Honeywell XNX-AM Series, Technical Manual

Page: 37 / 207

XNX Universal Transmitter
Installation and Operation 35
Note: CSA/FM certification does not cover daisy-chained XNX combustible gas transmitters.
NOTE
!
Power Source Selection
For each type of installation, selection of power supply is
important. Power supplies are rated by voltage and power. The
nominal voltage for all XNX transmitters is 24V with the power
required depending on the number of points using the same
power supply.
As a general guideline, the power supply should be capable
of providing more power than is required by the installation. A
10 watt power supply is fine for a single XNX mV with catalytic
sensor (6.5 watts required, see the following table) but is
inadequate for a single XNX IR with Searchpoint Optima Plus (10
watts required).
XNX Universal Transmitter Maximum Power Consumption
Configuration
-40°C to +65°C -10°C to +65°C
HART
over
4-20mA
(watts)
HART over 4-20mA
with Relay, Modbus
®
, or
Foundation
TM
Fieldbus
(watts)
HART
over
4-20mA
(watts)
HART over 4-20mA
with Relay, Mod-
bus, or Foundation
Fieldbus
(watts)
transmitter with toxic
sensors
5.1 6.2 3.4 4.5
transmitter with
catalytic sensors
5.4 6.5 3.7 4.8
transmitter with
infrared cartridge
5.4 6.5 3.7 4.8
XNX Universal Transmitter Maximum Power Consumption
Configuration
-40°C to +65°C -10°C to +65°C
HART
over
4-20mA
(watts)
HART over 4-20mA
with Relay, Modbus
®
, or
Foundation
TM
Fieldbus
(watts)
HART
over
4-20mA
(watts)
HART over 4-20mA
with Relay, Mod-
bus, or Foundation
Fieldbus
(watts)
transmitter with
Searchpoint Optima
Plus
8.6 9.7 6.9 8.0
transmitter with
Searchline Excel
12.1 13.2 10.4 11.5
To determine the wattage required, add the maximum power
requirements of all the points that will share the power supply.
For example, consider a system with two XNX mV transmitters
with catalytic sensors (6.5 watts each) and one XNX IR with
Searchpoint Optima Plus (10 watts). A 25 watt power supply
would probably handle this installation, but a 30 watt power
supply would be a better choice.
Wire Selection
The type of wire used for connections has an effect on the
distance of the installation. This is because some of the voltage
is dropped across the cable between the power supply and the
transmitter.
Thinner wire (i.e., 18 AWG) will lose more voltage than thicker
wire (i.e., 12 AWG). The amount of voltage lost depends on how
much current is being drawn through the wire; more current
means more loss. If too much voltage is ropped across in the
wiring, there may not be enough at the distant point to allow the
transmitter to operate.