
15
THERMOSTATIC EXPANSION VALVE (TXV)
All 581J units have factory-installed nonadjustable thermostatic
expansion valves (TXV). The TXVs are bleed port expansion
valves with an external equalizer. TXVs are specifically designed
to operate with Puron
®
or R-22 refrigerant. Use only factory au-
thorized TXVs. See Fig. 18.
Fig. 18 — Thermostatic Expansion Valve (TXV) Operation
TXV Operation
The TXV is a metering device that is used in air conditioning and
heat pump systems to adjust to the changing load conditions by
maintaining a preset superheat temperature at the outlet of the
evaporator coil. See Fig. 19.
The volume of refrigerant metered through the valve seat is de-
pendent upon the following:
1. Superheat temperature is sensed by the cap tube sensing
bulb on suction the tube at the outlet of evaporator coil.
This temperature is converted into pressure by refrigerant
in the bulb pushing downward on the diaphragm which
opens the valve using the push rods.
2. The suction pressure at the outlet of the evaporator coil is
transferred through the external equalizer tube to the
underside of the diaphragm.
3. The needle valve on the pin carrier is spring loaded, exert-
ing pressure on the underside of the diaphragm. Therefore,
the bulb pressure equals the evaporator pressure (at the
outlet of the coil) plus the spring pressure. If the evapora-
tor load increases, the temperature increases at the bulb,
which increases the pressure on the topside of the dia-
phragm, pushing the carrier away from the seat, opening
the valve and increasing the flow of refrigerant. The
increased refrigerant flow causes increased leaving evapo-
rator pressure which is transferred through the equalizer
tube to the underside of the diaphragm. This causes the pin
carrier spring pressure to close the TXV valve. The refrig-
erant flow is effectively stabilized to the load demand with
a negligible change in superheat.
Fig. 19 — TXV Sensor Bulb Location
OUTLET
INLET
PUSHRODS
DIAPHRAGM
NEEDLE
VALVE
SPRING
DISTRIBUTOR
FEEDER TUBES
CAPILLARY TUBE
COIL
BULB
EXTERNAL EQUALIZER TUBE
TXV SENSOR
BULB
CLAMP
CIRCUIT 1
CIRCUIT 2
TXV
(CIRCUIT 2)
TXV
(CIRCUIT 1)
TXV SENSOR
BULBS
TXV
SENSOR
BULBS
Содержание 581J 17-28 Series
Страница 18: ...18 COOLING CHARGING CHARTS Fig 21 Cooling Charging Chart 15 Ton ...
Страница 19: ...19 Fig 22 Cooling Charging Chart 17 5 Ton ...
Страница 20: ...20 Fig 23 Cooling Charging Chart 20 Ton ...
Страница 21: ...21 Fig 24 Cooling Charging Chart 25 Ton ...
Страница 36: ...36 Fig 47 Unit Control Box IGC Location IGC Board IGC Board Side view Front view ...
Страница 39: ...39 Fig 50 Integrated Gas Control IGC Board RED LED STATUS ...
Страница 45: ...45 Fig 56 RTU Open Overlay for Economizer Wiring ...
Страница 46: ...46 Fig 57 VFD Overlay for W2770 Controller Wiring ...
Страница 84: ...84 Fig B 581J 17 28 Control Diagram 208 230 3 60 460 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Страница 85: ...85 Fig C 581J 17 28 Power Diagram 208 230 3 60 APPENDIX D WIRING DIAGRAMS ...
Страница 86: ...86 Fig D 581J 17 28 Power Diagram 460 3 60 APPENDIX D WIRING DIAGRAMS ...
Страница 87: ...87 Fig E 581J 17 28 Power Diagram 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Страница 88: ...88 Fig F 581J 17 28 Control Diagram with Perfect Humidity System APPENDIX D WIRING DIAGRAMS ...
Страница 89: ...89 Fig G 581J 17 28 Power Diagram 208 230 3 60 with Perfect Humidity System APPENDIX D WIRING DIAGRAMS ...
Страница 90: ...90 Fig H 581J 17 28 Power Diagram 460 3 60 with Perfect Humidity System APPENDIX D WIRING DIAGRAMS ...
Страница 91: ...91 Fig I 581J 17 28 Power Diagram 575 3 60 with Perfect Humidity System APPENDIX D WIRING DIAGRAMS ...
Страница 92: ...92 Fig J RTU OPEN Wiring Diagram APPENDIX D WIRING DIAGRAMS ...
Страница 93: ...93 Fig K RTU OPEN Wiring Diagram with Perfect Humidity System APPENDIX D WIRING DIAGRAMS ...