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SL-31080 Product Specification/Installation Sheet page 1 6/03 (Rev. 0)
TEMPERATURE /HUMIDITY TRANSMITTER - WALL (4-20 MA)
Description
The THW420 combination
temperature/humidity transmitter
is designed to meet applications
that require local indication of both
temperature and humidity in a
single, aesthetically pleasing
enclosure.
This device incorporates a 10K ohm
(Ω) platinum RTD. The transmitter
requires 24 VDC. The sensor provides an
accurate and predictable four-wire, 4-20 mA
output signal for temperature and a second
4-20 mA output signal for humidity.
Dimensions
Specifications
Termination
The THW420 transmitter must be powered from a
24 VDC supply. The combination temperature/
humidity sensor is terminated as follows:
•The humidity transmitter requires a three-wire
termination for the 4-20mA output using 24 VDC.
•The temperature sensor also requires a three-
wire termination. In most cases, it obtains power
from the analog input to which it is connected and
no external power is required.
Though interference from external sources is not a
major problem with current transmitters, Liebert
recommends separating the wiring from line voltage
wiring and from wiring used to supply highly induc-
tive loads such as motors, generators and coils. Lie-
bert also recommends making power connections
with twisted pair wire of at least 22 AWG and crimp-
type connectors.
Ordering Information
Output 4 to 20 mA
Sensor 10K Ω platinum RTD
Supply Voltage 24 VDC
Tolerance of Resistance
(Accuracy)
±1.5°F (±0.83°C)
±2% RH (from 15 to 95% RH)
Response Time 20 seconds for a 63% step
Environmental Operating
Range (Transmitter)
45°F to 96°F; 0 to 100% RH
(7°C to 35°C); 0 to 100% RH
4.5"
(1143mm)
2.25"
(572mm)
2.75"
(699mm)
0.95"
(241mm)
0.75"
(191mm)
FRONT
VIEW
SIDE
VIEW
TOP VIEW
Wall
!
CAUTION
Liebert recommends wiring the sensor
WITHOUT power applied because
accidental arcing may damage the product
and will void the warranty.
X
U3
Terminations
+24VDC should be
used at all times
SW2 OUTPUT SELECT
ON
0-5V
0-5V
0-5V
CALRUN
RESIST.
4-20ma
4-20ma
SW2
C9
Gnd
V+
Ch1
Ch2
J2
J3
DISPLAY CYCLE
IN SECONDS
10
3
T
POT1
20
H
Ch3
CAL
Temp
Temp
R19
T&B
SWITCH
Short
Norm
Open
SW1
RTH1 RTH2
J1
%RH
Ch3
Ch2
Ch1
Building Automation
Products, Inc.
Copyright 2000
REV. 101600
XCOMBO T&B
4-20 mA
Input #1
Ground
4-20 mA
Input #2
+
-
+
-
Controller
To GND (common)
of controller*
From +24VDC
of controller or
power supply
To controller’s
analog input
(humidity signal,
4-20mA)
To controller’s
analog input
(temperature signal,
4-20mA)
* NOTE:
The GND (common)
terminal is common
between the Power
and Sensor
Quantity Part # Description
THW420 Combination Temperature/Humidity Transmitter Wall 4-20 mA @ 45°F to 96°F and 0 to 100% RH