VAV-SVX02B-EN
10
Model 3501
The model 3501 Pneumatic Volume
Regulator (PVR) is capable of operating
with normally-open or normally-closed
air valves and can operate with either
direct-acting (DA) or reverse-acting
(RA) thermostats.
Adjusting the Reset Span (3501)
The reset span is factory-set at 5 psi.
This is the thermostat pressure differ-
ence from which the PVR delivers
flow from minimum to maximum
setpoints. This range is not normally
changed unless a special control
scheme is used where control
operation must be changed.
To field adjust a different reset span,
follow these steps:
1. Connect an accurate gage to port “G”.
2. Apply 20 psi to port “T”.
3. Adjust reset span to indicate the
desired span on port “G”.
4. LO-stat and HI-stat delta P must now
be readjusted (see following
calibration procedure).
Installation
1. Attach bracket either vertically or
horizontally to the installation surface.
Horizontal is preferred, vertical is
acceptable, any other position is
not acceptable.
2. Insert controller into its bracket.
Controller may be face up, face down,
face left, or face right. The controller
LO and HI stat delta P must be
calibrated in the same position that it
is installed.
Selecting Direct- or Reverse-Acting
Thermostat (3501)
The model 3501 PVR must be calibrated
to operate with either a direct-acting or
reverse-acting thermostat. The control
must also be changed when used with
a normally-open or normally-closed
air valve.
Use the following procedure to set-up
the PVR:
1. Select damper action (NO or NC).
Loosen damper selection switch
screw and align to either the NO or
NC pointer with damper pointer and
tighten screw.
2. Now determine the type of thermostat
that will be used. If a direct-acting
thermostat is used, the reset start
pressure is typically 8 psi. If a reverse-
acting thermostat is used, the reset
start pressure is typically 3 psi.
3. With an accurate gage (0–30 psi)
connected to port “G”, regulate the
thermostat pressure to port “T” to
10.5 psi.
4. Adjust reset start to indicate 2.5 psi on
port “G”
Model 3501—Pneumatic
Volume Regulator
