System information

24
Check defrost thermostat
There is a liquid header with a brass distributor and feeder tube
going into outdoor coil. At the end of one of the feeder tubes,
there is a 3/8-in. OD stub tube approximately 76 mm long. The
defrost thermostat should be located on stub tube. Note that
there is only one stub tube used with liquid header, and on most
units it is the bottom circuit. The defrost thermostat (Fig. 24)
signals heat pump that conditions are right for defrost or that
conditions have changed to terminate defrost. It is a thermally
actuated switch clamped to outdoor coil to sense its tempera-
ture. Normal temperature range is closed at -1°C ± 2 K and
open at 27°C ± 3 K.
NOTE: The defrost thermostat must be located on the liquid
side of the outdoor coil on the bottom circuit and as close to
the coil as possible.
Troubleshooting
Refer to the troubleshooting chart (Table 9) for troubleshooting
information.
Start-up checklist
Use the start-up checklist to ensure proper start-up procedures
are followed.
Heat pumps with Puron - quick reference guide
Puron refrigerant operates at 50-70% higher pressures than R-22.
Be sure that servicing equipment and replacement components
are designed to operate with Puron. Puron refrigerant cylinders
are rose-coloured.
• Puron refrigerant cylinders manufactured prior to March 1,
1999 have a dip tube that allows liquid to flow out of the
cylinder in upright position. Cylinders manufactured on
March 1, 1999 and later DO NOT have a dip tube and
MUST be positioned upside down to allow liquid to flow.
• Recovery cylinder service pressure rating must be 2758 kPa.
DOT 4BA400 or DOT BW400.
• Puron systems should be charged with liquid refrigerant.
Use a commercial metering device in the manifold hose.
• Manifold sets should be 5171 kPa high-side and 1379 kPa
low-side with 3585 kPa low-side retard.
• Use hoses with 5171 kPa service pressure rating.
• Leak detectors should be designed to detect HFC refrigerant.
• Puron, as with other HFCs, is only compatible with POE oils.
• Vacuum pumps will not remove moisture from oil.
• Only use factory specified liquid-line filter driers with
rated working pressures no less than 4137 kPa.
• Do not install a suction-line filter drier in liquid line.
• POE oils absorb moisture rapidly. Do not expose oil to
atmosphere.
• POE oils may cause damage to certain plastics and roofing
materials.
• Wrap all filter driers and service valves with wet cloth
when brazing.
• A Puron liquid-line filter drier is required on every unit.
• Do not use an R-22 TXV.
• Never open system to atmosphere while it is under a vacuum.
• When system must be opened for service, break vacuum
with dry nitrogen and replace filter driers.
• Do not vent Puron into the atmosphere.
• Observe all warnings, cautions, and bold text.
• Do not leave Puron suction line driers in place for more
than 72 hours.
High flow valves
Located on the compressor hot gas and suction tubes are high
flow valves. Large black plastic caps distinguish these valves
with O-rings located inside the caps. These valves cannot be
accessed for service in the field. Ensure the plastic caps are in
place and tight or the possibility of leakage could occur.
System information
Phase monitor control
1. 3-phase scroll compressors are rotational sensitive
2. A flashing LED on phase monitor (Fig. 23) indicates
reverse rotation.
3. This will not allow contactor to be energised.
4. Disconnect power to unit and interchange 2 field wiring
leads on unit contactor.
Follow these steps to properly start up the system:
1. Fully back seat (open) liquid and vapour tube service
valves.
2. Unit is shipped with valve stem(s) front seated (closed)
and caps installed. Replace stem caps after system is
opened to refrigerant flow. Replace caps finger-tight and
tighten with wrench an additional 1/12 turn for back-
seating valves (male square stem).
3. Close electrical disconnects to energise system.
4. Set room thermostat desired temperature. Be sure set point
is below indoor ambient temperature.
5. Set room thermostat to COOL and fan control to ON or
AUTO mode, as desired. Operate unit for 15 minutes.
Check system refrigerant charge.
Sequence of operation
Turn on power to indoor and outdoor unit. Transformer is
energised. On a call for cooling, thermostat make circuits R-Y
and R-G. On three phase models with scroll compressors, the
units are equipped with a phase monitor (Fig. 23) to detect if
the incoming power is correctly phased for compressor
operation. If the phasing is correct, circuit R-Y energises
contactor, starting outdoor fan motor and compressor circuit.
R-G energises indoor unit fan relay, starting indoor fan motor
on high speed.
NOTE: If the phasing is incorrect, the contactor will not be
energised. To correct the phasing, interchange any two of the
three power connections on the field side.
When the thermostat is satisfied, its contacts open, de-energising
contactor and fan relay. Compressor and motors stop. If indoor
unit is equipped with an off-delay circuit, the indoor fan can be
run up to an additional 120 seconds to increase the system
efficiency.
Loss-of-charge switch
The loss-of-charge switch is a protective device wired into
control circuit (low voltage). It shuts off the compressor if
abnormally low pressures are present in the refrigeration circuit.
NOTE: Because these switches are attached to refrigeration
system under pressure, it is not advisable to remove this
device for troubleshooting unless you are reasonably certain
that a problem exists. If switch must be removed, remove and
recover all system charge so that pressure gauges read 0 kPa.
Never open system without breaking vacuum with dry nitrogen.