Replacement Transformer. This is a 50 VA generic transformer with 24 VAC output. The input can be anything from 120 to 240 VAC single-phase power. It can be used to power anything requiring 24 VAC input, like a humidifier, UV unit, furnace, zone control, etc...This transformer is required to operate the MSP180, MS24, and MS24OZ UV air purifiers. The transformer is not included with the air purifiers and must be purchased separately.