This HVAC Ladder Diagram Example depicts numbers on the left denoting lines or circuits and numbers on the right indicating circuit lines with relays or switches. Contacts normally closed will be represented by underlined numbers on the right side. This HVAC Ladder Diagram Example will assist you in determining where power is coming from, which switches control which loads, how the switches are controlled, and the system's normal sequence of operation. Pictorial diagrams contain the same information as ladder diagrams but are formatted differently. A dotted line is frequently used in visual diagrams to indicate where the wiring needs to go during installation. This is primarily for installers, but HVAC technicians may find it useful.