Please explain why KT-602-1 describes the simplest parallel connection of the crankcases of two compressors with a pipe for equalizing the oil level without using an oil level regulator, and nothing is said about equalizing the pressure of gases, i.e. a pipe is supposed to be mounted above the oil level and connects two compressors while equalizing the pressure of the gases. And please answer how reliable the control will be consistent work compressors without "logic" by means of RD, i.e. one of the compressors will always turn on first and therefore work more. Thank you!
07 07 2012 // Nail Alekperov
Answer:
Are you sure that you saw this scheme in? This manual is for parallel connection of compressors of the OCTAGON series. For them, connecting the crankcases with any tubes is generally not desirable.
By the way, this manual has already been updated to KT-602-2 Parallel compounding of OCTAGON compressors.
Please send the diagram you are interested in. Let's discuss.
It is necessary to connect two 4DC-5.2 compressors in one unit for a negative chamber (R404a) consumer one point (evaporator) The customer does not want to equip the compressor with oil level regulators and other accessories. lotions (the beetle is still the same), how to be and how to get out of this situation, thank you in advance
09 07 2012 // Nail Alekperov
Answer:
The most suitable solution for your installation is the 44DC-10.2 tandem, or even an already assembled unit based on the LH124/44DC-10.2 tandem
If your installation has a small length of pipes, there are all the necessary slopes and oil lifting loops, the evaporator is regularly defrost, then, even if parallel connection two 4DC-5.2, there is no need to install an oil separator, no oil level control systems in the crankcases, nor any equalization pipes connecting the crankcases of the compressors. It is only necessary to make a symmetrical suction manifold, see instructions.
Re(1): Parallel connection
Forgive me for importunity, but what about when one of the compressors is idle? Do you think that with the correct symmetry of the manifold, etc., I can avoid the carryover of oil from an idle compressor? The length of the pipeline is only 4 meters, the controller with the auto-defrost function, it was supposed to install an oil separator at the discharge and a liquid separator at the suction, the serial switching on of the compressors is controlled by the RD, the switching on and off of the fans on the condenser is also via the RD. Thanks to
09 07 2012 // Nail Alekperov
Answer:
Yes, both in tandem and in parallel, with the correct symmetry of the collector, when one of the compressors is idle, no oil is carried away from it - where?
If the evaporator is correctly selected, i.e. its performance corresponds to that of the compressor if regular defrosts of the evaporator are carried out, i.e. its complete freezing is not allowed; A suction fluid accumulator does not need to be installed.
Oil circulates through the system - there is nothing wrong with that. In your installation, a short and unbranched circuit, i.e. oil can't go anywhere. Why then spend money on an oil separator, an oil receiver and a system for regulating oil levels in the crankcases of compressors?
Re(3): Parallel connection
On your advice, the guys and I assembled a unit of two Bitzer 7.2 compressors without oil level regulators, and the oil anyway goes somewhere, especially from the first compressor, the suction pressure is high 2.5 per temperature regime we don’t go out, it seems to me that the evaporator is flooding with oil ?! I'm attaching a photo, please help!
18 07 2012 // Nail Alekperov
Answer:
Thanks for your photo
Your intake manifold looks pretty. And the injection turned out to be terrible!
Example correct location for discharge nozzles see in the photo and in the answer to the question
Budget models air compressors are not always equipped with a pressure switch, since similar devices are installed on the receiver. Therefore, manufacturers of this equipment believe that visual control of the pressure developed by the compressor based on the readings of pressure gauges is quite enough. However, at long-term work, in order to avoid overheating of the engine, it is advisable to install a pressure switch on the compressor. Then the drive will turn on and off automatically.
The device and diagram of the pressure switch to the compressor
All compressor pressure switches are divided into two types:
- Switching off the compressor motor when the air pressure in the network exceeds the permissible limits (such designs are called normally open);
- Including the compressor motor when the pressure in the network drops below the permissible limits (such designs are called normally closed).
The actuating element of the pressure switch for the compressor are springs, the compression force of which is changed by a special screw. In the factory settings, the compression force of the springs is usually set to a pressure in the pneumatic network from 4 to 6 atm, as reported in the user manual. Since the rigidity and flexibility of spring elements depend on the ambient temperature, all designs of industrial pressure switches are designed for stable operation in the temperature range from -5 to +80ºС.
Selection of compressors with pressure switch
The design of the pressure switch includes two mandatory subassemblies - an unloading valve and a mechanical switch. The unloading valve is connected to the air supply line between the receiver and the compressor. It controls the operation of the electric motor. If the compressor drive is turned off, then the unloading valve on the receiver dumps the excess compressed air(up to 2 atm) into the atmosphere, thereby unloading the moving parts of the compressor from the excess force that they will have to develop when the compressor is turned on again. This prevents a critical overload of the engine in terms of the permissible torque. When the unloaded motor is started, the valve closes and does not overload the actuator.
