Overview:

Setting the air flow is critical in all HVAC systems, it is no different in Odyssey. There are a couple different methods of changing the fan speeds depending on what type of air handler you may have installed. 

Evaporator Fan Performance Tables

The evaporator fan performance tables can be found in the product catalog by following the link: Odyssey Light Commercial - Product Catalog. 

The design air flow ranges listed on the charts at full fan capacity with a wet coil. If you are outside the design range, system performance and condensate management can be a problem. Typically, the normal design range is 320-480 cfm/ton with some exceptions listed in the notes below the tables. Heat pumps or air handlers with electric heat will always be between the normal design range. 

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

Adjust the motor sheave – close the sheave in for more fan RPM’s, 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 chooses to reduce the Supply Fan Maximum Speed Setpoint, it will effectively reduce the maximum VFD output 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 minimum reference setting in the VFD (25Hz from the factory). With the Supply Fan Minimum Speed Setpoint at a value of 0% and parameter 3-02 in the VFD at its default value of 25hz, the minimum VFD output will be 25Hz. If the user chooses to increase the Supply Fan Minimum Speed Setpoint, it will effectively increase the minimum VFD output 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 a calculation based on the VFD speed and range of the supply fan reference.

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 air flow (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 air flow (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 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 indicator in 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.

WARNING:

Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.