82 UNT Controller—Unitary Controller (UNT)
Rooftop units experiencing nuisance resets require an application upgrade.
Use HVAC PRO for Windows, Version 6.05 or greater, and the following
procedure:
1. Run HVAC PRO for Windows, 6.05 or greater.
2. Go to the Upload menu.
3. Select Upgrade Controllers.
4. Select Multiple Controllers.
5. Highlight the rooftop controllers experiencing the nuisance resets.
6. Select OK.
7. Save each configuration when prompted.
Note: Factory downloaded applications in all UNT controllers have been
upgraded effective December 15, 1997; however, even on the new
units, if controller applications are modified, the modifications
must be performed using HVAC PRO for Windows, Version 6.05
or greater.
Rooftop units with 460 VAC or greater primary voltage require
additional changes under the following conditions:
•
If the controller Date Code is less than 9618, perform the following
procedure:
a. Loosen the 24 VAC and COM screws of the input power
connector.
b. Insert the terminals of a Harris V47ZA7 Transient Voltage
Suppressor into the 24 VAC and COM slots of the input power
connector.
c. Tighten the 24 VAC and COM screws of the input power
connector.
•
If a separate transformer is used to supply the binary output
voltage, install a Metal Oxide Varistor (MOV) according to the
following procedure (see Figure 38):
a. Order an AS-MOVKIT-0 as needed. Each kit contains
12 Metal Oxide Varistor (MOV) assemblies.
b. Remove the field wire that currently connects to the triacs terminal.
c. Attach the field wire to the male terminal of the MOV assembly.
Nuisance
Resets in
Rooftop Units
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