Data Aire dap4 Supplement Manual page 5

In the STDBY (standby) mode there are two scenarios:
1. The unit that has been selected to always run (ONbyZM – Primary as shown in the master unit
display) will operate non-stop providing all cooling, heating, dehumidifi cation and humidifi cation
functions required. The blower will run continuously for ventilation and provide airfl ow across the
sensors for accurate temperature and humidity requirements even if no cooling, heating, dehu-
midifi cation and humidifi cation are required.
2. The standby units that are not required to always run will hold off the blower and all cooling,
heating, dehumidifi cation and humidifi cation functions unless among the units which are ONbyZM
the average return air temperature in the zone is more than the average setpoint plus average
deadband plus 1.5°. If this occurs, one of the STBbyZM will change its status to ONbyZM. The
blower of the standby unit will start and the standby unit will then be allowed to regulate cooling as
if it was in the ON mode. Normal operation messages will be displayed whenever a standby unit
has been reactivated for operation.
If the temperature and humidity condition at the standby unit are satisfi ed, it will return to inactive
(STBbyZM) when the average zone temperature is maintained below the average setpoint plus
the average deadband for 15 minutes (this is adjustable and has a range from 30 to 999 sec-
onds).
If the temperature or humidity condition at the standby unit isn't satisfi ed even though the zone's
average temperature is maintained below average setpoint plus deadband for 15 minutes (adjust-
able), the unit will continue to run until its temperature and humidity is satisfi ed. Its status will be
RUNtoSTB (run to standby). Once its own temperature and humidity setpoint is reached, if the
zone average temperature is below setpoint plus deadband, the zone master will turn the unit to
standby and the status will be STBbyZM.
Example - With four units assigned to a Zone, two units must be always ON and one unit always
OFF, the settings are as follows:
Zone Master
Zone ID: 1
Units in Zone: 4
Units Online: 4
Primary Schedule Only
Number of Units On: 2
Zone Master
Note: U1 is the Master
Unit #1: Stdby
Unit #2 Stdby
Unit #3 Stdby
Unit #4 Off
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