York YLAA0041, Installation Operation & Maintenance

Page: 179 / 208

Johnson Controls
179
Section 8: Unit operation
Form 150.72-ICOM6
Issue date: 12/19/2023
8
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.
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 con-
trol by discharge pressure will work according to the
tables on the following pages. See Table 24 on page
181 and Table 25 on page 182 . 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 differential
over the next 20 seconds.
Condenser fan locations are shown in
Figure 50 on
page 180 . Detailed Standard Fan Control operation
is shown in
Table 24 on page 181
and
Table 25 on
page 182 .
VSD fan
VSD fans are equipped and controlled to extend the
minimum starting ambient temperature to -10°F
(-23.3°C).
The number of compressors running in the system, the
programmed fan speed references, and the fan ramp
speed determine the speed of the VSD.
For the YLAA fan speed control, there are the follow-
ing options:
• SINGLE SPEED or STANDARD fans
• YLAA TWO SPEED FANS
• YLAA VSD FANS
To enable fan inverter control, set the fan speed control
in SERVICE MODE to YLAA VSD FANS.
Changing the switch point of the
thermal dispersion flow switch
To change the factory-set LED 7, complete the follow-
ing steps:
1. Press the ◄ or ► push button. The switch point
LED flashes.
2. Press the ◄ or ► push button as many times as re -
quired in less than 2 seconds between each press.
Each press of the push button shifts the LED by
one position in the indicated direction.
3. Stop pressing the button when the switch posi-
tion LED changes to the required position. The
flow switch automatically returns to the operating
mode with the new setting in 2 seconds.
4. To prevent unintentional settings, press both push
buttons simultaneously for at least 10 seconds in
operating mode to lock the switch electronically.
To unlock the flow switch, perform the same oper -
ation again. The setting remains the same in case
of power failure.