EngA ENGINEERED AIR base - He Direct Fired; He Timing

base A
26
IOM74 November 2020 R105
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 base will then disable the pilot valve. The burner is allowed to operate to maintain
the requested discharge air temperature from the base by modulating the control valve. If heating is not
required the burner will be disabled, and then shut down.
Profile pressure monitoring is from the onboard differential pressure sensor for HE direct fired appliances.
HE TIMING
Flame failure alarm
15 seconds
lockout on ignition control
60 seconds on burner
Pilot opening time
10
seconds
Mode change time
60 seconds
Damper delay off
20 seconds
Improper gas valve wiring alarm
5
seconds
Supply air low airflow alarm
30 seconds
Shorted damper end switch alarm
1 second
Supply air shorted air switch alarm
30 seconds
Profile Pressure Setpoint
Non-adjustable trip setpoints noted in the table below, measured as in.wc. (Pa). If the unit is designed for
variable air volume, the pressure trip points are scaled slightly to allow the profile damper actuator time to
move and rebalance the profile pressure drop.
Natural Gas
Propane
Very Low
0.12 (30)
0.17 (42)
Low
0.18 (45)
0.25 (62)
High
0.75 (187)
1.00 (249)
Time to trip on failures:
Heating Enabled Response Time No Heat (Ventilation) Response Time
Actual less than
Very Low
1 Second
Actual less than Very
Low
1 Minute
Actual less than Low 40 Seconds Actual less than Low 1 Minute
Actual greater than
High
90 Seconds
Actual greater than
High
No failure