Production Process of Wotech Heat Pumps

Wotech Electrical Limited

Refrigerant water leakage check:

Connect the heat exchanger with water pipes and charge water pressure up to 4 bar to see if water leaks from the PVC shell. 100% check on every heat exchanger with 4 bar water pressure and 6 bar as random check on some pieces.P.S.: Water pressure for normal pool system is 2 bar only.

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PART A COMPONENTS INSPECTION

1. Titanium heat exchanger ( for pool heat pump)

A round green QC passed sticker will be put on the heat exchanger to show this is QC passed.A green square sticker will put on the heat exchanger to show this passed 6 bar random check. Flow switches been checked before they are installed on the heat exchangers so green stickers are also on each flow switch here.

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Refrigerant circuit leakage check:

Titanium heat exchangers are kept at high pressure of nitrogen in the titanium coil inside for 48 hours to check refrigerant circuit leakage before being assembled, this is 100% check.

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• After 48 hours workers will unscrew the gas valve to check if any gas pressure inside the titanium coil to find the leaks. 100% check. Those fail will be rejected to suppliers.

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2.Evaporator

Weld the evaporator with the refrigerant distributing copper pipes (one side blocked)

Charge 30 bar gas pressure (nitrogen) into the evaporator and drop it into the water to find leaks. 100% check.

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• Connect each shell in tube heat exchanger with water pipes and charge 6 bar water pressure to see if any leaks on copper pipes inside the heat exchanger. 100% check.

3. Tube in shell heat exchanger

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• Pressure gauges are treated the same• for 72 hours with notes marking pressure status. Leakage can be

easily found during the process. 100% check.• Those which pass the test will be put green QC passed stickers on

the back.

4.Pressure gauges

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• All mother boards and control displays will be connected with electricity, they would be tested under big range of electricity fluctuation– 177 volt to 264 volt for 72 hours. Electronic components with poor quality will easily fail in this test. 100% check.

5.Mother board and control display

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• All fan motors are to be checked by this equipment, it shows main phase current, vice phase current and etc, make sure if the specification meets Wotechrequirement. 100% check.

6. Fan motor

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7. Flow switch

• Flow switches will be connected with water and power, set certain flow to see if they function. 100% check.

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Part B Preproduction

1. Subassembly of electronic system

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• Electronic system is built QC will check the wiring connections. Different bulbs standing for compressor, water pump, fan motor, 4-way valve and etc will be on only when the wiring is correct. QC will also check if the program is written per customer’s request. 100% check.

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2. Fan motor subassembly

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2. Copper pipe work subassembly

Workers are welding copper pipe work Carefully.

Copper pipe work subassembly readyfor production.

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Part C ,Production

1. Building refrigeration system

When all important components are checked and QC passed they would be built on the heat pumps. first step is to build refrigeration system, compressor, evaporator, condenser and copper pipe work.

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During soldering nitrogen is blown into the pipe work to avoid soldering residues dropping into the tubing and stuck refrigerant system.

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2. First leakage check on refrigeration system

Refrigeration system will be charged with nitrogen when bubble testing starts. Soap-subs will be brushed on all the soldering points to check if any leakage. This is the first time leakage check on refrigeration on production line. High pressure and low pressure switch will be also checked if they function or not.

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After bubble testing system will be vacuumed for 25 minutes before being charged refrigerant.

3. Vacuum refrigeration system

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4. Refrigerant charge

Refrigerant charge equipment will first check the heat pump refrigeration system is vacuumed well enough to reach the set Standard before it charges refrigerant , or would give alarm and stop charging.

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Refrigerant charge equipment is calibrated frequently by official measuring bureau and marked with green stickers on all the measur-ing components.There are 2 different refrigerant charge system inside R407c and R410a.

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• There are scale indication calibrators which enable it to to make sure at different ambient temperature the right volume is charged.

• To make sure the refrigerant always work well after charging the refrigerant by this equipment the first unit of same model of the order will be checked the volume by electronic weight. If the volume is correct production will be proceeded on the rest heat pump.

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It is necessary to blow away the residues of refrigerant on the heat pumpBefore the second leakage check on refrigerant system.All the soldering points and all possible weak points will be checked by gasSniffer equipment.

5. Second leakage check on refrigerant system

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Freon leak detector can findleakage of 2g/year on the Refrigerant system. It alarms When freon leak is found above 2 g/year.

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6. Connect electronic system to refrigerant system

Wirings between mother board and components for compressor, fan motor,4-way valve, high & low pressure switches, sensors and etc must be connected properly.

Wirings and insulations look neat and tidy .

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7. Electrical safety items testing

Each heat pump must be checked with electrical safety items and standards:

A. Grounding: within 5 seconds <100 mΩB. Withstand voltage: within 3 seconds 1800V, <5mAC. Insulation: 500 V, >2 MΩD. Leakage: within 2 seconds 234V <0.75mA

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Each heat pump will have to be tested 30 mins for heating and 30 mins for cooling (if there is cooling mode) . Water flow willBe fixed, sensors will be installed on important positions to check if heat pump performs as designed. All test results will be marked on the unique product ID check list. Those which does not perform well enough will be taken off from production line for investigation.

8. Performance testing

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9. Dry the heat pump

After performance testing water in the heat exchanger will be dried and blowaway.

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After performance testing refrigerant will run through the system . If any leaks it Would be much easier to find now.

10. Third time leakage check on refrigeration system

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11. Heat pump second start-up

Before packed in carton each heat pump will be connected with power to seeIf all wirings are still in good contact. It is aware that when the heat pump is Dried out the water, wirings is got loose and in bad contact.

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12. Cleaning , labeling and accessory bag, packaging

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13. Heat pump ready for loading

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14. Product traceability

Each heat pump has its own product ID check list with serial nr. on right upper corner during the whole production. All the process are printed and to be marked if they are properly done. After the heat pump is packed QC will keep all these check list for filing and future reference. Serial nr. are also marked on side panel, fan motor, capacitor and etc, for this we can always trace them back.

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There is a product ID check list with each unit marking down all the process of the unit, each step will have 3 persons checked and marked on the sheet as a record, if problems found during production remarks would be written on the sheet and products sent back to be reworked and solve the problem until everything is ok.

We have technical operation instruction at each stage of the production line to instruction workers how to meet our requirements of quality and workmanship.

Part D ,Quality control

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The EndThank you.

Prepared by: Stella Yau

Date: Oct. 27th.2012