User guide

D900-22-00 2 I56-1453-012R
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 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.
Candela
FWR Max. Operating
Current – Strobe
(mA RMS)
DC Max. Operating
Current – Strobe
(mA RMS)
15 68 64
15/75 77 78
30 107 113
75 197 205
95 239 274
115 298 325
177 399 489
Figure 1B: Horn Sound Measurements (dBA)
Selectable Horn Tones
16-33V
Temporal Low
Volume
Electromechanical 75
3000 Hz Interrupted 75
High
Volume
Electromechanical 80
3000 Hz Interrupted 81
Non-
Temporal
Low
Volume
Electromechanical
79
3000 Hz Interrupted 79
High
Volume
Electromechanical 84
3000 Hz Interrupted 86
Figure 1C: Horn Current Draw Measurements (RMS)
Selectable Horn Tones
16-33 (VDC) 16-33 (VFWR)
Temporal Low
Volume
Electromechanical 23 23
3000 Hz Interrupted 33 23
High
Volume
Electromechanical 53 44
3000 Hz Interrupted 57 40
Non-
Temporal
Low
Volume
Electromechanical
37 29
3000 Hz Interrupted 32 33
High
Volume
Electromechanical 49 49
3000 Hz Interrupted 56 58
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.
Temporal Non-Temporal
Low Volume High Volume Low Volume High Volume
Candela Setting Electromechanical 3000 Hz Electromechanical 3000 Hz Electromechanical 3000 Hz Electromechanical 3000 Hz
15 73 73 76 78 75 75 81 86
15/75 89 89 91 92 89 90 96 98
30 126 125 128 128 125 125 131 134
75 225 222 222 222 219 219 221 222
95 272 270 271 271 266 265 269 270
115 297 297 296 296 291 290 292 293
177 512 504 501 496 491 493 491 496
Figure 1D: 24V DC Horn/Strobe Current Draw
Measurements (mA RMS)