The pressure regulator for the compressor with own hands

Pressure switch with their own hands

If you have at home a functioning thermostat from an old refrigerator, as well as some skills, you can easily make a pressure switch for the compressor with your own hands. However, it is worth warning in advance that such a solution can not differ in great practical opportunities, as the upper pressure with such an approach will be limited only by the strength of the rubber bellows.

Most convenient to remake in a pressure switch thermostat KTS 011, because they differ in reverse sequence of operation. when reducing the temperature in the chamber are turned off, when increasing. are included.


After opening the lid, the location of the required contact group is found out, for this purpose the circuit is wired. First of all it is necessary to improve the connection of the compressor with the thermostat: contact groups are connected to the terminals of the electric motor circuit and the unloading valve is connected to the outlet pipe with the control manometer. The adjusting screw is located under the cover of the thermostat.

At start of the compressor is carried out smooth rotation of the screw, at the same time you need to monitor the manometer readings. It is worth taking care that the compressed air reservoir is 10-15 percent full! To reach the minimum pressure it is necessary to move smoothly the stem of the front button. To this end, the cover is placed in its original place, after which the setting is carried out almost blindly, since there is no place to install a second pressure gauge.

For safety reasons, it is not recommended to set the pressure of the thermostat beyond 1-6 atm! Subject to the use of devices with a stronger bellows, the maximum range can be raised to 8-10 atm, which is usually sufficient for most applications.

Capillary tube should only be cut after you are sure of the effectiveness of the relay. After releasing the refrigerant inside, the end of the tube is placed inside the relief valve and soldered.

The next step is to connect the self-made pressostat for the compressor to the control circuit. For this purpose, the relay is fixed to the control board with a nut. A lock nut is screwed onto the stem thread, thus making it possible to correct the air pressure.

Bearing in mind that the contact group of thermal relays from any refrigerator is designed to work with large currents, they can commutate quite powerful circuits, such as secondary circuits when working with a compressor motor.

Pressure switch: function and principle of operation

Pressostat is a device (actuator), by means of which the compressor motor is switched on or off. It is mounted on the reservoir (receiver) and connected to its check valve and compressor head.

The pressostat provides automatic operation of the entire product. It is used to maintain the required air pressure in the air reservoir.

The principle of operation of such a relay is to use a normally closed contact in the electric motor control circuit. Depending on the air pressure in the pneumatic system, the circuit is either closed or opened. This starts the motor when the air pressure is insufficient or de-energizes it when the maximum value is reached.

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The operating mechanism of the pressostat uses springs of differing stiffness, which react differently to changes in the air pressure in the air reservoir. The operating mechanism is actuated by the elastic deformation forces of the springs as a result of the pressure of the compressed air in the air reservoir. This causes the motor power contact to close or open.


The pressostat is generally included (maximum setting):

Pressure relief valve. Important element in pressostat kit

Each of these devices has a specific function:

  • The relief valve opens when the motor stops and relieves the pressure from the pneumatic line. The next time the electric motor is switched on and accelerates, the check valve closes, which facilitates starting the whole device from the OFF position.
  • A thermal motor protection relay limits the amount of current in the windings. A special regulating element is used to set the permissible current value, exceeding which the motor will be switched off.
  • A mechanical switch enables automatic operation of the product (AUTO position) and allows forced shutdown of the motor (OFF position).
  • A safety valve is triggered if the compressor pressure switch fails and performs emergency dumping of compressed air from the air reservoir, preventing an increase in pressure over the permissible value.

Wiring diagram

Existing air pressure switches for 220 V compressor are used in various load circuits.

  • In the case of single-phase electric motor use the pressostat with two contact groups, designed to work in a network of 220 V.
  • If a three-phase motor is used, a relay with an operating voltage of 380 V with three contact groups is used.

WARNING! It is not recommended to use a single-phase air pressure switch (220V) to connect a three-phase motor.

The pressostat is connected to the electrical circuit of the compressor using special contactors (connectors) built into its body.

Connection flanges

Connect the pressostat to the receiver using a threaded flange with a standard 1/4 inch female thread. Many pressure switches are equipped with a 4-way flange that allows up to three auxiliary devices, for example, to be connected if necessary:

If it is not necessary to connect additional appliances, the flanges are closed with special plugs.

IMPORTANT: Threaded holes on the flanges are 3/8 or 1/2 in. The accessories must also be adequately threaded.


The compressor pressure switch is mounted directly on the compressor tank (1/4-inch threaded center flange). If necessary, install additional devices through the loose flanges. If there is no need in additional devices, the threaded holes of flanges are closed by special stopping plugs.

The compressor motor ON/OFF control circuit is connected to the pressure switch contacts.

WARNING! If the load current exceeds the relay contact rating, a mains contactor (magnetic contactor) must be used for switching.


No adjustment is necessary on commercially available pressostats. However, during compressor operation situations may occur, when it is necessary to change the thresholds of its actuator. Procedure for carrying out the adjustment work:

  • Determine the range of variation of compressed air pressure.
  • Disconnect the product from the mains.
  • Remove the top cover of the pressostat.
  • Set the necessary values of the thresholds of the relay with two special spring-loaded adjustment screws under the cover. The value of the set values is monitored with a manometer.
  • Adjustment of the pressostat upper threshold, at which the electric motor is switched off, is carried out with the help of the adjusting screw, marked with the symbol “P”. To change the threshold of the actuator, turn the screw in the direction of the arrow corresponding to the designations “” and “-“.
  • To set the lower pressure switch threshold, at which the motor will automatically start, turn the second adjusting screw with the symbol “5P” in the direction of the signs “” and “-“.
  • Replace the top cover of the air pressure switch.
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the air pressure regulator for the compressor with own hands

Decided to share how I assembled my compressor and what difficulties I encountered.

