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HEAT PUMP THERMOSTAT CROSS REFERENCE/SELECTION GUIDE
Chronotherm IV Electronic Deluxe Heat Pump Thermostats
The T8611 Chronotherm IV thermostat models provide up to three-stage heat and two-stage cool control for heat pump
systems, using manual or automatic changeover. These models provide full 7-day programming capability. Models with
programmable fan operation are available for homeowner comfort. Backlighting on the large display makes the LCD very
easy to read. Adaptive Intelligent Recovery™ control brings the room temperature to the desired temperature setpoint at the
programmed time, maximizing comfort and energy savings. First stage heat anticipation is fixed; second stage heat
anticipation is selectable.
Adaptive Intelligent Recovery™ Control (Night Setback and Heat Pumps)
Heat pump applications are ideal for night setback and energy savings. However, in order to maximize the energy saved
in a night setback mode, use the T8611 Chronotherm® III or T8611 Chronotherm® IV Thermostats with Adaptive
Intelligent Recovery™ control.
Adaptive Intelligent Recovery™ control assures that the comfort setting is achieved at the programmed time regardless
of weather conditions. Conventional recovery starts recovery at the beginning of the programmed time period and uses
the equipment to achieve the comfort settings as soon as possible.
Unlike the Chronotherm III models, the Adaptive Intelligent Recovery control can be turned off in the Installer Set-up
mode in the Chronotherm IV thermostat. Honeywell does not recommend this because the auxiliary heat comes on
when the program time begins, and runs continuously until the setpoint is reached.
Applications Requiring Special System Hookups
Using a Chronotherm III T8611G or T8611M on Systems Requiring Separate W
Terminals
The Chronotherm III T8611G and T8611M are designed with only one common compressor terminal. The Y terminal is
energized on a call for stage 1 heat and stage 1 cool. However, some multistage heat pump equipment requires one
terminal to be energized on a call for stage 1 heat (W
In order for the T8611G or T8611M to accommodate this requirement, a separate switching relay must be added to the
installation. See the following wiring diagrams for heat pumps that provide changeover in the heating mode and for heat
pumps that provide changeover in the cooling model.
Heat Pumps with Heating Mode Changeover
Here is how the switching relay allows the system to work properly:
* The Y terminal is connected to the equipment terminal W1 through the normally closed contacts on the R8222B
Switching Relay. When the thermostat calls for heat, the thermostat Y terminal activates the first stage of heating.
* The O terminal is connected to the coil terminals on the R8222B Switching Relay. When the system switch is in the
COOL position, the O terminal is energized, reversing the logic of the Chronotherm III T8611G and T8611M Y
terminal. Now when the thermostat calls for cooling, the Y terminal activates the first stage of cooling.
) and one terminal to be energized on a call for stage 1 cool (Y
1
and Y
1
1
).
1
70-6627 • 7
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