UL 5085-3 PDF

1 Scope

1.1 As noted in Low Voltage Transformers – Part 1: General Requirements, UL 5085-1, or CSA C22.2 No. 66.1, Low Voltage Transformers – Part 1: General Requirements, the requirements in Part 3 cover Class 2 transformers for use with Class 2 circuits in accordance with the National Electrical Code, ANSI/NFPA 70, or the Canadian Electrical Code, Part I, CSA C22.1. They are intended for connection to essentially sinusoidal supply sources.

Advisory Note

: For transformers intended for use in the United States, these requirements also cover Class 3 transformers for use with Class 3 circuits in accordance with the National Electrical Code, ANSI/NFPA 70, unless otherwise specified in this standard. See Annex D for Class 3 requirements.

1.3 In addition to the items specified in Clause 1.3 of Part 1, the requirements of Part 3 do not cover:

1. a) Power supplies (a transformer provided with a rectifier is considered a power supply);

2. b) Toy transformers;

3. c) Cord and plug connected transformers other than Class 3;

4. d) Direct plug-in transformers;

5. e) Transformers intended for use in audio, radio, or television type appliances; or

6. f)  Other special types of transformers covered in requirements for other electrical devices or appliances.

Advisory Note:

The requirements of Part 3 do not cover transformers intended for use in the United States having a nominal primary rating of more than 600 V and transformers having overvoltage taps rated over 660 V.

1.7 This part is intended to be used in conjunction with Part 1. The numbering of the clauses in Part 3 corresponds to the numbered clauses in Part 1. The requirements in Part 1 apply unless modified by Part 3.

1.8 A Class 2 transformer that includes a separate current-limiting impedance such as a resistor or a positive temperature coefficient device (PTC) is covered by these requirements.

1.9 A Class 2 transformer that includes a resonance regulating circuit is covered by these requirements.

Summary of Topics

This revision of ANSI/UL 5085-3 dated January 28, 2022 is being issued to update the title page to reflect the most recent designation as a Reaffirmed American National Standard (ANS). No technical changes have been made.

As noted in the Commitment for Amendments statement located on the back side of the title page, UL and CSA are committed to updating this harmonized standard jointly. However, the revision pages dated January 28, 2022 will not be jointly issued by UL and CSA as these revision pages only address UL ANSI approval dates.