Honeywell PRESTIGE THX9321 - Manual (Page 85)

THX9321 PRESTIGE ® 2.0 AND THX9421 PRESTIGE ® IAQ WITH EIM
85 68-0311—02
Advanced Features
ADAPTIVE INTELLIGENT RECOVERY (RESIDENTIAL USE
ONLY)
Over time, the Prestige® thermostat “learns” how long it takes
your system to reach your programmed temperature setting.
The thermostat turns on the heating/cooling system early and
assures that the programmed temperature setting is reached at
the programmed time regardless of weather conditions. For
example, if the Wake program period is set to 6:00 am with a
heat setting of 70 degrees, the heat will turn on before 6:00
am, so the temperature is 70 degrees at 6:00 am. The
thermostat displays "In Recovery" when it turns the system on
early.
Adaptive Intelligent Recovery® calculates the recovery ramp
based on how far the room temperature is away from the
temperature setting, previous equipment performance and
weather history, allowing the thermostat to start recovery at the
optimal time so it can reach the programmed temperature
setting at the programmed time.
The Prestige® thermostat uses two recovery ramps when
setup to control a heat pump system. One ramp for the
compressor and one ramp for the auxiliary heat. Once the
room temperature intersects the compressor ramp, the
compressor turns on until the setpoint is reached. If the room
temperature does not rise quickly enough and intersects the
second ramp, the auxiliary heat turns on. It takes about one
week for the thermostat to adjust to weather conditions,
equipment performance and construction of the home. If the
temperature setting is reached too early or too late, the ramp is
adjusted for the next day's recovery. See Fig. 142.
Fig. 142.
DEHUMIDIFICATION AWAY MODE
Your system can be set to control indoor climate while your
home is vacant during the humid season. Before you leave,
touch MENU, then select Dehumidification Away Mode.
Temperature and humidity will be kept at levels that protect
your home and possessions. When you return, touch Cancel to
resume normal operation.
COMPRESSOR PROTECTION
The thermostat keeps the compressor off for a few minutes
before restarting, to prevent equipment damage. During this
“off” time, the message “waiting for equipment” is displayed on
screen.
PRE-OCCUPANCY PURGE (COMMERCIAL USE ONLY)
This feature turns on the fan 1 to 3 hours before each
“occupied” time period, to provide a comfortable workplace
when you arrive.
P + I CONTROL
A conventional mechanical or electronic thermostat does not
control temperature precisely at setpoint. Typically there is an
offset (droop) in the control point as the system load changes.
Many factors contribute to offset including the switch
differential, thermal lag, overshoot, cycle rates and system
load.
The Prestige® thermostat however, works much differently
than a conventional mechanical or electronic thermostat. The
proprietary algorithm in the thermostat eliminates the factors
causing offset (droop). This makes temperature control more
accurate than the conventional mechanical or electronic
thermostat. The temperature control algorithm is called
proportional plus integral (P + I) control.
The thermostat sensor or a remote indoor sensor senses the
current space temperature. The proportional error is calculated
by comparing the sensed temperature to the setpoint
temperature. The deviation from the setpoint is the proportional
error.
The thermostat also determines integral error, which is a
deviation based on the length of error time (how long the
sensed room temperature has been away from the setpoint
temperature). The sum of the two errors is the (P + I) error. The
cycle rate used to reach and maintain the setpoint temperature
is computed using the P + I control algorithm. The addition of
the integral error is what differentiates the thermostat from
many other mechanical and electronic thermostats. See Fig.
143.
Fig. 143.
WAKE
COMPRESSOR SETPOINT
AUXILIARY HEAT SETPOINT
ROOM TEMPERATURE
M6406A
HEATING COOLING
PERCENT LOAD
TEMPERATURE
THERMOSTAT
HEAT SETPOINT
P+I CONTROL
POINT
PROPORTIONAL COOL
CONTROL POINT
THERMOSTAT
COOL SETPOINT
P+I CONTROL POINT
PROPORTIONAL HEAT
CONTROL POINT
M4414
100 50 0 50 100