Need reality check on 240v circuit installation
#1
04-18-03, 07:58 PM
Need reality check on 240v circuit installation
I'm looking at an air compressor with a 240v 15A motor, and I want to put this thing in the basement (where nobody hears you scream...)
I'm obviously going to need to run a 240v circuit from the service panel to the appropriate location. I have read a good chunk of "Wiring Simplified" (H.P. Richter, et al) and have what I think is a good idea of how to accomplish this. Just want to get some input from this forum.
The plug from this motor is three pronged, what is the functional difference between this and a four wire setup for something like an electric clothes drier? The wiring diagram in the owners manual PDF (see bottom of post) describes two hot wires and a grounding pin -- so where does the return current go? I feel dumb.
Looking at these tables it looks like 12 gauge or maybe even 10 gauge would be appropriate (there's no harm in a slightly larger gauge than required, right?); two current carrying wires and a bare grounding wire, so the cable would be 12/2 or 10/2 with ground?
Would a 240V/20A recepticle be preferable here since they are "pin compatible" with a 240V/15A plug and offer a higher ampacity?
Should I utilise armoured cable or a raceway conduit for this? The distance from the back of the service panel (that would be the hole on the inside of the basement where the wires come through, since the panel is on the outside of the house) to where I want this recepticle is approx 15 feet, but I would like to put a switch up in the garage (directly above) however this would involve feeding the cable up through a top & bottom plate and at that point I'd be lost -- there is an existing 120v recepticle in the garage but it's about 3 studs to the left of the hole through which its cable is routed up from the service panel. No conduit is in place so feeding it through isn't an option, and I don't want to rip off the drywall! I guess placing a switch above where the existing top plate hole is would be an option?
Is there anything in the NEC that specifies the height of a recepticle in a basement? The leads on these compressors aren't very long and extend from the motor at the top of the "chassis", so the receptical would need to be quite high. I also want to mount the thing on a little corner platform upon rubber insulators to reduce vibration, so I would expect the receptical to be about 5 foot from the ground at that point (4 foot from the base of this platform.)
I'm strapped for room in my service panel, so at the very least I would be converting some of the single pole breakers to slimline versions to free up some slots. Any caveats for this? There are already some of these slimline breakers in there already.
I'm guessing that I will need a permit and inspection to perform this work myself; is this the case?
FWIW, here's a PDF of the owners manual for this class of compressor from CH: http://www.chpower.com/free_download...s%20Manual.pdf
It has some wiring information in there.
I'm obviously going to need to run a 240v circuit from the service panel to the appropriate location. I have read a good chunk of "Wiring Simplified" (H.P. Richter, et al) and have what I think is a good idea of how to accomplish this. Just want to get some input from this forum.
The plug from this motor is three pronged, what is the functional difference between this and a four wire setup for something like an electric clothes drier? The wiring diagram in the owners manual PDF (see bottom of post) describes two hot wires and a grounding pin -- so where does the return current go? I feel dumb.
Looking at these tables it looks like 12 gauge or maybe even 10 gauge would be appropriate (there's no harm in a slightly larger gauge than required, right?); two current carrying wires and a bare grounding wire, so the cable would be 12/2 or 10/2 with ground?
Would a 240V/20A recepticle be preferable here since they are "pin compatible" with a 240V/15A plug and offer a higher ampacity?
Should I utilise armoured cable or a raceway conduit for this? The distance from the back of the service panel (that would be the hole on the inside of the basement where the wires come through, since the panel is on the outside of the house) to where I want this recepticle is approx 15 feet, but I would like to put a switch up in the garage (directly above) however this would involve feeding the cable up through a top & bottom plate and at that point I'd be lost -- there is an existing 120v recepticle in the garage but it's about 3 studs to the left of the hole through which its cable is routed up from the service panel. No conduit is in place so feeding it through isn't an option, and I don't want to rip off the drywall! I guess placing a switch above where the existing top plate hole is would be an option?
Is there anything in the NEC that specifies the height of a recepticle in a basement? The leads on these compressors aren't very long and extend from the motor at the top of the "chassis", so the receptical would need to be quite high. I also want to mount the thing on a little corner platform upon rubber insulators to reduce vibration, so I would expect the receptical to be about 5 foot from the ground at that point (4 foot from the base of this platform.)
I'm strapped for room in my service panel, so at the very least I would be converting some of the single pole breakers to slimline versions to free up some slots. Any caveats for this? There are already some of these slimline breakers in there already.
I'm guessing that I will need a permit and inspection to perform this work myself; is this the case?
FWIW, here's a PDF of the owners manual for this class of compressor from CH: http://www.chpower.com/free_download...s%20Manual.pdf
It has some wiring information in there.
#2
04-19-03, 05:23 AM
Re: Need reality check on 240v circuit installation
Originally posted by mcm
[B]
The air compressor does not have any 110 volt requirements like a dryer does, so the neutral ( 4th wire mentioned ) is not needed.
The current gets ate up by the motor and your light bill goes up ! 
# 14 would work for a 15 amp circuit. But I would prefer at least #12
{QUOTE]Would a 240V/20A recepticle be preferable here since they are "pin compatible" with a 240V/15A plug and offer a higher ampacity?
[B]
The plug from this motor is three pronged, what is the functional difference between this and a four wire setup for something like an electric clothes drier?
