28
•
SF-VSC: Supply Fan with Variable Speed Control
—
The SF-VSC will modulate its speed based upon the SF
Differential Pressure Transmitter (SF-DPT) signal to
maintain the supply duct static pressure set point.
•
Optional
— For constant air volume (CAV), select
“Manual Override” in the Equipment Touch keypad and
input the required speed (%) as determined in the field
by Test and Balancing.
Exhaust fan (EF) — At the same time the SF turns on, the EF
will be enabled to run. The EF shall be enabled to run continu-
ously while the unit is in the Occupied mode. When the system
reaches the end of the Occupied mode period, the EF will be
enabled to run for an additional 2 minutes before turning off.
•
EF-VSC: Exhaust Fan with Variable Speed Control
— If
the EF Differential Pressure Transmitter (EF-DPT) sig-
nal is above the building static pressure set point, the
EF-VSC will modulate its speed based upon the EF-
DPT to maintain the set point. If the EF-DPT signal is
below the building static pressure set point, the EF will
modulate down to 0% (adjustable) speed.
•
Optional
— For constant air volume (CAV), select
“Manual Override” in the Equipment Touch keypad and
input the required speed (%) as determined in the field
by Test and Balancing.
Energy Conservation Wheel (ECW) — After the OA damper
opens and the SF turns on, the ECW turns on. The ECW By-
Pass Damper will open when the ECW is off and it will close
when the ECW is on.
•
ECW Standard Operation —
When the OAT is 3°F
(adjustable) or more above or below the RAT, the ECW
will be on, otherwise it is off.
•
ECW with VFD Controlled Defrost (WM-VFD)
— When
the OAT is 3°F (adjustable) or more above or below the
RAT, the ECW will be on. It will be off, if the OAT is
less than 3°F (adjustable) above or below the RAT. It
will decrease speed or stop as the WExAT goes below
25°F (adjustable) to allow for wheel defrosting. It will
start back up and increase speed when the WExAT rises
toward 25°F (adjustable) or more.
Cooling Mode — Cooling mode is available when the Enter-
ing Coil Air Temperature (ECAT) is above the ECAT cooling
lower limit (55°F, adjustable) and there is a demand for cool-
ing. When the Entering Coil Air Temperature (ECAT) is 1°F
(adjustable) or more above the Supply Air Temperature (SAT)
cooling set point (72°F, adjustable), compressor no. 1 turns on.
When the SAT is 2°F (adjustable) or more above the SAT cool-
ing set point (72°F, adjustable), compressor no. 2 turns on – not
less than 10 minutes (adjustable) after compressor no. 1 turned
on. When the SAT is 2°F (adjustable) or more below the SAT
cooling set point (72°F, adjustable), compressor no. 2 turns off.
When the ECAT is 1°F (adjustable) or more below the Supply
Air Temperature (SAT) cooling set point (72°F, adjustable),
compressor no. 1 turns off.
•
Optional
— When enabled, if there is a call for first
stage cooling, second stage cooling will be enabled after
a 10-minute (adjustable) delay. Both compressors modu-
late to maintain the cooling set point. Default is “OFF.”
Compressor enabling logic includes a 5-minute (fixed)
minimum run-time and a 5-minute (fixed) minimum
time off delay to prevent compressor short cycling.
•
Digital Compressors
— The controller regulates the
capacity of the digital compressors by rapidly loading
and unloading the compressors in 15-second intervals.
The digital compressor will modulate based upon the
DX Leaving Air Temperature (DX LAT) sensor and set
point (55°F, adjustable). If the DX LAT drops to 38°F or
less, the controller will fix the compressor at 10%
(adjustable). If the DX LAT drops to 35°F or less for 10
minutes, the controller will issue an alarm and the com-
pressor stops. When the DX LAT warms back up to 55°F
or more, the compressor turns back on. If there is a cur-
rent call for first stage cooling and compressor no. 1 is
shut down due to an alarm (HPS1, LPS1, or DX LAT1),
compressor no. 2 will be turned on to take its place until
it returns.
•
Hot Gas Reheat (HGRH) – On/Off
— When the SAT is
1°F (adjustable) or more below the SAT cooling set
point, HGRH turns on and cycles to maintain the SAT
cooling set point. When SAT is 2°F (adjustable) or more
above the SAT cooling set point, HGRH turns off.
•
Hot Gas Reheat (HGRH) – Modulating
— When the
SAT is 1°F (adjustable) or more below the SAT cooling
set point, HGRH turns on and modulates to maintain the
SAT cooling set point. When the SAT is 2°F (adjustable)
or more above the SAT cooling set point, HGRH turns
off.
•
Switchable subcooling
— When either of the compres-
sors are enabled and the SAT is equal to or below the
SAT cooling set point (72°F, adjustable), the subcooling
coil is enabled. When the SAT is 1°F (adjustable) or
more above the SAT cooling set point (72°F, adjustable),
the subcooling coil is disabled.
Dehumidification Mode — Dehumidification mode is avail-
able if the ECAT is greater than 60°F (adjustable) and there is
no call for heating. If there is no demand for cooling, when the
Entering Coil Relative Humidity (EC-RH) is 1% (adjustable)
or more above the Supply Air Relative Humidity (SA-RH) set
point (55% RH, adjustable), Dehumidification mode is en-
abled. After the minimum time-off delay, compressor no. 1
turns on. If there is a current demand for cooling, when the SA-
RH is 1% (adjustable) or more above the SA-RH set point
(55% RH, adjustable), Dehumidification mode is enabled.
When SA-RH is 2% (adjustable) or more above the SA-RH set
point (55% RH, adjustable), and after minimum time-off delay,
compressor no. 2 turns on
–
not less than 10 minutes (adjust-
able) after compressor no. 1 turned on. Both compressors re-
spond in sequence and run at full cooling. HGRH is enabled to
operate as necessary to maintain the SAT cooling set point
(72°F, adjustable). When SA-RH is 1% (adjustable) or more
below SA-RH set point (55% RH, adjustable), compressor no.
2 turns off. If there is still no demand for cooling, when the EC-
RH is 2% (adjustable) or more below the SA-RH set point
(55% RH, adjustable), compressor no. 1 turns off and Dehu-
midification mode is disabled. If there is a current demand for
cooling, when the SA-RH is 2% (adjustable) or more below the
SA-RH set point (55% RH, adjustable), Dehumidification
mode is disabled.
•
Digital Compressors
— The controller controls the
capacity of the digital compressors by rapidly loading
and unloading the compressor in 15-second intervals.
The digital compressor will modulate based upon the
DX LAT sensor and the DX LAT Dehumidification set
point (48°F, adjustable). If the DX LAT drops to 38°F or
less, the controller will fix the compressor at 10%
(adjustable).
•
Hot Gas Reheat (HGRH) – On/Off
— When the SAT is
1°F (adjustable) or more below the SAT cooling set
point, HGRH turns on and cycles to maintain the SAT
cooling set point. When SAT is 2°F (adjustable) or more
above the SAT cooling set point, HGRH turns off.
•
Hot Gas Reheat (HGRH) – Modulating
— When the
SAT is 1°F (adjustable) or more below the SAT cooling
set point, HGRH turns on and modulates to maintain the
SAT cooling set point. When SAT is 2°F (adjustable) or
more above the SAT cooling set point, HGRH turns off.
•
Switchable subcooling
— When either of the compres-
sors are enabled and the SAT is equal to or below the
SAT cooling set point (72°F, adjustable), the subcooling
coil is enabled. When the SAT is 1°F (adjustable) or
more above the SAT cooling set point (72°F, adjustable),
the subcooling coil is disabled.
