Component Locations; Sequence Of Operation; Control Sequence - Greenheck DGX Installation, Operation And Maintenance Manual

Make-Up Air Units showing Make-Up Air Units showing

Component Locations

Component Locations
Evaporator Coil Evaporator Coil
Direct Gas-Fired Burner Direct Gas-Fired Burner
Outdoor Outdoor
Air Intake Air Intake
Unit Control Center Unit Control Center
Model DGX Make-Up Air Unit
Model DGX Make-Up Air Unit Model DGX Make-Up Air Unit
Outdoor Outdoor
Air Intake Air Intake
Evaporator Coil Evaporator Coil
Model IGX Make-Up Air Unit
Model IGX Make-Up Air Unit Model IGX Make-Up Air Unit
Outdoor Outdoor
Air Intake Air Intake
Evaporator Coil Evaporator Coil
Model MSX Make-Up Air Unit
with Electric Heat
10
Packaged DX Module for Make-Up Air Unit
Indirect Gas-Fired Indirect Gas-Fired
Furnace Furnace
Unit Control Center Unit Control Center
Unit Control Unit Control
Center Center
Model MSX with Electric Heat Model MSX with Electric Heat

Sequence of Operation

Sequence of Operation
The compressors are energized by an outdoor air The compressors are energized by an outdoor air
thermostat TS5, located in the unit control center. The thermostat TS5, located in the unit control center. The
thermostat sensor is located in the intake airstream thermostat sensor is located in the intake airstream
upstream of the DX coil. The thermostat can be a upstream of the DX coil. The thermostat can be a
single or dual stage thermostat depending on the single or dual stage thermostat depending on the
number of compressors. The first stage of cooling number of compressors. The first stage of cooling
will energize when the outdoor air temperature rises will energize when the outdoor air temperature rises
above the thermostat set point plus the differential. above the thermostat set point plus the differential.
The thermostat is factory set at 80°F with a differential The thermostat is factory set at 80°F with a differential
of 5°F but can be field adjusted. The second of 5°F but can be field adjusted. The second
stage of cooling will energize when the outdoor air stage of cooling will energize when the outdoor air
temperature rises above the second stage offset plus temperature rises above the second stage offset plus
the differential. The second stage offset is factory set the differential. The second stage offset is factory set
at 10°F and the second stage differential is set at 5°F. at 10°F and the second stage differential is set at 5°F.
See the chart below for a graphical representation of See the chart below for a graphical representation of
the control operation. the control operation.
To summarize the To summarize the
cooling controls, cooling controls,
the first stage of the first stage of
cooling will turn cooling will turn
on at 85°F and the on at 85°F and the
(+10° F) (+10° F)
second stage of second stage of
cooling will turn cooling will turn
on at 95°F. The on at 95°F. The
second stage of second stage of
cooling will turn cooling will turn
off at 90°F and off at 90°F and
Setpoint Setpoint
Temperature Temperature
the first stage of the first stage of
(factory set at 80° F) (factory set at 80° F)
cooling will turn cooling will turn
off at 80°F. off at 80°F.

Control Sequence

1. Heating/Cooling switch (S4) is closed between
terminal R and Y1.
2. N.O. contact on fan relay (RF) is energized and
closed.
3. When the outdoor air temperature is above the
set point plus the differential power passes
through N.O. contacts on outdoor air thermostat
(TS5) and energizes the cooling relay (RC1).
4. When the pressure switches LPS (refrigerant
low pressure switch) and HPS (refrigerant
high pressure switch) are in their normal state
relay R10 will energize. Starting the first stage
compressor contactor.
5. When the outdoor air temperature is above the
second stage offset plus the differential power
passes through N.O. contacts on outdoor air
thermostat (TS5) and energizes the cooling relay
(RC2).
6. When the pressure switches LPS and HPS
(refrigerant high pressure switch) are in their
normal state relay R11 will energize, starting the
second stage compressor contactor.
ON ON
OFF OFF
ON ON
(+5° F) (+5° F)
OFFSET OFFSET
(factory set (factory set
at 10° F) at 10° F)
OFF OFF
FIRST FIRST SECOND SECOND
STAGE STAGE STAGE STAGE
COOLING COOLING COOLING COOLING
®