Operation - Honeywell T8511 Manual

OPERATION

Thermal Performance
During severe weather, the thermostat actually controls closer
to the setpoint than a conventional control. This is because
the heat anticipator is replaced by two electronic control
strategies—cycling by heat anticipation and proportional plus
integral control.
Electronic cycling by heat anticipation acts like a traditional
heat anticipator except that it never needs adjusting for
various control circuit load currents. It cycles the heating
system off slightly before the room temperature reaches the
setpoint to keep the heat left in the ductwork from overheating
the room.
In severe weather, a conventional control with a heat
anticipator tends to turn off the system too soon so the
effective setpoint is somewhat below the setpoint. In very cold
weather, the difference between setpoint and effective control
point can be 5°F or 6°F (2°C or 3°C) with a conventional
control. This phenomenon is called droop .
Proportional plus integral action eliminates droop by adjusting
the on time of the stage that is cycling longer or shorter until
the control point matches the setpoint. The thermostat
maintains the space temperature within 1°F of the setpoint.
The zero droop performance provides improved occupant
comfort and energy savings. Occupants do not need to
continually adjust thermostat settings to maintain desired
temperature, even during severe weather.
Table 8. T8511 Sequence of Operation for Separate Compressor Terminal (Y and W1) Models.
Fan Selection System Selection
Auto Off
Auto Off
On Off
Auto Cool
Auto Cool or Auto
Auto Heat
Auto Heat or Auto
Auto Heat or Auto
Auto Em Heat
Auto Em Heat
Auto Em Heat
Auto Auto
a
System selection is displayed.
T8501 AND T8511 DELUXE ELECTRONIC THERMOSTATS
Operation Sequence
The thermostat energizes specific terminals depending what
the Fan and System are set to. The LCD will display symbols
and words to report the condition of system. See Tables 7 and
8 for specific information.
Selection
Auto
On
Auto
Auto
Auto
Auto
Auto
a
b
c
d
Call Energize
None None
Fan G
None G
None O
Cooling O, G, Y
None B
Heating B, W1
Heating B, W1, W2
None B
Stage 1 heating B, E
Stage 2 heating B, E, W2
b
None
O or B
b
Based on last piece of equipment called (cooling = O or heating = B)
and Installer Setup selection.
11
Table 7. T8501 Sequence of Operation.
Fan System
Selection Call
Off None
Off None
Cool None
Cool or Auto Cooling O
Heat None
Heat or Auto Heating B
Auto None
System selection is displayed.
Only available on select models.
When electric heat fan is selected, G is energized and fan
symbol is displayed.
Based on last piece of equipment called (cooling = O or
heating = B) and Installer Setup selection.
None
None
and
None
and
, , and Aux Ht
Em Ht
, and Em Ht
, , Em Ht and Aux Ht
None
a
Energize Display
None None
G
b
None
O
b
, G, Y
and
b
None
B
b c
, W
d
None
O or B
a
Display
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