Effective April 30, 2018

Standard Information
Standard Number:
UL 5085-3 / CSA C22.2 No. 66.3
Standard Name:
Low Voltage Transformers — Part 3: Class 2 and Class 3 Transformers
Standard Edition and Issue Date:
1st Edition Revised April 17, 2006
Date of Revisions:
November 30, 2012
Date of Previous Revisions to Standard:
1st Edition Revised May 24, 2011
Effective Date of New/Revised Requirements

Effective Date: April 30, 2018

Impact, Overview, Fees and Action Required

Impact Statement: A review of all Listing Reports is necessary to determine which products comply with new/revised requirements and which products will require re-evaluation. NOTE: Effective immediately, this revised standard will be exclusively used for evaluation of new products unless the Applicant requests in writing that current requirements be used along with their understanding that their listings will be withdrawn on Effective Date noted above, unless the product is found to comply with new/revised requirements.

Overview of Changes:

  • Reinstatement of Requirements for the Separation of Circuits
  • Addition of Leakage Current Test for Cord-Connected Class 3 Transformers

Specific details of new/revised requirements are found in table below.

If the applicable requirements noted in the table are not described in your report(s), these requirements will need to be confirmed as met and added to your report(s) such as markings, instructions, test results, etc. (as required).

Client Action Required:

Information – To assist our Engineer with review of your Listing Reports, please submit technical information in response to the new/revised paragraphs noted in the attached or explain why these new/revised requirements do not apply to your product (s).

Current Listings Not Active? – Please immediately identify any current Listing Reports or products that are no longer active and should be removed from our records. We will do this at no charge as long as Intertek is notified in writing prior to the review of your reports.

Description of New/Revised Technical Requirements
11.6 Reinstatement of Requirements for the Separation of Circuits

New section added;

Separation of internal wiring circuits
11.6.1 Except as noted in, unless provided with insulation rated for the highest voltage involved, insulated conductors of different circuits shall be separated by barriers or shall be segregated and shall be separated or segregated from uninsulated live parts connected to different circuits. In a compartment or enclosure where provision for Class 1 power, lighting, nonpower limited fire alarm, or medium power network-powered broadband communication circuit conductors is available for connection to Class 2 or 3 circuits, Class 2 and 3 circuit conductors may be separated from the conductors of other circuits by the following methods:
    a) A reliable barrier, clamping or routing means that maintains a minimum spacing of 6.4 mm (1/4 inch) between the conductors of different circuits; or
    b) When all circuit conductors operate at 150 volts or less to ground, the Class 2 and Class 3 circuits may be installed using minimum CL3, CL3R, CL3P, or cables determined equivalent. These cables shall extend beyond the jacket and be separated by a minimum of 6.4 mm (1/4 inch) or by an insulating sleeve or barrier from all other conductors.
11.6.2 Segregation of insulated conductors shall be accomplished by clamping, or an equivalent means that provides permanent separation from insulated or uninsulated live parts of a different circuit.
11.6.3 A barrier used to separate or segregate internal wiring, or used to separate or segregate low voltage field wiring from line voltage parts, shall have mechanical strength. It shall be held in place to provide permanent separation and shall be rated for the temperature involved.
11.6.4 An insulating barrier shall have a minimum thickness of 0.71 mm (0.028 inch) and shall be of material as described in Clause 11.2.2 of Part 1.
D1.4 Addition of Leakage Current Test for Cord-Connected Class 3 Transformers

New section added;

A cord-connected Class 3 transformer shall be subjected to the test described in Clauses D1.4.2 – D1.4.8. The results are acceptable when the leakage current does not exceed 0.5 milliamperes (see standard for section/test details).

CUSTOMERS PLEASE NOTE: This Table and column "Verdict" can be used in determining how your current or future production is or will be in compliance with new/revised requirements.

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