A request has been submitted to interpret the following section of Standard 49:
5.28 Gauges
Pressure gauges indicating the differential pressure across the recirculated air filter, if provided, shall be installed in accordance with the manufacturer's instructions. Hose connections to the gauge and sampling port shall be secured by positive compression clamps. If threaded connections are used to penetrate the plenum, an engagement of three continuous threads shall be required.
Requesters interpretation:
An electronic pressure transducer (EPT) is not a gauge and should not be subject to the requirements of 5.28 for a gauge. The electronic pressure transducer can be a much more fragile device than the traditional Magnehelic or Minihelic gauge that would have been referenced in this stated requirement.
Back when this requirement was placed into the standard, only large gauges (Magnehelic or Minihelic) were used. The tubing sample from the contaminated plenum (positive or negative) was brought directly to the gauge without any filtration and if it fell off could possibly allow contaminated air in the control center creating a safety hazard. Since then, the standard now requires any positive or negative contaminated air brought out of the cabinet to be filtered or remain contained in the cabinet. Today’s result means even if the tubing falls off, it does not represent a safety hazard.
Do you agree or disagree with the requester’s interpretation, specifically that an electronic pressure transducer is not a gauge within this context?
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