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| w_tom wrote:
quote:
> indago wrote:
>
>
> But again, how reliable is the source when short term
> amperage for an 18 AWG zip cord is more than sufficient to
> safety trip a 20 amp breaker. The important parameter is
> time. Those 'more than 20 amps' must exist only for a short
> period. 18 AWG wire is more than sufficient to trip a 20 amp
> breaker during a short 'short circuit'.
You may be interested in this - from the Product Safety Technical
Committee of the IEEE EMC Society:
In North America, wire sizes
for power cords, including extension
cords, are selected to always
be capable of blowing the 15 or
20 amp building fuse in the event
of a steady-state short-circuit at
the end of the power cord.
The power cord wire size together
with its insulation rating
must have a sufficiently low
impedance to withstand the
overheating of the short-circuit
until the 20-amp circuit breaker
clears the circuit. (Cord-connected
electrical heating appliances often
have high temperature insulation
on their power cords to account
for steady-state high current conditions.
To meet this criterion, the
minimum wire size for flexible
cords is AWG 18, except for
specific applications, in which
case there are extensive insulation
robustness tests designed to
preclude insulation failure.
Ampacity ratings of cords and
cordsets are given in UL 817,
Table 90. These ratings are for
normal conditions.
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