George’s CBAS Tips, January 2020

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Computrols Building Automation Systems Low Voltage Blog

Controller Voltage

Did you know that Binary Outputs can be locked out if your power supply is inadequate? 

If the power being supplied to the controller is inadequate, all binary outputs will be locked in the OFF state until adequate power is returned. This way the controller continues to run, and if you have alarms setup, you will be notified that the equipment did not start. To know for sure whether this is Binary Lockout or your controller is defective, you must check Controller Diagnostics.

Controller Diagnostics can be found in Real Mode only: In Hardware View, find the controller on the controller channel, click it, and then click Show Controller Diagnostics. 

Looking at the row labeled Binary Enable, if the Binary Lockout was in effect, the value would be OFF.  A value of ON indicates that the Binary Outputs are enabled and working normally.

The row labeled AC Power can be useful when troubleshooting.  The threshold for Binary Lockout is around 18 volts. The incoming voltage and current draw are both used in determining when to lockout the Binary Outputs.

In the case of an X-line controller, you access Diagnostics in the same manner. Controller Diagnostics can be found in Real Mode only: In Hardware View, find the controller on the Controller Channel, click it then click Show Controller Diagnostics.

In the top right, you will see Low Power Lockout, YES when binaries are locked out. The same concept applies to the X-line controllers as the LX controllers. The labels on the controllers mention power requirements at the bottom in the power section: “You must supply a 24VAC Class II transformer to power the controller. The minimum transformer size is XXVA, plus the requirements of all connected devices.”

Of course, each controller size requires a different minimum power. The connected devices that use power are mainly binary outputs. Near the top of the controller label, you can see the binary output section which mentions that the output is 24VDC and the maximum current is 50mA. So the relays used cannot require more than 50mA. Add up the number of relays and multiply by the current they require. 

Our R&D team recently came out with new minimum power requirements for our LX controller line. You can find those requirements detailed below and the LX controller labels have been updated accordingly. 

8-LX – 50VA (No end devices or loop source) – recommended is 100VA

16-LX – 75VA (No end devices or loop source) – recommended is 150VA

32-LX – 100VA (No end devices or loop source) – recommended is 250VA

64-LX – 200VA (No end devices or loop source) – recommended is 300VA

For UNI-B and VAV-B controllers, the power requirements are:

VAV-B-AP/P/X – 2VA (No end devices or loop source) – fully loaded is 75VA

UNI-B-AP/P/X – 2VA (No end devices or loop source) – fully loaded is 75VA

 

About George Hingle

George has been a part of the Computrols family since 2001. He graduated from Loyola University with a Bachelor of Arts Degree in Music and also has an Associate’s Degree in Computer Networking. Furthermore, George also has experience in networking, PC, and server maintenance along with computer and networking component purchasing. He has also worked as a Field Technician here at Computrols and has assisted in the testing of new products and features. As part of the in-house Technical Support team, George answers technical support questions over phone and e-mail. He often guides our customers step-by-step to help them fix/correct any technical issues when needed.