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SEMI S22-1103a © SEMI 2003, 2005 14 NOTE 24: A mechanical interlock is preferable to an e lectrical interlock. 9.4 Cord and Plug Connections used as Facility Connection 9.4.1 When a cord and plug connect ion is intended …
SEMI S22-1103a © SEMI 2003, 2005 13
b) the connections should be located within the main electrical enclosure located near the top, with adequate
bending space provided for supply conductor installation and no equipment located above the supply
terminals. Parts on the supply side of the main disconnecting means in the equipment which remain energized
when the main disconnecting means is switched off should be guarded (finger safe) to prevent accidental
contact by service personnel; or
c) the connections should be located within the main electrical enclosure, where other equipment is mounted
above the supply terminals. Parts on the supply side of the main disconnecting means in the equipment which
remain energized when the main disconnecting means is switched off should be guarded to prevent accidental
contact by service personnel or by a tool that may be dropped from above. The opening should be such that a
1-mm (0.04 inch) rod cannot come into contact with the energized parts.
EXCEPTION: Machines with a power consumption totaling 1492 Watts (2 HP) or less may be connected to a
remotely mounted main disconnecting means through a flexible cord, cable, or conduit provided that the main
disconnecting means is in sight from, readily accessible to, and no more than 6 m (20 feet) from the machine
operator work station.
9.3.4 Wire bending space should be provided for the facility supply conductors at the main disconnecting means as
specified by Appendix 1, Tables A1-1 through A1-5.
EXCEPTION: Equipment that meets the wire bending space requirements of NFPA 70 will also meet these criteria.
9.3.5 When placed in the off position the main disconnecting means should satisfy the following criteria:
a) All unearthed conductors of the supply circuit should be disconnected simultaneously.
b) Earthed conductors (neutral or grounded) should not be disconnected.
EXCEPTION: The earthed conductor (neutral) may be disconnected provided that it is disconnected simultaneously
with the unearthed conductors.
NOTE 23: Some jurisdictions require disconnection of the earthed conductor (neutral).
9.3.6 The main disconnecting means should have a minimum of two marked positions, “Off” (isolated) and “On”.
These positions should be clearly marked with IEC 60417 symbol 5008 for “Off” and IEC 60417 symbol 5007 for
“On”.
9.3.7 The actuator of the equipment’s main disconnecting means should be readily accessible and a maximum of 2
meters above the standing surface, measured from the center of the grip.
9.3.8 Each facility main disconnecting means for the incoming electrical supply should be mechanically or
electrically interlocked, or both, with the electrical disconnect enclosure door.
EXCEPTION 1: A main disconnecting means used only for maintenance of lighting circuits within electrical
enclosures should not be interlocked with the electrical enclosure door. A hazard warning label should be provided
when exposed parts may be energized within the main disconnect enclosure when the enclosure door is open.
EXCEPTION 2: Where an attachment plug is used as the main disconnecting means.
EXCEPTION 3: Where a remotely mounted main disconnecting means is provided, a tool is required to open the
equipment enclosure door, and a hazard warning label is attached to the electrical enclosure warning of hazardous
voltage inside and advising isolation of the power before opening.
EXCEPTION 4: The considerations stated in ¶9.3.8 do not apply to equipment rated less than 5KVA that has the
other protections against electric shock stipulated in this document.
9.3.9 The main disconnecting means (lock-out) handle should not disengage from the main disconnecting means
when the enclosure door is opened.
9.3.10 Interlocking should be provided between the main disconnecting means and its associated door to prevent
both of the following:
a) closing of the main disconnecting means while the enclosure door is open, unless the interlock
disconnecting power is overridden by a deliberate action (see §13), and
b) closing of the main disconnecting means until the door hardware is fully closed.
SEMI S22-1103a © SEMI 2003, 2005 14
NOTE 24: A mechanical interlock is preferable to an electrical interlock.
9.4 Cord and Plug Connections used as Facility Connection
9.4.1 When a cord and plug connection is intended to be used as a main disconnecting means, it should either be
capable of being under the exclusive supervision of the person carrying out the work, or be provided with a means
for lockout (see discussion of conductors and cables in §16).
9.4.2 If a supply cord is provided with the system, the cord, as well as the installation instructions, should comply
with applicable local codes where it will be installed, or the equipment should have provisions for hard wiring using
a raceway.
9.4.3 If there are provisions for hard wiring, a cord and plug should not be used as a main disconnecting means.
9.4.4 If the cord and plug is used for the main disconnecting means the equipment should also have an on-off
control.
NOTE 25: Uses preferred for cord and plug connection to the facility include:
a) equipment with an attachment plug and powered from a receptacle outlet to connect movable equipment to facilitate
frequent interchange, and
b) the fastening means and mechanical connections of the equipment are designed to permit removal for maintenance or
service.
