Honeywell W7750A 用户手册
EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER
61
74-2958—1
cooling control algorithm compares the current space
temperature to the EffectiveHeatSetPt, and calculates a PID
error signal. This error signal causes the heating 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.
temperature to the EffectiveHeatSetPt, and calculates a PID
error signal. This error signal causes the heating 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, the space temperature gets
further away from the setpoint, or is remaining below the
setpoint as time elapses, additional stages of heating are
energized until, if PID error reaches 100 percent, all
configured stages are on.
further away from the setpoint, or is remaining below the
setpoint as time elapses, additional stages of heating are
energized until, if PID error reaches 100 percent, all
configured stages are on.
The PID control algorithm used to control staged heating 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, that is based on the
cycles per hour user setting (HeatCycHr). The minimum
interstage time delay ranges from 90 seconds (at 12 cycles
per hour) to eight minutes (at two cycles per hour). See Table
17. The user has the option to disable the minimum run timer
for heating (DisMinHtTimer). 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 two 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, that is based on the
cycles per hour user setting (HeatCycHr). The minimum
interstage time delay ranges from 90 seconds (at 12 cycles
per hour) to eight minutes (at two cycles per hour). See Table
17. The user has the option to disable the minimum run timer
for heating (DisMinHtTimer). 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 two and 12 cycles per hour (cph).
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.
CASCADE CONTROL OF MODULATING COOLING/HEATING
The Excel 10 W7750 Controller supports modulating cooling
and heating valves. These valves can be controlled directly
from the space temperature (like the staged control) or, if the
CascCtrl flag is set, they are modulated to maintain the
discharge air temperature at its setpoint. The discharge air
setpoint is calculated based on the space temperature
deviation from the space setpoint. This is commonly called
cascade control. In the W7750 Controller, cascade control is
available for use with PWM (W7750B,C only) and Series 60
modulating heating and cooling, but not for use with staged
heating/cooling.
and heating valves. These valves can be controlled directly
from the space temperature (like the staged control) or, if the
CascCtrl flag is set, they are modulated to maintain the
discharge air temperature at its setpoint. The discharge air
setpoint is calculated based on the space temperature
deviation from the space setpoint. This is commonly called
cascade control. In the W7750 Controller, cascade control is
available for use with PWM (W7750B,C only) and Series 60
modulating heating and cooling, but not for use with staged
heating/cooling.
Setpoints for the PID gains and for the control band allow for
unit-by-unit adjustment of the control loops, if required;
however, any change from the default values should be
minimal. Also, the W7750 Controller uses an adaptive
algorithm (patent pending) to continuously assess the validity
of the calculated discharge setpoint, and adjust it, as needed,
to ensure precise, accurate control.
unit-by-unit adjustment of the control loops, if required;
however, any change from the default values should be
minimal. Also, the W7750 Controller uses an adaptive
algorithm (patent pending) to continuously assess the validity
of the calculated discharge setpoint, and adjust it, as needed,
to ensure precise, accurate control.
SERIES 60 MODULATING CONTROL
Series 60 Control is also commonly referred to as Floating
Control. The Excel 10 W7750A,B,C Controllers can drive
Series 60 type actuators to control a modulating cooling valve,
a heating valve, and economizer dampers. When floating
control is used, the full-stroke motor drive time of the actuator
must be entered into the configuration parameter CoolMtrSpd
(for cooling), HeatMtrSpd (for heating), or EconMtrSpd (for the
economizer dampers).
Control. The Excel 10 W7750A,B,C Controllers can drive
Series 60 type actuators to control a modulating cooling valve,
a heating valve, and economizer dampers. When floating
control is used, the full-stroke motor drive time of the actuator
must be entered into the configuration parameter CoolMtrSpd
(for cooling), HeatMtrSpd (for heating), or EconMtrSpd (for the
economizer dampers).
PULSE WIDTH MODULATING (PWM) CONTROL
The Excel 10 W7750B,C Controllers can drive a PWM-type
actuator to control a modulating cooling valve, a heating
valve, and economizer dampers. PWM control positions the
actuator to control a modulating cooling valve, a heating
valve, and economizer dampers. PWM control positions the
actuator based on the length, in seconds, of the pulse from
the digital output. The controller outputs a pulse whose length
consists of two parts, a minimum and a maximum. The
minimum pulse time represents the analog value of zero
percent (also indicates a signal presence) and the maximum
pulse length that represents an analog value of 100 percent. If
the analog value is greater than zero percent, an additional
time is added to the minimum pulse time. The length of time
added is directly proportional to the magnitude of the analog
value. If PWM control is used, the configuration parameters
for the PWM operation must be specified. These are
PwmPeriod, PwmZeroScale, and PwmFullScale. These three
parameters are shared by all configured PWM outputs; this
means the heating, cooling, and economizer actuators must
be configured to accept the same style of PWM signal.
the digital output. The controller outputs a pulse whose length
consists of two parts, a minimum and a maximum. The
minimum pulse time represents the analog value of zero
percent (also indicates a signal presence) and the maximum
pulse length that represents an analog value of 100 percent. If
the analog value is greater than zero percent, an additional
time is added to the minimum pulse time. The length of time
added is directly proportional to the magnitude of the analog
value. If PWM control is used, the configuration parameters
for the PWM operation must be specified. These are
PwmPeriod, PwmZeroScale, and PwmFullScale. These three
parameters are shared by all configured PWM outputs; this
means the heating, cooling, and economizer actuators must
be configured to accept the same style of PWM signal.
