Installation

December 16, 2019

© S&C Electric Company 1949-2019, all rights reserved Instruction Sheet 252-525

Power Fuses Type SM, SML, and SME★ – Indoor DistributionType SM – Outdoor Distribution (4.16 kV through 34.5 kV)

SM-4® and SM-5® Refill Units

Table of Contents

Section Page Section Page

IntroductionQualified Persons . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Read this Instruction Sheet . . . . . . . . . . . . . . . . . . . 2Retain this Instruction Sheet . . . . . . . . . . . . . . . . . . . 2Proper Application . . . . . . . . . . . . . . . . . . . . . . . . . . 2Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Warranty Qualifications . . . . . . . . . . . . . . . . . . . . . . 3

Safety InformationUnderstanding Safety-Alert Messages . . . . . . . . . . . 3Following Safety Instructions . . . . . . . . . . . . . . . . . . 3Replacement Instructions and Labels . . . . . . . . . . . 3

Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . 4

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Fusing Holders Equipped with a Silencer, Snuffler,

Super Snuffler, Muffler, or Sneezer Exhaust-Control Device . . . . . . . . . . . . . . . . . . . . 5

Holders Not Equipped with a Silencer, Snuffler, Super Snuffler, Muffler, or Sneezer Exhaust-Control Device . . . . . . . . . . . . . . . . . . . . 6

Re-Fusing Blown Fuses . . . . . . . . . . . . . . . . . . . . . 8

Changing the Ampere Rating of an Unblown Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

★ Type SME Power Fuses are available in S&C PME Pad-Mounted Gear models only .

2 S&C Instruction Sheet 252-525

Introduction

Qualified Persons WARNINGOnly qualified persons who are knowledgeable in the installation, operation, and maintenance of overhead and underground electric distribution equipment, along with all associated hazards, may install, operate, and maintain the equipment covered by this publication . A qualified person is someone who is trained and competent in:

• The skills and techniques necessary to distinguish exposed live parts from nonlive parts of electrical equipment

• The skills and techniques necessary to determine the proper approach distances corresponding to the voltages to which the qualified person will be exposed

• The proper use of special precautionary techniques, personal protective equipment, insulated and shielding materials, and insulated tools for working on or near exposed energized parts of electrical equipment

These instructions are intended ONLY for such qualified persons . They are not intended to be a substitute for adequate training and experience in safety procedures for this type of equipment .

Read this Instruction Sheet

NOTICEThoroughly and carefully read this instruction sheet and all materials included in the product’s instruction handbook before installing or operating your Type SM, SML, and SME Power Fuses . Familiarize yourself with the Safety Information and Safety Precautions on pages 3 and 4 . The latest version of this publication is available online in PDF format at sandc.com/en/support/product-literature/ .

Retain this Instruction Sheet

This instruction sheet is a permanent part of your Type SM, SML, and SME Power Fuses. Designate a location where you can easily retrieve and refer to this publication.

Proper Application WARNINGThe equipment in this publication is only intended for specific fusing applications . The application must be within the ratings furnished for the equipment . Ratings for Type SM, SML, and SME Power Fuses are listed in the ratings table in Specification Bulletins 242-31 and 252-31 . The ratings are also affixed to the product .

Warranty The warranty and/or obligations described in S&C’s Price Sheet 150, “Standard Conditions of Sale–Immediate Purchasers in the United States,” (or Price Sheet 153, “Standard Conditions of Sale–Immediate Purchasers Outside the United States”), plus any special warranty provisions, as set forth in the applicable product-line specification bulletin, are exclusive. The remedies provided in the former for breach of these warranties shall constitute the immediate purchaser’s or end user’s exclusive remedy and a fulfillment of the seller’s entire liability. In no event shall the seller’s liability to the immediate purchaser or end user exceed the price of the specific product that gives rise to the immediate purchaser’s or end user’s claim. All other warranties, whether express or implied or arising by operation of law, course of dealing, usage of trade or otherwise, are excluded. The only warranties are those stated in Price Sheet 150 (or Price Sheet 153), and THERE ARE NO EXPRESS OR IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. ANY EXPRESS WARRANTY OR OTHER OBLIGATION PROVIDED IN PRICE SHEET 150 (OR PRICE SHEET 153) IS GRANTED ONLY TO THE IMMEDIATE PURCHASER AND END USER, AS DEFINED THEREIN. OTHER THAN AN END USER, NO REMOTE PURCHASER MAY RELY ON ANY AFFIRMATION OF FACT OR PROMISE THAT RELATES TO THE GOODS DESCRIBED HEREIN, ANY DESCRIPTION THAT RELATES TO THE GOODS, OR ANY REMEDIAL PROMISE INCLUDED IN PRICE SHEET 150 (or PRICE SHEET 153).

