ISSUE DATE: 01/06/2012

PROGRAM INFORMATION BULLETIN NO. P12-01

FROM: LINDA F. ZEILER

 Director of Technical Support

 KEVIN G. STRICKLIN

 Administrator for 

Coal Mine Safety and Health 

 NEAL H. MERRIFIELD

 Administrator for 

Metal and Nonmetal Mine Safety and Health

SUBJECT: MSHA Intrinsic Safety Evaluation Number IA-13827-0 and Information 

Related to KH Controls Inc. Power Supply Models ISS1 and ISS3

Scope

MSHA personnel, operators of underground coal or metal and nonmetal mines, 

independent contractors, miners’ representatives, mine product manufacturers, repair 

shops, and other interested parties should have this information.

Purpose

The purpose of this Program Information Bulletin (PIB) is to alert the mining industry on 

the MSHA Approval status of KH Controls Inc. power supply Models ISS1 and ISS3. 

Model ISS1 power supplies providing current above 2.00 amperes that are currently in 

service will no longer have MSHA approval as of January 1, 2014.

Information

KH Controls Inc. was granted modification of MSHA Intrinsic Safety Evaluation Number 

IA-13827-0 to correct problems discovered during testing at MSHA’s Approval and 

Certification Center. The modification involves safety upgrades to the Model ISS1 

power supply with a current limit above 2.00 amperes. The modified power supply is 

identified as Model ISS3. 

The modification of Model ISS1 to ISS3 requires the following:
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• KH Controls is not permitted to provide a new Model ISS1 power supply 

with a current limit above 2.00 amperes. 

• KH Controls is required to convert each Model ISS1 power supply with a 

current limit above 2.00 amperes received for service to a Model ISS3. 

• MSHA will not issue a new approval incorporating the KH Controls Model 

ISS1 power supply with a current limit greater than 2.00 amperes. 

• MSHA will not issue modifications to existing MSHA approvals or other 

actions that incorporate a Model ISS1 power supply with a current limit 

greater than 2.00 amperes unless the application specifies a Model ISS3 

or other acceptable power supply as an alternate component. This 

restriction applies to applications requesting modification independent of 

the power supply. 

• All Model ISS1 power supplies with a current limit greater than 2.00 

amperes must be removed from service by January 1, 2014.

KH Controls can continue to provide a Model ISS1 power supply with a current limit at 

or below 2.00 amperes. 

Background 

The KH Controls Model ISS1 power supply was used in testing for approval of an 

intrinsically safe lighting system. The approval criteria require the system to pass tests 

with a safety factored power supply set at elevated voltage and current limits. Power 

supplies with current limits set at greater than 2.0 amperes failed tests involving a short 

circuit with a load of one ohm. KH Controls modified the power supply to prevent failure 

at these conditions. 

Model ISS1 power supplies currently installed may remain in service until retrofitted with 

a safety upgraded Model ISS3 power supply. This determination is based on the 

following factors:

• The installed Model ISS1 power supplies are set at nominal voltage and current 

limits 33% less than a safety factored unit. When tested under the same 

conditions, power supplies set at nominal limits have not failed any tests.

Additionally KH Controls has tested the Model ISS1 power supply at 

approximately 80% of safety factored levels without failure.

• The one ohm load short circuit system fault is not a typical system failure. If this 

unlikely fault occurs, the system will not function and will not operate until the 

fault is repaired.

The Model ISS1 power supply is used in many pieces of mining equipment such as 

longwall systems, continuous mining machines, and roof bolters. The two primary uses 

are as part of control systems provided by KH Controls or other manufacturers and 
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longwall lighting systems. The power supply is available with various current limits up to 

8.1 amperes. The model number of the KH Controls power supply specifies the voltage

and current limits of the unit. For example, Model number ISS3- 13.0 – 6.80 is limited to

13.0 volts and 6.80 amperes.

The ISS3 and ISS1 models rated at 2.00 amperes or less are identical in function. The 

ISS3 model incorporates additional protection at levels above 2.00 amperes. 

Recommended Actions

MSHA is recommending that users of the KH Controls Model ISS1 power supply take 

the following steps: 

1. Determine if your mining machines or equipment incorporate the Model ISS1 

power supply. Applications of the power supply will include but are not limited to 

the following: 

• Each system covered by or incorporating MSHA intrinsic safety evaluation 

number IA-13827-0 and installed before August 2010. 

• Lighting systems manufactured by KH Controls prior to August 2010. 

• Many other intrinsically safe components of MSHA approved machines and 

longwalls. 

2. Check the model number to determine the current limit of the Model ISS1 power 

supply. If the current limit is greater than 2.00 amperes, you should follow steps 

3 and 4. If the current limit is 2.00 amperes or less, no further action is required.

3. Contact KH Controls or the equipment manufacturer to determine whether the 

Model ISS3 power supply will provide for proper functioning of the system. KH 

Controls expects recently designed intrinsically safe control systems will operate 

satisfactorily with a Model ISS3 power supply, but ISS3 power supplies are 

more sensitive to some control circuit designs than the prior model. Older 

control systems may not function properly with a new model supply. In those 

cases, an MSHA approved alternate power supply or modification of the control 

system may be required. 

4. Contact the equipment manufacturer to verify that the MSHA approval 

incorporates the Model ISS3 power supply. If not, the manufacturer may revise 

the MSHA approval to include the Model ISS3 or mine operators may submit a 

Field Modification Request to the Approval and Certification Center to include the 

Model ISS3 power supply.

KH Controls will provide ISS3 power supplies in quantities controlled by the company’s 

manufacturing capability. KH Controls has taken steps to increase production, but 

shortages may occur due to high demand. Users should plan to update first their most 

critical applications or those for which no alternate power supply or alternate product is 

available. 
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Notice!

KH Controls Model ISS3 and Model ISS1 power supplies must be calibrated by an 

MSHA evaluated procedure to be considered intrinsically safe. Only KH Controls 

should repair or adjust Model ISS3 or ISS1 power supplies. Failure to follow the 

MSHA evaluated procedure will result in an unsafe condition.

Authority 

The Federal Mine Safety and Health Act of 1977; 30 CFR Parts 18, 57 and 75.

Internet Availability

This Program Information Bulletin may be viewed on the World Wide Web by accessing 

the MSHA home page (http:/www.msha.gov) then choosing “Compliance Info” and 

“Program Information Bulletins.” 

Issuing Office and Contact Persons

Technical Support, Approval and Certification Center

Bill Beasley, (304) 547-2050

E-mail: beasley.William@dol.gov 

Kevin Dolinar, (304) 547-2014

E-mail: dolinar.Kevin@dol.gov 

Coal Mine Safety and Health, Safety Division

John Arrington, (202) 693-9549

E-Mail: arrington.john@dol.gov 

Distribution

MSHA Program Policy Manual Holders

Underground Mine Operators

Special Interest Groups

Miners’ Representatives

Mine Product Manufacturers

Repair Shops