NOTE 26: Materials are restricted by ¶16.3.1.
10 Protection Against Electric Shock
10.1 General The electrical equipment should provide protection to persons against electric shock under normal
operating conditions and under any reasonably foreseeable single fault condition.
10.2 Protection Against Electric Shock During Normal Operation
10.2.1 Where operator access to a hazardous voltage is controlled through the use of a grounded conductive or non-
conductive enclosure, that enclosure should either:
1) require a tool to open and be labeled with the hazard against which it protects personnel, or
2) be interlocked.
Reference Jointed Finger Probe Access Test. Reference IEC61010-1 Annex B for the test finger.
NOTE 27: IEC 60529 “Degrees of Protection Provided by Enclosures” may be used as a reference.
10.2.2 Spacing between uninsulated energized parts and conductive enclosures should be maintained in compliance
with Appendix 1 Tables A1-12 and A1-13 or determined to be adequate by dielectric testing in accordance with §22.
10.2.3 Energized parts protected by insulation should be completely covered with insulation that can be removed
only by destruction. Such insulation should be capable of withstanding the mechanical, chemical, electrical, and
thermal stresses to which it may be subjected under normal operation.
10.2.4 Protection Against Electric Shock Hazards Resulting from Fault Conditions — Use of measures to prevent
the occurrence of a hazardous touch voltage may include one or more of the following:
a) Double or reinforced insulation may be used to prevent a hazardous touch voltage through contact with
exposed conductive parts that results from the failure of basic insulation of the energized parts of that circuit,
b) Electrical separation (clearance and creepage) may be used to prevent a hazardous touch voltage through
contact with exposed conductive parts that results from the failure of basic insulation of the energized parts of
that circuit,
c) Automatic disconnection of the supply of any circuit affected by the occurrence of an insulation failure that
results in a ground fault may be used to prevent contact with a hazardous voltage.
NOTE 28: See definition of GFCI.
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10.3 Maintenance and Service Personnel Potential Exposure to Hazards
10.3.1 Energized Electrical Work The equipment should be designed to minimize the need to calibrate, modify,
repair, test, adjust, or maintain equipment while it is energized, and to minimize work that should be performed on
components near exposed hazardous energized circuits. The equipment design should move as many tasks as
practical from Type 4 to Types 1, 2, or 3. Routine Type 4 tasks, excluding troubleshooting, should have specific
written instructions in the maintenance manuals. General safety procedures (e.g., appropriate PPE and barriers) for
troubleshooting, including Type 4 work, should be provided in the maintenance manual.
10.3.2 Protection of Service Personnel Service personnel should not be exposed to inadvertent contact with
hazardous potentials or hazardous energy levels. This may be accomplished by using touch safe terminals or
providing additional barriers over exposed terminals.
10.3.3 Manual Adjustment Equipment requiring manual adjustment should be so designed that adjustment does
not expose personnel to electrical or mechanical hazards.
10.3.4 Access Maintenance and service access should be provided for maintaining and servicing equipment.
10.3.5 Internal Barriers Non-conductive or earthed (grounded) conductive physical barriers or equivalent means
should be provided:
a) where it is necessary to reach over, under or around, or in close proximity to hazards,
b) where dropped objects could cause short circuits or arcing,
c) where failure of liquid fittings from any part of the equipment could result in the introduction of liquids into
electrical parts,
d) where maintenance or service tasks are likely to allow inadvertent contact with un-insulated energized parts
containing either: potentials greater than 30 Volts rms, 42.4 Volts peak, or 60 Volts DC; or power greater than
240 volt-amps in dry locations.
NOTE 29: Removable nonconductive and noncombustible covers are preferred.
10.3.6 Test Points When test points are provided they should satisfy the following:
a) located to provide unobstructed access,
b) marked or identified in the documentation,
c) protected against incidental contact, and
d) provide adequate access for a test probe.
10.3.7 Isolated Power Systems This section applies only to 50-60 Hz AC applications operating at a hazardous
voltage.
NOTE 30: The common purpose for using isolated power systems is to reduce sources of electronic noise by not deliberately
referencing the output circuit conductors to earth (ground).
NOTE 31: Auto transformers do not provide electrical isolation.
10.3.7.1 All accessible conductive components that are likely to become energized under fault conditions should be
effectively bonded to the protective earthing conductor.
EXCEPTION: If the process technology requires conductive parts that are not grounded when they are inaccessible,
but grounded when they are accessible, then the intent of ¶10.3.7.2 is satisfied by ensuring such conductive parts are
grounded when they become accessible.
10.3.7.2 Isolated circuits should meet the following:
a) the transformer or power supply, and any components (devices) connected to their output, should be clearly
labeled adjacent to the isolated circuit(s) or on the enclosure to warn operators and service personnel of the
unearthed condition, and