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switching load of < 15A on 20A circuit

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switching load of < 15A on 20A circuit deans@wdeans.com 09-10-2006
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Posted by chili palmer on September 13, 2006, 11:37 am

deans@wdeans.com wrote:

>
> Thank you very much Doug. Your responses are always of the highest
> quality.

<handing dean a tissue, pointing to his brown nose>

You missed some dean


Posted by on September 10, 2006, 4:15 pm

>
>>>Greetings,
>>>
>>>Can I switch a load of < 15A (say a baseboard heater) on 20A circuit
>>>with a 15A rated switch or does the switch need to be rated at 20A
>>>because that is the rating of the circuit?
>>
>> Per Code, switches are to be rated for the loads they control -- so if
>> you're
>> switching a load of less than 15A, it's ok to use a 15A rated switch. Even
>> on
>> a 20A circuit.
>>
>I am sure you are right... but it doesn't make sense. Can you document
>that?
>

404.14 Rating and Use of Snap Switches.
Snap switches shall be used within their ratings and as indicated in
404.14(A) through (D).

(A) Alternating Current General-Use Snap Switch. A form of general-use
snap switch suitable only for use on ac circuits for controlling the
following:
(1)        Resistive and inductive loads, including electric-discharge
lamps, not exceeding the ampere rating of the switch at the voltage
involved .


Posted by Toller on September 11, 2006, 9:35 am

>
>>
>>>>Greetings,
>>>>
>>>>Can I switch a load of < 15A (say a baseboard heater) on 20A circuit
>>>>with a 15A rated switch or does the switch need to be rated at 20A
>>>>because that is the rating of the circuit?
>>>
>>> Per Code, switches are to be rated for the loads they control -- so if
>>> you're
>>> switching a load of less than 15A, it's ok to use a 15A rated switch.
>>> Even
>>> on
>>> a 20A circuit.
>>>
>>I am sure you are right... but it doesn't make sense. Can you document
>>that?
>>
>
> 404.14 Rating and Use of Snap Switches.
> Snap switches shall be used within their ratings and as indicated in
> 404.14(A) through (D).
>
> (A) Alternating Current General-Use Snap Switch. A form of general-use
> snap switch suitable only for use on ac circuits for controlling the
> following:
> (1) Resistive and inductive loads, including electric-discharge
> lamps, not exceeding the ampere rating of the switch at the voltage
> involved .
>
Don't mean to be argumentative...
Switches must be as large as their loads. Couldn't possibly disagree with
that.
But isn't there a general rule that all components must be as large as the
breaker that protects them?
There is no contradiction between the two; just because the switch must be
as large as the load doesn't mean is shouldn't also be as large as the
breaker. Certainly the breaker will be at least as large as the load.



Posted by Doug Miller on September 11, 2006, 10:07 am


>But isn't there a general rule that all components must be as large as the
>breaker that protects them?

No. For example, the NEC explicitly permits the use of 15A receptacles on a
20A circuit. And, as we were discussing here, switches need to be rated only
for the loads they control, not the rest of the circuit.


--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Posted by on September 11, 2006, 11:41 am

>Don't mean to be argumentative...
>Switches must be as large as their loads. Couldn't possibly disagree with
>that.
>But isn't there a general rule that all components must be as large as the
>breaker that protects them?
>There is no contradiction between the two; just because the switch must be
>as large as the load doesn't mean is shouldn't also be as large as the
>breaker. Certainly the breaker will be at least as large as the load.
>
You can plug a table lamp into a 20a circuit but you certainly could
not switch a 20a load with that little switch in the lamp holder.
Another example would be the 18 ga wiring in a light fixture which
could be on a 15 or 20a circuit. The load (a couple light bulbs)
controls the amount of current that flows in normal operation. They
only size the wire to deal with a short and an 18ga wire would sustain
a dead short until a 20a breaker could trip.

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