Honeywell W7750A specifications Prepare Wiring Diagrams, General Considerations

EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

LINE VOLTAGE GREATER THAN 150 VAC

24 VAC

TRANSFORMER

1

EARTH

GROUND

1

W7750

• To minimize EMI noise, do not run Triac output wires

in the same conduit as the input wires or the LON-

WORKS Bus communications wiring.

• Unswitched 24 Vac power wiring can be run in the

same conduit as the LONWORKS Bus cable.

• Make earth ground connections with the shortest

possible wire run using 14 AWG (2.0 mm2) wire. A

good earth ground is essential for W7750 operation.

Ideally, connect the earth ground to the ground bus

at a motor control center or circuit breaker panel.

However, if the nearest ideal earth ground is inac-

cessible, consider an alternate source for earth

ground. Metal water pipe is generally a good ground,

but do not use sprinkler pipe if prohibited by local

EARTH

GROUND

1IF THE W7750 CONTROLLER IS USED IN UL 1995 EQUIPMENT AND THE PRIMARY POWER IS MORE THAN 150 VOLTS, GROUND 24 VAC COM

SIDE OF TRANSFORMER SECONDARY. M10088A

Fig. 24. Transformer power wiring details for one Excel 10 used in UL 1995 equipment (U.S. only).

IMPORTANT

Notes on power wiring:

•All field wiring must conform to local codes and ordi- nances or as specified on installation wiring dia- grams.

•To maintain NEC Class 2 and UL ratings, the instal- lation must use transformers of 100 VA or less capacity.

•For multiple controllers operating from a single trans- former, the same side of the transformer secondary must be connected to the same input terminal in each controller (21 on the W7750A and 24 on the W7750B,C) and the ground terminals must be con- nected to a verified earth ground for each controller in the group. See Fig. 23. (Controller configurations are not necessarily limited to three devices per trans- former.)

•For the W7750B,C Controller (which has Triac out- puts), all output devices must be powered from the same transformer as the one powering the Excel 10 W7750 Controller.

•Use the heaviest gauge wire available, up to 14 AWG (2.0 mm2) with a minimum of 18 AWG (1.0 mm2) for all power and earth ground connections.

codes. Attention must be given when duct work, con-

duit, or rebar are to be considered as ground

sources. It is the responsibility of the installer to

assure that these structures are tied back to a known

earth ground.

Step 4. Prepare Wiring Diagrams

General Considerations

The purpose of this step is to assist the application engineer in developing job drawings to meet job specifications. Wiring details are included for the W7750A,B,C Controllers and the T7770 and T7560A,B Wall Modules. The drawings detail I/O, power, and LONWORKS Bus communication wiring connections.

NOTE: For field wiring, when two or more wires, other than 14 AWG (2.0 mm2) are to be attached to the same connector block terminal, be sure to twist them together. Deviation from this rule can result in improper electrical contact. See Fig. 25.

The connector block terminals on the W7750 Controllers and on the T7770 Wall Modules accept 14 through 22 AWG (2.0 to

0.34mm2) wire. The connector block terminals on the T7560A,B Wall Modules accept 18 through 22 AWG (1.0 to

0.34mm2) wire. Table 9 lists wiring types, sizes, and length restrictions for Excel 10 products.

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