Trane Horizon OAKD Series Installation, Operation And Maintenance Manual page 40

Startup
Dehumidification, Disable Economizer Mode, Disable
ERV. If two heaters are installed, test heating with split
manifold first by overriding burner 2 OFF. Override
heating Output Command to 100.0 percent if one
heater is installed and to 49 percent if two heaters are
installed. Override Heat Cool Mode Active to Heat. This
will enable call for heat to split manifold heater.
Depending on outdoor air temperature, at time of
startup, heater high limit temperature may be
exceeded causing limit switch to trip. Limit switch is
auto-reset. Limit switch must be jumpered out of the
circuit if OA temperature dictates.
With limit switch closed, the draft inducer will run on
high speed for 10 seconds for proof of high and low
airflow switch closure, then begin a 30-second pre-
purge period. At the end of the pre-purge the direct
spark will be energized and On-Off gas valve will open
for a 5-second ignition trial. Following successful
ignition, the inducer remains on high for 10-second
flame stabilization, followed by 30-second warm up.
Should the flame go out or the burner fail to light, an
ignition retry will initiate following a 15-second inter-
purge period.
Following successful ignition, manifold pressure
should be 1.2 in. wc during the warm-up period. The
manifold pressure will rise to 3.5 in. wc at 100 percent
firing rate. Following these sequences to check low fire
gas pressure for modulating section, reduce Heating
Output Command to 0 percent. Inducer speed will
reduce to low speed. Correct gas pressure for
modulating manifold section of heater at 0 percent
output signal or low fire will be 0.25 - 0.30 in. wc. For
modulating sections, the outlet gas pressure from
main/regulator valve into the modulating valve is
5-in. wc.
Main On-Off valves in 1/2-in. gas line require 3/32-in.
Allen wrench to adjust outlet gas pressure. Valves in
3/4-in. gas line require flat blade screwdriver to adjust
outlet gas pressure. Following these sequences,
inducer speed will reduce to low speed and will now be
speed-controlled by the heater controller based on gas
input to burners.
With heating command at 100 percent and with a
single split manifold heater installed, the On-Off
section of the heater will require the modulating
section to prove ON before the On-Off section will
enable. Inducer speed high at all times the On-Off
section is in ignition sequence or firing. On-Off section
sequence includes a 1-second ignition pre-purge
followed by 4-second ignition trial. Ignition or flame
failure will be followed by 30-second inter-purge for
two ignition retry then 5-minute lockout period if both
retry attempts fail. Correct manifold gas pressure for
On-Off heater section is 3.5 in. wc.
For units including an additional separate On-Off
heater, set heat command output to 49 percent to run
modulating heater startup. When complete with
40
modulating heater startup, increase heat output
command to 100 percent to start up the second heater.
High Fire and Low Fire Adjustment
To adjust high fire or low fire setting, please refer to
EXA STAR Modulating Valve document. This
document will ship with all gas heat units.
Failure to Ignite
• On the initial startup, or after unit has been off long
periods of time, the first ignition trial may be
unsuccessful due to need to purge air from
manifold at startup.
• If ignition does not occur on the first trial, the gas
and spark are shut-off by the ignition control and
the control enters an inter-purge period of
15 seconds, during which the draft inducer
continues to run.
• At the end of the inter-purge period, another trial for
ignition will be initiated.
• Control will initiate up to three ignition trials on a
call for heat before lockout of control occurs.
• Control can be brought out of lockout by cycling call
for heat at the Main Unit Display.
Prior to completing the startup, check the appearance
of the main burner flame. Refer to
characteristics of properly adjusted natural gas
systems.
Figure 32 for flame
OAU-SVX01H-EN