Wshp Open Controller; Thermostatic Expansion Valves - Carrier AQUAZONE 50PTH Installation And Service Instructions Manual

90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
0.0 20.0 40.0
Temperature (degF)
Fig. 37 — Thermistor Nominal Resistance
WSHP Open Controller —
troller option, the 100 most recent alarms can be viewed using
6
the BACview alarm status and alarm history.
To view the alarms:
1. Navigate to the Alarm Status screen from the Home
screen using the arrow softkeys. The screen will display
the current alarm status, either normal or Alarm, and al-
low for scrolling through the unit's alarm status.
2. From the Alarm Status screen, press the Alarm softkey to
view the 100 most recent alarms which are labeled with
date and time for easy reference.
NOTE: Active faults can be viewed by scrolling down,
these faults indicate a possible bad sensor or some condi-
tion which may not merit an alarm.
3. To view alarms which have been corrected, scroll down
through the Alarm screen to Return Top Normal screen.
NOTE: Alarms are automatically reset once alarm con-
dition has been corrected.
See Table 32 for possible alarm cause and solution.
Thermostatic Expansion Valves —
ic expansion valves (TXV) are used as a means of metering the
refrigerant through the evaporator to achieve a preset superheat
at the TXV sensing bulb. Correct superheat of the refrigerant is
AIRFLOW
(°F)
THERMISTOR
CONDENSATE
OVERFLOW
LEGEND
COAX — Coaxial Heat Exchanger
Airflow
Refrigerant Liquid Line Flow
60.0 80.0 100.0 120.0 140.0
With the WSHP Open con-
Thermostat-
AIR
COIL
AIRFLOW
(°F)
EXPANSION
VALVE
FP2 FP1
LIQUID
(CO)
LINE
AIR COIL
WATER
FREEZE
COIL
PROTECTION
PROTECTION
Fig. 38 — FP1 and FP2 Thermistor Location
important for the most efficient operation of the unit and for the
life of the compressor.
Packaged heat pumps typically use one bi-flow TXV to me-
ter refrigerant in both modes of operation. When diagnosing
possible TXV problems it may be helpful to reverse the refrig-
erant 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 oper-
ating 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 refrigerant 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 dia-
phragm 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 inade-
quate flow for the heat pump to operate.
The TXV sensing bulb must be properly located, secured,
and insulated as it will attempt to control the temperature of the
line to which it is connected. The sensing bulb must be located
on a dedicated suction line close to the compressor. On a pack-
aged heat pump, the bulb may be located almost any place on
the tube running 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.
COAX
WATER IN WATER OUT
46
CAUTION
SUCTION
COMPRESSOR
DISCHARGE