9
# ISU
ISU Name
ISU Options (factory default in bold)
221
Heat Stages / Backup Heat Stages
Heat Stages:
1
, 2
Backup Heat Stages: 0,
1
230
Fan Control in Heat
1 = Equipment Controls Fan
2 = Thermostat Controls Fan
253
Aux/E terminal control (Fixed to
“0” setting on all models except
TH6320U)
0 = Drive both Aux & E together
1 = Aux and E independent
255
Backup Heat Source
(Heat Pump Only)
(TH6320U / TH6220U only)
1 = Electric Forced Air
2 = Gas/Oil Forced Air (or Fossil Forced Air)
256
Emergency Heat Source (TH6320U
only)
1 = Electric Forced Air
2 = Gas/Oil Forced Air (or Fossil Forced Air)
260
External Fossil Fuel Kit
(TH6320U / TH6220U only)
0 = Thermostat Controls Backup Heat
1 = External Fossil Fuel Kit Controls Backup Heat
300
System Changeover
0 = Manual
1 = Automatic
303
Auto Changeover Differential
0 °F
to 5 °F
0.0 °C
to 2.5 °C
Note: Differential is NOT deadband. Resideo uses an advanced algorithm that
fixes deadband at 0 °F. The differential setting is the minimum number of degrees
from set-point needed to switch from the last mode running (heat or cool) to the
opposite mode when the thermostat is in auto-changeover. This is more advanced
than previous thermostats.
340
Backup Heat Droop
0 = Comfort
2 = 2 °F
3 = 3 °F
4 = 4 °F
5 = 5 °F
6 = 6 °F
7 = 7 °F
8 = 8 °F
9 = 9 °F
10 = 10 °F
11 = 11 °F
12 = 12 °F
13 = 13 °F
14 = 14 °F
15 = 15 °F
Note: 0 (comfort) setting only available if backup heat (ISU 255) is set to electric.
350
Upstage Timer for Backup Heat
0 = Off
1 = 30 minutes
2 = 45 minutes
3 = 60 minutes
4 = 75 minutes
5 = 90 minutes
6 = 2 hours
7 = 3 hours
8 = 4 hours
9 = 5 hours
10 = 6 hours
11 = 8 hours
12 = 10 hours
13 = 12 hours
14 = 14 hours
16 = 16 hours
355
Compressor Lockout / Balance Point
-- = Off
5 °F to 60 °F (in 5 °F increments)
-15.0 °C to 15.5 °C (in 2.5 °C or 3.0 °C increments)
Note: Use a wired sensor to set compressor lockout / balance point on TH6320U
/ TH6220U.
356
Outdoor Lockout Backup Heat
-- = Off
5 °F to 65 °F (in 5 °F increments)
-15.0 °C to 18.5 °C (in 2.5 °C or 3.0 °C increments)
365
Compressor Cycle Rate (Stage 1)
1 - 6
366
Compressor Cycle Rate (Stage 2)
1 - 6
370
Heating Cycle Rate (Stage 1)
1 - 12
371
Heating Cycle Rate (Stage 2)
1 - 12
375
Heating Cycle Rate Auxiliary Heat
1 - 12
378
Heating Cycle Rate Emergency Heat
(TH6320U only)
1 - 12
Advanced setup options (ISU)
