Honeywell W7750A specifications Construction, Controllers

EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

PWM Pulse Width Modulated output; allows analog modulating control of equipment using a digital output on the controller.

RTD Resistance Temperature Detector; refers to a type of temperature sensor whose resistance output changes according to the temperature change of the sensing element.

Subnet A LONWORKS Bus segment that is separated by a router from its Q7750A Zone Manager.

TOD Time-Of-Day; the scheduling of Occupied and Unoccupied times of operation.

TPT Twisted Pair Transceiver.

VA Volt Amperes; a measure of electrical power output or consumption as applies to an ac device.

Vac Voltage alternating current; ac voltage rather than dc voltage.

VAV Variable Air Volume; refers to either a type of air distribution system, or to the W7751 Excel 10 VAV Box Controller that controls a single zone in a variable air volume delivery system.

VOC Volatile Organic Compound; refers to a class of common pollutants sometimes found in buildings. Sources include out-gassing of construction materials, production-line by-products, and general cleaning solvents. A VOC is occasionally used as a measure of indoor air quality.

W7750 The model number of the Excel 10 CVAHU Controllers (also see CVAHU).

W7751 The model number of the Excel 10 VAV Box Controllers (also see VAV).

Wall Module The Excel 10 Space Temperature Sensor and other optional controller inputs are contained in the T7770 or the T7560A,B Wall Modules. See Application Step 5. Order Equipment for details on the various models of Wall Modules.

XBS Excel Building Supervisor; a PC based tool for monitoring and changing parameters in C-Bus devices.

Construction

Controllers

The Excel 10 W7750 Controller is available in three different models. The W7750A Model, which is a low cost controller made for simple single zone air handlers and heat pump controls. The W7750B,C Models are intended for more complex applications.

The W7750B,C Models use Triacs for their digital outputs, where as the W7750A Model uses dry-contact relays. The W7750C Model also has three analog outputs available on terminals 16, 17 and 18.

All wiring connections to the controller are made at screw terminal blocks. Connection for operator access to the LONWORKS Bus is provided by plugging the SLTA connector cable into the LONWORKS Bus communications jack.

The W7750A,B,C Models consist of a single circuit board that is mounted in a sheet metal subbase and protected by a factory snap-on cover. The three controllers have the same physical appearance except for terminals 16 through 20 (W7750A) and different labels next to the wiring terminals (see Fig. 3, 5 or 6). Wires are attached to the screw terminal blocks on both sides of the controller. The controllers mount with two screws (see Fig. 4 or 7). The W7750 can also be mounted using DIN rail. To mount the W7750 on DIN rail, purchase two DIN rail adapters (obtain locally) part number TKAD, from Thomas and Betts, see Fig. 8, then snap onto standard EN 50 022 35 mm by 7.5 mm (1-3/8 in. by 5/16 in.) DIN rail. DIN rail is available through local suppliers.

A channel in the cover allows the controller status LED to be visible when the cover is in place. There are no field- serviceable parts on the circuit board and, therefore, it is intended that the cover never be removed.

The W7750A,B,C can be mounted in any orientation. Ventilation openings were designed into the cover to allow proper heat dissipation regardless of the mounting orientation. See Fig. 4 and 7.

The input/output and control differences between the two models are summarized in Table 2. The I/O points in Table 2 are the free I/O points that are not reserved for Wall Module use.

Table 2. List of Differences in W7750A and W7750B,C Controllers.

	W7750A Model	W7750B,C Models
Digital Outputs	Six Relay Outputs	Eight Triac Outputs
Digital Inputs	Two	Four
Wall Module	One*	One*
Analog Outputs	None	Three 4 to 20 mA Outputs (W7750C only)
Analog Inputs	One (Resistive Input Only)	Four (Two Resistive and two Voltage/Current Inputs)
DC Power	None	20 Vdc available to power optional sensors
Floating (Series 60) Control	Economizer Only	Heating, Cooling, and/or Economizer
PWM Control	None	Heating, Cooling, and/or Economizer

*The T7770 or the T7560 Wall Modules includes I/O points for two analog inputs for the space temperature and the setpoint knob, a digital input for the Bypass pushbutton, and a digital

output for the LED Bypass Indicator. These W7750 I/O points are configurable, but are normally used for the Wall Module.

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