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Resetting Cooling and Ignition Lockouts
Cooling Failures and Ignition Lockouts are reset in an identical
manner. Method 1 explains resetting the system from the
space; Method 2 explains resetting the system at the unit.
Method 1
To reset the system from the space, turn the “Mode” selection
switch at the thermostat to the “Off” position. After approxi-
mately 30 seconds, turn the “Mode” selection switch to the de-
sired mode, i.e. Heat, Cool or Auto.
Method 2
To reset the system at the unit, cycle the unit power by turn-
ing the disconnect switch “Off” and then “On”.
Unit Economizer Control (ECA) Test Procedures
Electro Mechanical Control
This series of tests will allow you to diagnose, and deter-
mine where, and if a problem exists in the system econo-
mizer operation. Test 1 determines if the problem is in the
Unit, or if it is in the ECA. Test 2 tests sensor inputs. Test 3
tests the resistors and sensors. Conduct the tests in numeri-
cal order until problem is found.
Test 1
Verifying that the economizer actuator (ECA) is functional:
1. Using the “Test Mode” described in the “System Start-Up”
section, put the unit into the economizer mode and verify
that the economizer actuator (ECA) drives fully open (ap-
proximately 90 seconds).
2. If the ECA is not driving the dampers, verify that 24 VAC is
between the ECA terminals TR and TR1 is present. If 24
volts is not present, a wiring or terminal problem exists
from the control transformer. Make any necessary repairs,
see wiring diagrams to troubleshoot.
3. If 24 VAC is present, adjust the minimum position potenti-
ometer fully clockwise. If the actuator does not drive, the
economizer actuator is bad. Replace the ECA.
Test 2
Testing the ECA resistors and sensors
1. Testing the Mixed Air Sensor (MAS). Disconnect the wires
connected to T and T1 on the ECA, and;
a. Measure the resistance of the sensor between the
wires 180B and 181B.
b. Measure the temperature at the MAS location. Using
the Temperature versus Resistance chart, verify the
accuracy of the MAS.
Replace the sensor if it is out of range.
2. Testing the Outdoor Air Switch. If the temperature is above
60 degrees, it will need to be chilled. Measure the resis-
tance of the sensor on the ECA SO and +.
The resistance should be approximately 390 Ohms.
Replace the Switch if it is open.
Replace the ECA if it is out of range.
3. Testing the R1 Resistance.
Measure the resistance of the sensor on the ECA SR
and +.
The resistance should be approximately 420 Ohms.
Replace the ECA if it is out of range.
4. Testing the R2 Resistance.
Measure the resistance of the sensor on the ECA P and
P1.
The resistance should be approximately 130 Ohms.
Replace the ECA if it is out of range.
Trouble Shooting
Содержание YHC033A
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