Honeywell W7750A User Manual
EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER
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STAGED COOLING CONTROL
The Excel 10 W7750 Controller supports up to four stages of
D/X cooling. As space temperature rises above the current
Cooling Setpoint, the controllers mode of operation is
switched to the COOL mode. When in the COOL mode, all
heating outputs are driven closed or off (with the exception
that occurs during IAQ Override Operation, see above), and
the staged cooling outputs are enabled for use. When in the
COOL mode, the PID cooling control algorithm compares the
current space temperature to the EffectiveCoolSetPt, and
D/X cooling. As space temperature rises above the current
Cooling Setpoint, the controllers mode of operation is
switched to the COOL mode. When in the COOL mode, all
heating outputs are driven closed or off (with the exception
that occurs during IAQ Override Operation, see above), and
the staged cooling outputs are enabled for use. When in the
COOL mode, the PID cooling control algorithm compares the
current space temperature to the EffectiveCoolSetPt, and
calculates a PID error signal. This error signal causes the
cooling stage outputs to be cycled as required to drive the
space temperature back to the setpoint. Fig. 50 illustrates the
relationship between PID error and staged output activity. As
the error signal increases and the space temperature is
getting farther away from setpoint, or is remaining above
setpoint as time elapses, additional stages of cooling are
energized until, if PID error reaches 100 percent, all
configured stages are on.
cooling stage outputs to be cycled as required to drive the
space temperature back to the setpoint. Fig. 50 illustrates the
relationship between PID error and staged output activity. As
the error signal increases and the space temperature is
getting farther away from setpoint, or is remaining above
setpoint as time elapses, additional stages of cooling are
energized until, if PID error reaches 100 percent, all
configured stages are on.
Fig. 50. Staged output control versus PID Error.
If economizer dampers are configured, and the outdoor air is
suitable for free cooling, the economizer operates as the first
stage of cooling. For example, if a controller was configured
with two stages of mechanical cooling and an economizer, the
application should be viewed in Fig. 50 as a three-stage
system.
suitable for free cooling, the economizer operates as the first
stage of cooling. For example, if a controller was configured
with two stages of mechanical cooling and an economizer, the
application should be viewed in Fig. 50 as a three-stage
system.
Setpoints for the PID gains allow for unit-by-unit adjustment of
the control loop, if required; however, any change from the
default values should be minimal.
the control loop, if required; however, any change from the
default values should be minimal.
The PID control algorithm used to control staged cooling is
anticipator-driven, and is similar to the algorithm used in the
T7300 commercial thermostat. All staging events are subject
to a minimum interstage time delay, which is based on the
cycles per hour user setting (CoolCycHr). The minimum
interstage time delay ranges from 90 seconds (at 12 cycles
per hour) to 8.5 minutes (at two cycles per hour), see Table
17. The user has the option to disable the minimum run timer
(DisMinClTimer for cooling). If the minimum run timer is
disabled, the interstage time delay is fixed at 20 seconds. The
cycling rate is separately selectable for heating and cooling
between 2 and 12 cycles per hour (cph).
anticipator-driven, and is similar to the algorithm used in the
T7300 commercial thermostat. All staging events are subject
to a minimum interstage time delay, which is based on the
cycles per hour user setting (CoolCycHr). The minimum
interstage time delay ranges from 90 seconds (at 12 cycles
per hour) to 8.5 minutes (at two cycles per hour), see Table
17. The user has the option to disable the minimum run timer
(DisMinClTimer for cooling). If the minimum run timer is
disabled, the interstage time delay is fixed at 20 seconds. The
cycling rate is separately selectable for heating and cooling
between 2 and 12 cycles per hour (cph).
Table 17. Interstage Minimum Times
STAGED HEATING CONTROL
The Excel 10 W7750B,C Controller supports up to four stages
of heating. As space temperature falls below the current
Cooling Setpoint, the controller mode of operation is switched
to the HEAT mode. When in the HEAT mode, all cooling
outputs are driven closed or off, and the staged heating
outputs are enabled for use. When in the HEAT mode, the PID
of heating. As space temperature falls below the current
Cooling Setpoint, the controller mode of operation is switched
to the HEAT mode. When in the HEAT mode, all cooling
outputs are driven closed or off, and the staged heating
outputs are enabled for use. When in the HEAT mode, the PID
NO. STAGES
CONFIGURED
PID
ERROR
ONE STAGE
TWO STAGES
THREE STAGES
FOUR STAGES
0%
25% 33%
50%
66%
75%
100%
> 100%
CYCLING
STAGE 1
CYCLING
STAGE 1 LOCKED ON
STAGE 2 CYCLING
STAGE 1
CYCLING
STAGE 1 LOCKED ON
STAGE 2 CYCLING
STAGE 1,2 LOCKED ON
STAGE 3 CYCLING
ALL STAGES
LOCKED ON
ALL STAGES
LOCKED ON
ALL STAGES
LOCKED ON
ALL STAGES
LOCKED ON
STAGE 1
CYCLING
STAGE 1
LOCKED ON
STAGE 2
CYCLING
STAGE 1,2
LOCKED ON
STAGE 3
CYCLING
STAGE 1,2,3
LOCKED ON
STAGE 4
CYCLING
M10112
Cycles/Hour Selection
Minimum On/Off time (Min.)
2
8.5
3
5.5
4
4.0
5
3.5
6
3.0
7
2.5
8
2.0
9
2.0
10
2.0
11
1.5
12
1.5