Transcript Slide 1

ERICSON UNIVERSITY LIVE TRAINING
SESSION: 4-1 & 4-2
GFCI
April 2010
GFCI
Ground Fault Circuit Interrupter
Preventing Electrical Equipment Hazards
I.
Insulation
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Non-conductive material around conductors – wire insulation (THHN, SOW)
Insulation materials in tools and motors (single and double)
Air gap is normally the second insulation in double insulated tools
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Breakdown of insulation results in contact with live conductors
Insulation materials in tools become saturated with carbon brush dust – arc trail
“…Insulation may be damaged by hard usage on the job or simply by aging.
If this damage causes the conductors to become exposed, the hazards of
shocks, burns, and fire will exist. Double insulation may be used as
additional protection on the live parts of a tool, but double insulation does
not provide protection against defective cords and plugs or against heavy
moisture conditions.” - OSHA
Preventing Electrical Equipment Hazards
II. Grounding
“…Consider, for example, the metal housing or enclosure around a motor or the metal box
in which electrical switches, circuit breakers, and controls are placed. Such enclosures
protect the equipment from dirt and moisture and prevent accidental contact with exposed
wiring. However, there is a hazard associated with housings and enclosures. A malfunction
within the equipment—such as deteriorated insulation—may create an electrical shock
hazard.
Many metal enclosures are connected to a ground to eliminate the hazard. If a "hot" wire
contacts a grounded enclosure, a ground fault results which normally will trip a circuit
breaker or blow a fuse. Metal enclosures and containers are usually grounded by
connecting them with a wire going to ground. This wire is called an equipment grounding
conductor. Most portable electric tools and appliances are grounded by this means. There
is one disadvantage to grounding: a break in the grounding system may occur
without the user's knowledge.” - OSHA
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Grounding conductors can be cut, panel ground bad, ground pins pulled out, etc
Plugs replaced on portable tools can be wired incorrectly
Metal gang (job) boxes used as portable power are extremely dangerous!
Anatomy of an Electric Shock
Double insulated tool issues:
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Carbon dust trails
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Moisture trails
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Cracked housings
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Miswired plugs
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Drill chucks are connected
to the armature – metal
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Cord fraying
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Strain relief damage
GFCI shuts off power in
25 msec to prevent injury
Faster than the human can
sense an electric shock!
Metal Gang Box Death Trap
Line of Protection
NOT Protected
Protected
Code Violation
Problem # 4
• Metal gang
Ground at panel
Neutral bond bad
• Use
GFCI
boxes are for PERMANENT INSTALLATIONS
( non-moving)
Problem # 3
damage
rubberizedCord
boxes
that
are UL tested for Portable Power Tap use
• Use GFCI inline near the plug or at source
Problem # 1
Loss of Ground
(ungrounded box)
Problem # 2
Hot wire touching box
Anatomy of a GFCI
Line
Load
Relay
Sense ring
.5 amp
H
N
Rules of GFCI:
- 6 mA max
- 25 mSec release
- break both sides of the line
.5 amp

.4 amp

Electronics
Gnd
Target = > 6 mA
OSHA REQUIREMENTS
• OSHA ( 29 CFR) 1926.404(b)(1)(i)
General. The employer shall use either ground fault circuit interrupters as specified in paragraph (b)(1)(ii) of
this section or an assured equipment grounding conductor program as specified in paragraph (b)(1)(iii) of
this section to protect employees on construction sites. These requirements are in addition to any other
requirements for equipment grounding conductors.
Ground-fault circuit interrupters. All 120-volt, single-phase 15- and 20-ampere receptacle outlets on
construction sites, which are not a part of the permanent wiring of the building or structure and which are
in use by employees, shall have approved ground-fault circuit interrupters for personnel protection.
Receptacles on a two-wire, single-phase portable or vehicle-mounted generator rated not more than 5kW,
where the circuit conductors of the generator are insulated from the generator frame and all other
grounded surfaces, need not be protected with ground-fault circuit interrupters.
Assured Equipment Grounding Continuity Program – cover next month E.U. Session
Interpretation Letter from OSHA (dated May 2002) states the following Q & A:
Question (1): Does the requirement in 29 CFR 1926.404(b)(1)(i) to have either a ground-fault circuit
interrupter protection (GFCI) or an assured equipment grounding conductor program (AEGCP) apply
only to 120 V circuits, or does it also apply to a 240 V circuit?
Answer: Yes. §1926.404(b)(1)(i) provides: (b) Branch circuits -- (1) Ground-fault protection - (i)
General. The employer shall use either ground fault circuit interrupters as specified in paragraph
(b)(1)(ii) of this section or an assured equipment grounding conductor program as specified in
paragraph (b)(1)(iii) of this section to protect employees on construction sites. These requirements are
in addition to any other requirements for equipment grounding conductors. Under this provision,
employers must provide protection against ground-fault by using either a GFCI or AEGCP. The
provision, by its terms, is not limited to 120 V circuits. Employers are required to protect employees
under this provision with respect to 240 V circuits as well.
Question (2): What are the requirements when a temporary service panel has both a 120 V and a 240
V circuit? Would protecting the 120 V circuit with a GFCI comply with the standard, or does the 240 V
circuit also have to be protected by a GFCI or an assured equipment grounding conductor program?
Answer: The 240 V circuit must be protected as well. Installing a GFCI designed for a 120 V circuit in a
panel that also has a 240 V circuit will not provide ground-fault protection to the 240 V circuit.
While technically the option of using GFCI under (b)(1)(ii) is available only for 120 V circuits, that
limitation was put in the standard only because GFCIs for 240 V were generally unavailable when the
standard was promulgated. Employers may choose to use GFCIs designed for 240 V to protect 240 V
circuits; the technical violation of (b)(1)(ii) would be considered de minimis. De minimis violations are
those which have no direct or immediate relationship to safety or health. Citations are not issued for de
minimis violations.
GFCIs and NEC 2008
• Article 590.6 calls for basically all
receptacles that are in use to be GFCI
protected. Again OSHA considers this
violation minor and citations are not being
given at this time.
GFCIs and Lighting
• OSHA does not call for lighting circuits to
be GFCI protected.
• NEC 525.23(c) specifically states that
egress lighting shall not be GFCI
protected.
Auto vs Manual
• Auto = Auto powerup start
• Manual = Manual powerup start
– RESET button serves as initial “start” button
• ALL GFCIs must be physically RESET after a fault trip
• Automatically Reseting GFCIs do not exist
GFCI Offerings
Industrial Grade
Commercial Grade
90 Degree Plug
Inline Style
• Add-a-cord
• Some corded models
Panel Mount
Custom Industrial Grade
Protector Series Launch
Distribute Point to Point Only
Cordsets
Distribute / Split Phases / GFCI Protection
Oscars Gen Cords
Big-E Jr
Big-E
Distribute Multiple Taps
Distribute / High Power ( 480 or 600 V )
“Y” “W”
480V Big-E
Power Stringers
6000 7000 8000 Series
Transform / Distribute / GFCI Protect
Distribute with GFCI Protection
e-Cart Jr.
GFCI
1060/1070
e-Cart
END OF SESSION