Anemostat EST - Manual (Page 27)

27
1220 Watson Center Road • Carson, CA 90745
Tel: (310) 835-7500 • Fax: (310) 835-0448
www.anemostat.com • [email protected]
General Troubleshooting
To troubleshoot suspected problems, a 0-1”w.g. Magnehelic, a voltmeter and a 0-20 psi pressure gauge are required.
• Be sure there is airflow through the terminal. The central (primary) fan must be on, the damper open, etc.
• Power must be supplied to the terminal. This includes line voltage to the fan circuit and transformer, 18 psi
minimum to the pneumatic circuit, or 24VAC to the electronic circuit.
Pneumatic Controls
If overcooling or undercooling occurs, the problem must be isolated as follows:
Tubing Connections
• Visually check the tubing connections and compare them with the proper control schematic. Check to be sure that
each tube is tightly connected. Verify that 20 psi main air is available.
Thermostat
• Set the position of the thermostat temperature adjustment lever to the full cooling position. Connect the 0-1” w/g
gauge to the balance tap and compare the signal pressure with the signal marked on the terminal label. These
signals should be approximately equal.
• Move the lever to the minimum cooling position. If the thermostat is working properly, the inlet valve will close off
causing the signal pressure to approach its minimum setpoint or zero.
• Results other than those above indicate a temperature adjustment must be made. Move the thermostat lever to a
position slightly warmer or colder than the original setting.
• If the inlet valve does not reduce CFM when the thermostat is set for minimum cooling, check the pressure in the
thermostat line. It should be 0 psi for a direct-acting thermostat and 20 psi for a reverse-acting thermostat. If the
pressure is not as indicated, the thermostat may need to be replaced.
Pneumatic Motor (actuator)
• Check the motor for leaks and check the shaft setscrews to verify they have not come loose.
CFM
Overcooling can also occur due to excessive CFM at minimum air setting. Ventilation air may have to be reduced or
reheat added to maintain temperature control.
Undercooling may be an indication of insufficient duct pressure (air) and/or insufficient system cooling capacity. The
following procedure is required:
• Check the inlet pressure to see that minimum pressure for CFM required is available at the terminal.
• Check the supply air cold duct temperature.
Electronic Analog Controls
• Check for loose wires at the connections.
• Compare the control diagram located on the fan control access door to the wiring connections.
• Check for proper primary and secondary voltages.
• Verify that the supply voltage between the controller and the thermostat is approximately 16 VDC when measured
between terminals 4 and 5. If not, the controller may need to be replaced.
• Verify the velocity sensor and duct pressure tubing is connected securely, taps are covered and no leakage is
occurring.
• Verify the thermostat maximum and minimum potentiometer voltage. If minimum and maximum cannot be adjusted
between 0 and 10 VDC, the thermostat may need to be replaced.