S&C Instruction Sheet 252-525 3

Introduction

Safety Information

Warranty Qualifications

The following instructions are for installation of S&C SM-4 and SM-5 Refill Units in S&C Type SM-4Z, SML-4Z, SME-4Z, SM-5S, and SM-5SS Power Fuses, Indoor Distribution, and S&C Type SM-4 and SM-5 Power Fuses, Outdoor Distribution, as well as preceding models of these fuses.

The standard warranty contained in the seller's standard conditions of sale (as set forth in Price Sheet 150) also does not apply when fuses not manufactured by S&C are used in conjunction with S&C live parts or when S&C refill units are used in mountings not manufactured by S&C.

Understanding Safety-Alert Messages

Several types of safety-alert messages may appear throughout this instruction sheet and on labels and tags attached to Type SM, SML, and SME Power Fuses. Familiarize yourself with these types of messages and the importance of these various signal words:

DANGER“DANGER” identifies the most serious and immediate hazards that will likely result in serious personal injury or death if instructions, including recommended precautions, are not followed .

WARNING“WARNING” identifies hazards or unsafe practices that can result in serious personal injury or death if instructions, including recommended precautions, are not followed .

CAUTION“CAUTION” identifies hazards or unsafe practices that can result in minor personal injury if instructions, including recommended precautions, are not followed .

NOTICE“NOTICE” identifies important procedures or requirements that can result in product or property damage if instructions are not followed .

Following Safety Instructions

If you do not understand any portion of this instruction sheet and need assistance, contact your nearest S&C Sales Office or S&C Authorized Distributor. Their telephone numbers are listed on S&C’s website sandc.com, or call the S&C Global Support and Monitoring Center at 1-888-762-1100.

NOTICE

Read this instruction sheet thoroughly and carefully before installing Type SM, SML, and SME Power Fuses .

Replacement Instructions and Labels

If additional copies of this instruction sheet are needed, contact your nearest S&C Sales Office, S&C Authorized Distributor, S&C Headquarters, or S&C Electric Canada Ltd.

It is important that any missing, damaged, or faded labels on the equipment be replaced immediately. Replacement labels are available by contacting your nearest S&C Sales Office, S&C Authorized Distributor, S&C Headquarters, or S&C Electric Canada Ltd.

4 S&C Instruction Sheet 252-525

Safety Precautions

DANGERType SM, SML, and SME Power Fuses operate at high voltage. Failure to observe the precautions below will result in serious personal injury or death.

Some of these precautions may differ from your company’s operating procedures and rules . Where a discrepancy exists, follow your company’s operating procedures and rules .

1 . QUALIFIED PERSONS. Access to Type SM, SML, and SME Power Fuses must be restricted only to qualified persons . See the “Qualified Persons” section on page 2 .

2 . SAFETY PROCEDURES. Always follow safe operating procedures and rules .

3 . PERSONAL PROTECTIVE EQUIPMENT. Always use suitable protective equipment, such as rubber gloves, rubber mats, hard hats, safety glasses, arc-flash clothing, and fall-protection, in accordance with safe operating procedures and rules .

4 . SAFETY LABELS. Do not remove or obscure any of the “DANGER,” “WARNING,” “CAUTION,” or “NOTICE” labels and tags . Remove tags ONLY if instructed to do so .

5 . ENERGIZED COMPONENTS. Always consider all parts live until de-energized, tested, and grounded .

6 . MAINTAINING PROPER CLEARANCE. Always maintain proper clearance from energized components .

7 . Do not leave fuse units installed in the fuse mounting hanging open. When closed in, the fuse units will not be damaged by rain or high humidity . However, the watertightness of the exhaust end of the fuse units cannot be guaranteed; therefore, as a precaution, fuse units should not be left hanging open . Any rain or snow that might enter could affect the solid-material lining . Moreover, when in storage, these fuse units should be protected from excessive moisture .

8 . Do not remove the fuse unit from its carton until ready to use.

9 . Handle fuse units with care. Do not drop or throw them .

10 . Do not place a hand over the upper seal of the fuse unit when handling. There is the remote possibility the current-responsive section of the fuse unit may have been weakened in shipping or handling . As a result, the spring-loaded actuating pin may be unpredictably released and driven forcibly through the upper seal .

SM-4B Muffler

SM-4D Sneezer

SM-4S Snuffler

SM-4Z, SML-4Z, and SME-4Z Silencer

SM-5B, SM-5C Muffler

SM-5D Sneezer

SM-5S Snuffler

SM-5SS Super Snuffler

Figure 1. Exhaust-control devices for Type SM Power Fuse Holders.

S&C Instruction Sheet 252-525 5

Overview

NOTICERefill units should be stored in a dry place and kept in the carton until used .

