Ventilation Fan Control (Isu 10060); Ventilation Priority (Isu 10125); Set Up Ventilation; Ventilation — Outdoor Condition Lockouts - Honeywell THX9321 Prestige 2.0 Product Data

Ventilation Fan Control (ISU 10060)

• Thermostat Controls Fan
The thermostat turns on the ventilator and the fan when
ventilation is needed.
• Equipment Controls Fan
The thermostat turns on the ventilator when ventilation is
needed. The fan is controlled by the equipment.

Ventilation Priority (ISU 10125)

• Lockouts are Priority
The thermostat places a priority on lockouts versus the
ASHRAE 62.2 ventilation standard. The thermostat will not
run ventilation during the following lockout conditions (if
configured) unless you manually call for ventilation:
— Lockout Ventilation during Outdoor Conditions (ISU
10130)
— Lockout Ventilation on Humidification or Dehumidifica-
tion Calls (ISU 10140)
— Lockout Ventilation during "Sleep" (Residential) or
"Unoccupied" (Commercial) program periods. Note:
This option is set by the user on the Ventilation screen
in the Menu.
• ASHRAE is Priority
ASHRAE requires additional ventilation following a long off
cycle. The thermostat meets the ASHRAE 62.2 ventilation
standard by running additional ventilation when outdoor
conditions are favorable. If ASHRAE cannot be met when
outdoor conditions are favorable, the thermostat will
override the outdoor lockouts and run ventilation. When
using this option, it is recommended to increase the rate
(CFM) of the ventilation equipment to meet the ASHRAE
62.2 ventilation standard in a shorter run time.
NOTES: ISU 10140 "Lockout Ventilation on Humidification or
Dehumidification Calls" is not an option when you
select "ASHRAE is Priority".
The ability to lockout ventilation during the "Sleep" or
"Unoccupied" program periods is not an option when
you select "ASHRAE is Priority".
Ventilation — Outdoor Condition Lockouts
(ISU 10130)
Ventilation will not operate when outdoor conditions exceed the
lockout settings unless you manually call for ventilation or
Ventilation Priority (ISU 10125) is set to ASHRAE is Priority
and ventilation is needed to meet ASHRAE. Lockouts can
prevent ventilation during extreme weather conditions to keep
humid, hot, and cold air out of the home.
NOTE: This feature requires an outdoor sensor.
If the outdoor sensor also measures humidity, ventilation will
not be allowed when the outdoor dewpoint is above the level
you set. Options are:
• Ventilation Low Temperature Lockout Setpoint
(Off, -20° to 40° F)
• Ventilation High Temperature Lockout Setpoint
(Off, 80° to 110° F)
• Ventilation High Dewpoint Lockout Setpoint
(Off, 65° to 85° F)
Refer to the information below if you need assistance setting
the High Dewpoint Lockout.
• Higher than 80: Extremely uncomfortable
• 75 to 80: Very uncomfortable
®
THX9321 PRESTIGE 2.0 AND THX9421 PRESTIGE
• 70 to 74: Quite uncomfortable
• 65 to 69: Somewhat uncomfortable
Ventilate on High Indoor Humidity (ISU
10160)
If set to ventilate on high indoor humidity, the ventilator turns on
to remove excess humidity if the indoor humidity is 10% above
the Humidification setting. The thermostat must be in the heat
mode to ventilate on high indoor humidity.

Set up Ventilation

Some screens shown in this section may not appear on the
thermostat, depending on how you set up ventilation.
1. Select the Ventilation Type in ISU 10000. See Fig. 248.
2. Select the terminals wired to the Ventilator (or Fresh Air
Damper). See Fig. 249.
3. Select the Ventilation Control Method. See "Ventilation
Control Methods (ISU 10050)" on page 112 for more
information. See Fig. 250.
113
®
IAQ WITH EIM
Fig. 248.
Fig. 249.
Fig. 250.
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