Name: Resideo AT175A1008/U General Purpose Transformer with Foot Mounting
Brand: Resideo
SKU: HONE-AT175A1008/U
Price: 79.70 USD
Availability: InStock

General Purpose Transformer with Foot Mounting

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Frequency	60 Hz
Electrical Ratings	Primary voltage--120 Vac, 208 Vac, 240 Vac; Secondary voltage--27.5 V.O.C.
Mounting	Foot mounted, plate mounted on 2x4 in. or 4x4 in. outlet box , clamp mounted using outlet box knockout, or panel mounted
Includes	Metal end bells
Dimensions	3 3/16 in. high x 2 3/8 in. wide x 3 5/8 deep
UL	UL Listed: A,C,F models. File # E14881
CSA	CSA Certified: A & B models.
Temperature Range (F)	-20 F to +122 F
Electrical Connections (Primary)(in.)	9 in. leadwires
Electrical Connections (Secondary)(in.)	(2) screw terminals
Electrical Ratings, Output	24 Vac at 75 VA

Product Data for AT120A-E; AT140A-E; AT150A,B,D-F; AT160B; AT175A-D,F Transformers (Englis PDF ↗
Installation Instructions for AT120, AT120A, AT140, AT140A, AT150A, AT175A Universal Trans PDF ↗
Maintenance/Product Reference Materials-Residential Combustion Application Selection and C PDF ↗

The AT175A1008 is a control transformer from Resideo (Honeywell Home), 175 VA, foot mount.

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 that the thermostat, the zone valves, the relays and the gas valve all share.

Size it by VA, not by voltage. VA is the load the transformer can carry, and every device on the control circuit adds to it — a zone valve pulls current while it drives, a relay coil holds current the whole time it is energized, and a Wi-Fi thermostat draws continuously. A transformer sized for the original equipment will not carry the same system after two zones and a smart stat have been added, and the symptom is intermittent: things work alone and fail together.

Mounting matters more than it looks. The transformer has to land where the enclosure has room and where the leads reach, and a foot-mount body will not sit in a knockout that was made for a plate mount.

Brand: Resideo (Honeywell Home)
Manufacturer Part #: AT175A1008/U
Type: Control transformer
Rating: 175 VA
Secondary: 24 Vac
Mounting: Foot
Shipping weight: 2.8 lb
Category: Transformers

Full Specifications

Application	Power To 24 VAC Circuits In Heating and Cooling Systems
NEMA Rating	No
Primary Connection Size	9 in, 229 mm
Primary Input Voltage	120/208/240 V ac
Secondary Connection Type	(2) screw terminals
Secondary Open Circuit Voltage	27.5 V.O.C.
VA Rating	75 VA
Frequency	60 Hz
Approvals and Standards	UL Listed: A,C,F models. File # E14881, CSA Certified: A & B models
Includes	Clamp, Mounting Plate, Mounting Feet
Color	Metallic
Ambient Operating Temperature (Max)	105 °F, 41 °C
Ambient Operating Temperature (Min)	-20 °F, -29 °C
Product Height	3.19 in
Product Length	2.38 in
Product Width	3.13 in