27
FORM CIM 0203
Option 2 is field installed in the form of a duct heater
and must be installed a minimum of 4' downstream
from the unit in the evaporator discharge duct. A
separate power supply is required for the heat. Con-
sult wiring diagrams on inside of control box cov-
ers, which are inside Item and Item , Figure 5,
page 6, and on the electric heater. See Figure 7,
page 7, for photo details of wiring.
ELECTRIC REHEAT
On a call for dehumidification the compressor
comes on and the evaporator coil removes the mois-
ture from the air passing through it. The electric
heater then reheats the air passing through it to
maintain the temperature in the space that needs to
be conditioned.
STEAM COIL
The steam coil is located directly behind the DX
cooling coil. The coil is copper tube/aluminum fin.
Connections exit the cabinet at the coil location.
Standard steam coils and non-freeze steam coils are
available. Controls and valves for steam coils are
supplied by others.
HOT WATER COILS
The hot water coil is located directly behind the
DX cooling coil. The coil is copper tube/aluminum
fin. Connections exit the cabinet at the coil loca-
tion. Controls and valves for hot water coils are
supplied by others.
LOW AMBIENT DAMPER CONTROL
For use where air conditioner is expected to oper-
ate with outdoor ambients below 60°F, the damper
will maintain the condensing pressure at approxi-
mately 220 PSIG down to an ambient of 0°F.
The damper is installed directly onto the condenser
inlet duct connection. The damper actuator cylin-
der must be in the upright position with the threaded
connection “up”. A 1/4" copper tube is connected
to the pressure operator with a flare nut. The other
end of the 1/4" tube (with flare nut) is run through
a grommet in the condenser panel (Item , Figure
6, page 6), to the liquid access fitting (marked “Low
Ambient Damper”), located in the condensing sec-
tion.
NOTE: On 4 to 15 Ton units, with dual or
triple refrigerant circuits, it is EX-
TREMELY IMPORTANT that the 1/4" tube
from the damper pressure operator be con-
nected to the liquid line access fitting of Sys-
tem No. 1. Connection to System No. 2 or 3
will cause malfunction. The systems are
clearly identified on the unit.
FAN CYCLING
This option controls the head pressure by cycling
the condenser blower motor off and on. The effec-
tive range of use for this option is down to 40°F. A
fan cycling bypass thermostat (optional) is also
available. This is an adjustable thermostat that is
typically set between 65°F and 70°F. This thermo-
stat will bypass the fan cycling control above the
set point to minimize rapid or quick fan cycling at
moderate outdoor temperatures.
FLOODED CONDENSER
When the outdoor ambient falls, the condensing
pressure falls. This causes the discharge pressure
to fall as well. Since the pressure differential across
the thermostatic expansion valve port affects the
rate of refrigerant flow, low head pressure gener-
ally causes insufficient refrigerant to be fed to the
evaporator. Failure to have sufficient head pressure
will result in low suction pressure and/or iced
evaporator coils. The effective range for this op-
tion is down to -30°F.
The purpose of a flooded condenser is to hold back
enough of the condensed liquid refrigerant so that
some of the condenser surface is rendered inactive.
This reduction of active condensing surface results
in a rise in condensing pressure and sufficient liq-
uid line pressure for normal system operation.
A three-way modulating valve and a receiver make
up the flooded condenser refrigerant components.
Summary of Contents for 4CA1901
Page 2: ...2 FORM CIM 0203 ...
