Trane OA1D OA2D OA3D (Indirect Gas-Fired/Electric Heat) Manuale Di Manutenzione

OAU-SVX01E-EN

37 

Open door to unit vestibule housing the gas heater. 
Move gas control lever to “OFF” position. Remove 

 

1/8-in. pressure taps (see 

) from both 

modulating and on-off sections of the split heater 
manifold. Install a barbed fitting in both 1/8-in. tapped 
holes for connection to individual gas manometers. 

Wait 5 minutes for any gas to clear. If you smell gas, see 

 and correct leak. If you don’t smell gas or have 

corrected any leaks, go to 

 illustrates indirect gas-fired furnace 

components.

Turn manual gas cock “ON”.

Open all manual gas valves. Turn power on at unit’s 
main disconnect switch. Open gas supply manual shut-
off valve. Using unit display (or computer with Trane 
Tracer TU), proceed to System Status Display and 
Override all Compressor stages OFF, Disable 
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 0.17 in. 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 start-up. When complete with 
modulating heater start-up, increase heat output 
command to 100 percent to start up the second heater.

On the initial start-up, 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 start-up.

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.