Honeywell W7750A specifications Overview, Plan the System, Determine Other Bus Devices Required

EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

APPLICATION STEPS

Overview

The seven application steps shown in Table 6 are planning considerations for engineering an Excel 10 W7750 System. These steps are guidelines intended to aid understanding of the product I/O options, bus arrangement choices, configuration options and the Excel 10 W7750 Controller role in the overall EXCEL 5000 OPEN SYSTEM architecture.

	Table 6. Application Steps.
Step No.	Description
1	Plan The System
2	Determine Other Bus Devices Required
3	Lay Out Communications and Power Wiring
4	Prepare Wiring Diagrams
5	Order Equipment
6	Configure Controllers
7	Troubleshooting

Step 1. Plan the System

Plan the use of the W7750 Controllers according to the job requirements. Determine the location, functionality and sensor or actuator usage. Verify the sales estimate of the number of W7750 Controllers, T7770 and T7560 Wall Modules required for each model type. Also check the number and type of output actuators and other required accessories.

When planning the system layout, consider potential expansion possibilities to allow for future growth. Planning is very important to be prepared for adding HVAC systems and controllers in future projects.

T7560 Wall Modules can only be hard-wired, they have no

LONWORKS Bus access. T7770 Wall Modules can be installed as either hard-wired I/O-only devices or additional wiring can be run to them (for the LONWORKS Bus network) to allow a CARE/E-Vision operator terminal to have access to the LONWORKS Bus. The application engineer needs to determine how many wall modules, T7770s and T7560s are required. All T7770 Wall Modules, except the T7770A1006 and the T7770A1014, can be connected via the LONWORKS Bus jack. Also the application engineer needs to know how many T7770s without LONWORKS Bus network connections are being installed on the job, and then clearly document which wall modules (if any) have network access. This information is required during installation to ensure that the proper number and type of wires are pulled to the wall modules, and the building operators are informed about where they can plug in to the LONWORKS Bus network with a portable operator terminal (see Fig. 18, 19 and 20). Refer to Step 4. Prepare Wiring Diagrams for details, about the about the wiring differences between the two types.

	EXCEL 10
	W7750
	CVAHU
	CONTROLLER
NOTEBOOK PC
	SHIELDED
	INTERFACE
	CABLE
EIA-232	Q7752A
SERIAL
PORT	SLTA
CABLE
PART		LONWORKS BUS
NO. 205979
		PORT

M15120A

Fig. 18. Connecting the portable operator terminal

to the LONWORKS® Bus.

The FTT communication wiring, (LONWORKS Bus) between controllers is a free topology scheme that supports T-tap, star, loop, and mixed wiring architecture. Refer to the LONWORKS Bus Wiring Guidelines form, 74-2865 for complete description of network topology rules. See Application Step 3. Lay Out Communications and Power Wiring, for more information on bus wiring layout, and see Fig. 27 through 35 in Application Step 4. Prepare Wiring Diagrams, for wiring details.

The application engineer must review the Direct Digital Control (DDC) job requirements. This includes the Sequences of Operation for the W7750 units, and for the system as a whole. Usually there are variables that must be passed between the W7750 Controllers and other zone controller(s), or central plant controller(s) that are required for optimum system-wide operation. Typical examples are the TOD Occ/ Unocc signal, the outdoor air temperature, the demand limit control signal, and the smoke control mode signal.

It is important to understand these interrelationships early in the job engineering process to ensure implemention when configuring the controllers. (See Application Step 6. Configure Controllers, for information on the various Excel 10 parameters and on Excel 10 point mapping.)

Step 2. Determine Other Bus Devices Required

A maximum of 62 nodes can communicate on a single

LONWORKS Bus segment. Each W7750 (CVAHU) Controller constitutes one node. If more nodes are required, a Q7751A,B Router is necessary. Using a router allows up to 125 nodes, divided between two LONWORKS Bus segments. The router accounts for two of these nodes (one node on each side of the router); a Q7750A Excel 10 Zone Manager takes one node and two nodes are available for operator terminal nodes, leaving 120 nodes available for Excel 10 Controllers. All 120 controllers are able to talk to each other through the router. A Q7750A Excel 10 Zone Manager is required to connect the LONWORKS Bus to the standard EXCEL 5000 OPEN System C-Bus. Each Excel 10 Zone Manager supports up to 120 Excel 10 Controllers. This limit is set in the Excel 10 Zone Manager database as an absolute maximum.

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