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INSTALLING DETECTOR WIRING
Figure 2-17.  Wire Size/Length/Resistance Graph

TM-10-6665-297-13P Bacharach Combustibles Gas Alarm System NSN 6665-00-410-4982 Manual
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TM 10-6665-297-13&P 2-6 DETECTOR INSTALLATIONS   (continued) 2-6.2 Installing Detector Wiring  (continued) 1.   When both wire runs are within 20 percent of equal distance, consult Table 2-2 for appropriate wire gauge,  and  install  same-size  wire  for  both  runs.    Use  of  #16  AWG  wire  is  desirable  even  for  very short runs, and may be used to simplify wire selection where cost of wire is not greatly significant. 2.   If the two wire runs are of unequal lengths:  First choose wire size from Table 2-2 for the longer run (if marginal,  choose  next  size  larger),  then  determine  exact  wire  resistance  from “OHM-PER-FOOT” column of Table 2-2.  Next, for the second detector, choose a smaller wire gauge from Figure 2-17 to obtain as nearly as possible the same resistance as the wire for a longer run.  (Both sensors must operate at nearly the same voltage; hence voltage drops in the two wire runs must be nearly equal. Voltage drop in wires can be computed by determining resistance in ohms for the length and size of wire, then multiplying by 0.28 amps detector current.  Where differences in voltage drops between leads must be reconciled, set detector operating voltage between the values measured at detectors for each in accordance with paragraph 2-6.9, step 7.) 3.   Signal return wires to terminals C1 and C2 may be #20 AWG or larger for distances to 1100 feet, or #18 or larger for greater distances. AWG Ohms/1000 Ft. Feet/Ohm at 68°F at 68°F 6 .40 2531 8 .63 1593 10 1.0 1000 12 1.6 630 14 2.5 396 16 4.0 249 18 6.4 157 20 10.2 99 Table   2-2.      Resistance   of   Standard   Annealed   Copper   Wire   (Values   are approximately,  and  will  vary  depending  upon  resistivity  of  specific  conductor used.) (See also Resistance Graph, Figure 2-17.) 2-6.2.1  Installing Single Detector on CD800/830 or CD802/832 Control Unit.  Install a single detector as follows (Figures 2-8 through 2-11): NOTE:  Do not disconnect 15-ohm paired resistors factory-installed on DET 2 terminals A, R, and C. 1. Connect  a  green  wire  between  detector  active  element  lead  (green,  banded “A”)  and  control module terminal marked DET 1, A. 23-9617 7/1/76 2-23







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