Advanced Features; Adaptive Intelligent Recovery; Compressor Protection; P + I Control - Honeywell C7189R2002-2 User Manual

Advanced Features

ADAPTIVE INTELLIGENT RECOVERY

Over time, the T10 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 T10 thermostat uses two recovery ramps when setup to control a heat pump system with electric aux heat and droop set
to "Comfort". 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.

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.

P + I CONTROL

A conventional mechanical 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 T10 thermostat however, works much differently than a conventional mechanical thermostat. Droop is always set to comfort
and not adjustable when controlling a 2 stage furnace or 2 stage heat pump without aux heat. 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 mechanical thermostats.
* The T10 only uses droop for control of the aux heat on systems with a heat pump and either electric heat strips or a gas/oil
furnace as backup heat. In these cases the droop setting locks out the aux heat unless the droop condition or upstage timer
setting allows the aux heat to run. When electric strips are used as the aux heat, a "Comfort" setting is typically used instead of a
droop setting. This is configured by the installer.
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