1 Aug
2001
1 Aug
'01
10:46 a.m.
Certainly in the US. Typical branch circuits are 15 or
20A at a nominal
115V (although voltages between 110 and 130 are common, largely as a
function of how the single phase was derived). The NEC doesn't >consider
the fact that a given appliance that's plugged into such a >branch circuit
may have an attached cord that is rated at less that >the rating of the
branch to be an issue; it simply requires that in >the absence of a
overcurrent that the rating of the cord match be >appropriate for the
current draw of the appliance.
You sure about that?
From what I understand, every conductor must be capable
of carrying a
current greater than the breaker that protects it. Otherwise, the
cord would
be the first thing thing to fail in a overcurrent situation. This would
present a very significant fire danger.
Even the cheapest kitchen appliances have fairly heavy power cords. It's not
because they draw a lot of current or the manufacturers are generous, it's
because the fuses / breakers in your kitchen have a higher amperage rating
than in other places in the home. So, those appliances must have heavier
cords to offer protection.
SteveRob
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1 Aug
1 Aug
11:19 a.m.
Steve Robertson wrote:
You sure about that?
Yep. I asked my local NEC language lawyer about it before posting.
From what I understand, every conductor must be
capable of carrying a
current greater than the breaker that protects it. Otherwise, the cord
would
be the first thing thing to fail in a overcurrent
situation. This would
present a very significant fire danger.
In the context of building wiring, yes. Not in the context of appliance
wiring. 22GA zip cord, such as found on US lamps, isn't capable of
sustaining 20A@115V without heating -- and you can certainly plug a
15A plug into a 20A receptacle. In a catastrophic overcurrent situation,
i.e. a dead short, the breaker will long before the cord even warms. It's
the failure mode where the appliance draws more than it's designed to
draw but less that the branch protection rating that the problem occurs --
which is why most consumer electronic devices have mains protection sized
to their demand and most kitchen appliances have self-resetting thermal
overload cut-outs.
Even the cheapest kitchen appliances have fairly heavy
power cords. It's
not
because they draw a lot of current or the
manufacturers are generous, it's
because the fuses / breakers in your kitchen have a higher amperage rating
than in other places in the home. So, those appliances must have heavier
cords to offer protection.
Your home, maybe :-). Every branch in mine is rated at 20A. The reason
_most_
kitchen appliances have heavy cords is because _most_ of them are double
insulated. Then again, I've got an electric kettle that has a regular zip
cord on it -- and yes, it heats up during operation.
--
Chris Kennedy
chris(a)mainecoon.com
http://www.mainecoon.com
PGP fingerprint: 4E99 10B6 7253 B048 6685 6CBC 55E1 20A3 108D AB97
11:56 a.m.
I believe the basic idea of the NEC is to keep
you from having an unseen fire in the walls.
What happens to the exposed power cords is your
problem.
11:20 a.m.
On Wed, 1 Aug 2001, Steve Robertson wrote:
From what I understand, every conductor must be
capable of carrying a
current greater than the breaker that protects it.
Take a look at a string of Christmas tree lights.
Otherwise, the cord would
be the first thing thing to fail in a overcurrent situation. This would
present a very significant fire danger.
It does.
11:41 a.m.
Even the cheapest kitchen appliances have fairly heavy
power cords. It's not
because they draw a lot of current or the manufacturers are generous, it's
because the fuses / breakers in your kitchen have a higher amperage rating
than in other places in the home. So, those appliances must have heavier
cords to offer protection.
Kitchen appliances often DO draw a large current and the guage of wire is
based on what the appliance needs, which is why they have power cords of
various sizes, 12, 14, 16, 18 guage. Don't judge the wire by its cover, fat
wires can have thin conductors. I doubt you will ever see more than 16 awg
on a hand mixer though.
Nothing but 20 amp circuits in my house except for the AC, Dryer, etc.
which have dedicated outlets and most of the time are 220. All the 120 volt
outlets in my house are standard 15 amp, 20 amp uses a slightly different
blade size, but isn't something typical for a kitchen.
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bills＠adrenaline.com -
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