Storage indoors in a clean, dry place is required for indoor-style holders and is recommended for outdoor-style holders. If an unloaded outdoor holder is stored outdoors, it must not be left so the glass-epoxy tube inside the porcelain housing can get wet. Store the holder in an upright position, and keep the lower ferrule opening closed by the cork inserted at the factory.

The gravity-operated rain shield on the lower ferrule of outdoor disconnect 180º opening vertical-style holders helps to prevent water from entering the holder when it is left hanging open for short periods of time. However,

because the rain shield is not a positive sealing device, the holder should be removed from the mounting when it is not in service.

Handle holders with care, especially those with refill units installed. Do not drop or throw them.

NOTICES&C Power Fuse Refill Units have silver or nickel-chrome fusible elements that are nondamageable . Consequently, there is no need to replace unblown companion fuses (on three-phase systems serving three-phase loads) on suspicion of damage following a fuse operation .

Fusing

Holders Equipped with a Silencer, Snuffler, Super Snuffler, Muffler, or Sneezer Exhaust-Control DeviceType SM Power Fuse Holders have been furnished with a number of different exhaust-control devices over the years. As the procedure for fusing these holders varies somewhat according to the particular exhaust-control device furnished, it is important that the exhaust-control device be properly identified. Refer to the photos below and determine which device was furnished. See Figure 1 on page 4.

Complete the following steps to install refill units in new SM Power Fuse holders.

Note: Steps 1, 2, 9, and 10 apply only to the following Type SM Power Fuse Holders in the disconnect style: SM-4B, SM-5B, and SM-5C Holders furnished with a

muffler; SM-4D and SM-5D Holders furnished with a sneezer; and SM-4S Holders furnished with snuffler. Steps 1, 2, 9, and 10 do not apply to any non-disconnect style holders (including SM-5SS Holders furnished with a super snuffler), or to the following holders in the disconnect style; SM-4Z, SML-4Z, and SME-4Z Holders furnished with silencer; or SM-5S Holders furnished with a snuffler.

STEP 1. Loosen the two bolts that secure the lower end fitting to the lower ferrule of the holder. See Figure 2.

STEP 2. Loosen the clamp bolt and pry the clamp apart slightly. See Figure 3.

STEP 3. Unscrew and remove the exhaust-control device (silencer, snuffler, super snuffler, muffler, or sneezer). A bar or wrench handle can be used to loosen it. See Figure 4.

Figure 3. Location and loosening of clamp bolt.

Figure 2. Location and loosening of bolts on the end-fitting.Figure 4. Removal of exhaust-control drive.

6 S&C Instruction Sheet 252-525

Fusing

Figure 5. Removal of holder-cap with spring-and-cable assembly.

Exhaust ferrule1/8-inch (3 mm)approx .

DROP-BACK POSITION

MAXIMUM PULL-THROUGH POSITION

Contact fingersKnurled collar

Figure 6. Installation of refill-unit onto spring-and-cable assembly.

Figure 7. Installation of refill-unit into holder.

Figure 8. Drawing the pull-cord through the holder.

STEP 4. Unscrew and withdraw the holder cap, to which is attached the spring-and-cable assembly. See Figure 5.

STEP 5. Screw a refill unit of correct ampere and voltage rating tightly onto the lower end of the spring-and-cable assembly using the knurled terminal on the spring-and-cable assembly to impart a final, hard twist. Do not use a wrench. Before proceeding to Step 6, check whether the knurled collar at the other end of the refill unit is tight against the shoulder of the refill-unit ferrule. See Figure 6.

STEP 6. Insert the combination of spring-and-cable assembly and refill unit into the holder and screw the cap down tight. The final fractional turn should be made with a wrench. See Figure 7.

STEP 7. Carefully draw the refill pull-cord out through the holder, against spring tension, until the contact fingers of the holder latch behind the knurled collar of the refill unit. Avoid jerking and excessive overtravel, which may damage low-ampere refill units. Release the refill pull-cord slowly, permitting the collar to rest on the

contact fingers. Remove and discard the cord. Do not bend or otherwise alter the shape of the contact fingers. See Figure 8.

STEP 8. Replace the exhaust-control device, screwing on firmly. To ensure adequate electrical contact with the contact fingers—essential to the proper performance of the fuse—the final, fractional turn of the exhaust-control device must be made with a bar or wrench handle.

STEP 9. Tighten the two bolts that secure the lower end-fitting to the lower ferrule of the holder.

STEP 10. Tighten the clamp bolt.

Holders Not Equipped with a Silencer, Snuffler, Super Snuffler, Muffler, or Sneezer Exhaust-Control DeviceSTEP 1. If the holder is equipped with a clamp-on type

rain shield, loosen the clamp and remove it. (Gravity-operated rain shields, as furnished on outdoor disconnect 180º opening vertical-style holders need not be removed.) See Figure 9. Remove the hexagonal clamping nut from the end of the holder.