The wiring diagram in the owners manual PDF (see bottom of post) describes two hot wires and a grounding pin -- so where does the return current go? I feel dumb.
The current gets ate up by the motor and your light bill goes up ! 
Looking at these tables it looks like 12 gauge or maybe even 10 gauge would be appropriate (there's no harm in a slightly larger gauge than required, right?); two current carrying wires and a bare grounding wire, so the cable would be 12/2 or 10/2 with ground?
{QUOTE]Would a 240V/20A recepticle be preferable here since they are "pin compatible" with a 240V/15A plug and offer a higher ampacity?
Should I utilise armoured cable or a raceway conduit for this?
Is there anything in the NEC that specifies the height of a recepticle in a basement? The leads on these compressors aren't very long and extend from the motor at the top of the "chassis", so the receptical would need to be quite high. I also want to mount the thing on a little corner platform upon rubber insulators to reduce vibration, so I would expect the receptical to be about 5 foot from the ground at that point (4 foot from the base of this platform.)
I'm strapped for room in my service panel, so at the very least I would be converting some of the single pole breakers to slimline versions to free up some slots. Any caveats for this? There are already some of these slimline breakers in there already.
#3
04-21-03, 07:23 AM
Just a couple of comments:
1) In a single-phase system, the current flows from one phase to a grounded neutral of 0 volts potential. In a 120V 1-phase ckt, the voltage changes from 0V to ~170V positive, back to 0 and then ~170V negative. It repeats 60 times/second. The current flows from hot to neutral during the positive half, from neutral to hot during the negative half.
The voltage from a 240V, 2 -phase ckt varies the same way. However, while one phase is moving negative, the other is moving positive. Current flows back and forth between these conductors. No neutral path (0 volt) is required, unless 120V is required to operate timers or other control devices as in a dryer or oven.
2) Any vibrating equipment should have a flexible whip connecting a hard piped conduit system to the connection box on the eqiuipment. Any place wires enter or leave the connection box must be protected with a non-metallic bushing, to prevent abrading the insulation. Be very thorough in your grounding connections, especially if you're mounting it on insulating dampers. If possible, use multi-stranded conductors. Check the electrical connections periodically.
1) In a single-phase system, the current flows from one phase to a grounded neutral of 0 volts potential. In a 120V 1-phase ckt, the voltage changes from 0V to ~170V positive, back to 0 and then ~170V negative. It repeats 60 times/second. The current flows from hot to neutral during the positive half, from neutral to hot during the negative half.
The voltage from a 240V, 2 -phase ckt varies the same way. However, while one phase is moving negative, the other is moving positive. Current flows back and forth between these conductors. No neutral path (0 volt) is required, unless 120V is required to operate timers or other control devices as in a dryer or oven.
2) Any vibrating equipment should have a flexible whip connecting a hard piped conduit system to the connection box on the eqiuipment. Any place wires enter or leave the connection box must be protected with a non-metallic bushing, to prevent abrading the insulation. Be very thorough in your grounding connections, especially if you're mounting it on insulating dampers. If possible, use multi-stranded conductors. Check the electrical connections periodically.
#5
04-22-03, 02:50 PM
Originally posted by grignon
Just a couple of comments:
1) In a single-phase system, the current flows from one phase to a grounded neutral of 0 volts potential. In a 120V 1-phase ckt, the voltage changes from 0V to ~170V positive, back to 0 and then ~170V negative. It repeats 60 times/second. The current flows from hot to neutral during the positive half, from neutral to hot during the negative half.
The voltage from a 240V, 2 -phase ckt varies the same way. However, while one phase is moving negative, the other is moving positive. Current flows back and forth between these conductors. No neutral path (0 volt) is required, unless 120V is required to operate timers or other control devices as in a dryer or oven.
2) Any vibrating equipment should have a flexible whip connecting a hard piped conduit system to the connection box on the eqiuipment. Any place wires enter or leave the connection box must be protected with a non-metallic bushing, to prevent abrading the insulation. Be very thorough in your grounding connections, especially if you're mounting it on insulating dampers. If possible, use multi-stranded conductors. Check the electrical connections periodically.
Just a couple of comments:
1) In a single-phase system, the current flows from one phase to a grounded neutral of 0 volts potential. In a 120V 1-phase ckt, the voltage changes from 0V to ~170V positive, back to 0 and then ~170V negative. It repeats 60 times/second. The current flows from hot to neutral during the positive half, from neutral to hot during the negative half.
The voltage from a 240V, 2 -phase ckt varies the same way. However, while one phase is moving negative, the other is moving positive. Current flows back and forth between these conductors. No neutral path (0 volt) is required, unless 120V is required to operate timers or other control devices as in a dryer or oven.
2) Any vibrating equipment should have a flexible whip connecting a hard piped conduit system to the connection box on the eqiuipment. Any place wires enter or leave the connection box must be protected with a non-metallic bushing, to prevent abrading the insulation. Be very thorough in your grounding connections, especially if you're mounting it on insulating dampers. If possible, use multi-stranded conductors. Check the electrical connections periodically.
The compressor motor has a power cable coming from it (flexible, looks like your average heavy duty power tool cable) and I would say this is sufficient to isolate vibration away from the recepticle. I'm intending to use #10 wire for this, does it come in stranded variety?
-mike
