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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.
Table 22: Single Stage Gas Heat Limit Control Setting
Unit
Capacity, MBH
(Tons)
Input
Output
3
50
40
3
100
80
4
75
60
4
125
100
5
100
80
5
125
100
Table 23: 2 Stage Gas Heat Limit Control Setting
1st Stage
Unit
Capacity
(Tons)
Input
Output
Input
(MBH)
(MBH)
(MBH)
3
45
36
3
69
55
115
4
45
36
4
75
60
125
5
45
36
5
75
60
125
Error Messages
The UCB will initiate an error message associated with errors
within the system. Refer to UNIT CONTROL BOARD Error
Messages.
Resets
Remove the call for heating by lowering the thermostat setting
lower than the conditioned space temperature. This resets any
error messages.
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.
Table 24: Gas Heat Anticipator Setpoints
Gas Valve
Honeywell VR8204M
White-Rogers 36E36
Johnson Controls Unitary Products
Limit Control Opens, °F
Direct Drive
Belt Drive
240
170
210
165
170
165
2nd Stage
Limit Control Opens,
Capacity
°F
Output
Direct
(MBH)
Drive
75
61
210
92
200
75
61
210
101
165
75
61
210
101
165
Anticipator Setpoints
0.60 amp
0.54 amp
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
240
SUPPLY AIR CFM" on page 41.
210
240
7.
Measure evaporator fan motor's amp draw.
210
210
8.
Set the room thermostat fan switch to off.
210
9.
Turn unit electrical power off.
Operating Instructions
1.
Turn unit electrical power on.
Belt
2.
Set the room thermostat setting to lower than the room
Drive
temperature.
240
200
3.
Compressor will energize after the built-in time delay (five
240
minutes).
210
210
Post Start Check List
210
1.
Verify proper system pressures.
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 amp draw.
Shut Down
1.
Set the thermostat to highest temperature setting.
2.
Turn off the electrical power to the unit.
Start-up (Gas Heat)
Pre-start Check List
Complete the following checks before starting the unit.
1.
Check the type of gas being supplied. Be sure that it is the
same as listed on the unit nameplate.
2.
Make sure that the vent and combustion air hoods have
been properly installed.
5121817-TIM-A-0515
47
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