why have a 12 amp limit on electric appliances when we can have
multiple outlets plugged into a wall socket? i need to have a machine
run on 110 volt but i have multiple motors and other resistive loads
and if they all come on at the same time they draw about 23 amp .
what is the regulation/legislation and regulatory body about this topic? |
Request for Question Clarification by
redhoss-ga
on
15 Aug 2005 05:50 PDT
I am curious. Where did you hear about this 12 amp limit.
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Clarification of Question by
aldol-ga
on
15 Aug 2005 11:41 PDT
i observed that no 110 volt appliance on the market ( in the US) has
more than approximately 1800-2000 watts and i assumed that there was a
limitation on amperage due to wiring codes
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Clarification of Question by
aldol-ga
on
19 Aug 2005 04:49 PDT
i was wrong in my assumption of a 12 amp limit.
what is the limit then on the amperage for 110 volt circuits in the US?
how is the limit established. what are the parameters that define this
limit. how do i let's say have an appliance with several circuits that
let' say draw 5500 watts or about 50 amps at 110volts?
think for example of a pc plus printer plus a space heater plus strong
light torchiere plus a vacuum cleaner all coming out of the same
wall socket and going to the various appliances . theoretically we
could have in excess of 40 amps on that socket and still not trip the
breaker. so why we have limitations on th power of some appliances:
example: hair dryers : you do not see hair dryers with a rating higher
than 1875 watts
or space heaters: not higher than 1500 watts
or vacuum cleaners not higher than 12 amps
etc.
let's say we wanted to make a vacuum cleaner that draws 30 amps.
couls=d we do that?
or a space heater that produces 3000 watts
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Request for Question Clarification by
byrd-ga
on
19 Aug 2005 09:18 PDT
Hi aldol-ga,
This question relates to your idea for an electrical appliance
invention, right? Well, my husband is an electrical engineer, so I
showed him your question First he mentioned that motors are inductive
loads, not resistive, and then expounded about how watts = volts x
amps, and how buildings in the US are wired such that you end up with
the wattage limitation you've noticed on appliances you plug into the
wall. Of course, if you have 220 volt outlets, you can use appliances
with higher wattage. He also mentioned that breakers are graduated.
For instance, you can have a breaker that will carry x amount of load
for x number of seconds before tripping. Also, he said that, for
example, if you had an in-house vacuum like they have in many office
buildings, expensive homes, etc., because it's wired direct, you can
have a much higher wattage than one you plug in the wall outlet, since
those are restricted to 15 or 20 amps. I'd carry on, but now I'm
confusing myself. :-)
I also learned that the National Fire Protective Agency (NFPA) is the
top watchdog that oversees the code, i.e. generates and enforces the
National Electrical Code (NEC). My husband thought you had to purchase
the code, and if you want to, he recommended getting the explanatory
handbook that comes with it, as that has more detailed and
understandable explanations with diagrams, etc. However, the 2005
code IS available online, here:
http://www.nfpa.org/freecodes/free_access_agreement.asp?id=7005SB
Here's a link to the handbook:
http://www.nfpa.org/catalog/product.asp?catalog%5Fname=NFPA+Catalog&pid=70HBCD02&query=NEC+handbook&link%5Ftype=search&src=nfpa
And the main page for the NFPA is here: http://www.nfpa.org
So I'm not sure if I've made things better or worse, but wanted to
pass along what little I knew in hopes some of it may be of some help
to you. Of course, since your original question asked for information
about the regulatory body overseeing these matters, if you'd like to
accept that information, i.e. the NFPA, as the official answer, let me
know and I'll be happy to post it in the answer box.
Best,
Byrd-ga
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Clarification of Question by
aldol-ga
on
19 Aug 2005 10:19 PDT
this is in refernce to the request for clarification by Byrd-ga
thank you for your explanation and i will cetainly look over the link you sent.
certainly going to 220 volt circuit can increase not only your wattage
simply because for the same amperage you double the power compared to
110 volt but also because in the building codes 220 volt circuits
generally are sized for much higher amps.
i do need some clarification though on your message. what do you mean
that in hotels the vacuum cleaners are wired directly?
thank you
again
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Request for Question Clarification by
byrd-ga
on
19 Aug 2005 11:35 PDT
Hi aldol-ga,
Ok, discussion about various vacuum systems is another topic
altogether, but the short answer to that is that (and it's not only
hotels) rather than using a traditional vacuum cleaner that plugs into
the wall, one may opt instead for a central vacuum system. This
consists of a remote power unit that does not plug in to a household
outlet, but is wired directly, as a furnace or hot water heater. This
unit is connected by tubing to inlet valves placed throughout the
house or building. You plug a hose with a "power brush" or cleaning
head unit into these outlets, which turns on the power and suction
that allows you to vacuum. Because they are wired directly into the
home's power source, these motors can be much stronger than
traditional vacuum cleaner motors, which have to be plugged into a
wall outlet.
One company says that portable vacuum motors "fall somewhere between 5
and 10 amps," while their own "smaller unit is 15.5 amps and our
larger ... draws almost 28 amps."
http://builtinvacuum.com/faq/0059.html
Here's another link to information on these central vacuum systems:
http://home.howstuffworks.com/central-vacuum1.htm
You might also find useful this excerpt from an e-book on "Power,
lighting and structured wiring," which mentions amperage of electrical
services, particularly in residential buildings/homes, and talks about
such high amp users as central vacuum systems.
Oh - and as to the original title of your question: I found a bit of
info on that too. It refers to the part of the code that limits the
"maximum plugged device to 80 percent of a socket rating." This would
mean that a device (or appliance) plugged into a 15 amp socket would
be limited to 12 amps, though this limitation is usually for devices
that are plugged in for a long time. Also, some newer homes have 20
amp outlets, which would increase the maximum of the device 16 amps.
Here's a discussion about it:
http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00DAv1 (scroll
down to the second post, by "Kelly Flanigan")
Hope this helps,
Byrd-ga
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Request for Question Clarification by
byrd-ga
on
19 Aug 2005 11:39 PDT
Sorry, forgot to paste the link to the e-book mentioned above. Here
it is: http://www.builderswebsource.com/book/electrical.htm
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Clarification of Question by
aldol-ga
on
19 Aug 2005 12:35 PDT
my reference to vacuum cleaner was just an example
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