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Zone Temperature - Heating
Relies on input from a sensor located directly in the space, while a system is in the occupied
"Heating" mode or an unoccupied period, to stage the heat "on and off" or to modulate the heating
valve (hydronic heat only) as required to maintain the zone temperature to within the heating
setpoint deadband. The supply fan will be requested to operate any time there is a requested for
heat. On gas heat units, the fan will continue to run for 60 seconds after the furnace is turned off.
Supply Air Tempering
On CV Zone Temperature Control units, if the supply air temperature falls 10°F below the zone
temperature setpoint up to half of the available heat capacity will be brought on until the supply
air temperature reaches 10°F above zone temperature setpoint.
Single Zone Variable Air Volume (SZVAV) Only
The IntelliPak controls platform will support Single Zone VAV as an optional unit control type in
order to meet ASHRAE 90.1. The basic control will be a hybrid VAV/CV configured unit that provides
discharge temperature control to a varying discharge air temperature target setpoint based on the
space temperature and/or humidity conditions. Concurrently, the unit will control and optimize the
supply fan speed to maintain the zone temperature to a zone temperature setpoint.
Supply Fan Output Control
Units configured for Single Zone VAV control will utilize the same supply fan output control scheme
as on traditional VAV units except the VFD signal will be based on zone heating and cooling demand
instead of the supply air pressure.
VFD Control
Single Zone VAV units will be equipped with a VFD-controlled supply fan which will be controlled
via a 0-10VDC signal from the Rooftop Module (RTM). With the RTM supply fan output energized
and the RTM VFD output at 0VDC, the fan speed output is 37% (22Hz) from the VFD by default; and
at 10VDC the fan speed output is 100% (60Hz). The control scales the 0-10VDC VFD output from the
RTM linearly to control between the 37-100% range. The VFD will modulate the supply fan motor
speed, accelerating or decelerating as required to maintain the zone temperature to the zone
temperature setpoint. When subjected to high ambient return conditions the VFD will reduce its
output frequency to maintain operation. Bypass control is offered to provide full nominal airflow
in the event of drive failure.
Ventilation Control
Units configured for Single Zone VAV control will require special handling of the OA Damper
Minimum Position control in order to compensate for the non-linearity of airflow associated with
the variable supply fan speed and damper combinations. Units configured for TRAQ with or
without DCV will operate identically to traditional units with no control changes.
Space Pressure Control
For units configured with Space Pressure Control with or without Statitrac, the new schemes
implemented for economizer minimum position handling require changes to the existing Space
Pressure Control scheme in order to prevent over/under pressurization. The overall scheme will
remain very similar to VAV units with Space Pressure Control with the exception of the dynamic
Exhaust Enable Setpoint.
For SZVAV an Exhaust Enable Setpoint must be selected during the 100% Fan Speed Command.
Once selected, the difference between the Exhaust Enable Setpoint and Design OA Damper
Minimum Position at 100% Fan Speed Command will be calculated. The difference calculated will
be used as an offset and added to the Active Building Design OA Minimum Position Target in order
to calculate the dynamic Exhaust Enable Target, which will be used throughout the Supply Fan
Speed/OA Damper Position range.
RT-SVX36G-EN
General Information
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