I decided to assemble the compressor, because I decided to switch to painting models with an airbrush. And t.к. without a compressor airbrush will not blow and costs normal from 5 thousand koi was not available, decided to do with their own hands.

The compressor from the refrigerator was lying in the garage for over 3 years, and frankly thought that it would not work. But after a test run was surprised at how quiet it is. The starting device was attached directly to the compressor, so that there was no problem with connecting to the mains.

Still to be found

  • Fire extinguisher (receiver)
  • Pressure switch (to automatically turn on when the pressure is low, and turns off when the maximum pressure)
  • A water separator filter (preferably two.) an air filter for air inlet to the compressor (gasoline filter is ok)
  • Pressure regulator with pressure gauge (outlet pressure adjustment)
  • Manometer (monitor the pressure in the receiver (fire extinguisher)
  • Fitting (adapters 1/4, 1/2, tees, etc.).д. all sorts of minor things that are not difficult to find at any market)
pressure, regulator, compressor, hands

Total needed 1600 with the account that the compressor and a fire extinguisher I got in for free. Installation with all components took about 2 hours with adjustment.

What were the difficulties

350gr.) When sawed off the hole (it’s always sealed) I forgot where it is. There are always 3 of them in the compressor. (air intake, air outlet and oil fill). If it is not difficult to find the air outlet, the oil filling, at first, was stumped. When searching for this information on the Internet from various sources, people specify that the fill oil can be any tube on the compressor except for air output, which I did for 2 months no problems all works. I used ESSO 5-50 synthetic oil.

Another question as to how to connect the compressor output to the fire extinguisher itself (receiver). People usually thread the body of the fire extinguisher, but how to thread it if it is not cast as they were before and it is welded and the sheets are too thin to thread, have too little thickness. Solved this problem with an ordinary soldering iron, the thin walls are easy to solder flux. Drilled a hole. д.

10mm, stripped this place to metal, tinned, inserted the pre-shrunk and tinned tube (used in faucets for the sink (water connection) or in the air conditioning) and all sealed, on the other hand ordinary collet clamp is 3 copecks in any market. This connection held pressure of 6 atmospheres, I did not try further, because the limit on the pressure switch is set at 5.5 atmospheres, switching at 2.8 atmospheres (adjustment of the pressure switch is simple: two screws one set the level of the middle of the range of work such as I need the range, so the middle of this range is somewhere in the 4.

2 atm, and the second one adjusts the on/off range, t.е. it can be expanded, for example, not as I have, and make for example from 2 to 6 atmospheres or narrow from 3 to 4 atmospheres. The water separator filter must be always placed vertically t.к. It has a place to drain the moisture.

Problems with the purchase

I have been looking for a long time, the pressure regulator, I am from Moscow. The crux of the problem, you can buy in an online store and find in stock turned out to be difficult, so even for delivery should be about 300 pay. At a price of 350 for the regulator itself, it was not very interesting. In general, I bought in a shop in Praktik, the last one in the showcase.

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The filters water separator bought in an auto store in a department where they sell everything for painting (compressors, spray guns and connectors with hoses. Do not confuse this is not the department where they sell putty, paint and polish. When working with an airbrush is very convenient to regulate the pressure with the regulator in our case is important.

The compressor is practically does not warm up when painting a surface with half a sheet of A4 turned on once, heaped up the pressure to the maximum and you can paint another, the same surface. When turning on the receiver smoothes all the jolts and drops, the painting during the power on does not affect.

What you have to pay attention to

  • Fire extinguisher not less than 5 liters and preferably cast not welded
  • the tube for air into the receiver is better to be placed farther away from the receiver outlet and lower to the bottom of the fire extinguisher (this will improve oil and moisture separation and reduce the shock of the compressor in the systems). When I use this circuit, when draining the water separator, I did not notice the presence of oil, only moisture.
  • Don’t forget the air pressure regulator, they say the water pressure regulator is a little different.
  • The scheme is better to work out at home, then go buy all the basic elements, arrange them in a sequence of connections and record all the necessary adapters, for which you will need once again to go to the construction market.

I would be glad if someone was able to help with this article to create their own compressor. Good luck to all!


The self-made pressostat is very difficult to make. Requires sophisticated technology and excellent knowledge. The mechanism is triggered when an electric current passes through certain elements. At certain values of current they heat up and turn the unit on or off. Even with a lot of experience, such a mechanism is difficult to make. Relays from old refrigerators are used for homemade compressors.

Pressostat for the compressor wears out, working under difficult conditions, and fails. It is unprofitable and difficult to repair it. It is more profitable to just buy a new relay.There are inexpensive models. If you choose branded devices, it is better to buy a new compressor for that kind of money.

The air compressor is a versatile tool, which is needed in various repair and construction works.

Homemade pressure switch from a refrigerator

An air-powered device is safe and convenient, unlike a gasoline or electric. There are also additional devices that work with pressurized air: guns for inflating tires, painting, flushing, blowing guns, extensions and others.

With the help of the relay for the compressor the system works automatically, the necessary pressure in the receiver is constantly maintained.

Airbrush Air Pressure Regulator | Perfectly Fit | Set | Adjust PSI | Airbrush Set Up (2020 Set Now!)

The air pressure switch for the compressor is an important element of the mechanism, its component. Without it, if the compressor can work, it will not last long. And the resulting temporary result will be monstrous. The pressure at the output will be jumpy, and the electric motor will fail quickly.

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