Calibration Pressure Set Point And Selection Of System Pressure Set Point - Carrier 33CS Installation, Service And Instructions

Fig. 5 — Pressure Sensor Average Flow Locations
PRESSURE SENSOR RE-ZEROING PROCEDURE FOR
THE BYPASS CONTROLLER — To re-zero the pressure
sensor perform the following:
1. Power the pressure sensor.
2. Configure the Pressure Sensor Range, category 5, option
5. If using a pressure sensor pick-up (33CSPS-02), set
the value to 2.0 in. wg. If using a velocity pressure probe
(33CSPS-01), set the value to 0.5 in. wg.
3. Select the Auto-Zero Enable function in category 5,
option 6. Set the option to ON. The bypass controller will
automatically deenergize the equipment supply air fan.
The bypass controller will wait until the fan-off time has
expired before the Auto-Zero function is started. The pres-
sure sensor Auto-Zero Enable function will automati-
cally calibrate the pressure sensor to zero. After the Auto-
Zero Enable function completes the pressure sensor re-
zeroing, the bypass controller display will return the Auto-
Zero Enable function to OFF.
NOTE: For bypass controller stand-alone operation, the Auto-
Zero Enable function will not be available. To zero the pres-
sure sensor, turn off the system fan and allow the pressure to
dissipate. Enter category 5, option 8 for pressure sensor cali-
bration. Press the left upper and lower information buttons
simultaneously. The current pressure reading will be saved
as the zero pressure reading.
Calibration of Pressure Sensor (with Pressure
Pick-Up) and Selection of System Pressure Set
Point
— This section explains how to configure the sys-
tem pressure set point for the bypass controller when using
a pressure pick-up.
NOTE: Before performing this procedure, re-zero the pres-
sure sensor of the bypass controller.
To configure the system pressure set point, perform the
following procedure:
1. Set the System Setup Enable function (category 5,
option 7) to ON. The bypass controller deenergizes the
system heating/cooling equipment, closes the bypass damp-
er(s), and opens all the zone dampers in the VVT system
to their Maximum Damper Position. The bypass control-
ler also energizes the system supply air fan relay. This
option forces the system into a static condition so that a
stable system pressure can be obtained. By adjusting the
minimum and maximum damper positions at individual
zones, the system can be adjusted to balance airflow and
obtain an acceptable noise level. The bypass damper will
display the highest address found in its scan.
2. Use the Zone Damper Control function to close, one at a
time, the zone dampers farthest away from the equipment
supply air fan. Each time a zone damper is closed, check
the noise level and objectionable drafts in the zones that
remain open. Check the ability of the system supply air
fan to maintain supply airflow above the minimum re-
quired supply airflow. Refer to the Zone Damper Control
section on page 7 for more information on Zone Damper
Control.
Continue closing individual zone dampers until the noise
or drafts, due to increased supply airflow, becomes ob-
jectionable in any zone or until the equipment supply air
fan cannot maintain the minimum cfm requirements of
the unit.
NOTE: For systems utilizing temperature diversity, close
dampers at an opposing solar exposure while leaving the
other dampers open. Perform Step 2. The system should
be balanced while performing this task to assure de-
signed airflow.
3. When either noise level and/or drafts, due to supply air-
flow, becomes objectionable or the system static pressure
approaches the upper static pressure limit, use Zone Damper
Control to reopen the last zone damper that was closed.
Open zone dampers until the noise level and/or drafts in
every zone is acceptable or the unit supply air fan is able
to exceed the minimum airflow requirements. This de-
termines the maximum supply air static pressure the by-
pass controller should allow for the system.
4. Calibrate the pressure sensor. To calibrate the pressure
sensor, select category 5, option 8. The current pressure
reading will be displayed on the bypass controller screen.
Use the left information buttons to adjust the value until
the pressure matches the system pressure on the manom-
eter or Magnehelic gage.
5. Press the select button to modify the Auto Pressure Set
Point option (category 5, option 9). The current system
pressure will blink. Press the select button again. System
Setup Enable will end and the new system pressure set
point will be stored.
6. From the system balance report, determine the equip-
ment supply air fan operating rpm. From the equipment
application information, determine the minimum operat-
ing cfm for both the cooling and heating cycles. These
quantities are typically 300 to 350 cfm/ton.
From the equipment fan performance curve or table, de-
termine the maximum static pressure the fan can over-
come at its fixed operating rpm. Verify the fan can de-
liver the minimum operating cfm required by the equipment
cooling and heating cycles.
If the external static pressure value determined for the
equipment maximum operating static pressure approaches
or exceeds the System Pressure Set Point of the bypass
controller, the System Pressure Set Point must be
reduced.
NOTE: The bypass controller cannot use a velocity pres-
sure probe.
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