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TM

INSTALLATION GUIDE

H740

opEration

The H740 is a current-sensitive transducer that monitors current (amperage) in the 
conductor passing through it. The integrated relay provides On/Off control. The status 
output is suitable for connection to building controllers or other appropriate data 
acquisition equipment operating at up to 30 volts. The H740 requires no external 
power supply to generate its output.

troublEshooting

Problem

Solution

No Reading at Controller

• Check for control power at sensor (<30 V; <1.0 A)
• Check for amperage in monitored conductor (>0.5 A)

Relay chatters or will not 

change state

• Ensure that not more than 24 VAC/DC has been applied to 

the coil.

• Parallel applications with AC transformers can damage the 

relay. Use appropriate snubbing device.

DANGER: 5A CTs can present hazardous voltages. 

Install CTs in accordance with manufacturer's instructions. 

Terminate the CT secondary before applying current.

H68xx-5A CT

240A 

300A:

5A 

> 200 A (Sensor max.)

CAUTION 

RISK OF EQUIPMENT DAMAGE

•  Derate the product’s maximum current for the number of turns 

through the sensing window using the following formula.

Rated Max. Amps ÷ Number of Turns = Max. monitored Amps
e.g. :  100A ÷ 4 Turns = 25 Amps max. in monitored conductor

•  Failure to follow these instructions can result in overheating 

and permanent equipment damage.

< 0.5 A (Sensor Min.)

4x

0.5A

0.2 A

notEs

For load currents greater than sensor maximum rating:

 

Use a 5 Amp (H68xx series) Current Transformer (CT) as shown. This technique can be 
combined with wrapping (see below) to add range for a low current load on a high 
current source.

For load currents less than sensor minimum rating:

 

Wrap the monitored conductor through the center window and around the sensor 
body to produce multiple turns. This increases the current measured by the 
transducer.

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