INSTALLATION, OPERATIONS AND MAINTENANCE MANUAL 11
Torque specifications
Switchboards are furnished with medium carbon
steel hardware with the tensile strengths listed
in Table 1. Similar hardware must be used for any
additional bolting. For both copper and aluminum
connections, use a torque wrench when tightening
to the nominal values given.
Use flat and lock washers for all connections.
Do not place washers under the heads of
carriage bolts.
For equipment wiring terminal torque values see
Table 3. For device terminal torque values reference
the appropriate device installation guide.
Electrical clearances
Maintain the minimum clearances listed in Table
2 except at terminals of circuit breakers and
switches. A through-air spacing of not less than ½
inch is acceptable at a circuit breaker or a switch,
other than a snap switch, and between grounded
dead metal and the insulated neutral of a 277/480
VAC three-phase, four-wire panelboard or
switchboard. Where neutral-to-phase is involved,
spacing may be based on the normal voltage
between them.
A through air spacing of not less than 12.5 mm (½ inch) may be used:
1. At a circuit breaker or a switch, other than a snap switch;
2. Between uninsulated live parts of a meter mounting base and grounded metal; and
3. Between grounded metal and the neutral of a 3-phase, 4-wire switchboard.
Note 1 – Exceptions to these minimum spacings covered in UL891 8.1.16.2-8.1.16.6.
Note 2 – The SI units are minimum values and are not a direct conversion from the coresponding values in inches.
Reference: NMX-J-118/2-ANCE-2019 CSA C22.2 No. 244:19, UL891
Bolt size [in] Tensile strength [psi] Torque [lb-ft]
Belleville Washer
Hardware type
Hardware
size
Cable size
[AWG/MCM]
Torque
[lb-in]
larger
larger
Hex,
Hex with slot
larger
Internal hex size
-
Voltage involved
Minimum spacing through air
and over surface between live
parts and grounded metal
Greater
than Maximum
Through air Over surface
mm (in) mm (in)
(½) (¾) ½
(¾) ½
—
—
—
Neutral-to-ground spacing should be based on the
same spacing required for the other conductors.
A through-air spacing of not less than ½ inch is
acceptable at a circuit breaker or a switch, other
than a snap switch, and between grounded dead
metal and the insulated neutral of a 277/480 VAC
three-phase, four-wire panelboard or switchboard.
Where neutral-to-phase is involved, spacing may
be based on the normal voltage between them.
Neutral-to-ground spacing should be based on the
same spacing required for the other conductors.
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