The Trane BAY24VRPAC52DC Relay Panel is the s and brawn of your Trane HVAC system, particularly those with 24-volt controls. Think of it as a translator, allowing the HVAC system (the brawn) and your thermostat (the intellect) to communicate. This small panel, measuring about 8" in width and 9.3" in height, converts low-voltage signals from your thermostat. https://www.partshnc.com/bay24vrpac52dc-trane-relay-panel