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order. Hoses shall be complete with leak-free disconnect cou-
plings and in good condition.
The recovered refrigerant shall be processed according to local
legislation in the correct recovery cylinder, and the relevant waste
transfer note arranged. Do not mix refrigerants in recovery units
and especially not in cylinders.
If compressors or compressor oils are to be removed, ensure that
they have been evacuated to an acceptable level to make certain
that flammable refrigerant does not remain within the lubricant.
The compressor body shall not be heated by an open flame or oth-
er ignition sources to accelerate this process. When oil is drained
from a system, it shall be carried out safely.
Air Coil Fan Motor Removal
CAUTION
Before attempting to remove fan motors or motor mounts,
place a piece of plywood over evaporator coils to prevent coil
damage.
Disconnect motor power wires from motor terminals before motor
is removed from unit.
1.
Shut off unit main power supply and apply lock-out/tag-out.
2.
Loosen bolts on mounting bracket so that fan belt can be
removed.
3.
Loosen and remove the 2 motor mounting bracket bolts on
left side of bracket.
4.
Slide motor/bracket assembly to extreme right and lift out
through space between fan scroll and side frame. Rest motor
on a high platform such as a step ladder. Do not allow motor
to hang by its power wires.
TROUBLESHOOTING
When troubleshooting problems with a WSHP, consider the
following.
UNIT PROTECTION MODULE (UPM)
All Carrier WSHPS are equipped with a 24V low voltage control
circuit. Units are selectable to be provided with no controls for
control via a field installed thermostat or 3rd party DDC or to be
provided with a factory installed Carrier i-Vu DDC for advanced
equipment control and monitoring. Regardless of the selection all
units will be equipped with a unit protection module. The UPM
board should be one of the first areas to start with troubleshooting
an equipment issue. See Fig. 20. Refer to Step 9, UPM Configura-
tion and Alarms.
Thermostatic Expansion Valves
Thermostatic expansion valves (TXV) are used as a means of me-
tering the refrigerant through the evaporator to achieve a preset su-
perheat at the TXV sensing bulb. Correct superheat of the refriger-
ant is important for the most efficient operation of the unit and for
the life of the compressor. Refer to Fig. 50 for refrigerant diagram.
Packaged heat pumps typically use one bi-flow TXV to meter re-
frigerant in both modes of operation. When diagnosing possible
TXV problems it may be helpful to reverse the refrigerant flow to
assist with the diagnosis.
Geothermal and water source heat pumps are designed to operate
through a wide range of entering-water temperatures that will
have a direct effect on the unit refrigerant operating pressures.
Therefore, diagnosing TXV problems can be difficult.
TXV FAILURE
The most common failure mode of a TXV is when the valve fails
while closed. Typically, a TXV uses spring pressure to close the
valve and an opposing pressure, usually from a diaphragm, to
open the valve. The amount of pressure exerted by the
diaphragm will vary, depending on the pressure inside of the
sensing bulb. As the temperature of and pressure within the bulb
decreases, the valve will modulate closed and restrict the refrig-
erant flow through the valve. The result is less refrigerant in the
evaporator and an increase in the superheat. As the temperature
at the bulb increases the diaphragm pressure will increase, which
opens the valve and allows more refrigerant flow and a reduction
in the superheat.
If the sensing bulb, connecting capillary, or diaphragm assembly
are damaged, pressure is lost and the spring will force the valve to
a closed position. Often, the TXV will not close completely so
some refrigerant flow will remain, even if there is inadequate flow
for the heat pump to operate.
The TXV sensing bulb must be properly located, secured, and in-
sulated as it will attempt to control the temperature of the line to
which it is connected. The sensing bulb must be located on a dedi-
cated suction line close to the compressor. On a packaged heat
pump, the bulb may be located almost any place on the tube run-
ning from the compressor suction inlet to the reversing valve. If
the bulb is located on a horizontal section, it should be placed in
the 10:00 or 2:00 position for optimal performance.
Use caution when tightening the strap. The strap must be tight
enough to hold the bulb securely but caution must be taken not
to over-tighten the strap, which could dent, bend, collapse or
otherwise damage the bulb.
The bulb must be secured to the pipe using a copper strap. The use
of heat transfer paste between the bulb and the pipe will also help
ensure optimum performance.
The bulb must also be properly insulated to eliminate any influ-
ence on valve operation by the surrounding conditions. Cork tape
is the recommended insulation as it can be molded tight to the
bulb to prevent air infiltration.
Causes of TXV Failure
The most common causes of TXV failure are:
1.
A cracked, broken, or damaged sensing bulb or capillary can
be caused by excessive vibration of the capillary during ship-
ping or unit operation.
If the sensing bulb is damaged or if the capillary is cracked or
broken, the valve is considered failed and must be replaced.
Replacement of the TXV "power head" or sensing bulb, cap-
illary, diaphragm assembly is possible on some TXVs. The
power head assembly screws onto most valves, but not all are
intended to be replaceable. If the assembly is not replaceable,
replace the entire valve.
2.
Particulate debris within the system can be caused by several
sources including contaminated components, tubing, and ser-
vice tools, or improper techniques used during brazing opera-
tions and component replacement.
Problems associated with particulate debris can be com-
pounded by refrigerant systems that use POE (polyol ester
oil). POE oil has solvent-like properties that will clean the
interior surfaces of tubing and components. Particulates can
be released from interior surfaces and may migrate to the
TXV strainer, which can lead to plugging of the strainer.
3.
Corrosive debris within the system may happen after a fail-
ure, such as a compressor burn out, if system was not prop-
erly cleaned.
4.
Non-condensables may be present in the system. Non-
condensables includes any substance other than the refriger-
ant or oil such as air, nitrogen, or water. Contamination can be
the result of improper service techniques, use of contami-
nated components, and/or improper evacuation of the system.
74
CAUTION
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