System Sensor SP2R1224MCK - Manual (Page 2)

Figure 2. Speaker Voltage and Power Selection:
25.0V
70.7V
2W
1W
1/2W
1/4W
25.0V
70.7V
2W
1W
1/2W
1/4W
CORRECT
SW1
SW
1
INCORRECT
Table 1. Sound levels for each transformer power tap:
INPUT
VOLTS
2 W 1 W 1 /
2
W 1 /
4
W
25.0 89 87 85 81
70.7 90 87 84 81
CAUTION
Signal levels exceeding 130% rated signal voltage can dam-
age the speaker. Consequently, an incorrect tap connection
may cause speaker damage. This means that if a 25V tap
is selected when a 70.7V amplifier is being used, speaker
damage may result. Therefore, be sure to select the proper
taps for the amplifier voltage/input power level combina-
tion being used.
D900-40-00 2 I56-2609-002R
A0101-00
A0102-00
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 wiring
(total length=outgoing+return). The voltage at the end of
the loop is 0.050 amps per device × 10 devices × 3 ohms/
1,000 ft. × 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.
Installation
All wiring must be installed in compliance with the National
Electrical Code (NEC) and applicable local codes as well as
special requirements of the authority having jurisdiction,
using the proper wire size. This also includes all applicable
NFPA Standards, ANSI/UL 1480, UL 1971 and NEC 760.
Electrical
1. Connect the speaker/strobe as shown in Figure 1. Keep
in mind that even though the speaker and strobe are a
single mechanical unit, they are electrically independent
and require separate power sources.
NOTE: Do NOT loop electrical wiring under terminal
screws. Wires connecting the device to the control
panel must be broken at the device terminal connec-
tion in order to maintain electrical supervision.
Figure 1. Electrical connections:
TO NEXT
STROBE OR EOL
INPUT FROM
POWER SUPPLY
INPUT FROM
AMPLIFIER
TO NEXT
SPEAKER OR EOL
STROBE SPEAKER
NOTE: Supply power for strobe must be continuous for
proper operation.
2. See Figure 2 as an example of how to select a 1 ⁄
4
Watt
input when a 25 volt amplifier is being used. Notice that
the header, SW1, has two shunts. One shunt is used to
select either 25 or 70.7 volts input. The other shunt is
used to select input power of
1 ⁄
4
, 1 ⁄
2
, 1 or 2 Watts. Table 1
lists the UL reverberant and anechoic output sound levels
for each power tap on the SP2 series speaker/strobes.
UL
Reverberant
(dBA @ 10 ft.)