Honeywell T8524, Данные о продукции, Страница: 11 / 16

T8524 DELUXE ELECTRONIC THERMOSTAT
68-0202
11
OPERATION
P+I Control
The thermostat microprocessor based control requires that
the user understands temperature control and thermostat
performance. A conventional electromechanical 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. This is a phenonemon that most people
in the industry know and accept. Many factors contribute to
offset including switch diffewrential, thermal lag, overshoot,
cycle rates and system load.
The thermostat microprocessor simultaneously gathers,
compares and computes data. Using this data, it controls a
wide variety of functions. The special proprietary algorithm
(program) in the thermostat eliminates the factors causing
offset. This makes temperature control more accurate that the
conventional electromechanical or electronic thermostats. The
temperature control algorithm is called proportional plus
integral (P+I) control.
The thermostat sensor, located on the thermostat or remote,
senses the current space temperature. The proportional error
is calculated by comparing the sensed temperature to the
programmed setpoint. The deviation from the setpoint is the
proportional error.
The thermostat also determines the integral error, which is a
deviation based on the length of error time. The sum of the
two errors is the (P+I) error. The cycle rate used to reach
and maintain the setpoint temperature in computed using the
P+I. The addition of the integral error is what differentiates the
thermostat from many other electronic and electromechanical
thermostats. See. Fig. 13.
Operation Sequence
The thermostat energizes specific terminals depending what
the Fan and System are set to. The LCD will display the time,
room temperature, system and fan selection. symbols will be
displayed when the heating, cooling or fan is energized. See
Table 7 for specific information.
Table 7. Multistage System Sequence of Operation.
Fig. 13. Proportional temperature
versus P+I temperature control.
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
a
G is energized and fan symbol is displayed on dual fuel
models when set for electric heat.
b
Based on last piece of equipment called (cooling=O or
heating=B) and Installed Setup section.
System
Fan System Call Energize Display
Auto Off None None None
On Off None G
Auto Cool None O None
Auto Cool or Auto Stage 1
Cooling
O, G, Y1
and
Auto Cool or Auto Stage 2
Cooling
O, G, Y1
and Y2
and
Auto Heat None B None
Auto Heat or Auto Stage 1
Heating
B, G
a
, and
W1
and
Auto Heat or Auto Stage 2
Heating
B, G
a
, W1
and W2
and
Auto Auto None
O or B
b
None