Best Replacement Options for Obsolete Fuses

About this list

This list covers approaches, not companies, ordered roughly from least to most engineering effort. DENCO's own options are described using only what DENCO publishes on its cross-reference page and catalog. Brand-history facts were checked on 22 September 2026 and are cited below.

1. 1. Look for the original line under its current owner

In short: Parts from brands that have been acquired or reorganized

Many fuses that look obsolete are still made under another name. Eaton completed its acquisition of Cooper Industries in December 2012, and Cooper Bussmann products are now sold as Eaton's Bussmann series. The G.E. 9F60 series of E-rated fuses is now cataloged by Mersen, which lists 9F60 part numbers on its site today.

Search the part number, not just the brand, and ask the current owner whether a successor part exists. Keep the original marking on file so the substitution is traceable.

2. 2. Use an equivalence a manufacturer publishes

In short: Oil-immersed transformer and E-rated fuses covered by DENCO's catalog equivalences

Some manufacturers publish which legacy parts their products can substitute for. DENCO's catalog states six, listed in the table below and on DENCO's cross-reference page: GE CLF, Cooper ELSP, Cooper CBUC.., Hi-Tech HTSS.., Mersen 9F59CCF.. and the G.E. 9F60 series. The trailing ".." is DENCO's notation for the whole series, any rating suffix.

Even a published equivalence is a candidate for review, not a guarantee of interchangeability. DENCO engineering assesses ratings, physical fit, standards and the application before a substitution is confirmed.

See the DENCO range

3. 3. Send the part number for engineering review

In short: Discontinued medium and high voltage parts with no published equivalent

DENCO manufactures replacements for fuses that are obsolete, discontinued or no longer supported by their original maker, including medium and high voltage ranges. The part families it is regularly asked about include the 9F60 and 9F62 series, EJ-1 and EJO-1 types, and Amp-Trap, Ferraz Shawmut and Gould Shawmut references.

Outside the six published equivalences, every request is reviewed rather than answered from a table. Send the part number and DENCO engineering will confirm what it can supply. DENCO quotes a 30-day lead time on all products; lead times elsewhere in the industry are commonly longer.

• Original maker and part number exactly as marked
• System voltage, AC or DC
• Continuous current and required interrupting rating
• Dimensions and mounting
• Indicator or microswitch requirement, required standard, and a photo

See the DENCO range

4. 4. Replace cutout expulsion fuse-links with current-limiting dropouts

In short: Overhead distribution cutouts where the original link type is no longer available or current limiting is wanted

Where an expulsion fuse-link in a distribution cutout is the problem, a current-limiting dropout fuse is one route. DENCO's DHS and DHHS current-limiting dropout fuses are designed as replacements for cutout expulsion fuse-links.

Changing from expulsion to current-limiting operation changes the time-current characteristic and the let-through, so it is a protection change, not only a parts change. Confirm the cutout mounting with DENCO engineering and check coordination with upstream and downstream devices.

See the DENCO range

5. 5. Change the mounting when the holder is also obsolete

In short: Equipment where the clips, holder or Bay-O-Net assembly can no longer be sourced

If the holder is as hard to find as the fuse, replacing both lets you move to a current fuse and mounting system rather than chasing two obsolete parts. In pad-mounted transformers, for example, DENCO supplies Bay-O-Net holders and links plus oil-submersible current-limiting backup fuses.

Any change to a holder in energized-class equipment must respect the equipment maker's clearances, ratings and any listing on the assembly. Get the equipment maker's agreement where the change affects it.

See the DENCO range

6. 6. Move to a different, current fuse type with a coordination review

In short: Old installations whose original fuse type has no modern counterpart

Sometimes the right answer is a different fuse class rather than a like-for-like copy. ANSI C37.40 defines expulsion and current-limiting fuses and the full-range, general-purpose and back-up current-limiting classes; a back-up fuse, for example, is not designed to clear low overcurrents on its own, so it cannot simply replace a full-range fuse.

Rating systems also differ by application. Under ANSI/IEEE C37.46, an E-rated fuse of 100 A or less melts in 300 seconds at 200 to 240 percent of its rating, and above 100 A melts in 600 seconds at 220 to 264 percent; an R-rated motor fuse melts in 15 to 35 seconds at 100 times its R number. These definitions tell you what class you need; the coordination study tells you which rating.

See the DENCO range

7. 7. Buy remaining original stock, with care

In short: Short-term continuity while a permanent replacement is qualified

Distributors and surplus sellers may still hold new original parts. That can keep equipment running while you qualify a long-term substitute. Check provenance, packaging and date codes, look for physical damage, and confirm the stock has been stored dry and undamaged. Treat it as a bridge, not a plan.

See the DENCO range

8. 8. Redesign the protection when no fuse fits

In short: End-of-life switchgear or starters where fuse replacement is no longer practical

If the equipment itself is past support, replacing the fuse may only delay a larger job. A protection engineer may recommend new fused switchgear, a relay and breaker scheme, or replacement of the equipment. Use the fuse search to inform that decision: if no manufacturer can offer a reviewed replacement, that is useful evidence for the capital plan.

The six equivalences DENCO publishes

These are quoted from DENCO's January 2025 catalog and shown on DENCO's cross-reference page. They are the only equivalences DENCO publishes. For any other part, send the part number and DENCO engineering will confirm.

• GE CLF: DENCO DCLF (oil-immersed transformer fuses)
• Cooper ELSP: DENCO DCLF (oil-immersed transformer fuses)
• Cooper CBUC.. series: DENCO DEFTH (oil-immersed transformer fuses)
• Hi-Tech HTSS.. series: DENCO DEFTH (oil-immersed transformer fuses)
• Mersen 9F59CCF.. series: DENCO DEFTH (oil-immersed transformer fuses)
• G.E. 9F60 Series: DENCO E-Rated Type EJ-1 (E-rated fuses)

Before you order any replacement

Whatever route you take, the replacement has to match the original's job, not just its label.

• Confirm voltage class and AC or DC service
• Check interrupting rating against available fault current
• Compare time-current curves and let-through with the original
• Confirm dimensions, mounting, and any indicator or microswitch
• Confirm the standard or approval the installation requires
• Record the substitution in the equipment file

Frequently asked questions