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_at_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_at_mainecoon.com
http://www.mainecoon.com
PGP fingerprint: 4E99 10B6 7253 B048 6685 6CBC 55E1 20A3 108D AB97
Received on Wed Aug 01 2001 - 15:19:56 BST