Honeywell Sensepoint XCD RFD, Technical Handbook

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Sensepoint XCD RFD Technical Manual SPXCDHMRFEN Issue 4_08-2016
20
6.3 Power for UL/CSA Version
taking into account the voltage drop due to cable resistance.
The maximum loop resistance in the field cable is calculated as follows
R
loop
= (V
controller
– V
detector min
) / I
detector
Example;
The controller is supplying a nominal 24Vdc
(V
controller
)
, the detector minimum allowable
voltage is 12Vdc
(V
detector min
)
, therefore the maximum allowable voltage drop between the
controller and detector is 12Vdc; this means a voltage drop of 6V in each core (+ve core
and -ve core).
Power consumption of the detector is 5.0W. The current required to drive the detector at
the minimum voltage is (I = P / V), 5.0 / 12 = 416.7 mA (I detector).
So, the maximum ieldcable loop resistance (R loop) = 12 / 0.42 = 28.8 Ohms, or 14.4 Ohms
per core, (allowing for component variations, losses, etc.).
The following tables show the maximum cable distances between the controller and
transmitter assuming a voltage drop of 4V in each core and for different cable parameters.
The tables are examples only and actual cable parameters and source power supply
voltage for the application should be used to calculate the maximum cable distance
allowed at the installation site.
Typical cable data Maximum Cable length (L)
Cable size
(cross sectional area)
Cable resistance
Ω/km (Ω/mi)
Meters Feet
0.5mm2 (20AWG*) 36.8 (59.2) 353 1158
1.0mm2 (17AWG*) 19.5 (31.4) 666 2185
1.5mm2 (16AWG*) 12.7 (20.4) 1023 3356
2.0mm2 (14AWG*) 10.1 (16.3) 1287 4222
2.5mm2 (13AWG*) 8.0 (12.9) 1621 5318
*nearest equivalent **example for 24Vdc supply voltage
Table 2: Maximum cable distances
+24V
+18 V
(wrt Controller 0V)
+6V
(wrt Controller 0V)
0V
4-20mA
Field Cable (L)
Signal
Diagram 7: Power Connection
12V
(min)
Controller
XCD
The Sensepoint XCD transmitter(UL/CSA versions)requires a power supply from the controller
of between 12Vdc and 32Vdc. Ensure that a minimum supply of 12Vdc is measured at the
sensor,