Key Interlock Systems

Factory-installed only on heavy duty and double throw safety switches.

Interlocks help protect against unauthorized operation. Not available on hazardous location devices (NEMA 7/9) or fiberglass reinforced polyester (NEMA 4X).

The key interlock system is a simple and easy method of applying individual key interlock units and assemblies to the above equipment so as to require operation in a predetermined sequence. UL Listed.

Quoting: Contact Schneider Electric for catalog number, availability and pricing prior to quoting a job.

Ordering: Order cannot be released for production until the following information has been provided:

• End User—Company name, address.

• Function of each lock (e.g., switch to be locked open with key removed, key held when switch is closed).

• Existing Equipment—if switch is to be interlocked with equipment already on site, provide brand of existing lock and key number.

• Other New Equipment—if switch is to be interlocked with new equipment not yet installed at the site, then provide contact person and phone number so that locks may be coordinated.

• Additional information may be required upon order entry.

Use these suffixes on switch catalog numbers:

• KI = 1 lock per switch

• KI2 = 1 lock with 2 cylinders per switch

• KIKI = 2 separate locks per switch

Key Interlock Sample Applications

Sample Application—1 (see Figure 1)

To protect against two devices from being closed simultaneously.

Two devices are shown in Figure 1. In operation they are not closed at the same time. With the interlocks arranged as shown only one key is required in the interlocking system. Both devices are shown open, therefore, the key is free. To close any one device the key is inserted and turned in that particular lock, the key is held in this lock until the device is again locked open. This simple interlocking sequence lends itself to a multitude of applications. The procedure is the same for two devices, neither of which is to be opened at the same time.

Sample Application—2 (see Figure 2)

To protect against opening of switch A when circuit breaker B is closed.

Switch A and circuit breaker B are in closed position. Key A-1 is held in circuit breaker B interlock.

• Open circuit breaker.

• Turn key A-1 in L-O-R interlock on circuit breaker B to lock open. Key A-1 is now free.

• Insert key A-1 in L-C-R interlock on switch A and turn to unlock.

• Open switch A. Key A-1 is now held. Reverse sequence to restore service.

Sample Application—3 (see Figure 3)

To protect against operation of switch A when circuit breaker B is closed. Permits re-closing of circuit breaker for servicing when switch is locked open.

Switch A and circuit breaker B are in closed position. Key A-1 is held in circuit breaker interlock.

• Open circuit breaker.

• Turn key A-1 in L-O-R interlock on circuit breaker B to lock open. Key A-1 is now free.

• Insert key A-1 in L-O-C-R interlock on switch A and turn to unlock.

• Open switch A.

• Turn key A-1 in L-O-C-R interlock on switch A to lock open. Key A-1 is now free.

• Return key A-1 to circuit breaker interlock and unlock for operation during servicing period.

Reverse sequence to restore service.

Sample Application—4 (Main-Tie-Main) (See Figure 4)

To protect against paralleling of lines A and B; two loads, fed from either source.

Circuit breaker A is closed to supply load M. Circuit breaker B is closed to supply load N. Tie-circuit breaker C is open. Keys A-1 are held in interlocks on both circuit breakers A and B. Tie-circuit breaker C cannot be closed unless either A or B is locked open.

To transfer load N to circuit breaker A, proceed as follows:

• Open circuit breaker B.

• Turn key A-1 in L-O-R interlock on circuit breaker B to lock open. Key A-1 is now free.

• Insert Key A-1 in L-O-R interlock on tie-circuit breaker C and turn to unlock. Key A-1 is now held.

• Close tie-circuit breaker C.

• Reverse sequence to restore service.

• Load M can be supplied through circuit breaker B in a similar manner.

Locking Position—Designations

Diagram Symbols