Plumbing - Electrical Safety Part 2

A proper grounding path must do two things:

1. Prevent electricity from flowing between the enclosure of an electrical circuit or system.

2. Provide a path for fault current to flow back to its source that is less resistant than other paths.

1. The path to ground must be permanent and continuous.

2. The path must have ample capacity to cause the operation of the over current device.

3. The path must have low resistance.

4. All circuit parts must be bonded together.

Circuit interruption.

Circuit interrupters break a electrical loop or a circuit, so the electricity does not flow.

1. Circuit breakers or fuses for wiring and equipment protection.

2. Ground fault protection for shock protection.

Circuit breakers or fuses connect in the path of the hot wire. When hot wire flow is over the rating of the circuit breaker or fuse , it opens. This interrupt the circuit before the wire or equipment is damaged.

1. Grounding problem. Overload.

Only qualified electricians.

A circuit breaker's job is to protect equipment from heat build-up caused by overload and faults.
For protection from electrocution, you need Ground Fault Protection.

If a short circuit or ground fault happens, electricity should return along the ground path to the source. At the source, this higher rate of current flow opens the circuit breaker or fuse.

1. GGCI or ground fault circuit interrupter.

| 2. Assured equipment grounding program.

GFCI stands for ground fault circuit interrupter. They are installed in the path between the hot and neutral wires of a circuit. The GFCI is not an overcurrent device. A GFCI only cares about the difference in current between the hot and neutral conductors. So a GFCI cannot replace circuit breakers for overcurrent protection. GFCIs are used in combination with - not instead of - fuses or circuit breakers. While circuit breakers and fuses protect wiring and equipment, GFCIs protect you from shock.

By detecting differences in current between the hot and neutral wires. If the difference exceeds 5 milliamps, or 5/1,000th of an amp (.005 amp), the GFCI opens the circuit. This difference in current flow is typically well below the threshold of a circuit breaker or fuse. As a result, ground faults-which would never open a circuit breaker will open the GFCI.
For example, if a ground fault directs 6 mA (.006 amp) of current through you, it reduces the current returning to the source on the neutral by the same amount. Because the difference is less than 15 amps, the circuit breaker will not open. But the GFCI will trip because the difference is greater than 5 mA. You are saved from a shock.

A GFCI opens at 5!milliamps. You might experience a painful shock, if you have dry skin. But you can let go of the wire. So even if your skin is wet or you are standing on a wet surface, the GFCI will open before you experience harmful effects. This flow is well below the threshold for lung paralysis, heart failure, heart paralysis, or burns.
By contrast, a 15 amp fuse or circuit breaker does not open until 15,000 milliamps of power flow through it. This means enough current can flow through you so that you can't let go of the power.

On all 120-volt single-phase 15 and 20-amp receptacle outlets used by employees on the construction site - accept outlets which are part of the permanent wiring of the building or structure.
GFCIs are installed almost anywhere anywhere in the electrical circuit:

1. At the service entrance panel.

2. At the branch circuit panel.

3. At the outlet level.

4. On every extension cord used for power delivery.

An assured equipment grounding program.

1. Written program.

2. Competent person(s).

3. Inspection.

4. Testing.

5. Equipment availability.

6. Record-keeping.

Available for inspection and copying by OSHA or any affected employee.

To do daily inspection and periodic testing.

Each day before work, inspect for defects:

1. All cord sets.

2. Attachment caps.

3. Plugs and receptacles.

4. Any equipment connected by cord and plug even if fixed and not exposed.

Continuing testing on all equipment ground conductors before first use, following repairs, and at least every three months.

All equipment is inspected and tested before use.

The employer keeps a record of all test and inspections. The NECA color coding scheme is one way to keep track of inspections.

Subpart K also includes detailed wiring designs, methods, and installation practices.

For portable power tools and appliances, OSHA permits only 3-wire extension cord sets designed for hard or extra hard usage.

1. Wire size.

2. Number of conductors.

3. Cord type.

4. AMP rating.

1. Hard use: S, ST, SO, STO. Junior hard use: SJ, SJO, SJT, SJTO.

1. Do not pass through holes in walls, floors, or ceilings or through windows or doors.

2. Do not run behind building walls, ceilings, or floors.

3. Do mot attach to building surface (including hanging them from nails, staples or bare wire).

4. Do not use as a substitute for the fixed wiring of a structure.

When cords are plugged in, a lot of pressure is applied th the prongs or to the connectors. This can loosen the prongs or the connection of the conductors to the prongs. The easiest way to prevent this problem is by using strain relief on the cords.

Pull on the plug, not the cord. This prevents stressing the terminals where the conductors connect to the plug.

Removing the ground connection.

Clean, inspect, coil, and store extension cords. Wipe with a dry reg.

Using a figure 8, regular coil, reverse coil, or winding armature.

Away from oil, dirt, solvents, acids, caustics, or moisture. Keep away from sharp tools.

Visually at least once each day, before use:
Check the insulation for cracks, cuts, or breaks. Look for insulation damage and for bent or weakened conductors. Are connections at the plug ends frayed?
Check the plug attachment. Are male plug ends damaged or bent?
Extension cords should have ground continuity testing at least every 90 days.

With a GFCI extension cord, when defects in isolation or grounding happen, the GFCI can shut down the current in the extension cord before a shock. A GFCI extension cord reduces the possibility of false shutdowns caused by normal current loss in a circuit - as often happens when GFCIs are located father away in outlets or in circuit boxes.