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The latest knowledge of central air-conditioning maintenance, installation and after-sales

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Author : sherry
Update time : 2020-11-25 14:57:14
Unit installation
Pipe connection
After the unit is installed in place, install the water system pipes, or connect the arranged water system pipes with the water pipes of the evaporator and condenser of the unit.
 
General requirements
1. The water inlet and outlet pipelines shall be connected according to the requirements of identification on the unit. The general regulations are as follows: the condenser water pipe goes in and out; The refrigerant connecting pipe side of evaporator is the chilled water inlet side.
 
2. The water system must be equipped with pumps with appropriate flow and lift to ensure the normal water supply of the unit. In addition to the shockproof soft joint connection, the water pump shall be connected with the unit and the water system pipeline, and its own bracket shall be set to avoid the force of the unit. Welding during installation shall avoid damage to the unit.
 
3. Install flow switches on the outlet pipes of evaporator and condenser. Interlock the flow switch with the input contact in the control cabinet. The installation requirements are as follows:
 
Both sides of the flow switch should have at least 5 times the straight pipe section of the pipe diameter; Do not install it near bends, orifice plates and valves; To prevent the flow switch from shaking, all gases in the water system should be discharged. Adjust the flow switch so that it is in the separated state when the water flow is lower than the  flow (the flow is 40% of the design flow). When the water flow meets the requirements, the water flow switch should be kept closed.
 
4. The water filter must be installed before the water inlet pipeline of the unit. The water system is designed to withstand water pressure and cannot be used under overpressure, so as to prevent damage to evaporator and condenser.
 
Warning: It is strictly forbidden to connect the pipeline with the unit before washing it clean.
Condenser piping connection

Note: A pipe shall be installed in the cooling water outlet pipeline for water discharge in winter, and a bypass pipe shall be provided at the inlet and outlet of the cooling water pipeline for pipeline cleaning and maintenance.
 
1. The cooling water piping system must be equipped with shockproof soft joint, thermometer, pressure gauge, drain valve, stop valve, water filter, non-return valve, target flow controller, etc., and then connected to the inlet and outlet water pipes of the cooling tower.
2. The water supply pipeline should be as short as possible, and the specifications of the pipeline should be determined according to the effective lift, pipeline flow and flow rate of the pump, not according to the joint specifications.
 
3. The nozzle direction of condenser can be changed according to the requirements of users. Pay attention to the following points when changing:
 
It is necessary to confirm the correct baffle position and use a new rubber sealing ring; When disassembling and assembling the end cover of the water chamber, tighten the bolts in a certain order: gently tighten the first bolt, and then gently tighten the bolt located in the direction of 180. Continue to tighten the third bolt in this order, and then gently tighten the fourth bolt which is 180 with the third bolt. And so on.
Piping connection of evaporator
1. The chilled water pipeline system must be equipped with shockproof soft joint, thermometer, pressure gauge, water filter, electronic scale remover, non-return valve, target flow controller, exhaust valve, drain valve, stop valve, expansion tank, etc.
 
2. The expansion tank should be installed 1 ~ 1.5m higher than the highest point of the system (floor-mounted constant pressure water replenishing device can also be used). The water tank capacity is about 1/10 of the total system water volume. The evaporator cylinder is equipped with water drainage and exhaust connectors.
 
3. Install thermometers and pressure gauges on straight sections of water inlet and outlet pipelines, and avoid installing them too close to bends. Each low point shall be equipped with a water drain connector to drain the remaining water in the system. Before operating the unit, connect the cut-off valve to the drain pipe and install it near the inlet and outlet joints. There should be a bypass pipe between the water inlet and outlet pipes of the evaporator, which is convenient for pipeline cleaning and maintenance. Using flexible joints can reduce the transmission of vibration.
 
4. The chilled water pipeline and expansion water tank shall be insulated, and the valve joint shall be set aside for maintenance and operation.
Electrical part of power supply
After the unit arrives at the site, it is necessary to connect the power cord to the unit control cabinet. Connect the power line to the terminals A, B, C, N and PE, and after 24 hours (the shortest time allowed), re-tighten the terminals.
 
Note: The power supply of water pump and cooling tower fan should be equipped with power supply box separately.
 
