Odyssey Symbio Airflow Adjustments and Calculations

You can find the evaporator fan performance tables in the product catalog using the link below. 

• Odyssey Light Commercial - Product Catalog. 

Constant Volume Units (Unit model number digit 15 = "1")

• Adjust the motor sheave: close the sheave in for more fan RPMs, and open it for less.

2 Stage Airflow/Single Zone VAV (Symbio Cond Only) - (Unit Model Number Digit 15 = “D”)

• The Symbio 700 controller provides integrated Supply Fan speed setpoint control for paired air handler units with VFDs for SZVAV and two-speed fan operation. These setpoints can be manipulated through the Symbio 700 user interface (including the Symbio Service and Installation app) or through a connected BAS if required. 

Supply Fan Maximum Speed Setpoint 

(Range: 50-100%, Default: 100%) 

The Supply Fan Maximum Speed Setpoint correlates to the maximum reference setting in the VFD (defaulted to 60Hz from the factory). With the Supply Fan Maximum Speed Setpoint at its default value of 100%, and parameter 3-03 in the VFD at its default value of 60Hz, the maximum VFD output will be 60Hz. If the user reduces the Supply Fan Maximum Speed Setpoint, the maximum VFD output will be reduced from its configured value. 

• Example:
  Parameter 3-03 in the VFD = 60Hz
  Supply Fan Maximum Speed Setpoint = 80%
  Effective Supply Fan Maximum VFD Output = 80% x 60Hz =48Hz

Table 1 -  Maximum fan speed setpoints and effective supply fan maximum VFD output

Supply Fan Minimum Speed Setpoint 

(Range: 0-100%, Default 0%) 

The setpoint correlates to the VFD's minimum reference setting (25Hz from the factory). With the Supply Fan Minimum Speed Setpoint at 0% and parameter 3-02 in the VFD at its default value of 25Hz, the minimum VFD output will be 25Hz. If the user increases the Supply Fan Minimum Speed Setpoint, the minimum VFD output will increase from its configured value up to the Effective Supply Fan Maximum VFD Output, as determined by the Supply Fan Maximum Speed Setpoint. See the examples below.

Example 1:

• Parameter 3-02 in the VFD = 25 Hz 
• Parameter 3-03 in the VFD = 60 Hz
• Supply Fan Maximum Speed = 100%
• Effective Supply Fan Maximum VFD Output (based on Supply Fan Maximum Speed Setpoint) = 60Hz
• Supply Fan Minimum Speed Setpoint = 50%
•  Effective Supply Fan Minimum VFD Output = (Effective Supply Fan Maximum VFD Output – VFD Parameter 3-02) x Supply Fan Minimum Speed Setpoint + VFD Parameter 3-02 = (60 - 25) x 0.50 + 25 = 42.5Hz 

Example 2: 

• Parameter 3-02 in the VFD = 25 Hz 
• Parameter 3-03 in the VFD = 60 Hz
• Supply Fan Maximum Speed = 90%
• Effective Supply Fan Maximum VFD Output from Table 1 = 54Hz
• Supply Fan Minimum Speed Setpoint = 30%
•  Effective Supply Fan Minimum VFD Output = (Effective Supply Fan Maximum VFD Output – VFD Parameter 3-02) x Supply Fan Minimum Speed Setpoint + VFD Parameter 3-02 = (54 - 25) x 0.30 + 25 = 33.7Hz 

Table 2- Minimum fan speed setpoints and effective supply fan minimum VFD output

Supply Fan Speed Command Status Calculation

The supply fan speed command status is calculated based on the VFD speed and the supply fan reference range.

The calculation is as follows:

• From Example 1: (42.5-25) / (60 - 25) = 50%
• From Example 2: (33.7-25) / (60 - 25) = 24.9%

2 Stage Airflow (Electromechanical Cond Only) (Unit Model Number Digit 15 = “C”)

• For 2-Speed VFD-controlled units, the desired maximum airflow (High Speed) is set by reprogramming parameter 4-15 on the VFD to the frequency value that best meets the RPM requirement as shown in the catalog fan tables.
• You can increase the minimum airflow (Low Speed) by adjusting parameter 4-12 in the TR150 VFD.
• You can run the supply fan on low speed by energizing the T-stat G terminal on Relay Board J5-4. High speed will require T-stat G plus either Y2, W1, or W2. 

Example TR-150 Programming Procedure

The Main Menu accesses all parameters.

• Press the [Menu] key twice until the indicator on the display is placed above “Main Menu”.
• Press [▼] to 4-** Limits/Warnings
• Press [Ok]
• Press [▼] to 4-1* Motor Limits
• Press [Ok]
• Press [▼] to 4-14 Motor Speed High Limit [Hz]
• Press [Ok]
• Press [▲] [▼] to set/change.
• Press [Ok] to save changes.
• Press [Back] until you get to the main screen.