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Forum topic by RBWoodworker posted 02-03-2012 04:49 PM 1648 views 1 time favorited 12 replies Add to Favorites Watch
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441 posts in 3374 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 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

12 replies so far

View NBeener's profile


4816 posts in 3196 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

View Sawkerf's profile


1730 posts in 3091 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 reveals it.

View RBWoodworker's profile


441 posts in 3374 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

View Bertha's profile


13529 posts in 2715 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


132 posts in 2333 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


198 posts in 2686 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

View a1Jim's profile


117114 posts in 3599 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.

-- wood crafting & woodworking classes

View David's profile


198 posts in 2686 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

View RBWoodworker's profile


441 posts in 3374 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

View Scot's profile


344 posts in 3418 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


1135 posts in 2388 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


651 posts in 2400 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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