Advanced Features; Adaptive Intelligent Recovery (Residential Use Only); Compressor Protection - Honeywell TH8321 Product Data

Advanced Features

ADAPTIVE INTELLIGENT RECOVERY (RESIDENTIAL
USE ONLY)
Over time, the VisionPRO® 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 VisionPRO® 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. 96.
Fig. 96.
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 Dehum 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 "Wait" 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.
COMPRESSOR SETPOINT
AUXILIARY HEAT SETPOINT
ROOM TEMPERATURE
WAKE
M6406A
VISIONPRO® 8000 SMART THERMOSTAT
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 VisionPRO® 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 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. 97.
PROPORTIONAL COOL
CONTROL POINT
P+I CONTROL
POINT
PROPORTIONAL HEAT
CONTROL POINT
THERMOSTAT
HEAT SETPOINT
HEATING
100 50
Installer Options
Installer options require a password and should only be
changed by a qualified technician.
51
THERMOSTAT
COOL SETPOINT
P+I CONTROL POINT
COOLING
0 50
PERCENT LOAD
Fig. 97.
MCR34100
Fig. 98.
33-00096—04
100
M4414