5168276-XIM-B-0216
42
Johnson Controls Unitary Products
signal from the flame sensor indicating the pilot flame is
properly ignited, then the main gas valve will not open. It will
continue to try and ignite the pilot for a maximum of 85 seconds,
then if the pilot flame is not detected, the ignition control will
lock out furnace operation until 24V power is removed from the
module either at the unit or by resetting the room thermostat.
Rollout Switch
This switch is located above the main burners in the control
compartment, which in the event of a sustained main burner
rollout shuts off and locks out both ignition controls closing both
gas valves. The ignition controls lock out furnace operation until
24V power is removed from the controls either at the unit or by
resetting the room thermostat.
The ICB monitors the Replace the primary limit.
Centrifugal and Rollout switches of gas heat units.
The control circuit includes the following safety controls:
Figure 27: Gas Valve and Controls
Resets
Remove the call for heating by lowering the thermostat setting
lower than the conditioned space temperature.
Gas Heat Anticipator Setpoints
It is important that the anticipator setpoint be correct. Too high
of a setting will result in longer heat cycles and a greater
temperature swing in the conditioned space. Reducing the
value below the correct setpoint will give shorter “ON cycles
and may result in the lowering of the temperature within the
conditioned space. Refer to Table 28 for the required gas heat
anticipator setting.
Start-Up (Cooling)
Prestart Check List
After installation has been completed:
1.
Check the electrical supply voltage being supplied. Be sure
that it is the same as listed on the unit nameplate.
2.
Set the room thermostat to the off position.
3.
Turn unit electrical power on.
4.
Set the room thermostat fan switch to on.
5.
Check indoor blower rotation.
• If blower rotation is in the wrong direction. Refer to
Phasing Section in general information section.
Check blower drive belt tension.
6.
Check the unit supply air (CFM).
7.
Measure evaporator fan motor's amp draw.
8.
Set the room thermostat fan switch to off.
9.
Turn unit electrical power off.
Operating Instructions
1.
Turn unit electrical power on.
2.
Set the room thermostat setting to lower than the room
temperature.
3.
First stage compressors will energize after the built-in time
delay (five minutes).
4.
The second stage of the thermostat will energize second
stage compressor if needed.
Post Start Check List
1.
Verify proper system pressures for both circuits.
2.
Measure the temperature drop across the evaporator coil.
3.
Measure the system amperage draw across all legs of 3
phase power wires.
4.
Measure the condenser fan amperage draw.
Table 27: Gas Heat Limit Control Setting
Units
(Tons)
Capacity, MBH
Limit Control
Opens, ºF
Input
Output
15 & 20
300
240
195
15 & 20
400
320
195
Burner Compartment
Sensor #2
Sensor #1
Rollout
Switch
Ignitor #2
Ignitor Control #1
Ignitor Control #2
GV2
Gas
Valve
GV1
Gas
Valve
Ignitor #1
Table 28: Gas Heat Anticipator Setpoints
Gas Valve
Anticipator Setpoint
1st Stage
2nd Stage
Honeywell VR8440
0.30 amp
0.11 amp
White-Rodgers
36C68
