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Old 03-20-2009, 12:37 PM   #16
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Quote:
Originally Posted by hayewe farm View Post
If the breaker is not tripping then changing the breaker or rewiring for 240v will accomplish nothing. I agree with 47 47 it sounds like you are useing the wrong type, dull, or cheap blade or you are feeding to fast when ripping.
Jack
Noit's not the blade new blade not cheap blad not feeding to fast

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Old 03-20-2009, 12:38 PM   #17
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no it's not the blade not feeding to fast
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Old 03-20-2009, 12:46 PM   #18
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Originally Posted by Bocolo View Post
The short answer is NO. Breaker amps are based on wire size or the other way around. If you have 12 awg wire on the circuit you can then put a 20 amp breaker. By code your 15 amp breaker should be using 14 awg wire. You can rewire the circuit with 12/2 and then change your breaker to 20 amps. You might be overworking your Dewalt. Post more details about the tool and some of the other guys here will be able to help you out.
hp1.5 amp 14/7 volts120/240 rpm3600 cy60 shop under house about 50 feet from box. about 6 recp but none with load except 2 lights on
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Old 03-20-2009, 12:52 PM   #19
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hp 1.5 amp 14/7 volts 120/240 rpm3600 cy60 shop under house about 50 feet from box 14 wire. other recp but non loads except 2 lights has regular plug
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Old 03-20-2009, 01:19 PM   #20
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Replace the saw with a known load, like a 10A hair dryer.

50' of #14 is about 260 milliohms resistance so at 10A you should see no more than a 2.6v rise when the dryer is switched off.

If there is more than that then you have a high resistance upstream of the saw. Could be a bad wirenut or bad breaker contacts.

Less likely, there is a high resistance inside the saw; bad switch contacts or bad brushes.

Last edited by Yoyizit; 03-20-2009 at 08:10 PM.
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Old 03-26-2009, 10:12 AM   #21
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Thanks for the in put. I rerouted a 220 line from another part of the house to the shop the dewalt has a switch for 120 /240. Ca i go ahead and hook this line to the saw?
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Old 03-26-2009, 04:02 PM   #22
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If there is a high resistance in the supply line, it will have less effect at the higher voltage. Try it.
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Old 03-27-2009, 09:09 PM   #23
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I did some searching, and the "dewalt power shop" is a 15-in-1 radial arm saw type thing from the 1960s.

It's extremely confusing that he is calling this tool a "shop".

I doubt that the tool is supposed to be on a 15 amp (120v) circuit with a 1.5 HP motor.
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Old 03-27-2009, 09:24 PM   #24
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Almost all Dewalt single phase radial arm saws are dual voltage. Most of the older ones had a 120/240 switch on the motor. Usually, there was some sort of a guard that you could put a pin through to prevent inadvertently switching to the wrong voltage.

If this switch is in the 240 volt position, then connecting it to a 240 volt circuit will make it run properly. You'll notice SUBSTANTIALLY more cutting power when operated at the higher voltage.

I always recommend that all dual voltage motors be operated at the higher voltage if at all possible.

Rob
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Old 03-27-2009, 09:37 PM   #25
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You'll notice SUBSTANTIALLY more cutting power when operated at the higher voltage.
Meaning the watts at 240v is more than the watts at 120v. In that case a high resistance in the line may have the same bad effect at either voltage.
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Old 03-28-2009, 12:18 AM   #26
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At 240 volts, the amps is 1/2 that of 120 volts. Therefore, voltage drop is less, and more power (watts) is available for the motor.

When a motor is loaded and voltage drops, current will increase, but only to a point. Once the voltage drops to about 10-15% less than the nameplate voltage, current is pretty much at its peak. Any further reduction in voltage will result in a reduction in watts, and thus, a rapid reduction in HP.

The efficiency (the ability to convert watts into HP) of a typical motor peaks at right around nameplate voltage, and falls off rapidly at around 15-20% less voltage.

Here's an actual home-brewed test of the effects of voltage on a motor; I have a 1HP air compressor in my van. I connected a dual voltage switch (115/230) when I built the compressor. Air compressors tend to start hard when they're cold. Out where the van is parked, there is a post with two receptacles mounted on it. One is a 20 amp 120 volt GFI, the other is a 20 amp 208 volt. Not 240 volt, my service is a 120/208 wye. Both receptacles are the same distance from the panel, and both are #12 wire.

On a fairly cold morning (30F or so), I connected about 200' of #14 extension cord to the 208 volt receptacle, set the switch for high voltage, and plugged the compressor in. It started, though somewhat slow. I didn't let it run for more than a second or so, so as to keep the pump cold. Next, I connected 200' of #12 extension cord to the 120 volt receptacle, set the switch for low voltage, and plugged the compressor in. This time, it almost didn't start. It cycled in and out of the start windings several times, then finally came up to speed.

This compressor is equipped with a 'load genie' type of unloader. This type of valve unloads the pump whenever there's no airflow out of it. I heard it unload after both tests, so I know the pump wasn't trying to start against pressure.

I know this likely defies basic physics, but that motor could produce considerably more torque on 208 with a smaller wire than it could on 120 with a bigger wire.

I didn't check voltage during this test, one of these days I'll repeat the test using a min/max voltmeter, and amps as well. It should be interesting.

Rob
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Old 03-28-2009, 09:16 AM   #27
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It may be useful to measure the voltage at the motor or at least at the receptacle it is plugged into. The tool should not be operated in a manner where a substantial voltage drop (ten percent or more) at the motor occurs.

An unknown still remains, whether a voltage drop is due to pulling way too many amperes (why did the breaker not trip) or is due to shortcomings in the circuit such as back stabbed receptacles in a daisy chain. This is where a current measurement comes in handy. Using the hair dryer (a known current draw) suggested above together with some math knowledge, you could figure out how much the tool is drawing using your voltmeter and not need a clamp on ammeter.

In addition, the motor must not be run on 240 (or 208) volts unless and until the voltage selector switch is adjusted to match or the motor wiring is configured appropriately.

A 30 amp in line fuse/breaker and a standard appliance cord and plug are an incongruous combination.

>>> not feeding too fast

But can you feed slower and will that cause the motor to draw fewer amperes?
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Last edited by AllanJ; 03-28-2009 at 09:31 AM.
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Old 03-28-2009, 10:15 PM   #28
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Thanks for everyone;s help. THE SAW IS FROM TH 60 S IT HAS A 120 AND 240 SWITCH ON IT IM GOING TO SWITCH IT TO THE 240 I HAVE A 220 LINE RUN IN

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