# 26.5A on a 20A circuit?

I just finished wiring in two 220V circuits to the shop -- 1 for the dust collector (5.5A), and the other for the tablesaw (14.5A), jointer (6.5A), and tbd.
Just for grins I put all of them onto the one circuit. So 5.5+14.5+6.5 26.5A. The 20A breaker did not trip. I even tried starting up the tablesaw while the others were running.
Now in practice, I will keep my dust collector (5.5A, 1.5HP) on it's own circuit, but apparently I could concurrently run both the tablesaw (14.5A) and the jointer (6.5A) and possibly even a 3rd TBD on that other circuit. How is that? The real load must be under 20A, or the 20A breaker allows more like 28A.
I first tried the TS and Jointer, and when they did not trip the breaker (total 21A), I added the DC. I was surprised all three did not trip the breaker. But I guess each was running with no load, so that is surely another reason.
Curious,
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On Thu, 27 Nov 2008 01:15:01 -0600, Kevin wrote:

Kevin:
I honestly think you know the answer to this one: The amperage rating is supposed to be the maximum current draw when operating under normal working conditions. That means when cutting wood.
Most of the posters to this newsgroup only run one such power tools at a time (they ain't a factory) so there is no problem with multiple power tools on a single circuit.
Get a friend to help out. You rip cut some 8/4 rock maple on the TS and let your friend do a 4 inch wide board face cut on the jointer (at the same time of course.) Circuit breaker will trip. (But why would you do this test in real life is way beyond my coffee starved brain's comprehension.)
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Those ratings are for machines with a maximum work load. In other words, a saw just spinning doesn't pull as many amps as one ripping a big piece of wood. If you put them to work instead of just spinning them up, your results would be different.
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On Nov 27, 7:15 am, snipped-for-privacy@optonline.net wrote:

Or, if you could switch them all on at the same time (starting load).
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Yeah, I know; this is mostly an academic discussion.
I did try to have the DC and jointer running, and then switched on the TS. That still did not trip it.
Pragmatically, what I've wired is exactly as I expect -- a dedicated DC circuit and one other for the tool solo use (TS, jointer, TBD).
Now my more pressing reality is that the 110 outlets and lighting are on another 20A circuit. I'm contemplating installing more ceiling outlets for about 12 shoplight fixtures (12x2x40 (maybe 32) ) or 768 watts or about 7 amps. That leaves 13A for the other 110 power tools ( 1 hp bandsaw, rated 10A, miter box, 12.5" planer, etc). I'm contemplating adding another 110 circuit for the lights.
wrote:

Or, if you could switch them all on at the same time (starting load).
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I would I hate being in the dark when you trip a breaker or it needs to be shut off, and you can still have light to work Just put all the lights on a 15-amp breaker You forgot the 80% rule Just because you didn't trip a breaker on your 20A Means nothing at all 20-amp breakers can only carry 16 amps-80 percent of their rating-on a continuous basis. Continuous basis is considered to be a circuit loaded to capacity for three hours or more. So dust collector (5.5A, 1.5HP) on it's own could have the lights added
Spud
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Yeah, there's a 20A circuit now that runs the outlets , 2 garage door openers, and 2 lights sockets inside and 2 outside. I'm going to see about intercepting the lighting circuit and put them on their own 20A service. I need to drop in a few ceiling outlets anyway for more fixtures, so hopefully it will be simple enough to drop in that extra circuit. Since I put in the two 220V circuits I have the wall about the panel opened up already.

I would I hate being in the dark when you trip a breaker or it needs to be shut off, and you can still have light to work Just put all the lights on a 15-amp breaker You forgot the 80% rule Just because you didn't trip a breaker on your 20A Means nothing at all 20-amp breakers can only carry 16 amps-80 percent of their rating-on a continuous basis. Continuous basis is considered to be a circuit loaded to capacity for three hours or more. So dust collector (5.5A, 1.5HP) on it's own could have the lights added
Spud
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snipped-for-privacy@optonline.net wrote:

Also, breakers don't trip instantly. They can take quite a long time for a marginal overload. BTW, for a big overload, like a short, they trip pretty fast.
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I was on the scene when a "smart" electrician (also young) said he could find the breaker by shorting the two 220V wires.(on a conveyor) He kept getting these huge arcs...and after numerous tries...gave up red-faced!
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Ah, they don't make Federal Pacific Electric breakers like they used to.....
(FPE have been known to fail. They get old, and they just don't trip, regardless of the load.)
--
Christopher A. Young
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snipped-for-privacy@gmail.com wrote:

He was trying to use the JESUS method to find the breaker. It only works if you shout "JESUS" at the right moment. *snicker*
TDD
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posted for all of us...

Don't tell holler butt that because he still uses that trick to find breakers and trip them.... -- Tekkie Don't bother to thank me, I do this as a public service.
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snipped-for-privacy@optonline.net wrote:

Hi, And motor starting surge current is for split second more than that. Quite unlikelt all 3 devices will be active simutaneously. Also circuit breaker has several different typr. One will trip instantly when overloaded. One will have a delay to trip and one which is temperature compensated, etc.
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Exactly. Sounds like an extreme case of of multihanded/multi tasking!
If all the appliances and services in our homes were switched on at the same instant and then continued to impose that requirement continuously, the load on the electrical supply system would be tremendous!!!!!!
For example there is 200 amp service into our house.
Our maximum load would be 200 x 230 = 46,000 watts. (46 kilowatts). If continuous over 24 hours that would be 46 x 24 = 104 k.watt.hrs. of consumption. In actual fact our average daily consumption (including electric heating) at the moment (late November) is around 40 to 50 k.watt.hrs per day; an average of less than 2 k.watt.hrs per hour! Sometimes even if/when our bench saw (Plugged into a 230 volt circut work shop outlet) jams on a piece of old wood it doesn't even then trip or blow the ancillary 20 amp fuses located between the breakered feed and the workshop outlets.
By the same token some people do overload one circuit and then wonder why they can't plug the coffee maker, an electric fry-pan, a toaster and the microwave oven all into one kitchen outlet circuit; and THEN switch them all on at the same time to make breakfast
When the breaker tends to trip (and wear out prematurely) they then blame it on 'an electrical problem' rather than 'user error'!
The same people would not try to put an 11 person soccer team plus all their gear into one small car. Have eight people take showers all at once in a single home bathroom. Put four cars in a two bay garage etc. etc.!
So it's hard to understand the lack of logical thinking that wires and circuits and most of the things we use are normally much more lightly loaded than the conditions designed to trip breakers (or blow fuses of the correct size) and protect against fire etc.
Seen a couple of recent installations with 20 amp outlets (as opposed to 15 amp) near kitchen counters. Individual outlets designated by NMEA outlets with a 'T' configuration of one of the pin sockets. Seems like a good idea?
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<...snipped...>

<...snipped...>
Invite a friend over, have him run the jointer taking off 3/16" thickness while you rip a 2" board. I'm pretty sure the braker will pop.
--
Make it as simple as possible, but no simpler.

Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
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