11
Single-Duct and Retrofit Terminal Units IOM
PREVENTATIVE MAINTENANCE
1. Inspect pneumatic tubing for loose connections or leaks.
2. Clean out pneumatic line filters regularly according to manufacturer’s recommendations.
TABLE 3: PNEUMATIC CONTROL TROUBLESHOOTING
PROBLEM
PROBABLE CAUSE
Controller does not reset to maximum or minimum set point during balance procedure
Balancer is using the thermostat for control signal. An artificial signal must be provided in place of
the thermostat.
Controller does not reset to maximum or minimum set point during operation.
Thermostat is not demanding maximum or minimum air volume. Main air pressure at the controller is
less than 15 psi.
Pneumatic actuator does not stroke fully.
Leak in pneumatic line between the controller and the actuator.Main air pressure at the controller is
less than 15 psi. Leak in the diaphragm.
Air valve stays in wide open position.
Inlet airflow sensor is blocked by an obstruction (sandwich bag, etc.). Insufficient supply air in the
inlet duct.
NOTE: Always check:
•
Main air pressure (15 psi to 25 psi) at the controller.
•
Proper thermostat signal and logic (Direct/Reverse Acting).
•
Disconnected or kinked pneumatic lines to the controller
•
Blocked inlet airflow sensor or insufficient primary supply air.
•
Quality of compressed air (oil or water in lines).
•
Leaks in the actuator diaphragm.
•
Mechanical linkage of the actuator/air valve.
Figure 10 – Analog Controller CSP 4702
INSTALLATION AND BALANCING PROCEDURES
The Analog Electronic Control System is a pressure
independent volume reset control that uses a KMC CSP-4702
controller-actuator (see Figure 10).
ANALOG CONTROLS
Adjustments for the minimum and maximum airflow
settings are made at the thermostat. The thermostat (CTE-
5202) operates on a 16 VDC power supply from the CSP 4702
controller and outputs a 0 to 10 VDC signal on the AO1 and
AO2 terminals. AO1 is used as the cooling output and AO2 is
used as the heating output
.