Vertiv Liebert THW420 Instructions d'installation

TEMPERATURE/HUMIDITY

TRANSMITTER-WALL (4-20 MA)

Product Specification/Installation Guide

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The Liebert THW420 combination

temperature/humidity transmitter is

designed to meet applications that

require local sensing of both

temperature and humidity in a single,

aesthetically pleasing enclosure.

This device incorporates a digital

solid state temperature and

capacitive humidity sensor. 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.

Termination

NOTE: Risk of accidental electric

arc. Can cause equipment damage.

Vertiv recommends wiring the

sensor WITHOUT power applied;

accidental arcing may damage the

product and will void the warranty.

The Liebert 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 threewire 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

inductive loads such as motors,

generators and coils. Vertiv also

recommends making power

connections with twisted pair wire

of at least 22 AWG and crimp-type

connectors.

From +24VDC of controller or

power supply

To controller’s analog input

(temperature signal, 4-20mA)

To controller’s analog input

(humidity signal, 4-20mA)

To GND (common) of controller*

4-20mA

Input #1

4-20mA

Input #2

* NOTE:

The GND (common) terminal

is common between the

Power and Sensor

+ 24VDC should be used

at all times

TERMINATIONS

TEMPERATURE/HUMIDITY TRANSMITTER - WALL (4-20 MA)

Product Specification/Installation Guide

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DIMENSIONS

SPECIFICATIONS

Output 4 to 20 mA

Sensor Temperature - Band gap semiconductor

Humidity

Supply Voltage 24 VDC

Tolerance of Resistance (Accuracy) � 1.2° F (�0.6° C)

� 2% RH (from 15 to 95% RH)

Response Time 8 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

Front face

2.86” (72.7 mm) 1.06” (26.9 mm)

4.5” (114.3 mm)

Front Wall

Side

NOTE: In a wall-mount application,

the wall temperature and the

temperature of the air within the

wall cavity can cause erroneous

readings. The mixing of room air

and air from within the wall cavity

can lead to condensation and

premature failure of the sensor.

To prevent these conditions, seal

the conduit leading to the junction

box and seal the hole in the drywall

by using an adhesive backed, foam

insulating pad.

Mounting hardware is provided for

both junction box and drywall

installation.

1. Pull the wires through the

opening in the base plate.

2. For junction box installation:

Secure the base to the box

using the #6-32 x 1/2”

mounting screws provided.

For drywall installation: Drill

two 3/16” holes 3-1/4” apart on

center. Insert the drywall

anchors and secure the base

using the #6 x 1” sheet metal

screws provided.

3. Terminate the unit according to

the guidelines in Termination

on page 1.

4. Attach the cover by latching it

to the top of the base, rotating

the cover down and snapping it

into place.

5. Secure the cover by backing

out the lock-down screws

using a 1/16” Allen wrench until

they are flush with the bottom

of the cover.

MOUNTING

Junction box

2” x 4”

Wall

Mounting

screws

Cover locking screws

1/16” Allen

TEMPERATURE/HUMIDITY TRANSMITTER - WALL (4-20 MA)

Product Specification/Installation Guide

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You will measure the humidity

output by placing an ammeter in

series with the controller input. The

controller input is connected to the

terminal marked “Ch1 or Ch2” on the

humidity board.

1. Verify the unit is terminated

properly using Figure 4 shown

below, and set your meter to the

“Volts” setting.

2. Verify you have 24 VDC

supplied to the unit by

measuring between the “V+”

and “GND” terminals at the

sensor, as shown below in

Figure 3.

3. Set your meter to “Amps” and

measure the output between

“Ch1 or Ch2” and the controller

input as shown below in Figure 3.

4. Use the following formula to

determine what humidity the

sensor is reading:

(mA - 4) / 0.16 = %RH

where mA is the current reading

from the ammeter (in mA)

TROUBLESHOOTING - Humidity Signal Verification

TROUBLESHOOTING GUIDE

PROBLEMS POSSIBLE SOLUTIONS

Unit will not operate • Check +24 VDC power supply at controller.

• Disconnect the sensor and check power wires for +24 VDC.

Humidity reading is maximum 20 mA or

100%

• Make sure the sensor is wired properly.

Humidity reading is minimum 20 mA or

• Verify that the humidity sensor is wired properly.

Humidity reading in software appears to

be off more than specified

• Check all software parameters.

• If available, check the sensor against a calibrated control such as a hygrometer.

• Determine if the sensor is exposed to an external source more than room.

Temperature sensor in front end software

is reading high

• Make sure wiring is correct.

• Disconnect wires and measure with a multimeter.

The following table lists common problems and possible solutions. For more information, consult your local

dealer, Liebert representative or the Liebert Worldwide Support Group.

Example:

If the current reading is

16 mA, then:

%RH = (16 - 4) / 0.16

= 12 / 0.16

= 75%

Figure 1 - Supply Voltage and 4-20mA Verification Figure 2 - 4-20mA Output Connection

ORDERING INFORMATION

PART # DESCRIPTION

THW420

Combination Temperature/Humidity Transmitter Wall 4-20 mA @ 45°F to 96°F

and 0 to 100% RH

To contact Vertiv Technical Support: visit www.VertivCo.com

trademarks or registered trademarks of their respective owners. While every precaution has been taken to ensure accuracy and completeness herein, Vertiv Co. assumes no

responsibility, and disclaims all liability, for damages resulting from use of this information or for any errors or omissions. Specifications are subject to change without notice.

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