Operation; Sequence Of Operation - York YD480 Series Installation Manual

5012886-YIM-B-0517
2. Move the system switch on the thermostat to the AUTO or
COOL position.
3. Reduce the setting of the room thermostat to energize the
compressor.
4. Check the operation of the evaporator unit per the
manufacturer's recommendations.
5. With an ammeter, check the compressor amps against the
unit data plate.
6. Check for refrigerant leaks.
7. Check for any abnormal noises and/or vibrations, and
make the necessary adjustments to correct fan blade(s)
touching shroud, refrigerant lines hitting on sheet metal,
etc.
8. After the unit has been operating for several minutes, shut
off the main power supply at the disconnect switch and
inspect all factory wiring connections and bolted surfaces
for tightness.

Operation

Unit Control Overview
This series of condenser units, comes factory equipped with
Smart Equipment™ controls to monitor all unit functionality and
safety controls. (2 Smart Equipment™ controls per system on
30, 40 and 50 Ton condensers.)
Safety Controls
The Smart Equipment™ control board incorporates features to
monitor safety circuits as well as minimize compressor wear
and damage. An anti-short cycle delay (ASCD) is utilized to
prevent operation of a compressor too soon after its previous
run. Additionally, a minimum run time is imposed any time a
compressor is energized to allow proper oil return to the
compressor. The ASCD is initiated on unit start-up and on any
compressor reset or lockout.
The Smart Equipment™ control board monitors the following
inputs for each cooling system:
• A high-pressure switch is factory installed to protect
against excessive discharge pressure due to a blocked
condenser coil or a condenser fan motor failure. During
cooling operation, if a high-pressure limit switch opens,
the Smart Equipment™ control board will de-energize the
associated compressors and initiate the 5-minute ASCD.
If the call for cool is still present at the end of the ASCD,
the control board will re-energize the halted compressor. If
a high-pressure switch opens three times within two hours
of operation, the Smart Equipment™ control board will
lock out the associated system compressors and will
display the fault on the on board LCD display.
• A low-pressure switch to protect the unit against
excessively low suction pressure is standard on all
condensing units. If the low-pressure switch opens during
normal operation, the Smart Equipment™ control board
will de-energize the compressor, initiate the ASCD, and
shut down the condenser fans. On startup, if the low-
18
pressure switch opens, the Smart Equipment™ control
board will monitor the low-pressure switch to make sure it
closes within one minute. If it fails to close, the unit will
shut down the associated compressor and begin an
ASCD. If the call for cool is still present at the end of the
anti-short cycle time delaying, the control board will re-
energize the halted compressor. If a low-pressure switch
opens three times within two hours of operation, the
Smart Equipment™ control board will lock out the
associated system compressors and will display the fault
on the on board LCD display.
• An ambient air sensor will lock out mechanical cooling at
40F. A field installed low ambient kit is available that
allows the unit to operate down to 0°F.
The refrigerant systems are independently monitored and
controlled. On any fault, only the associated system will be
affected by any safety/preventive action. The other refrigerant
system will continue to operate unless it is affected by the fault
as well.
Pump Out
The "Pump-Out on Start-Up" function is a standard feature on
the 30-50 ton matched split systems. These systems have dual
circuit indoor evaporator refrigerant circuits. Each circuit
includes 2 TXVs and 2 normally closed solenoid valves that are
utilized for the "Pump-Out on Start-Up" sequence of operation.
The pump-out sequence is designed to prevent liquid
refrigerant flooding of the compressors during startup.
The pump-out circuit is activated each time the first stage (Y1
of UCB 1) and/ or third stage (Y1 of UCB 2) compressors are
called for from the thermostat. On initial startup, the pump-out
circuitry does not allow the 1LLS (Pump-Out Solenoid System
1) or 3LLS (Pump-Out Solenoid System 2) located in the liquid
line just ahead of the TXVs to open, thus not allowing
refrigerant flow, or liquid refrigerant to enter the evaporator
during startup.
The 1LLS or 3LLS remains closed and will not allow refrigerant
flow through the system until the active refrigerant circuit's low
pressure switch (LPS 1 on UCB 1) or (LPS 1 on UCB 2) opens.
Once the low pressure switch opens or (5 minutes elapses), the
SE board(s) energizes the PR1 (Pump-Out Relay System 1) or
PR2 (Pump-Out Relay System 2), which then opens the 1LLS
or 3LLS (Pump-Out Solenoids) and allows refrigerant to begin
flowing through the active refrigerant circuit. The active
systems' low pressure switch is ignored for approximately 1
minute while the systems suction pressure rises above its cut in
point of 71 psi. at which point the LPS closes again for normal
operation and LPS function. The UCB - "CN-Fan" output
controls the pump out relay function. "Pump Out" function is
also possible with "Lead-Lag" enabled. Lead lag function should
be turned off anytime Hot Gas Bypass (HGBP) is installed.

Sequence of Operation

NOTE: The timing intervals described in the following
procedures are nominal. Some variations will naturally
occur due to differences in individual components, or
due to variations in ambient temperature or line/control
Johnson Controls Unitary Products