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2 I) Disable Minimum Position parameter
The VZ7260 zone controllers feature the DisMinPo (Disable Minimum Position) parameter that is used to
enable/disable the minimum damper’s minimum position parameter setting if the zone sequence (heat/cool)
is different than the controller’s demand (heat/cool).
The goal of this parameter is to prevent overcooling or overheating of zones that have demands that differ
from the general zone sequence due to the airflow through the damper opening (at the minimum position).
Most often, the zones affected are the internal zones (not on perimeter) whose demands are ignored by the
rooftop controller because they are not master zones (when it comes to cooling and heating weights).
Here are examples showing how the DisMinPo parameter setting affects the airflow.
DisMinPo set to Enable (minimum position enabled)
Minimum Position parameter:
15%
Zone Sequence:
Cool (cool supply air)
Zone Demand:
Heat
Damper Position: 15%
DisMinPo set to Disable (minimum position disabled)
Minimum Position parameter:
15%
Zone Sequence:
Cool (cool supply air)
Zone Demand:
Heat
Damper Position: 0%
IMPORTANT
: The DisMinPo parameter is only effective when the Zone Sequence and the zone demand
are different, here’s the table showing when this parameter is effective.
Zone Sequence
Zone Demand
DisMinPo effectiveness
Damper Position
Cool Cool Effective
Minimum
Position
Cool Heat Not
Effective
Closed
Cool
No Demand
Effective
Minimum Position
Heat Cool Effective
Minimum
Position
Heat Heat Not
Effective
Closed
Heat
No Demand
Effective
Minimum Position
2 J) Heating and Cooling Performances
The VZ7260 zone controllers also feature heating and cooling performance indexes that indicate the
performance of the zone controller in the last 90 minutes period (1.5 hours). The performances are
displayed at the end of the parameters list, as an average difference between the setpoint and the room
temperature for the last 90 minutes.
Example
:
If the heating performance index HT Perf displays 0.5°F, it means that the average difference between the
heating setpoint and the room temperature for the last 90 minutes was 0.5°F.
Invalid Performance Indexes Values
The performance indexes will be unreliable (invalid) if one of the following happens:
-
System mode is set to Off
-
Zone demand change between heating and cooling
-
Any setpoint change
-
Occupancy status change
The invalid value will be displayed as a random value higher than 83.5°F (Imperial) or 46.0°C (Metric).
To have a valid performance value, the controller has to be stable (no above changed) for 90 minutes.
