A brief introduction of Wotech production process will let you know more about how to manufacture our air source heat pumps and how professional we are. Our products are safe, green and cost-effective.
Production Process of
Wotech Heat Pumps
Wotech Electrical Limited
PART A COMPONENTS INSPECTION
1. Titanium heat exchanger ( for pool heat pump)
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
P.S.: Water pressure for normal pool system is 2 bar only.
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.
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.
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.
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.
3. Tube in shell heat exchanger
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.
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
5.Mother board and control display
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.
6. Fan motor
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 Wotech
requirement. 100% check.
7. Flow switch
Flow switches will be connected with water and power,
set certain flow to see if they function. 100% check.
Part B Preproduction
1. Subassembly of electronic system
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.
2. Copper pipe work subassembly
Workers are welding copper pipe work
Copper pipe work subassembly ready
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.
During soldering nitrogen is blown into the pipe work to avoid soldering
residues dropping into the tubing and stuck refrigerant system.
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
High pressure and low pressure switch will be also checked if they function
3. Vacuum refrigeration system
After bubble testing system will be vacuumed for 25 minutes before being
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
Refrigerant charge equipment is calibrated
frequently by official measuring bureau and
marked with green stickers on all the measur
There are 2 different refrigerant charge system
inside R407c and R410a.
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.
5. Second leakage check on refrigerant system
It is necessary to blow away the residues of refrigerant on the heat pump
Before the second leakage check on refrigerant system.
All the soldering points and all possible weak points will be checked by gas
Freon leak detector can find
leakage of 2g/year on the
Refrigerant system. It alarms
When freon leak is found above
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
Wirings and insulations look neat
and tidy .
7. Electrical safety items testing
Each heat pump must be checked with electrical
safety items and standards:
Grounding: within 5 seconds <100 mΩ
Withstand voltage: within 3 seconds 1800V, <5mA
Insulation: 500 V, >2 MΩ
Leakage: within 2 seconds 234V <0.75mA
8. Performance testing
Each heat pump will have to be tested 30 mins for
heating and 30 mins for cooling
(if there is cooling mode) . Water flow will
Be 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.
9. Dry the heat pump
After performance testing water in the heat exchanger will be dried and blow
10. Third time leakage check on refrigeration system
After performance testing refrigerant will run through the system . If any leaks it
Would be much easier to find now.
11. Heat pump second start-up
Before packed in carton each heat pump will be connected with power to see
If 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.
12. Cleaning , labeling and accessory bag, packaging
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
Serial nr. are also marked on side
panel, fan motor, capacitor and etc, for
this we can always trace them back.
Part D ,Quality control
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.
Prepared by: Stella Yau
Date: Oct. 27th.2012