Installation manual

035-16682-000-E-0303
74 Unitary Products Group
There are three sub-modes available in the Night Mode: Off,
Set-back, and Set-up. When the field supplied contact is
open for night mode operation, the unit is always in the
NIGHT OFF MODE
unless a field connected space thermo-
stat calls for set-back or set-up operation.
In the NIGHT OFF MODE
, the supply fan motor and optional
exhaust fan motor are disengaged. The optional inlet guide
vanes and optional exhaust dampers close. The optional
economizer outside air dampers close while the return air
dampers open. Heating and Cooling are disabled.
NIGHT SET-BACK MODE
is engaged when a contact clo-
sure is made between unit terminals N and W1 during the
NIGHT MODE. In this mode, the supply fan is operated at full
volume, optional unit heating is engaged at full capacity, the
optional power exhaust system is enabled, the economizer
outside air dampers close (return air dampers open), cooling
is disabled, and a contact closure is provided between termi-
nals D1 and D2 to signal the remote VAV boxes to open. This
operation continues until the N - W1 contact is broken or until
the unit enters DAY MODE.
NIGHT SET-UP MODE
is engaged when a contact closure is
made between terminals N and Y1 during the NIGHT MODE.
In this mode, the supply fan is engaged and its volume con-
trolled to maintain the duct static pressure. The optional
power exhaust system is enabled, the economizer is
enabled, and heating is disabled. The economizer and
mechanical cooling are used to maintain the discharge air
temperature to the DAY MODE setpoint. This operation con-
tinues until the N - Y1 contact is broken or until the unit enters
DAY MODE.
When the unit first enters DAY MODE
, it enters a morning
WARM-UP MODE
. In this mode, the supply fan is operated at
full volume, optional unit heating is engaged at full capacity,
the optional power exhaust system is enabled, the econo-
mizer outside air dampers close (return air dampers open),
cooling is disabled, and a contact closure is provided
between terminals D1 and D2 to signal the remote VAV boxes
to open. This operation continues until the return air tempera-
ture exceeds the adjustable setpoint of the Morning Warm-up
bulb thermostat (MWUP). Once MWUP is satisfied, a lock-in
relay engages to keep the unit in DAY COOLING MODE until
the remote time clock calls for the NIGHT MODE. In the day
cooling mode, the supply fan is engaged and its volume con-
trolled to maintain the duct static pressure. The optional
power exhaust system is enabled, the economizer is
enabled, and heating is disabled. The economizer and
mechanical cooling are used to maintain the discharge air
temperature to the DAY MODE setpoint.
UNIT CONTROLS
1. When contact is made between unit terminals TC and R
the unit enters DAY MODE operation as the time clock
relay (TCR) is engaged. When the TCR-1 contacts
close, the duct pressure controller is activated, the
optional power exhaust system is activated, power is
applied to the airflow proving switch (APS), and to the
supply fan motor starter (5M) to engage the supply fan. If
the supply fan operates correctly (proper rotation) the
pressure difference between the heating section and the
supply fan section increases and APS closes to enable
heating operation and power the cooling lockout control.
For units without optional head pressure control: If the
outside air temperature rises above 50°F Cooling lockout
switch 1 (CLO1) applies power to the coils of LOR1 and
LOR2 (Low Ambient Cooling Lockout Relays) to enable
all mechanical cooling stages by closing contacts LOR1-
1, LOR 1-2, LOR2-1, and LOR2-2. If the outside air tem-
perature falls below 40°F, then all mechanical cooling
stages are locked out.
For units with head pressure control: Cooling lockout
switch 1 (CLO1) applies power to the coil of LOR2 (Low
Ambient Cooling Lockout Relay) to enable third and
fourth (40 Ton only) stage mechanical cooling by closing
contacts LOR2-1 and LOR2-2 when the ambient temper-
ature rises above 50°F. If the outside air temperature
falls below 40°F, mechanical cooling stages 3 and 4 (40
Ton only) are locked out. Cooling lockout switch 2
(CLO2) applies power to the coil of LOR1 to enable first
and second stage mechanical cooling by closing con-
tacts LOR1-1 and LOR1-2 when the ambient tempera-
ture rises above 10°F. If the outside air temperature falls
below 0°F, all mechanical cooling stages are locked out.
2. While the return air temperature remains below the
adjustable setpoint of MWUP (Morning Warm-up), relays
FR1 and FR2 (Fan Relays) are engaged. Contact FR1-1
closes to engage the unit heat (optional) at full capacity.
Contact FR1-3 closes (FR1-2 opens) to replace the nor-
mal SSP2 (Switch, Static Pressure - Duct) damper open
signal with a constant 24 VAC signal, thus forcing the
inlet guide vane dampers to fully open during the warm-
up cycle. Contact FR2 makes contact between terminals
D1 and D2 to signal the remote VAV boxes to open. In
this WARM-UP MODE, CM-VAV and ELM (optional) are
disabled, so cooling is disabled and the optional econo-
mizer outside air dampers are closed.