Review on 🔌 Aprilaire 4010 Transformer - Reliable Power Supply for Optimal Performance by Jason Reed

This transformer is well suited for powering thermostats in situations where a C-wire is not present on the thermostat. You can mount it in a single switch box in the wall (must be metal); I made a clamp to hold it securely in the box. Then apply 110 VAC from a nearby outlet to the thermostat box on the primary side of the transformer; Apply 24 VAC from the secondary of the transformer to the thermostat (all wires inside the wall). Works like a champ.