13
DIGI3U TROUBLESHOOTING/SERVICE CHECKS
Malfunction
Probable Cause
Corrective Action
All thermostats will not call
Loss of 24V ac on R and C
Repair power source
Will not initiate cooling cycle
Controller in Heat mode
Delay prior to changeover
Check to verify O and B jumpers in Heat Pump mode
Correct as needed
Controller in changeover from heat mode
4-minute purge cycle must complete
Cooling calls short cycle
If LAT is installed, going off on low temp indicating flashing power LED light
Check bypass operation/adjust
Air flow too low over evaporator
Check filter and/or correct air flow
Will not initiate a heat call
Controller in Cooling mode
Check bypass operation
Check to verify O and B jumpers in Heat Pump mode
Correct as needed
Controller in changeover from cooling mode
4-minute purge cycle must complete
Heating calls short cycle
If LAT is installed, flashing power LED indicates high limit cutout
Check bypass operation/adjust
Air flow too low over heat exchanger
Check filter and/or correct air flow
Zone damper will not close
Loss of 24 volts to the dampers, TR1 and TR2
Repair power source
No output to damper terminal(s)
Verify thermostats are making a call
Damper incorrectly wired
Correct damper wiring
Emergency Heat does not Work
STAT 1 must make heat call in Emergency Heat
Verify heat call
STAT 2 and STAT 3 can make Emergency heat call after STAT 1
Verify STAT 1
Blower Runs Continually
Fan operation selected on any thermostat
Verify fan switch on all thermostats
Fan relay contacts in controller seized
Replace controller, check 24V AC
BAROMETRIC BYPASS SETUP
a)
Turn off all thermostats.
b)
Turn on Switching Center/Controller and set fan switch to “ON”
position. Allow fan to run for 5 minutes to equalize pressure.
Then make sure all dampers are open by checking for air flow
out of each damper.
c)
By moving counter weight up or down the lever arm, adjust it
so that the damper just wants to start opening.
d)
If the damper cannot be held closed with the counter weight all
the way to the bottom of the lever arm, then hold the damper
shaft, loosen the lever arm from the damper shaft, and rotate the
lever arm farther to the right and retighten. Repeat Step C.
e)
The barometric bypass damper is now calibrated.
BAROMETRIC BYPASS STARTUP TEST
a)
Have at least half of the zones call for either heating or cooling.
b)
Check to be sure the calling zone dampers are open (air is
flowing).
c)
Verify the bypass damper is open. Note, the damper may not
fully open.
d)
If the open zones are not noisy, the bypass damper is set.
BYPASS DAMPERS – BAROMETRIC
