UPS, GFCI, Wiring Methods, SLD, Electrical Class., Lighting Panels, Disconnects

Explain how single line diagrams are connected to the site electrical safety program

1. With up to date, correct, lines we can lock out the right equipment

2. Provide the proper connecting info for upstream power distribution systems

3. Determine the capacity and flash hazard of downstream equipment. Flash Hazard determines level of PPE

4. Document the bus bracing for the MCC

5. Let us know if equipment is overdutied or not

6. Accuracy of these lines are audited for the electrical KEA

Explain the differences between class 1 and class 2 hazardous locations

Class 1 - Ignitable concentrations of flammable gases, vapors or liquids

Class 2 - Ignitable concentrations of Combustible Dusts

Class 1 Division 1 vs Class 1 Division 2

Div 1 - Ignitable concentrations of flammable gases, vapors, or liquids CAN exist all of the time or some of the time under normal operations

Div 2 - Ignitable concentrations of flammable gases, vapors, or liquids NOT likely to exist under normal operation

Identify Hazardous Locations in Department

HDL Process Tank Farm

LFE Tank Farm

Perfume Storage

Determine Rating of a device by observing the device nameplate

Devices should have labeling designating UL Hazard Classification

Explain what each symbol is in a Single Line for an MCC

Covered “Fed From”

Incoming Breaker (Frame and Trip)

Horizontal Bus Ampacity

Combination Starter Symbol (With frame, fuse size, starter size)

Extents of MCC

External Wiring

Wire Labeling

Field Disconnects

Motor HP

Transformer Size and Config

Describe the different voltages that you would encounter in these panels

480/277v AC, depending on the 480v transformer secondary feeding the panel

Locate a lighting panel, point out the components

Main disconnect is generally at the top or bottom of panel, larger than the other breakers in there

Describe which components remain energized in a panel after a breaker has been de - energized

All breakers besides the one that is de energized, incoming cables, Bus bar, All wiring not connected to de-energized breaker

Describe the different levels of PPE required to work on energized Panels

Class 0-4, refer to PCP 650 PPE Matrix

Explain the operation of the electrical safety door interlock with NEMA switch

Door switch prevents door from being accidently being opened and helps prevent exposing energized components. Use a flat head screwdriver to override the safety for trouble shooting

Explain why operating switches or indicating lamps should not be installed on a local disconnect

The holes in the panel degrade the structural integrity of the disconnect

White, Grey Wire

Grounded Conductor (Neutral)

Black Wire

Line or Load Wire AC or DC over 24V

Blue Wire

24V Control Power

Green/Bare Wire

Grounding Conductor

Yellow Wire

Fed From outside source

Red Wire

120v AC control power

Brown Orange Yellow Wires

480v AC, A,B,C phase

Red, Black, Blue

208v AC, A,B,C 3 Phase

Identify the instances under which temporary installation of wire is permitted

Only there for less than 90 days, and approved by the Electrical System Owner or ESO, Found in NEC 590

What does UPS stand for?

Uninterruptible Power Supply (Battery Back-Up)

Describe which loads are currently connected to your UPS

• Rack Module Controls - DC modules to prevent a UL in motion from coming to an immediate stop (brake coil collapses) and so ACTIV will always know where inventory is.

  Data Center servers

  HDL Process TDC & PLC systems.

What is a Manual Transfer Switch?

Used to transfer power supply from an MCC to generator. Switch from "Normal" (MCC) to "Off" to "Aux" (generator). To use stop at off when switching. Do NOT switch under load. Not to be used as a disconnect. Arc flash could possibly energize other side of switch.

What is an Automatic Transfer Switch?

Automatically transfers power supply from an MCC to a generator. Does the transfer under load. Used in critical systems, such as distribution center or hospitals.

Explain how to correctly lock-out / tag out when an ATS is involved.

Lock out all possible sources of power, upstream and downstream. Remember that arc flash could energize either side.

Describe how equipment (MCC's / PDP's etc.) should be labeled if a generator is/can be connected

Caution: fed from two sources.

Explain the function of a Ground Fault Circuit Interrupter.

To detect current imbalance between hot & neutral and open the circuit.

Identify the current trip threshold for a GFCI designed for personnel protection.

5 mA

Describe the current trip threshold of a GFCI breaker for equipment protection. Explain what would happen if this device were installed to provide personnel protection.

30 mA

People could receive a potentially fatal shock without the GFCI tripping

Using a hand sketch of a GFCI circuit diagram, explain the theory of operation for a GFCI breaker or receptacle.

Hand sketch of two conductors with current transformer around BOTH phases.

If the same amount of current flowing to the load on the hot wire does NOT come back on the neutral, the GFCI will trip.

Explain how the test circuit in a GFCI works. Determine if a GFCI can be tested de-energized.

Test circuit drains a small amount of current (> 5 mA) from the circuit and trips the GFCI.

GFCI cannot be tested de-energized.

Identify the physical locations requiring a GFCI according to the National Electrical Code (include residential, commercial, and industrial settings).

Garages, Outdoors, Kitchens, Bathrooms, Hot Tubs, Pools, (anywhere within 10 ft of water source). Commercial and Industrial areas where portable cord-connected devices are used (except for office areas)

Identify the tasks requiring a GFCI according to NFPA 70E.

Testing of GFCI’s required by 70E.

Installation Requirements set by NEC.

Required In areas that have high risk of water, moisture, or earth ground contact

Explain why a GFCI will trip on a ground fault but not a short circuit.

Short circuit has all the current going to the load on the hot wire and returning from the load on the neutral – so NO current imbalance.

A ground fault lets current out of the normal circuit path – so Current Imbalance trips the unit.

Determine if any of your department substation breakers have Ground Fault protection. If so, explain the sensing mechanism for the ground fault and determine if this is for personnel or equipment protection.

No

Explain why a GFCI receptacle will function properly to provide personnel protection, even if a dedicated ground conductor is wired to the receptacle.

The ground wire is not in the sensing circuit. [Sensing circuit only uses the Hot & Neutral.] Doesn’t matter if ground is there or not for the GFCI to work.

Explain the testing requirements for a GFCI and why testing is important.

Test every month.

Legally required.

Explain what a Arc Fault Circuit Interrupter is and how it works.

Arc Fault interrupter senses the varying current spikes and trips based on a threshold set by the manufacturer.