Harmonization Update on 7th Edition of UL 60335-2-34 for Motor-compressors

By Barry Karnes, principal engineer – Refrigeration Products

UL Solutions announces the publication of a new Seventh Edition of UL 60335-2-34, the Standard for Household and Similar Electrical Appliances – Safety – Part 2-34; Particular Requirements for Motor-Compressors.  This Standard covers the safety of motor-compressors intended for use in heating, air conditioning and refrigeration appliances.

This new Seventh Edition of UL 60335-2-34 is expected to be published on March 31, 2025, and will be based on the Sixth Edition of IEC 60335-2-34, dated March 2021.

Consistent with the previous edition of UL 60335-2-34, the new Seventh edition is harmonized with the Canadian Standard for motor-compressors, CSA C22.2 No. 60335-2-34:25.

Key changes include:

A)  Providing requirements for:

• Multi-speed motor-compressors in which the speed can be set to different values;
• Variable capacity motor-compressors in which the capacity is controlled at fixed speeds;
• Electronically controlled or protected motor-compressors; and,
• Motor-compressors that may be operated by an adjustable speed drive (ASD), including a new test requiring certain ASD’s -- and in which the protective electronic circuit is incorporated or associated with the motor-compressor--to be subjected to 3 manually reset operations.

B)  A marking to specify the maximum rated current (MRC) for electronically controlled or protected motor-compressors denoting the maximum current under any possible loading conditions, such as maximum speed and load, including locked-rotor.  Manufacturers should deplete nameplate stock and transition to updated nameplates.

C)    For motor-compressors intended for use with a flammable refrigerant and except for components located inside the housing, requires arcing or sparking components to comply with one of the following:

• UL 60079-15, Explosive atmospheres – Part 15: Equipment protection by type of protection "n";
• UL 60079-1, Explosive Atmospheres – Part 1: Equipment Protection by Flameproof Enclosures “d”, as modified by Annex DD;
• UL 121201, Nonincendive Electrical Equipment for Use in Class I and II, Division 2 and Class III, Divisions 1 and 2 Hazardous (Classified) Locations; or,
• One of the relevant options in Clause 22.116DV of UL 60335-2-40, Household and Similar Electrical Appliances – Safety – Part 2-40: Particular Requirements for Electrical Heat Pumps, Air-Conditioners and Dehumidifiers, 4th Ed.

D)  Replacing the positive or negative temperature coefficient resistor (PTCR or NTCR) test presently in the 6th Edition with requirements specifying that a PTCR or NTCR is to comply with UL 60730-1, Automatic Electrical Controls – Part 1: General Requirements, or be entirely located within the motor-compressor housing or similar enclosure. 

E)  Eliminating the motor-compressor tie cords breaking (pull) test for North American motor-compressors; however, for compliance with the IEC requirements, the tie cord breaking test is still being required.

The new 7th edition of UL 60335-2-34 is expected to become effective upon publication. If desired, a motor-compressor manufacturer can begin immediately certifying their motor-compressors using this new edition. However, UL 60335-2-34, 6th edition is expected to remain effective until at least March 31, 2026, pending feedback from industry stakeholders.

As a safety science leader, UL Solutions can review your motor-compressors intended for use in heating, air conditioning and refrigeration appliances, to check that they meet the new requirements or start a new quote. Leverage our dedicated laboratory staff and their expertise in the motor compressors product category to help you find a path to testing and certification.