Name: Honeywell Home AT120B1028/U Foot Mounted 120 Vac Transformer
Brand: Honeywell Home
SKU: HONE-AT120B1028/U
Price: 23.93 USD
Availability: InStock

Resideo Foot mounted 120 Vac Transformer

Roll over image to zoom in Click on image to zoom

Frequency	60 Hz
Electrical Ratings	Primary voltage--120 Vac; Secondary voltage--27 V.O.C.
Mounting	Foot-mounted
Includes	Metal end bells
Dimensions	1 11/16 in. high x 3 3/16 in. wide x 1 3/4 in. deep
UL	UL Listed: A,C,F models. File # E14881
CSA	CSA Certified: A & B models.
Temperature Range (F)	-20 F to +105 F
Approvals, N.E.C.	NEC Class 2
Electrical Connections (Primary)(in.)	9 in. leadwires
Electrical Connections (Secondary)(in.)	9 in. leadwires
Electrical Ratings, Output	24 Vac at 20 VA

Installation Instructions for AT120, AT120A, AT140, AT140A, AT150A, AT175A Universal Trans PDF ↗

The AT120B1028 is a control transformer from Honeywell Home, 120 Vac primary, 24 Vac secondary, foot mounted.

Almost every heating and cooling control runs on 24 volts, and the transformer is what makes it. It takes line voltage in and delivers the low-voltage supply the thermostat, the zone valves, the relays and the gas valve all share.

Size it by VA, not by voltage. Every device on the control circuit adds load — a zone valve pulls current while it drives, a relay coil holds current the whole time it is energized, a Wi-Fi thermostat draws continuously. A transformer adequate for the original equipment is not automatically adequate after two zones and a smart stat have been added, and the symptom is intermittent.

Filed here under thermostat accessories, but this is a transformer and belongs with them.

Brand: Honeywell Home
Manufacturer Part #: AT120B1028/U
Type: Control transformer
Primary: 120 Vac
Secondary: 24 Vac
Mounting: Foot-mounted
Rating: 24 Vac at 20 VA
Leadwires: 9 in. leadwires
Operating range: -20 F to +105 F
UPC: 085267034920
Category: Transformers

Full Specifications

Application	Heating and or cooling control systems
NEMA Rating	No
Primary Connection Size	9 in, 229 mm
Primary Input Voltage	120 V ac
Secondary Connection Size	9 in, 229 mm
Secondary Connection Type	Leadwires
Secondary Open Circuit Voltage	27 V.O.C.
VA Rating	20 VA
Frequency	60 Hz
Approvals and Standards	CSA Certified: A & B models, NEC Class 2
Includes	Metal end bells
Warranty	1 Year
Color	Black, Metallic
Ambient Operating Temperature (Max)	105 °F, 41 °C
Ambient Operating Temperature (Min)	-20 °F, -29 °C