Carrier 50TCQD17-D24 Service And Maintenance Instructions page 10

Fig. 15 - - Heat Pump Accutrol — Flow as Condenser
Function/Entering Second Pass
DFT Location
(Outdoor Coils only)
Fig. 16 - - Heat Pump Accutrol— Flow as Condenser
Function/ Exiting Subcooler Pass
Each liquid line has a check valve to prevent back- - flow
through the liquid line in its opposite mode. This ensures
correct flow direction through the filter driers and the
strainers preventing emptying of off- - mode liquid lines
into the evaporator- - function coil circuits.
Reversing Valve and Check Valve Position
See Fig. 17 on page 11.
Table 1. Cooling Mode (each circuit)
Component
Reversing Valve
Check Valve CV--- 1
Check Valve CV--- 2
Check Valve CV--- 3
Table 2. Heating Mode (each circuit)
Component
Reversing Valve
Check Valve CV--- 1
Check Valve CV--- 2
Check Valve CV--- 3
To
Condensing
Circuit
From
Transfer
Header
C09231
From
Subcooler
Circuit
To
Liquid
Line
C09232
Status/Position
Energized
Closed
Open
Closed
Status/Position
De--- energized
Open
Closed
Open
Table 3. Defrost Mode
A04--- A07 and D08--- D09/Circuit 2:
Component
Defrost Thermostat
Outdoor Fan(s)
Reversing Valve
Check Valve CV--- 1
Check Valve CV--- 2
Check Valve CV--- 3
Troubleshooting Refrigerant Pressure
Problems and Check Valves
Refer to Fig. 12, on page 11, and the Cooling Mode and
Heating Mode tables (Tables 1 and 2) on page 12.
Coil Metering Devices (Outdoor Coils Only):
The metering devices are multiple fixed–bore devices
(Accutrolt) brazed into the horizontal outlet tubes from
the liquid header, located at the entrance to each
evaporator coil circuit path. These metering devices are
non–adjustable. Service requires replacing the entire
liquid header assembly.
Check for possible blockage of one or more of these
metering devices by creating a low load condition on the
evaporator- - function coil and then observing the frosting
pattern on the finned portion of the coil.
To check the indoor coil, disconnect the supply fan signal
(A04- - A06 direct- - drive fans) or contactor (IFC) coil, then
start the circuit in a Cooling Mode (jumper R to Y1 or
Y2) and observe the frosting pattern on the face of the
indoor coil. A frost pattern should develop uniformly
across the face of the indoor coil starting at each tube at
the Accutrol nipple locations.
To check the outdoor coil, disconnect the outdoor fan
motor. Start the circuit in a Heating Mode (jumper R to
W1 or W2) and observe the frost pattern on the face of the
outdoor coil.
Failure to develop frost at an outlet tube can indicate a
plugged or a missing orifice.
Refrigerant System Pressure Access Ports
There are two access ports in each circuit - - on the suction
tube and the discharge tube near the compressor. These
are brass fittings with black plastic caps. The hose
connection fittings are standard 1/4 SAE male flare
couplings.
The brass fittings are two- - piece High Flow valves, with a
receptacle base brazed to the tubing and an integral
spring- - closed check valve core screwed into the base. See
Fig. 17. This check valve is permanently assembled into
this core body and cannot be serviced separately. Replace
the entire core body if necessary. Service tools are
available from RCD that allow the replacement of the
check valve core without having to recover the entire
system refrigerant charge.
10
Status/Position
Closed
Off
Energized
Closed
Open
Closed