GENERAL
A Hot Gas Bypass valve is a fully modulating control that will
provide a metered flow of compressor discharge gas to the
system’s evaporator coil during reduced load operation to
prevent condensate from freezing on the surface of the evapo-
rator coil.
Hot Gas Bypass may be required when a CA condensing unit
is applied on:
1. A multi-zone (MZ) system,
2. A throttling-type variable air volume (VAV) system,
3. A system handling 100% outdoor air, or
4. Any system where condensate may freeze on the surface
of the evaporator coil during low load operation.
NOTE: The need for hot gas bypass can be reduced or
eliminated on some systems by splitting the coils
for row control instead of face control.
When hot gas bypass is required, York recommends that:
1. One end of the main bypass line be connected to the inlet
of the evaporator coil between the expansion valve and the
distributor of the system’s first stage of capacity. This ar-
rangement is required to maintain a high gas velocity and
good oil return through both the coil and the suction riser
during hot gas operation.
2. The other end of the main bypass line be connected to the
7/8" spud that is provided in the compressor discharge
header of the condenser coil. On units with two independent
systems (models CA480 and 600), the bypass line should
always be connected to the #1 system. Although the #2
system will also have a 7/8" spud connection, a second hot
gas bypass line should not be required unless systems 1
and 2 are applied with different evaporator units.
3. A pilot-operated valve (an Alco FA8-13H or equal) be used.
This valve includes a 24-volt solenoid which closes the
bypass line and permits the system to shut down after the
normal pumpdown cycle. See Figure 1.
NOTE: To use the recommended valve, the overall system
control circuit and the evaporator coil must have as
many capacity stages as the CA unit and each
stage of the evaporator coil must be equipped with
both an expansion valve and a solenoid valve. If a
system is not designed to unload to its minimum
capacity, a larger hot gas bypass valve may be
required.
4. A 1/4" pilot line be connected between the access port on
the hot gas bypass valve and one of the suction access
ports on the compressor. Use either the one labeled A or B
on Figure 2. The access port labeled C will already be
connected to the system’s low pressure control.
NOTE: When using port A, make the connection before the
system is charged because refrigerant will be lost
whenever this access port is opened. Although the
suction stop valve can be backseated to close port
B, port B may be needed for a suction pressure
control and/or a service connection.
AIR COOLED
SPLIT-SYSTEM AIR CONDITIONERS
INSTALLATION INSTRUCTION
Supersedes: 550.12-N6 (579)
550.13-N6Y (399)
HOT GAS BYPASS
MODELS H2CA600
®
FIG. 1- ALCO PILOT-OPERATED VALVE - FA8-13H
