5742640-TIM-A-0419
Johnson Controls Ducted Systems
53
If the voltage has been sensed at the GV for at least 15
seconds during the fan on delay for heating and the UCB no
longer senses voltage at the GV (W1 call for heat removed or
an ICB fault exists), then the UCB forces the indoor blower on
for the indoor blower heating off delay.
The gas valve is of the redundant type. If for any reason the
main gas valve fails in the open position, then the redundant
valve ahead of the main gas valve will shut off the flow of gas to
both the pilot and main gas valves.
Centrifugal Switch
The centrifugal switch is mounted on the end of the draft motor
and it is an integral part of the motor assembly. On a call for
heat, the ICB checks the centrifugal switch (CS) for open state
before it energizes the draft motor. If it is closed, then the ICB
will lock out the furnace and flash a code (Table 29). If open,
then the ICB will energize the draft motor and verify that the
switch closes before initiating the purging and ignition
sequence. If at any time during furnace operation the
centrifugal switch opens, then the ICB will de-energize the pilot
and main gas valves and monitor the centrifugal switch. If the
centrifugal switch closes and the call for heat still exists, then
the ICB will retry the purging and ignition sequence.
Roll-out Switch
This temperature sensitive switch is located in the burner
vestibule just above the right hand side of the burner assembly.
In the event of the flame spilling out into the burner manifold
area the roll-out switch will open, the ICB will close both the
main and pilot gas valves and flash a code (Table 29). The ICB
will not retry the ignition sequence during the same call for heat.
Flame Sense Circuit
The flame sensor is mounted on the left hand side of the burner
assembly and is positioned such that the pilot flame surrounds
the tip of the sensor. On a call for heat the ICB checks for the
flame sense circuit to be open. If open, then the ICB initiates the
purging and ignition sequence. Once the pilot flame is present,
the ICB monitors the flame sense circuit for pilot flame stability.
If the pilot flame is unstable or lost completely, then the ICB will
immediately close both the pilot and main gas valves. The ICB
will retry the purging and ignition sequence. If the flame is
unstable or lost more than 16 times during the same call for
heat, then the ICB will lock out furnace operation for 5 minutes.
Error Messages
The UCB will initiate an error message to the LCD Smart
Equipment™ Control.
Resets
Remove the call for heating by lowering the thermostat setting
lower than the conditioned space temperature. This resets any
lock outs.
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.
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). See “CHECKING
SUPPLY AIR CFM” on page 48.
7.
Measure evaporator fan motor's amp draw.
8.
Set the room thermostat fan switch to off.
Table 23: Single Stage Gas Heat Limit Control Setting
Unit
(Tons)
Capacity, MBH
Limit Control Opens, °F
Input
Output
Direct Drive
Belt Drive
3
50
40
240
240
3
100
80
170
210
4
75
60
210
240
4
125
100
165
210
5
100
80
170
210
5
125
100
165
210
6
100
80
170
210
6
125
100
165
210
Table 24: 2 Stage Gas Heat Limit Control Setting
Unit
(Tons)
1st Stage
Capacity
2nd Stage
Capacity
Limit Control Opens,
°F
Input
(MBH)
Output
(MBH)
Input
(MBH)
Output
(MBH)
Direct
Drive
Belt
Drive
3
45
36
75
61
210
240
3
69
55
115
92
200
200
4
45
36
75
61
210
240
4
75
60
125
101
165
210
5
45
36
75
61
210
210
5
75
60
125
101
165
210
6
45
36
75
61
210
210
6
75
60
125
101
165
210
Table 25: Gas Heat Anticipator Setpoints
Gas Valve
Anticipator Setpoints
Honeywell VR8204M
0.60 amp
White-Rogers 36E36
0.54 amp
