Back BOX Installation, Table B VAC Wiring Distances

Table B. 24 VAC Wiring Distances

The following are the recommended maximum distances for 24 VAC with a 10-percent voltage drop. (Ten percent is generally the maximum allowable voltage drop for AC-powered devices.)

Wire Gauge

	20	18	16	14	12	10

30 vA	94 ft	150 ft	238 ft	380 ft	603 ft	960 ft
	(28 m)	(45 m)	(72 m)	(115 m)	(183 m)	(292 m)

75 vA	37 ft	60 ft	95 ft	152 ft	241 ft	384 ft
	(11 m)	(18 m)	(29 m)	(46 m)	(73 m)	(117 m)

BACK BOX INSTALLATION

OPTIONAL PROCEDURE:

If you prefer, you may make the wiring connections in- side the back box before installing the back box in the ceiling.

To do this, loosen the thumbscrew inside the back box and open the hinged door (refer to Figure 10). Bring the wiring into the back box through the con- duit fitting. Follow the steps in the Back Box Connec- tions section and then return to this section.

CAUTION: The ceiling must be ca-

pable of supporting

16 pounds (7.3 kg) of weight. If the ceiling will not support this weight, provide additional reinforcement. Also, a suitable safety chain must be attached to the back box to support up to 16 pounds (7.3 kg) in the event of a ceiling failure.

1.Suspended Ceiling Only (for hard ceiling, go to step 2) – Install the ceiling tile with the back box. Attach a T-rail clip on each side of the ceiling tile as shown in Figure 7.

The clips for the ceiling tile are supplied with the back box. Attach the clip to the T-rail. Fasten the L-bracket to the clip with the supplied screw, lock washer and nut.

2.Install a safety chain or cable (not supplied) that will support up to 16 pounds (7.3 kg). Fasten one end to a support structure in the ceiling. Fasten the other end to the safety chain bracket (refer to Figure 5) to prevent the back box from falling.

3.Refer to Figure 10. Loosen the thumbscrew inside the back box and open the hinged door.

4.Bring the wiring into the back box through the conduit fitting. If the wiring is inside flexible conduit, connect the conduit to the fitting on the back box.

5.Hard Ceiling Only - Refer to Figure 6. Compress the spring clips on the back box with your hands and push the back box through the hole in the ceiling. The spring clips will spring out when they clear the ceiling. Refer to Figure 7. Tighten the screws until the spring clips hold the back box firmly to the ceiling. You will hear a clicking noise when the screws are tight.

Proceed to the Back Box Connections section.

THUMBSCREW

00096

Figure 10. Interconnect Door

12	Pelco Manual C1487M-C (7/99)