The mechanical switch performs the stand by function, preventing accidental starting of the engine. After pressing the button, the drive is switched on and the compressor operates in automatic mode. When the button is turned off, the compressor motor will not start even if the pressure in the pressure pneumatic network is lower than required.
In order to increase the safety of work, industrial designs of the compressor pressure switch are also equipped with a safety valve. It is useful, for example, in case of a sudden stop of the engine, piston breakage or other abnormal situation.
Optionally, a thermal relay can also be mounted in the pressure switch housing, with the help of which the current strength in the primary circuit is monitored. If for some reason this parameter increases, then, in order to avoid overheating and subsequent breakdown of the windings, the thermal relay will turn off the electric motor.
How to connect and set up a pressure switch?
In general circuit diagram compressor unit the pressure switch is located between the unloader valve and the secondary motor control circuit. Typically, the pressure switch is equipped with four threaded heads. One of them is designed to connect the device to the receiver, and the second - to connect the control pressure gauge. One of the other connectors can be used to install safety valve, and on the remaining one a regular threaded plug with a ¼ inch thread is placed. The presence of a free connector allows you to install a control pressure gauge in a place convenient for the user.
The pressure switch is connected in the following sequence:
- Attach the device to the unloading valve of the receiver.
- Install a control pressure gauge (if it is not necessary, then the threaded inlet is also plugged).
- Connect to the terminals of the motor control circuit terminals (taking into account the selected connection scheme - to normally open or normally closed contacts). In case of voltage fluctuations in the network, the connection is not made directly, but through network filter. This is also required when the power for which the contacts are rated exceeds the power of the motor load current.
- If necessary, adjust the relay to the desired values of compressed air pressure with adjusting screws.
When connecting, it is necessary to check whether the voltage in the network corresponds to the factory settings of the compressor pressure switch. For example, in a three-phase network with a voltage of 380 V, the relay must have a three-contact group (two phases + zero), and for a voltage of 220 V - two-contact.
The adjustment is made when the receiver is not less than two-thirds full. To perform this operation, the relay is disconnected from the mains, and, having removed top cover, change the compression of the two springs. Adjusting screw on which the spring axis is mounted larger diameter, is responsible for the upper limit of the working pressure. On the board next to it, the generally accepted symbol for pressure (P - pressure) is usually indicated, and the direction of rotation of the screw is also indicated, with which this pressure decreases or increases. The second, smaller, adjusting screw is responsible for setting the required pressure range (difference). It is labeled symbolΔP, and is also provided with a direction of rotation indicator.
To reduce setting time, in some designs the adjusting screw to change upper limit pressure is discharged outside the pressure switch housing. The control of the result is carried out according to the readings of the manometer.
DIY pressure switch
With known skills, as well as the presence of a working thermal relay from a decommissioned refrigerator, the pressure switch can be made independently. True, he will not have special practical capabilities, since the ability to hold upper pressure is limited by the strength of the rubber bellows.
Thermal switches of the KTS 011 type are most convenient for conversion into a compressor pressure switch, since they have a strictly reverse sequence of their operation: with an increase in temperature in cold store the relay turns on, and when it goes down, it turns off.
The essence and sequence of the work is as follows. After opening the cover, the location of the desired group of contacts is established, for which it is enough to ring the circuit. First, the connection of the thermostat to the compressor is being finalized. To do this, the outlet pipe, together with a control pressure gauge, is connected to the unloading valve, and the contact groups are connected to the terminals of the electric motor circuit. An adjustment screw will be found under the thermostat cover. When the compressor is turned on (the receiver must be filled with no more than 10 ... 15% of its nominal volume), the screw is sequentially rotated, controlling the result according to the pressure gauge. To set the lower position (determining minimum pressure air) you will have to gradually move the stem of the front button. To do this, the cover is put in place, and the adjustment is actually done blindly, since there is nowhere to connect the second pressure gauge.
For safety reasons, the pressure adjustment range using such a thermal switch cannot be more than 1 ... 6 atm, however, using devices with a stronger bellows, you can increase the upper range to 8 ... 10 atm, which in most cases is quite enough.
After checking the operability of the relay, the capillary tube is cut off and the refrigerant located there is released. The end of the tube is soldered into the unloading valve.
Next, work is carried out to connect a home-made pressure switch to the compressor control circuit: with the help of a nut, the relay is connected to the control board, a thread is made on the stem, and a lock nut is screwed on, turning which, you can adjust the limits of air pressure change.
Considering that the contact group of any thermal relay from the refrigerator is designed for sufficiently large currents, in this way it is possible to switch circuits of significant power, including - and secondary circuits compressor motor control.
