System Sensor SpectrAlert SC2415W Installation And Maintenance Instructions page 2

Wire Sizes
The designer must be sure that the last device on the circuit
has sufficient voltage to operate the device within its rated
voltage. When calculating the voltage available to the last
device, it is necessary to consider the voltage drop due to
the resistance of the wire. The thicker the wire, the less the
voltage drop. Generally, for purposes of determining the
wire size necessary for the system, it is best to consider all
of the devices as "lumped" on the end of the supply circuit
(simulates "worst case").
Typical wire size resistance:
18 AWG solid: Approximately 8 ohms/1,000 ft.
16 AWG solid: Approximately 5 ohms/1,000 ft.
14 AWG solid: Approximately 3 ohms/1,000 ft.
12 AWG solid: Approximately 2 ohms/1,000 ft.
Example: Assume you have 10 devices on a zone and
each requires 50 mA average and 2000 Ft. of 14 AWG wir-
ing (total length=outgoing +return). The voltage at the
end of the loop is 0.050 amps per device x 10 devices x 3
ohms/1,000 ft. x 2000 ft =3 volts drop.
The same number of devices using 12 AWG wire will pro-
duce only 2 volts drop. The same devices using 18 AWG
wire will produce 8 volts drop. Consult your panel manu-
facturer's specifications, as well as SpectrAlert's operating
voltage range to determine acceptable voltage drop.
NOTE: If class "A" wiring is installed, the wire length may
be up to 4 times the single wire length in this calculation.
Figure 1D: 24V DC Horn/Strobe Current Draw
Measurements (mA RMS)
Low Volume
Candela Setting Electromechanical
15 73
15/75 89
30 126
75 225
95 272
115 297
177 512
D900-22-00
Temporal
High Volume
3000 Hz Electromechanical 3000 Hz
73 76
89 91
125 128
222 222
270 271
297 296
504 501
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Figure 1A: Current Draw Measurements (RMS)
NOTE: All SC and PC strobes were only tested at the 16-33
Volt-FWR/DC limits. This does not include the 80% low
end or 110% high end voltage limits.
FWR Max. Operating
Candela Current – Strobe
(mA RMS)
15
15/75
30
75
95
115
177
Figure 1B: Horn Sound Measurements (dBA)
Selectable Horn Tones
Temporal Low Electromechanical
Volume
3000 Hz Interrupted
High Electromechanical
Volume
3000 Hz Interrupted
Non-
Low Electromechanical
Temporal
Volume
3000 Hz Interrupted
High Electromechanical
Volume
3000 Hz Interrupted
Figure 1C: Horn Current Draw Measurements (RMS)
Selectable Horn Tones
Temporal Low Electromechanical
Volume
3000 Hz Interrupted
High Electromechanical
Volume
3000 Hz Interrupted
Non- Low Electromechanical
Temporal Volume
3000 Hz Interrupted
High Electromechanical
Volume
3000 Hz Interrupted
NOTE: Regulated 24 VDC, max operating current 57.0 mA
24 V FWR, max operating current 57.5 mA
NOTE: 24VDC 2-wire horn/strobe current is shown in Figure
1D. Current draw for other horn/strobe power supplies can
be calculated by adding the strobe current draw (Figure 1A)
for chosen candela setting to the horn current draw (Figure
1C) for chosen setting.
Low Volume
Electromechanical 3000 Hz
78 75
92 89
128 125
222 219
271 266
296 291
496 491
2
DC Max. Operating
Current – Strobe
(mA RMS)
68 64
77 78
107 113
197 205
239 274
298 325
399 489
16-33V
75
75
80
81
79
79
84
86
16-33 (VDC) 16-33 (VFWR)
23 23
33 23
53 44
57 40
37 29
32 33
49 49
56 58
Non-Temporal
High Volume
Electromechanical 3000 Hz
75 81
90 96
125 131 134
219 221 222
265 269 270
290 292 293
493 491 496
I56-1453-012R
86
98