What is the secondary voltage on a step down control transformer for a residential furnace?

The secondary voltage on a step-down control transformer for a residential furnace is typically 24 volts. This voltage is standard in most residential heating and cooling systems. The 24 volts is important as it is compatible with most low-voltage control systems, including thermostats, relays, and safety circuits commonly found in HVAC equipment.

The use of a lower voltage such as 24 volts improves safety, reduces the risk of severe electrical shock, and allows for longer wire runs without significant voltage drop. This is essential when connecting multiple components in a system. In contrast, higher voltages like 120 or 240 volts are typically used for household power supply and larger appliances, not for control circuits in residential furnaces. Therefore, the correct voltage reflects the industry standards for control voltages in HVAC applications.