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3.3
4-Wire Smoke Detector Connections
Refer to the Device Compatibility Chart for suitable 4-wire smoke detectors.
TB1
1
2
A maximum of 200mA is available from the
+24VDC 4-wire smoke detector power circuit
on TB1 terminals 3 and 4. Any power that is
drawn from the +24VDC Non-Resettable
Power on TB2 terminals 1 and 2 must be
subtracted from available 4-wire detector
power. (see sections "Specifications" and
"Power" ).
Figure 3.3-1: Diagram of Connections for a 4-Wire Smoke Detector
Notes on Style B and Style D field wiring:
1)
2)
Where:
R
is the maximum resistance of the 24V wires.
MAX
V
is the minimum operating voltage of the detector or end-of-line relay, whichever is greater, in volts.
OM
N is the total number of detectors on the 24V supply loop.
I
is the detector current in standby.
S
N
is the number of detectors on the 24V power loop which must function at the same time in alarm.
A
I
is the detector current in alarm.
S
I
is the end-of-line relay current.
R
16
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+
-
3
4
+24VR
The Power Supervision Relay coil leads must be connected to the last detector base 24V
screw terminals.
Calculation of the maximum allowable resistance in the 24VDC detector power wiring:
R
=
MAX
MRP-4424
Document 15180
firealarmresources.com
24 VDC (+)
Common (-)
IDC(+)
IDC(-)
UL-listed 24 VDC
Four-Wire Smoke Detectors
TB4
B+
Style B Initiating Device Circuit
Initiating Device Circuits 1, 2, 3, or 4
can be used. Style D wiring can also be
employed.
(20.6 - V
)
OM
(N x I
) + (N
x I
) + (I
)
S
A
A
R
Rev D
03/12/97
15180:D
24 VDC (+)
Red
Common (-)
Black
IDC(+)
IDC(-)
UL Listed
4.7K, 1/2-Watt
ELR
A+
A-
B-
1
2
3
4
IDC #1
Listed
Power
Supervision
Relay
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