Code Change Summary: New code section on fuse reducers.

Fuse reducers are often used in the field to allow a smaller frame fuse than what a disconnect switch is designed for. Once in a while an electrician or homeowner comes up with a creative way to field fabricate a fuse reducer and although it might work, it’s better to use a fuse reducer that has been tested and certified for the purpose.

Field fabricating fuse reducers will likely create a poor connection. Over time a poor connection creates heating issues and could possibly result in a fire.

It is becoming commonplace to see 60-amp rated disconnect switches being installed in applications that require a 30-amp disconnect switch and then installing fuse reducers.

In the 2023 NEC^® new Section 240.60(E) requires fuse reducers to be listed. Product listing (certification) is done by Nationally Recognized Testing Laboratories such as UL.

UL certifies fuse reducers under product category code IZZR. The UL Guide Information on fuse reducers states that product category code IZZR “covers fuse reducers designed for use in cartridge fuse fuseholders to permit the insertion of fuses of smaller rating, Type S fuse adapters designed for use in Edison-base fuseholders to permit the insertion of Type S fuses, and special adapters designed to permit the use of miscellaneous plug fuses in Edison-base fuseholders to provide supplementary overcurrent protection.

Fuse reducers are primarily intended for use with open fuseholders. The use of fuse reducers in enclosed switches, panelboards, or other enclosures may introduce a hazard due to reduced spacings. Consideration should be given to spacings when fuseholders are used within enclosures”.

The intent of requiring fuse holders to be listed is to ensure a good connection.

Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2023 NEC^® edition of NFPA 70.