Dg Indirect Fired; Basic Operation; Dg Timing - EngA ENGINEERED AIR base Technical Manual

base

DG INDIRECT FIRED

For indirect heating appliances with DG and DJX200/300.

BASIC OPERATION

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 pilot flame. Once ignition is proven, it will then
open the main safety valve (SSOV). Once the pilot flame has been 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 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.

DG TIMING

Prepurge
Post purge
Flame failure
Pilot opening time
Open combustion air proving
Improper gas valve wiring
Blocked condensate trip
Blocked flue
Heat exchanger cool down
Heat exchanger warm up fan
delay
Burner cool down
IOM74
60 seconds.
5 minutes.
15 seconds lockout on ignition control and 60 seconds on burner.
8 seconds.
60 seconds.
5 seconds.
5 minutes.
10 seconds trip and 1 minute burner alarm.
90 seconds if the discharge air is above 50° (10°C), else none.
75 seconds if ambient air is less than 40°F (4°C) and discharge temperature
less than 90°F (32°C), else warm up is not required.
90 seconds.
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A
November 2020 R105