When controllers are located close together, what is recommended regarding transformers?

• A. One transformer per controller.
• B. One large transformer for supplying multiple controllers.
• C. No transformer is needed; battery power is preferred.
• D. Use separate transformers for grouped sets only.

Answer: (B)

When several controllers sit close to one another, sharing a single low-voltage supply is the practical approach. A single, appropriately sized transformer feeding the entire group minimizes wiring, reduces hardware cost, and lowers voltage drop along short runs from the supply to each controller. It also ensures all controllers operate from the same control voltage reference, simplifying coordination and signaling. Size the transformer to handle the total control load of all the controllers in that area, with some headroom for inrush, and use proper fusing and conductor sizing for safety and reliability.

The other options waste resources or aren’t practical for continuous control power: using a transformer for each controller increases cost and wiring, battery power isn’t suitable for standard 24 VAC control power, and limiting separate transformers to grouped sets loses the efficiency and simplicity of a shared supply when the controllers are together.