6021980-UIM-A-1120
Johnson Controls Ducted Systems
67
Operating instructions
Lighting the main burners
1.
Turn off electrical power to unit.
2.
Set the room thermostat to lowest setting.
3.
Turn the gas valve counter-clockwise to the ON position
(see Figure 32).
4.
Turn on electrical power to unit.
If the set temperature on the thermostat is above room
temperature, the main burners ignite. If a second stage of
heat is called for, the main burners for second stage heat
ignite for the second stage heat.
Post-start checklist
After the entire control circuit is energized and the heating
section is operating, perform the following checks:
1.
Check for gas leaks in the unit piping and the supply
piping.
2.
Check for the correct manifold gas pressures. See
3.
Check the supply gas pressure. It must be within the limits
shown on the rating nameplate.
Note:
You must check the supply pressure with all gas
appliances in the building at full fire. The standby gas
pressure must never exceed 10.5 in. or the operating
pressure drop below 4.5 in. for natural gas units. If the
gas pressure is outside these limits, contact the local
gas utility or propane supplier for corrective action.
Shutting down the unit
1.
Set the thermostat to the lowest temperature setting.
2.
Turn off electrical power to unit.
3.
Open the gas heat access panel.
4.
Turn the gas valve clockwise to the OFF position (see Figure
32).
Checking gas heat input
This unit has two stages of gas heat. The first stage is 60% of
the full fire input and is considered the minimum input for the
furnace. The intended input for each furnace is shown in
Table 30. The table applies to units operating on 60 Hz power
only.
Determining the rate of gas flow (second stage)
1.
Turn off all other gas appliances connected to the gas
meter.
2.
Turn on the furnace and verify that the thermostat is calling
for second stage (100% input) heat.
3.
Measure the time needed for one revolution of the hand on
the smallest dial on the meter. A typical gas meter has a 1/
2 or a 1 cubic foot test dial.
4.
Using the number of seconds it takes for one revolution of
the dial, calculate the cubic feet of gas consumed per hour
(see page 68).
5.
If necessary, adjust the high pressure regulator, see
Adjusting the manifold gas pressure
Note:
Do not over-fire the furnace on second stage. If in
doubt, it is better to leave the second stage of the
furnace slightly under-fired.
6.
Repeat Steps 1-5.
Determining the rate of gas flow (first stage)
1.
Turn off all other gas appliances connected to the gas
meter.
2.
Turn on the furnace and make sure the thermostat is
calling for first stage (60% input) heat.
3.
Wait for the initial second stage period to complete and
verify that the unit is in first stage.
Even when the thermostat is calling for first stage heat, the
unit lights on second stage and runs on second stage for 1
minute.
4.
Measure the time needed for one revolution of the hand on
the smallest dial on the meter. A typical gas meter has a 1/
2 or a 1 cubic foot test dial.
5.
Using the number of seconds it takes for one revolution of
the dial, calculate the cubic feet of gas consumed per hour
(see page 68).
6.
If necessary, adjust the low pressure regulator, see
Adjusting the manifold gas pressure
Note:
Do not under-fire the furnace on the first stage. If in
doubt, it is better to leave the first stage of the furnace
slightly over-fired (greater than 60% input).
7.
Repeat Steps 1-6.
This furnace is equipped with an automatic re-ignition
system. Do not attempt to manually light the pilot.
Fire or explosion hazard
Failure to follow the safety warning exactly could result
in serious injury, death, or property damage.
Never test for gas leaks with an open flame. Use a
commercially available soap solution made specifically
for the detection of leaks to check all connections. A fire
or explosion may result causing property damage,
personal injury, or loss of life.
