Honeywell W7750A specifications Economizer Control, Pneumatic Actuator Control

EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

SHARED	AUXILIARY
HEAT AND	HEAT
COOL COIL	STAGE(S)

ECONOMIZER CONTROL

Economizer control is available concurrently with any configuration in the W7750 when DOs are not all used by the heating and cooling equipment. Two types of economizer controls are supported by the W7750 Controller, modulating

MIXED

AIRFAN

FAN

STARTER

COMPRESSOR AND

CHANGEOVER VALVE

+

DISCHARGE AIR

control and enable/disable control. Modulating control can be either Series 60 Floating Control or PWM control (PWM control is available on the W7750B,C only). A discharge air temperature sensor is required for modulating economizer damper control. Enable/disable control is provided to emulate the Honeywell T7300 thermostat economizer operation, where a DO tracks the occupancy status of the controller. An external packaged economizer control then modulates the dampers. For modulating control, the economizer is enabled or disabled based on one of ten available strategies (see Appendix B— Sequences of Operation— Economizer Enable/

	COMP 1	CHANGEOVER
	COMP 2	RELAY
EXCEL 10
CVAHU		T7560A,B OR T7770

W7750A,B,C

M17493

Disable Control section, for further details). Fig. 16 illustrates a system with modulating economizer dampers (see Fig. 29, 31, 32 and 35 in Step 4. Prepare Wiring Diagrams section, for wiring details).

Fig. 15. Heat pump with two compressors and auxiliary

heat stage(s).

OUTDOOR	FAN
AIR

COOL HEAT

COIL COIL

-+

DISCHARGE AIR

M	FAN
	STARTER
PWM OR
SERIES 60	RETURN
FLOATING
	AIR
MOTOR
	EXCEL 10
	CVAHU
	W7750A,B,C

DISCHARGE TEMPERATURE SENSOR REQUIRED FOR ECONOMIZER CONTROL

T7560A,B OR T7770

M17494

Fig. 16. Economizer control.

PNEUMATIC ACTUATOR CONTROL

The W7750B,C Controller can control pneumatic actuators for any or all of the three modulating outputs provided by the control algorithm (heat, cool and economizer). Control of pneumatic water/steam valves and damper actuators is provided through a transducer device using either Series 60 Floating Control or PWM DOs. A floating-to-pneumatic, or a PWM-to-pneumatic transducer is required for each output signal. The W7750A Controller can drive Series 60 Floating

Control to modulate cooling valves, heating valves and economizers. There are no PWM outputs configurable on the W7750A model.

For projects with existing pneumatically actuated reheat valves, the Excel 10 W7750 Controller output must be converted to a pneumatic signal using a transducer device developed for use with Excel 10 Controllers. The transducer is

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