Figure 9. Removal of clamping nut.

S&C Instruction Sheet 252-525 7

Fusing

Figure 10. Removal of holder-cap with spring-and-cable assembly.

STEP 2. Unscrew and withdraw the holder-cap, to which is attached the spring-and-cable assembly. See Figure 10.

STEP 3. Screw a refill unit of correct ampere and voltage rating tightly onto the lower end of the spring-and-cable assembly using the knurled terminal on the spring-and-cable assembly to impart a final, hard twist. Do not use a wrench. Before proceeding to Step 4, check whether the knurled collar at the other end of the refill unit is tight against the shoulder of the refill-unit ferrule. See Figure 11.

STEP 4. Insert the combination of spring-and-cable assembly and refill unit into the holder and screw the cap down tight. The final fractional turn should be made with a wrench. See Figure 12.

STEP 5. Carefully draw the refill pull-cord out through the holder, against spring tension, until the contact fingers of the holder latch behind the knurled collar of the refill unit. Avoid jerking and excessive overtravel, which may damage low-ampere refill units. Release the refill pull-cord slowly, permitting the collar to rest on the contact fingers. Remove and discard the cord. Do not bend or otherwise alter the shape of the contact fingers. See Figure 13.

STEP 6. Replace the hexagonal clamping nut, screwing down firmly to lock the refill unit in place. To ensure adequate electrical contact with the contact fingers, which is essential to the proper performance of the fuse, the final fractional turn of the hexagonal clamping nut must be made with a wrench. If the holder is equipped with a clamp-on type rain shield, replace the rain shield and tighten the clamp. See Figure 14.

Figure 11. Installing refill unit onto spring-and-cable assembly.

Figure 12. Installation of refill-unit into holder.

Exhaust ferrule1/8-inch (3 mm) approx .

DROP-BACK POSITION

MAXIMUM PULL-THROUGH POSITION

Contact fingersKnurled collar

Figure 13. Drawing the pull-cord through the holder.

Figure 14. Installation of the clamping nut.

8 S&C Instruction Sheet 252-525

Re-Fusing Blown Fuses

Complete the following steps to replace refill units in blown SM Power Fuse holders.

STEP 1. Remove the exhaust-control device or the hexagonal clamp nut, as described in the “Fusing” section on pages 5 through 7.

STEP 2. Grasp the knurled collar of the blown refill unit and withdraw the refill unit from the holder. Discard the blown refill unit.

STEP 3. Unscrew the holder cap and withdraw the spring-and-cable assembly.

STEP 4. Unscrew and discard the arcing terminal of the blown refill unit. Wipe clean all contact surfaces, but do not clean with an abrasive because the silver plating may thus be damaged. If the spring is damaged, install a new spring-and-cable assembly.

STEP 5. After a high-magnitude fault, wipe clean the interior of the fuse holder to remove any dust and metallic particles that may be present.

STEP 6. After a high-magnitude fault, carefully inspect the inside of the exhaust-control device. If the copper mesh shows significant erosion caused by an extremely high fault, replacement of the exhaust-control device is recommended.

STEP 7. Using a new refill unit of correct ampere and voltage rating, fuse and reassemble as described in the “Fusing” section on pages 5 through 7.

Changing the Ampere Rating of an Unblown Fuse

S&C Power Fuse Refill Units have silver or nickel-chrome fusible elements that are nondamageable. Consequently, there is no need to replace unblown companion fuses (on three-phase systems serving three-phase loads) on suspicion of damage following a fuse operation. If an unblown refill unit is to be replaced, for example, to change ampere rating, follow these procedures:

STEP 1. Remove the exhaust-control device or the hexagonal clamp nut, as described in the “Fusing” section on pages 5 through 7.

STEP 2. Insert a cord or wire through the small hole in the projecting threaded portion of the ferrule of the refill unit. Pull the refill unit outward about 1/8-inch (3 mm) See Figure 15.

STEP 3. Unscrew and remove the knurled collar from the refill unit and allow the refill unit to slide slowly back into the holder.

STEP 4. Unscrew the holder cap and withdraw the spring-and-cable assembly and refill unit. Unscrew the refill unit from the spring-and-cable assembly, replace it with a refill unit of the desired ampere rating, and reassemble, as described in the “Fusing” section on pages 5 through 7.

NOTICEIf the replaced refill unit is not to be used immediately, place it in a polyethylene bag and then in a refill-unit carton . Mark the carton with the correct ampere rating and store it in a dry place .

Figure 15. Pulling the refill unit using a pull-cord.