Nora's step down transformer is an accessory offered to take 277V supply voltage and reduce it to 120V. The transformer is installed by a qualified electrician on a supply junction box before the 120V load. Dimming - Primary Side Dimming on the primary side must be done with a 277V low voltage magnetic dimmer Dimming - Secondary Side Dimming on the secondary side (120V) must be done with a recommended compatible dimmer for the secondary load type Minimum Clearance Must be a minimum of 3" from thermal insulation and 1/2" from adjacent building components Step Down Transformers are Made in the USA.