Example: To find the pulse width of a valve actuator (for
example stroke mid position - 50 percent) with the
PwmZeroScale = 0.1 seconds, PwmFullScale = 25.5
seconds, and the PwmPeriod = 25.6 seconds. There are 256
increments available, so the number of increments required
for 50 percent would be (0.5 X 256) or 128. The time for each
increment for this industry standard pulse time is 0.1 seconds.
The pulse width is the minimum time (0.1 second) + the
number of increments (128 times the (0.1 second) plus 0. 1) =
12.9 seconds. The W7750B,C Controllers would command
the valve output on for 12.9 seconds for the PwmPeriod of
25.6 seconds to maintain the valve position at 50 percent.
example stroke mid position - 50 percent) with the
PwmZeroScale = 0.1 seconds, PwmFullScale = 25.5
seconds, and the PwmPeriod = 25.6 seconds. There are 256
increments available, so the number of increments required
for 50 percent would be (0.5 X 256) or 128. The time for each
increment for this industry standard pulse time is 0.1 seconds.
The pulse width is the minimum time (0.1 second) + the
number of increments (128 times the (0.1 second) plus 0. 1) =
12.9 seconds. The W7750B,C Controllers would command
the valve output on for 12.9 seconds for the PwmPeriod of
25.6 seconds to maintain the valve position at 50 percent.
OUTDOOR AIR LOCKOUT OF HEATING/COOLING
A mechanism is provided in the W7750 to disable the heating
equipment if the outdoor air temperature rises above the
OaTempHtLkOut setpoint. Similarly, the cooling equipment is
disabled if the outdoor air temperature falls below the
OaTempClLkOut setpoint. The algorithm supplies a fixed 2
equipment if the outdoor air temperature rises above the
OaTempHtLkOut setpoint. Similarly, the cooling equipment is
disabled if the outdoor air temperature falls below the
OaTempClLkOut setpoint. The algorithm supplies a fixed 2
°
F
(1.1
°
C) hysteresis with the lock-out control to prevent short
cycling of the equipment.
ECONOMIZER DAMPER CONTROL
A mixed-air economizer damper package can be controlled to
assist mechanical cooling in maintaining the discharge air at
setpoint. Therefore, if modulating economizer damper control
is desired, a discharge air temperature sensor is required. If
the outdoor air is not currently suitable for cooling use (see the
Economizer Enable/Disable Control section), the outdoor air
damper is held at the user-settable minimum position
(EconMinPos) for ventilation purposes.
assist mechanical cooling in maintaining the discharge air at
setpoint. Therefore, if modulating economizer damper control
is desired, a discharge air temperature sensor is required. If
the outdoor air is not currently suitable for cooling use (see the
Economizer Enable/Disable Control section), the outdoor air
damper is held at the user-settable minimum position
(EconMinPos) for ventilation purposes.
Because the outdoor air can be used to supplement
mechanical cooling, the economizer operates as if it were the
first stage of cooling. So, if the outdoor air is suitable for
cooling use, the mechanical cooling (either staged or
modulating) is held off until the economizer has reached its
fully open position. Then, if the discharge temperature
continues to be above setpoint, the mechanical cooling is
allowed to come on. If the outdoor air is not suitable for
cooling use, the economizer is set to its minimum position,
and mechanical cooling is allowed to come on immediately.
mechanical cooling, the economizer operates as if it were the
first stage of cooling. So, if the outdoor air is suitable for
cooling use, the mechanical cooling (either staged or
modulating) is held off until the economizer has reached its
fully open position. Then, if the discharge temperature
continues to be above setpoint, the mechanical cooling is
allowed to come on. If the outdoor air is not suitable for
cooling use, the economizer is set to its minimum position,
and mechanical cooling is allowed to come on immediately.
When the controller is in the Heat mode, the economizer is
held at the minimum position setting (EconMinPos). The
minimum position setting is only used during Occupied mode
operation. When in Standby or Unoccupied modes, the
outdoor air dampers are allowed to fully close if there is no call
for cooling, or if the outside air is not suitable for cooling use.
held at the minimum position setting (EconMinPos). The
minimum position setting is only used during Occupied mode
operation. When in Standby or Unoccupied modes, the
outdoor air dampers are allowed to fully close if there is no call
for cooling, or if the outside air is not suitable for cooling use.