Zone 1/21 Exhaust Control System case study

February 10, 2010

Zone 1/21 Exhaust Control System case study

Extronics received an enquiry to build a Zone 1/21 exhaust control system installed in a weighbridge pit, utilising two redundant supplies and dual control circuits.


Zone 1/21 Exhaust Control SystemThe request to Extronics was to control 2 exhaust fans, duty and standby, which would keep the weighbridge pit clear of Hazardous atmosphere.

The control panel was to be fed from 2 different supplies and the main objective was to keep the area clear in the event of any or all of the following fault conditions:-

  1. Failure/ Shutdown of either incoming power supply
  2. Failure/ Shutdown of either duty or stand-by fan
  3. Failure/ Shutdown of either control circuit transformer

Extronics designed the control circuit that if any or all of the above occurred then the appropriate backup would automatically start and sound an alarm and/ or show a remote indicator, maintaining airflow through the hazardous area.


The finished Control Panel was Zone 1/ 21 ATEX certified for use in a IIB +H2 gas group area and was delivered to the customer complete with wiring schematics.

Zone 1/21 Exhaust Control System


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