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SECTION 8 – UNIT OPERATION
The pump will not run if the microprocessor panel
has been powered up for less than 30 seconds or if the
pump has run in the last 30 seconds to prevent pump
motor overheating.
Whenever the option "YORK HYDRO KIT PUMPS =
1" is selected under the OPTIONS key, the pump con-
trol will be as described above. DO NOT SELECT the
option "YORK HYDRO KIT PUMPS = 2" under the
OPTIONS key. If a dual pump option is installed, the
active pump is selected by the selector switch.
EVAPORATOR HEATER CONTROL
The evaporator heater is controlled by ambient air tem-
perature. When the ambient temperature drops below
40 °F (4.4 °C) the heater is turned ON. When the tem-
perature rises above 45 °F (7.2 °C) the heater is turned
OFF. An under voltage condition will keep the heater
OFF until full voltage is restored to the system.
PUMPDOWN CONTROL
Each system has a pump-down feature upon shut-off.
Manual pumpdown from the keypad is not possible.
On a non-safety, non-unit switch shutdown, all com-
pressors but one in the system will be shut OFF. The
LLSV will also be turned OFF. The final compressor
will be allowed to run until the suction pressure falls
below the cutout, or for 180 seconds, whichever comes
first.
154
STANDARD CONDENSER FAN CONTROL
Condenser fan operation must be programmed with
the OPTIONS key under "Fan Control." Condenser
fan must be selected for Discharge Pressure only. Fan
control by discharge pressure will work according to
the tables on the following pages (see Table 22 on page
156 and Table 23 on page 157). The fan control on
pressure and fan differential off-pressure are program-
mable under the PROGRAM key. Standard fan control
operates down to a temperature of 25° F.
The delay between turning ON and OFF fan stages is
always fixed at 5 seconds.
When a fan stage is turned ON by pressure, the on
pressure for the next stage is increased 20 PSIG and
ramped back to the programmed on pressure over the
next 20 seconds. Typically, standard ambient control
on pressure should be programmed at 385 PSIG with a
differential of 125 PSIG.
When a fan stage is turned OFF (programmed on pres-
sure minus programmed differential), the off pressure
for the next stage is decreased 20 PSIG and ramped
back to the programmed off pressure minus the differ-
ential over the next 20 seconds.
Condenser fan locations are shown in Figure 40 on
page 155. Detailed Standard Fan Control operation
is shown in Table 22 on page 156 and Table 23 on
page 157.
FORM 150.72-ICOM6
ISSUE DATE: 12/29/2017
JOHNSON CONTROLS
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Table of Contents
Troubleshooting
