240VAC 1-Phase vs. 120/240VAC 1-Phase

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Old 12-23-07, 10:37 PM
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Unhappy 240VAC 1-Phase vs. 120/240VAC 1-Phase

So is there a difference I should be concerned about?

Let me elaborate a bit more...

I am currently awaiting delivery of a Powermatic PM2000 table saw. The saw I have ordered is 3HP, 240VAC, 1-Phase.

I have purchased 8/3 SO cord, because the saw does not come with cord and cap. I also purchased, what I thought was the correct cap; two angle prongs & and "L" shaped prong. But as I read the directions for the cap, it says it is
"non-grounding". So I am guessing this is not the cap I need, since the directions for wiring the saw say it needs a grounded 240VAC circuit.

Since the wiring was pulled for the outlet when we bought the house, and it was feed from a 30Amp 2-pole circuit breaker, I just assumed everything was correct.

I guess the first thing I should do, is see what wires are now connected to the receptacle. And then see how they are connect at the panelboard.

So, I guess my first question would be: Can I use the current plug/receptacle configuration to connect the saw to power, if there is actually a ground routed back to the panelboard from the junction box?
 
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Old 12-23-07, 11:03 PM
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change the cap and get the correct one i will show this [6-30R]

and the wires should be at #10 size [ much thicker than the #12's is ] and typically if you see black, red wire and green or bare there then you are fine.

but if you see Black and White and bare or green wire there stop there for a sec go to the breaker box and check on the connections escpally on the white wire [ if used on 240 volts the white wire you have there must be remarked with either marker or tape ]

basically you should check this before you ruin the expensive motor.

Merci, Marc
 
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Old 12-24-07, 08:30 AM
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Originally Posted by RedCaliber View Post
So is there a difference I should be concerned about?

Let me elaborate a bit more...

I am currently awaiting delivery of a Powermatic PM2000 table saw. The saw I have ordered is 3HP, 240VAC, 1-Phase.

I have purchased 8/3 SO cord, because the saw does not come with cord and cap. I also purchased, what I thought was the correct cap; two angle prongs & and "L" shaped prong. But as I read the directions for the cap, it says it is
"non-grounding". So I am guessing this is not the cap I need, since the directions for wiring the saw say it needs a grounded 240VAC circuit.

Since the wiring was pulled for the outlet when we bought the house, and it was feed from a 30Amp 2-pole circuit breaker, I just assumed everything was correct.

I guess the first thing I should do, is see what wires are now connected to the receptacle. And then see how they are connect at the panelboard.

So, I guess my first question would be: Can I use the current plug/receptacle configuration to connect the saw to power, if there is actually a ground routed back to the panelboard from the junction box?
What does the manual say to breaker the saw at?

Usually you would only use a 240 vac 2 pole 20amp breaker.

You can use the larger 10 gauge wire already installed, then
put your 2 pole 20amp breaker in place of the existing 30 amp

you then buy a 240 volt 20 amp recepticle w/ground

240 volt 20 amps cord cap w/ground, then 12/3 sjo cord for the saw.

you only need 2 hot wires on a 240 volt motor.

You then need an equipment ground, so if it is 10/2 romex w/ground (black, white/bare ground)feeding the circuit you are fine. just mark the white wire with black or red tape at the ends to show it is a current carrying conductor.

If it is 10/3 w/ground feeding the ciircuit, the two hot wires are black and red then the ground would be bare. the white wire is not used.
 
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Old 12-24-07, 08:54 AM
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based on NEC '05, a 3 hp motor is listed at 17 amps. based on that, you will need a 30 up to 45 amp breaker. #12 would be adequate (due to special motor allowances) but I would use #10 wire minimum personally.

I cannot find the specific applicable sections but due to the hp rating of the motor and the application, you are also supposed to have a motor starter that is non-automatic resetting.

The hp rating requires overload protection sensitive to the motors current draw and due to it being a saw, the internal thermal protection, unless it is not automatic reset, is not acceptable.

The intent is to prevent that if the overload tripped and reset while a person was not in a position to be injured.

So, how are you turning it on and off? Is there internal thermal protection in the motor? Does it have an external reset or is it internal?

Does your switch have thermal protection? (makes it a motor starter rather than simply a switch)
 
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Old 12-24-07, 09:35 AM
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Rated @
13 [email protected] 230 volts 60htz

has a magnetic contactor switch with overloads already installed

I see a 20 amp circuit for this saw. Am I wrong with my calculations??
 
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Old 12-24-07, 11:32 AM
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it might trip the 20amp on start up

you are allowed to upsize the breaker with and only with a thermally protected motor.
 
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Old 12-24-07, 12:49 PM
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Originally Posted by brewaholic View Post
I see a 20 amp circuit for this saw. Am I wrong with my calculations??
I went by code listing which is 17 amps. As long as your overloads are in place, you can oversize the breaker to account for inrush current. You could use a 20 but a 30 is acceptable as well. Since you already have a 30 in place, there really is no need to replace it.
 
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Old 12-24-07, 01:21 PM
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240VAC, 2-Pole, 3-Wire, Grounded Circuit

I guess my biggest concern at this point is whether the original wiring installed by the previous home owner is directly grounded, and not routed to the neutral instead.
 
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Old 12-24-07, 07:16 PM
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Basically, all you need to do is

1. make sure the power to the recep is off.

2.then look to see what wires are landed at the recep.


3. Then look to see where the wires are landed at the panel.

You need only 3 wires. typically you would have 2 colored wires and either a bare or green.

Is your problem with the "non-grounding" plug? If so, what the thing is there is that plug was designed for a 120/240 volt circuit but did not include a ground, only 2 hots and a neutral. Just like an older 3 wire dryer or electric range circuit. Newer rules require a 4th wire (ground) to be included.

What you want for a saw would be a simple 240 volt (only) circuit. 3 wires is all you need.
 
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