: +11(± 4) °C
T - short circuit: -8 (± 4) °C

Also, this device also works as a thermal protection for the refrigerator, which breaks the circuit irrevocably when the temperature reaches 72 °C. This relay is designed for 1200 cycles, which is not so much, if one cycle is 12 hours, then we get 2 years of operation. Therefore, I think it is not correct to use this system, if you look at it from the client’s side, although if you look at it from the master’s point of view, then of course it is beneficial to have such refrigerators.
There are relays with different numbers of wires, but essentially they are all needed for one purpose and perform the function of turning off the heater and protecting against overheating.

4 wires (TAB-T-2, TC1-72C, PTR-201 )
3 wires (TAB-T-19, PTR-101, TAB-T-3)
2 wires (PTR-103, TT1-72S)

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Defrost timers

The second most important element of any No Frost system is the timer, which is responsible for the operating cycle of this system. There are a great many of them, but they can all be divided into two large groups:

Mechanical timers - a device for defrosting a household refrigerator, where switching between defrosting and freezing modes is carried out by mechanically switching contacts using an eccentric and a motor that rotates it through a gear transmission.

Electronic timers - defrosting is controlled through the operation of a microcircuit, which in turn supplies a control signal to an electromagnetic relay, thereby turning on the heater or starting the freezing stage. This relay has a button that is needed to switch the timer to defrost mode. These timers count down the cycle from the moment the warm relay first closes and start the defrost cycle.

Attention!!! If this timer has been supplied with voltage during the previous 4-8 hours, then you need to press the button manually! Since the refrigerator may not go into defrost mode, even after closing the thermal relay and 12 hours of operation.
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