The specification of power cord connected to control cabinet shall be selected according to RLA current on nameplate. The total power supply must be equipped with a certain margin, and the recommended value is more than 1.25 ~ 1.3 times of the unit parameters. The current carrying capacity of power supply cables (wires) should be slightly larger than the  operating current of the unit, and the influence of working environment should be considered. The electric cabinet is equipped with measures for connecting the ground wire and automatically breaking the circuit, and all the power supplies provided by the user must be equipped with these measures. Large-current units should be powered by two-way power supply, but the two-way power supply wires must have the same diameter and belong to the same brand.
 
The  allowable phase voltage imbalance is 2% and phase current imbalance is 10%. The unbalanced phase voltage is more than 2%, so it must not be started.
On-site commissioning steps of water-cooled chillers
Step 1: After arriving at the site, check whether the appearance of the host is cracked or bumped, and observe whether the indication of the high and low pressure meter is normal and whether fluorine leaks.
Step 2: Check whether the power supply conforms to the three-phase five-wire system and can meet the unit load. Check whether each terminal in the electric box is fastened and whether the electric control components are defective. Measure the relative ground resistance and the resistance between the three-phase line and the ground with an insulation resistance shaking table. The correct value should be 5 megohms.
Step 3: Connect the water flow switch control line, and short-circuit the unused input interlock wiring at the terminal. It is strictly forbidden to short-circuit the used protection contacts and terminals. Control and interlocking wiring of cooling pump, freezing pump and cooling tower fan.
Step 4: After confirming that the wiring is correct, send power to observe the phase sequence and voltage value, and adjust the phase sequence if the phase error light is on; If the voltage is abnormal (380 V 10%), Party A is required to adjust the voltage. Power on and preheat after the power supply is normal.
Step 5: Observe whether the parameters of cooling water pump, chilled water pump and cooling tower and the pipe diameter match with the host computer; Whether the host and the end match. Whether the cooling water and chilled water systems are equipped with automatic water replenishment devices, and whether there are filtration devices and water treatment equipment. Filters larger than 40 meshes are installed at the water inlets of condenser and evaporator.
Step 6: Confirm whether the water system has been cleaned. If it has been cleaned, start the water pump motor and check whether the water pump motor rotates forward or backward. If reversed, adjust the phase sequence. After the phase sequence is correct, start the cooling pump, observe the pressure before and after the pump and the inlet and outlet water of the condenser, deflate the water pump during operation, and start the chilled water pump after normal operation. The whole system should deflate the chilled water carefully until it is discharged. Clean the water filter after the cooling water system and chilled water system run for 1 hour.
Step 7: Start the cooling water pump, observe the state of the touch screen running water switch, the correct state is OFF, and then start the chilled water pump, and the correct value of the touch screen running water switch is ON. If the status is broken, the water system will bleed until the water flow switch status value is flexible. Shut down any one of the pumps, and the water flow switch state will be broken. If the status is incorrect, check the water switch to ensure correct installation and correct feedback (the water flow switch should be connected to the normally open point).
(Remarks: For units receiving fluorine before leaving the factory, supply 220v voltage to the liquid supply valve and open the liquid supply valve to make the equilibrium pressure normal).
Step 8: Observe Y-δ time delay relay, the correct value is 3.5 seconds, simulate operation, and start the loading sequence: 25% solenoid valve-liquid supply valve, compressor (at the same time)-50% solenoid valve-75% solenoid valve-100% solenoid valve. Observe Y-δ startup delay time, and adjust it if it is too long or too short. Shutdown process: 100% solenoid valve-25% solenoid valve-liquid supply valve and compressor (stop at the same time).
Step 9: Make sure that the water system (cooling and freezing) runs normally. After the simulated operation is normal, the unit will be preheated for at least 8 hours. Officially start the mainframe. Pay attention to the pointers of high and low pressure meters when starting the press. At the moment of starting, the pointer of high pressure meter rotates clockwise (rises) and the pointer of low pressure meter rotates counterclockwise (lowers). On the contrary, stop the machine urgently and check the phase sequence and the connection of the press. If the phase sequence is correct, use clamp ammeter to measure the running current, and under normal circumstances, it will gradually increase, and the current value will not be greater than the value marked on the famous brand of compressor; otherwise, stop the machine to find out the reason.
Step 10: After the main engine is started (the indication of high and low pressure meter is correct), first listen to the sound of the press, whether there is abnormal sound, and if there is any abnormality, stop the machine urgently to find out the reason. After normal start-up, the exhaust temperature should rise to above 50℃ within 5 minutes under 100% load. If the exhaust temperature cannot be raised in time, wet compression will occur, so corresponding measures (adjusting the cooling water temperature) and improving the operating conditions must be taken to ensure the normal operation of the main engine.


 
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