Appliance Types; Dj Style Indirect Fired; Dg Style Indirect Fired; He Direct Fired - EngA Base User Manual

base

APPLIANCE TYPES

DJ STYLE INDIRECT FIRED

For indirect fired equipment with DJ (E, S, X) style
burners up to size 140.
On a call for heating the combustion blower will be
enabled to full speed to prepurge the heat
exchanger. Once the prepurge time has elapsed
the combustion blower speed will reduce to ignition
speed and then enable the ignition control to start
and prove pilot flame, then open the main safety
valve (SSOV). After a time delay the pilot valve IS
disabled. The burner is allowed to operate from
low fire to high fire at a 15:1 turndown ratio to
maintain the requested discharge air temperature
by modulating the control valve and the
combustion blower speed. If heating is not
required the burner will be disabled and the
combustion blower will enter a post purge time,
and then shut down.
The base can control either a Maxitrol magnetic
style modulating valve or an actuator and ball valve
combination.
Combustion air blower modulation is controlled by
either the CD-XM expansion module. If using an
electronically commutated motor (ECM) modulation
is directly controlled from the base.

DG STYLE INDIRECT FIRED

For indirect fired equipment, DJX sizes 200 and
300, and all DG sizes. These use actuator
controlled air flow control damper and gas ball
valves.
On a call for heating the combustion blower will be
enabled and the air actuator will open to the
prepurge setpoint to purge the heat exchanger.
Once the prepurge time has elapsed the gas and air
actuators will move to ignition position and then
enable the ignition control to start and prove pilot
flame, then open the main safety valve (SSOV).
Once the pilot flame has proven and the main
flame is established, the base will then disable the
pilot valve. The burner is allowed to operate from
IOM67
high fire to low fire at a 20:1 turndown ratio to
maintain the requested discharge air temperature
by modulating the gas and air actuators. If heating
is not required the burner will be disabled and the
combustion blower will enter a post purge time,
and then shut down.

HE DIRECT FIRED

For direct fired HE style direct fired heaters.
On a call for heating, and with the supply blower
enabled, the ignition control will be enabled to
start and prove pilot flame, then open the main
safety valve (SSOV). Once the pilot flame has
proven and the main flame is established, the M-XM
will then disable the pilot valve. The burner is
allowed to operate from low fire to high fire to
maintain the requested discharge air temperature
by modulating the fuel control valve. The heating
will remain on as long as the heating enable circuit
is energized.
The base can control either a Maxitrol magnetic
style modulating valve or an actuator and ball valve
combination.
Variable air volume systems include a burner
bypass damper which modulates to maintain the
correct burner profile pressure drop.

STAGED COOLING

For staged compressor operation the base will
sequence on and off up to 5 compressor stages to
maintain the discharge temperature setpoint. As
with all staged systems, expect the discharge
temperature to fluctuate from setpoint as
compressors are turned on and off.
10 February 2021 R0