United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 84-78: Underrated Terminal Blocks That May Adversely Affect Operation of Essential Electrical Equipment

                                                           SSINS No.:  6835 
                                                           IN 84-78        

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                           WASHINGTON, D.C. 20555 

                              November 2, 1984 

Information Notice No. 84-78:   UNDERRATED TERMINAL BLOCKS THAT MAY 
                                   ADVERSELY AFFECT OPERATION OF ESSENTIAL 
                                   ELECTRICAL EQUIPMENT 

Addressees: 

All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP). 

Purpose: 

This information notice is to alert recipients of a potentially significant 
generic problem involving the use of terminal blocks that have improper 
voltage ratings. Using underrated terminal blocks may result in an 
electrical fault that could lead to loss of essential electrical equipment. 
It is expected that recipients will review the information for applicability 
to their facilities and consider actions, if appropriate, to preclude a 
similar problem occurring at their facilities. However, suggestions 
contained in this information notice do not constitute NRC requirements; 
therefore, no specific action or written response is required. 

Background: 

Underwriters Laboratories (UL) Standard 1059 (October 30, 1975) defines 
stringent criteria to determine voltage ratings for terminal blocks. 
Terminal blocks for general industrial use at 150, 300, and 600 volts must 
be tested to the requirements of UL Standard 1059 to be UL listed. The 
acceptance values of these tests are described in UL Standard 1059. Note 
that some models of terminal blocks have undergone testing more stringent 
than UL Standard 1059 to meet use-specific qualification requirements. 

Discussion: 

On May 4, 1984, under the provisions of 10 CFR 50.55(e), Detroit Edison 
reported a potential deficiency concerning underrated motor terminal blocks 
manufactured by Vernitron Incorporated (Beau Products Division) and 
installed in some Limitorque valve operators at Fermi 




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                                                         IN 84-78          
                                                         November 2, 1984  
                                                         Page 2 of 2       

Unit 2. The specific installation identified involved the use of Beau 
Products 76000 series terminal blocks in type SMC-04 Limitorque valve 
operators. The terminal blocks were being used in 480-V ac motor 
terminations; but, according to the terminal block manufacturer, the 
terminal blocks have a UL rating of 150 volts for general industrial use. 

In the absence of any other qualification testing of the suspect terminal 
blocks, there is a possibility of electrical shorting that could result in 
the failure of the motor to operate when required. Failure of the motor to 
operate could compromise the function of the safety system of which the 
valve is an integral part. 

Limitorque Corporation has stated that the Beau Products 76000 series 
terminal blocks, have been used only in the SMC-04 model valve operator. In 
addition, Limitorque has stated that there have been no failures reported as
a result of the Beau Products terminal blocks in question. The licensee at 
Fermi Unit 2 is replacing the affected Beau Products terminal blocks. 

It is suggested that the facility review of this information include other 
types of terminal blocks and equipment for similar applications. No specific
action or written response is required by this information notice. If you 
have any questions about this matter, please contact the Regional 
Administrator of the appropriate NRC regional office or this office. 


                                   Edward L. Jordan, Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  J. C. Stewart, IE 
                    (301) 492-4513 

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