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Forum topic by RBWoodworker posted 02-03-2012 04:49 PM 1168 views 1 time favorited 12 replies Add to Favorites Watch
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RBWoodworker

418 posts in 2099 days


02-03-2012 04:49 PM

I am currently moving my shop which is and hour and 20 minutes away from where I live to where I am living now.. the landlord has a huge structure that he said I could use no charge..anyways.. my question is.. for my tablesaw, which I have a powermatic 66 5 hp that draws 26 amps.. the landlord has an outlet for his motorhome that he’s not using but its hooked up to a 50 amp breaker..my question is..will a 50 amp outlet harm the lower amperage machines? the cords on the machines are all very heavy duty with #6 wires but I’m concerned about the motors having that much amperage going into them..

-- Randall Child http://www.racfurniture.com/


12 replies so far

View NBeener's profile

NBeener

4806 posts in 1921 days


#1 posted 02-03-2012 04:50 PM

The saw will only draw the amperage it needs. The 50A outlet will not “push” 50A into your saw.

Just make sure voltage is the same….. RVs don’t usually run on 220v. 5HP table saws … do.

-- -- Neil

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Sawkerf

1730 posts in 1816 days


#2 posted 02-03-2012 04:52 PM

A 50 amp circuit breaker doesn’t mean that the circuit actually carries 50 amps – it’s just protected to that level.

-- Adversity doesn't build character...................it reveals it.

View RBWoodworker's profile

RBWoodworker

418 posts in 2099 days


#3 posted 02-03-2012 04:54 PM

thanks guys..I was concerned.. but that helps alot..I’m good to go then..

-- Randall Child http://www.racfurniture.com/

View Bertha's profile

Bertha

12951 posts in 1440 days


#4 posted 02-03-2012 04:55 PM

You’re in good shape. Nice to have a fat line like that.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View hydrohillbilly's profile

hydrohillbilly

132 posts in 1058 days


#5 posted 02-03-2012 04:56 PM

Make sure the voltage is right your #6 wire is good for the amperage should be ok

-- Russel C

View David's profile

David

196 posts in 1411 days


#6 posted 02-03-2012 05:24 PM

Along with what everyone else said… as long as your saw has a built in breaker to protect itself from a stall condition, you will be fine.

-- Perilous to all of us are the devices of an art deeper than we ourselves possess. --Gandalf the Grey http://davidwahl.org/category/woodworking/

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a1Jim

112882 posts in 2324 days


#7 posted 02-03-2012 05:24 PM

Hey Randy
You might want to change the breaker to 30 amp to offer more protection for your saw.

-- http://artisticwoodstudio.com Custom furniture

View David's profile

David

196 posts in 1411 days


#8 posted 02-03-2012 05:26 PM

Or what Jim said, seems like he had the same thought I did :)

-- Perilous to all of us are the devices of an art deeper than we ourselves possess. --Gandalf the Grey http://davidwahl.org/category/woodworking/

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RBWoodworker

418 posts in 2099 days


#9 posted 02-03-2012 06:00 PM

Ok.. this is what I found.. I checked in my panel and I have a 2 wire 40 amp empty breaker.. which is perfect for my 220 needs.. and 3-20 amp breakers which is perfect for all the rest.. it looks like I’m good to go now guys.. thanks..

-- Randall Child http://www.racfurniture.com/

View Scot's profile

Scot

344 posts in 2143 days


#10 posted 02-04-2012 09:27 AM

Size your breaker so that the equipment does not draw more than 80 percent of its rating, or looking at it the other way, do not up size the breaker more than 20 percent of the equipment draw.
As per National electrical code the known load should not exceed 24 amps on a 30 amp circuit. If the load exceeds 24 amps then you have to go up to the next size breaker.
Now we have a real can of worms, because you have to ensure your wire is sized for the higher rated breaker.
As always there are always exception to the rules and I’m sure someone will point them out, however, as an electrician, not being there to see the installation, I am keeping to the safe side of things and not even going to get into the exceptions.

-- If the old masters had power tools, they would have used them. So get off your damn High Horse.

View ldl's profile

ldl

1135 posts in 1112 days


#11 posted 02-04-2012 04:17 PM

As was stated in the first post An RV 50a recepticle isn’t suitable for a 220 circuit. It is 2 120v circuits in one outlet.

-- Dewayne in Bainbridge, Ga. - - No one can make you mad. Only you decide when you get mad - -

View hhhopks's profile

hhhopks

565 posts in 1125 days


#12 posted 02-04-2012 06:04 PM

I have not read the first post.
Idl may be correct. There is a differenct between two 120 Vac circuits verses 220 Vac circuit. You should check to make sure. If you have two 120 Vac circuits (2 outlets), then at the panel, you should have two separate single pole CB. If you have one 220 Vac circuit (one outlet), the the panel would have a single 2-pole CB.

Your saw needs a 220 Vac, single phase. The CB should be a 2-pole breaker. You should be using line to line (color code likely to be black & red). Unless the saw calls out for it, you shouldn’t need a neutral (white wire). You will always use the ground wire (green or bare).

You will need to consider the motor starting in-rush current. A standard 30A circuit breaker will likely trip during starting of your saw due to motor inrush current. Get a CB that is rated for the motor load. Another words, a CB with a HP rating that matches your saw. This is the simplest approach. Since motor starting current is relatively short, you want a CB that could “Ride” throught that period of time and not trip. Whatever this “HP” rated CB’s amp rating is, your wire size shoudld match the CB size (assuming the circuit length is within reason). The CB not only protects the load. It also protects the wire. I think this is the safest approach.

Sizing a standard CB could be challenging and complicated. CB comes in differnet flavors (Ex: fast, normal, slow, very slow). To prove that your particular CB is adequate or not, you will need to know the exact Manufacturer, model of the CB; obtain the CB & motor trip current curves…...........................................No one is really interested in this. It doesn’t generate wood dust. Well, it might burn some.

-- I'll be a woodworker when I grow up. HHHOPKS

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