Instruction Manual
D200156X012
4194HA, HB, HC Controllers
July 2018
11
Supply pressure medium must be clean, dry, and noncorrosive and meet the requirements of ISA Standard 7.0.01 or
ISO 8573-1. A maximum 40 micrometer particle size in the air system is acceptable. Further filtration down to 5
micrometer particle size is recommended. Lubricant content is not to exceed 1 ppm weight (w/w) or volume (v/v)
basis. Condensation in the supply medium should be minimized.
Use a suitable supply pressure regulator to reduce the supply pressure source to 1.4 bar (20 psig) for an output signal
range of 0.2 to 1.0 bar (3 to 15 psig) and to 2.4 bar (35 psig) for an output signal range of 0.4 to 2.0 bar (6 to 30 psig).
Vent Connection
WARNING
Personal injury or property damage could result from fire or explosion of accumulated gas, or from contact with hazardous
gas, if a flammable or hazardous gas is used as the supply pressure medium. Because the controller case and cover
assembly do not form a gas‐tight seal when the assembly is enclosed, a remote vent line, adequate ventilation, and
necessary safety measures should be used to prevent the accumulation of flammable or hazardous gas. However, a remote
vent pipe alone cannot be relied upon to remove all flammable or hazardous gas. Vent line piping should comply with local
and regional codes and should be as short as possible with adequate inside diameter and few bends to reduce case pressure
buildup.
CAUTION
When installing a remote vent pipe, take care not to over‐tighten the pipe fitting in the vent connection. Excessive torque
will damage the threads in the connection.
If a remote vent is required, the vent line must be as short possible with a minimum number of bends and elbows. Vent
line piping should have a minimum inside diameter of 19 mm (3/4 inches) for runs up to 6.1 m (20 feet) and a
minimum inside diameter of 25 mm (1 inch) for runs from 6.1 to 30.5 m (20 to 100 feet).
If a remote vent is not required, the vent opening (figure 2‐2) must be protected against the entrance of any foreign
material that could plug it. Check the vent periodically to be certain it is not plugged.
Remote Set Point (suffix letter M) Connection
If the controller has the remote set point option, connect the remote set point pressure to the top of the controller
case at the location shown in figure 2‐2. If pressure is supplied to the remote set point connection with a regulator, a
small bleed orifice should be placed between the regulator and remote set point connection to prevent pressure
variations due to regulator lock‐up.
External Feedback Connections (4194HB Controllers Only)
When a secondary controller in an override application has this option, reset windup is minimized in the secondary
controller. Connect the external feedback connection of the secondary controller to the output of the
customer‐supplied high or low select relay. See figure 2‐2.
