INSTALLATION & OPERATIONS GUIDE | MICROSET 4
© Honeywell LT-MS4IOG Rev. 04 | Revised October 2015
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Operational overview
The Microset 4 operates in one of nine modes. In each mode, the Microset 4 displays data and has
operational features unique to that mode. Operating modes are listed in Table 5 on page 20 and Table 6
on page 21.
Review the different Microset 4 modes and determine which one is best for your application. Then set
BVs 64, 65, 80, and 81 according to Table 6 on page 21.
BACtalk data displays can directly reference data points in the Microset 4 reserved for Microset
operations. This offers the system operator flexibility and ease of use: with a mouse click, the system
operator can control Microset 4 operations.
Hotel vs. office modes
BV-81 controls hotel and office mode (BV-81 ON = hotel). The primary difference between hotel and
office mode is the function of the after-hours timer as compared to the function of the housekeeping
timer. See “After-hours override operation” and “Housekeeping override operation” herein. Other
operational details vary as well. See “Operating mode specifics” on page 20.
Fan-control vs. no-fan-control modes
BV-80 determines fan control mode (BV-80 ON = fan-control mode).
In fan-control modes, the occupant can select fan speed at the Microset 4. Fan-control modes are
typically used in fan-coil, air conditioning, or unit ventilator applications.
In no-fan-control modes, the occupant is unable to select fan speed. No-fan-control modes are typically
used in VAV or heat pump applications.
Cooling and heating setpoint calculation
The VLC calculates current heating and cooling setpoints (AV-99 and AV-100) using different logic in
occupied and unoccupied modes (as read from BV-67). Using the current setpoints (AV-99 and AV-100)
in your control DDC is most efficient because the VLC automatically calculates these setpoints
according to the operating status of the VLC.
Occupied setpoint logic (BV-67 ON)
• Current cooling setpoint (AV-99) = Occupant-selected space temperature setpoint
a
(AV-90) +
Cooling offset (AV-93) + Demand offset (AV-106)
• Current heating setpoint (AV-100) = Occupant-selected space temperature setpoint
a
(AV-90) –
Heating offset (AV-94) – Demand offset (AV-106)
Unoccupied setpoint logic (BV-67 OFF)
• Current cooling setpoint (AV-99) = Unoccupied cooling setpoint (AV-95)
• Current heating setpoint (AV-100) = Unoccupied heating setpoint (AV-96)
After-hours override operation
Unoccupied office modes (M2 and M5) offer an after-hours override feature, which enables the
occupant to override a scheduled unoccupied status at the Microset 4.
In override, the unit calculates current setpoints (AV-99 and AV-100) using occupied setpoint logic (see
“Cooling and heating setpoint calculation” on page 18). The occupant can increase or decrease the
timer to the next half-hour increment. The occupant can also adjust the setpoint and fan speed (if
applicable).
a
The system’s setpoint high limit (AV-91) and setpoint low limit (AV-92) limit this value.
