Install Instructions

Parallel Fan
If the controller is configured for a parallel fan, any time the Occupancy mode of the
controller is set to either OCCUPIED or STANDBY and there is a call for heat, the fan runs
continuously. The fan starts when the Heating loop is greater than 5% and stops when the
Heating loop is less than 1%.
When the unit Occupancy state is UNOCCUPIED, the fan starts and runs at minimum speed
only on a call for heating. The fan starts when the Heating loop is greater than 5% and stops
when the Heating loop is less than 1%.
Illustration 7–3 Parallel fan operation
MAX FAN SPEED
MIN FAN SPEED
FAN OFF
OCCUPIED
HTG SP ROOM TEMP INCREASE
UNOCCUPIED/
STANDBY
Reheat sequence
The SimplyVAV controllers can control four types of reheat installations.
l Modulating reheat
l Staged reheat
l Time proportioned reheat
l Floating reheat
All reheat is controlled by either the Heating loop or the Discharge Air Temp Limiting (DAT)
PID loop. Loops are described in the topic PID control loops on page 55.
l If Discharge Air Temp Limiting is enabled, reheat is controlled by the DAT PID loop.
l If DAT control is not enabled, reheat is controlled by the Heating loop.
In the following descriptions, the loop controlling reheat is referred to as the Reheat loop.
Modulating reheat
If the controller is configured for modulating reheat, it controls an analog reheat unit with 0-
10 volts DC at the analog reheat output. On a call for reheat, the reheat output is modulated
over the span of the Reheat loop. If the Reheat loop is less than 10%, the reheat output
remains at zero. The reheat is set to zero if the Cooling loop is active.
See the topic Modulating reheat on page 47 for an application drawing.
SimplyVAV Section 7: Sequences of operation
Revision G 59