American Dryer AD-120ES - Manual (Page 34)

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IMPORTANT: The dryer and its individual shut-off valve must be disconnected from the gas
supply piping system during any pressure testing of that system at test pressures
in excess of 1/2 psig (3.5kPa).
NOTE: The dryer must be isolated from the gas supply piping system by closing its individual
manual shut-off valve during any pressure testing of the gas supply piping system at test
pressures equal to or less than 1/2 psig (3.5kPa).