Model IGX Make-Up Air
33
®
OPTIONAL EXHAUST
Exhaust Fan Contact (S1) Closed (optional)
• Power passes to normally closed exhaust overload
contact (ST2 OL).
• Power passes to exhaust starter(s) ST2.
• Normally open exhaust starters are energized and
closed.
• Power passes to exhaust fans.
• Exhaust fan(s) (M2) start.
SUPPLY FAN
Supply Fan Contact (S2) Closed
• Power passes through normally closed field-
supplied fire system contact (FSC).
• Power passes through normally open exhaust fan
contact (ST2), which is closed when the exhaust
relay (ST2) is activated (optional).
• Power passes to normally closed supply overload
contact (ST1 OL or VFD).
• Power passes through normally closed contact
on optional freeze protection timer (RT4) which
remains closed if the temperature has remained
above the set point.
• Power passes to optional inlet damper which
opens.
• When damper is fully opened, optional normally
open damper limit switch (DL1) closes.
• Power passes to and energizes supply starter relay
(RF).
• Power passes to normally open fan contact (RF),
which is energized and closed.
• Supply starter (ST1) or variable frequency drive
(VFD) is energized.
• Supply starter contact (ST1) closes or VFD is
energized and power reaches and energizes
supply fan.
• Supply fan (M1) starts.
HEATING
Heat Contact (S4) Closed
• Power passes to normally open fan relay (RF or
ST1) which is energized and closed.
• Power passes to optional inlet air sensor contact
(TS4) which is closed if the inlet air temperature is
below the set point.
• Power passes to and energizes the heat relay (RH).
• Normally open heat relay contact (RH) closes.
OPTIONAL COOLING
Optional Cooling Contact (S4) Closed
• Power passes to normally open fan relay (RF or
ST1) which is energized and closed.
• Power passes to optional inlet air sensor contact
(TS5) which is closed if the inlet air temperature is
below the set point.
• Power passes to and energizes cooling relay (RC).
• Cooling sequence begins.
Cooling Sequence - Recirculating Pump
Evaporative Cooling
• Whenever the cooling relay (RC) is energized,
power passes through the normally open cooling
relay to the evaporative cooling pump (P1).
• The evaporative cooling pump(s) are energized and
cooling begins.
Cooling Sequence - Auto Drain and Fill Evaporative
Cooling
• Power passes to the evaporative cooling module
freeze sensor (FRZ) which is closed if the incoming
air temperature is above the set point.
• Power passes to the auto drain and fill timer (TC)
and the supply drain valve (VSD).
• The supply drain valve is energized and closed.
Run Time Period
• During the run time period, the auto drain and fill
timer (TC) passes power to the auto drain relay
(RA) and to the auto drain valves (VS, VD).
• The normally closed supply valve (VS) is energized
and opens. The normally open drain valve (VD) is
energized and closes. The normally open supply
drain valve (VSD) is energized and closes. This
allows water to fill the evaporative cooling sump.
• When the cooling relay (RC) and the auto drain
relay (RA) are energized, power passes through the
normally open cooling relay (RC) contacts and the
normally open auto drain relay (RA) contacts to the
evaporative cooling pump(s) (P1).
• The evaporative cooling pump(s) are energized and
cooling begins.
Drain Time Period
• When the run time period expires, the auto drain
relay (RA) and the auto drain valves (VS, VD) are
de-energized. The drain time period begins.
• When the auto drain relay (RA) is de-energized,
the normally open auto drain relay (RA) contacts
open and the evaporative cooling pump(s) are de-
energized.
• When the normally closed supply valve (VS) is
de-energized, the water supply to the evaporative
cooling module sump is stopped.
• When the normally open drain valve (VD) is
de-energized, the evaporative cooling sump is
drained.
Sequence of Operation
If the unit has a microprocessor, reference the
supplemental
Microprocessor Controller for Make-Up
Air Reference Guide
for more information.
