electrical safety for residential construction susan b. harwood grant training program

Developed under an OSHA Susan B. Harwood Grant, #46F4-HT01, by the Associated Builders and Contractors-Central Texas Chapter

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Electrical Safetyfor Residential Construction

Susan B. Harwood Grant Training Program


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Disclaimer/Usage Notes• Photos shown in this presentation may depict situations that are not

in compliance with applicable OSHA requirements. • It is not the intent of the content developers to provide compliance-

based training in this presentation, the intent is more to address hazard awareness in the residential construction industry, and to recognize the overlapping hazards present in many construction workplaces.

• It should NOT be assumed that the suggestions, comments, or recommendations contained herein constitute a thorough review of the applicable standards, nor should discussion of “issues” or “concerns” be construed as a prioritization of hazards or possible controls. Where opinions (“best practices”) have been expressed, it is important to remember that safety issues in general and construction jobsites specifically will require a great deal of site- or hazard-specificity – a “one size fits all” approach is not recommended, nor will it likely be very effective.


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Disclaimer/Usage Notes• No representation is made as to the thoroughness of the presentation,

nor to the exact methods of remediation to be taken. It is understood that site conditions vary constantly, and that the developers of this content cannot be held responsible for safety problems they did not address or could not anticipate, nor those which have been discussed herein or during physical presentation. It is the responsibility of the employer, its subcontractors, and its employees to comply with all pertinent rules and regulations in the jurisdiction in which they work. Copies of all OSHA regulations are available from your local OSHA office, and many pertinent regulations and supporting documents have been provided with this presentation in electronic or printed format. This presentation is intended to discuss Federal Regulations only - your individual State requirements may be more stringent.

• It is assumed that individuals using this presentation or content to augment their training programs will be “qualified” to do so, and that said presenters will be otherwise prepared to answer questions, solve problems, and discuss issues with their audiences.


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Disclaimer/Usage Notes• Areas of particular concern (or especially suited to discussion) have

additionally been marked with a ? symbol throughout the program…as a presenter, you should be prepared to discuss all of the potential issues/concerns, or problems inherent in those photos particularly.


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It’s Just Electricity

• Most people assume that electrical power is relatively harmless– Yet many people are killed each year – Most deaths involve 110 volt power


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Temporary Power• Electrical shocks

due to temporary power and cords can be controlled by– Ground Fault

Circuit Interrupters (GFCI)

– Covers on electrical equipment


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Temporary Power• Electrical shocks

due to temporary power and cords can be controlled by– Ground Fault

Circuit Interrupters (GFCI)

– Covers on electrical equipment


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GFCI Systems

• GFCI’s don’t eliminate electrical shock, – They reduce the magnitude and duration

• At 5 milliamps (mA) or less (Magnitude)• In 1/40th of 1 second (Duration)

– They terminate the flow of electricity

• But what is a milliamp?


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Amps and Milliamps

• One milliamp is one amp divided by 10001A/1000=1mA

• One mA is an electrical tingle– Similar to touching your tongue to a weak

9 volt battery– Through our skin, it is barely perceptible


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GFCI Systems

• At 10 mA nerve impulses are overridden by electrical impulses– This causes us to

“grasp and not let go”

– Even when we want to let go of a wire


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GFCI Systems

• At 70 to 120 mA– The heart goes into ventricular fibrillation

• The heart is not able to pump blood • Must be restarted by an Automatic External

Defibrillator (AED)


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Dry vs Wet and Ohms Law• If our body is dry

the electrical resistance is approximately 100,000 Ohms

Using Ohms Law120volts/100,000

Ohms equals 1.2 mA and is just a tingle


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Dry vs Wet and Ohms Law• If our body is wet

the electrical resistance is approximately 1000 Ohms

Under Ohms Law120/1000 Ohms

equals 120 mA and is enough to cause ventricular fibrillation


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GFCI Systems

• Most circuit breakers are 15 to 20 amps– This is 1500 to 2000 times the energy needed

to cause ventricular fibrillation • GFCI systems trip at 5 mA to avoid

ventricular fibrillation– This gives us a safety factor of 2

• GFCI systems will not prevent electrocution in a direct short


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• GFCI’s measure amperage on both the HOT and NEUTRAL of an electrical circuit

• Since AC voltage is balanced, both hot and neutral amperage should be the same

• If the imbalance is 5 mA or more– The GFCI trips, protecting the worker from

shock

GFCI Systems


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GFCI Systems

• When GFCI’s trip repeatedly, the cause is often equipment related

• Damaged extension cords often have internal damage, that allow ground faults


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GFCI Systems

• Replacing the GFCI will not fix the problem– Replace the

damaged tool or cord


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GFCI Systems

• GFCI systems must be tested DAILY before use– Use the test button

on the device– Use a tool to

assure the power stops

• GFCI’s can be wired incorrectly


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GFCI Systems

• Have a qualified electrician check GFCI systems periodically


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Overhead Power

• Regulations require we keep 10 feet or more from overhead power lines

• This includes;– Backhoes– Forklifts– Cranes– Pier drilling rigs– Concrete pump trucks


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Overhead Power

• Regulations require grounding and barriers or blankets to cut off power


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Questions?• Answers to additional questions can be

found in the following source materials– 29 CFR 1926 Construction Regulations– NEC (National Electric Code)

electrical safety for residential construction susan b. harwood grant training program

Documents

osha susan

osha regulations

associated builders

applicable osha requirements

physical presentation

local osha office

pertinent regulations

federal regulations