Applications Guide

CSC–2000 Series Pneumatic VAV Reset Volume Controllers 5 Applications Guide
Adjustments, Calibration, and Operation of BEIGE Controllers
Adjustments and Calibration
1. Check that there is 0 psi at the “T” Port.
2. Use a ow hood or “tee” a Magnehelic
®
(or equiv-
alent) dierential pressure gauge between the
controller and the ∆P pick-up.
3. The “LO” ow seing limit (center knob) must
be set rst. Temporarily adjust the thermostat
for a branch pressure lower than the 8 psig reset
start point (minimum cooling); typically 6 psig or
less is best. Removing the thermostat branch line
would be another acceptable method. Adjust the
“LO” knob (center knob) clockwise to increase or
counterclockwise to decrease ∆P limit. Normally
one-half turn will cause a 0.1 ∆P change. Allow
for reaction time. Depending on actuator size and
position, timing will vary. To position an actua-
tor/damper from closed to open may take several
minutes.
NOTE: If the “LO” ow seing limit must be set at
“0” (zero minimum), do not turn the “LO”
knob fully counterclockwise. The knob will
adjust three to four full turns aer a zero
minimum is reached. Turning the “LO”
knob fully counterclockwise will result in
a negative reset condition. This means that
when the controller is beginning to reset
at 8 psig from the thermostat, it must rst
overcome the negative adjustment and will
not begin to reset until a higher thermostat
reset pressure is reached. This negative
reset will also reduce the eective range
of the controller by reducing the high end
and narrowing the reset span. If a zero
minimum is required, adjust the “LO” knob
until the controller just begins to crack the
damper open, then back-o one-fourth turn
and verify zero airow.
4. The “HI” ow seing limit (outer knob) must be
set aer the “LO”. Temporarily adjust the ther-
mostat for a branch pressure higher than the 13
psig reset stop point (maximum cooling); typically
17 psig or greater is best. Removing the thermo-
stat branch line and teeing-in to the main air line
would be another acceptable method. Adjust the
“HI” knob (outer knob) clockwise to increase or
counterclockwise to decrease ∆P limit. Nominally
one-half turn will cause a 0.1 ∆P change. Allow for
reaction time.
5. Recheck the “LO” and the “HI” seings at least
twice, verify seings, and ne tune each time if
necessary. This procedure will remove internal
component tensions and conrm seings.
6. Reconnect the thermostat branch line if necessary,
and adjust the thermostat to the desired room tem-
perature setpoint.
NOTE: The “HI” adjustment limits the travel of
the reset mechanism. Therefore, the reset
span will be less than 5 psig, the upper limit
being less than 13 psig.
NOTE: Always make adjustments in the same
plane/orientation as the one in which the
unit will operate.
NOTE: No routine maintenance is required. Each
component is designed and manufactured
for reliability and performance. Careful
installation and use will ensure long-term
dependability.
NOTE: For information about GRAY controllers
see the Adjustments, Calibration, and
Operation of GRAY Controllers section.