Safety Switch Wiring Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

thepunisher · 06-29-2013, 04:23 PM

I've installed a safety switch for the new air compressor for my garage and I have a question about the ground. The box has a bridge for the neutral and the ground. The bridge is not grounded to the chassis of the box. What's the safest configuration for the ground? Should I also bridge the ground and neutral to the chassis as well or is that not necessary?

_Ogre · 06-30-2013, 11:42 PM

assuming it is a 220 volt compressor, it will have no neutral only 2 hots and a ground
normal hookup would use 8-2 wire to match your 35 amp fuses, those wires look a little smaller than #8
assuming you ran 8-3, just tie the white wire and bare wire together in the equipment ground lug
don't double up 2 wires in one lug if your going to be inspected

what is the amperage rating of your compressor?

thepunisher · 07-01-2013, 08:18 AM

Thanks Ogre for the reply. What's wired to the safety switch is 8-3. The vendor said I needed a 30 amp breaker for the compressor.

_Ogre · 07-01-2013, 10:00 PM

what amperage is the compressor? this is the deciding factor of wire, breaker and fuse size
with a 30 amp breaker you only need to run 10-2 wire, especially with the price of copper where it is
a 50 ft roll of 10-2 is $57, while 50 ft of 8-3 runs $104. almost half the price for the correct wire size.

you should also have the correct fuses for the motor, bigger is not better

thepunisher · 07-02-2013, 11:09 AM

The motor is 22 amps. I wired this with 8 gauge wire in case I ever got to the point of purchasing a different welder that needs a 40 AMP breaker. Obviously I wouldn't be able to run both at the same time but I'm wired to run whatever. The time delay fuses are 35 AMP fuses per Square D's recommendation.

Why would the 8 gauge wire be an issue if the breaker is properly sized?

I recognize the cost difference, I was able to purchase the wire through a local electrical supply house at $1.22 a foot (considerably less than HomeDepot). I needed 25' so it was ~$30 worth of wire.

_Ogre · 07-02-2013, 01:49 PM

pre-planning for a welder is a good idea.
just making you aware of the wire size and cost.

thepunisher · 07-02-2013, 02:03 PM

Awesome, thanks Ogre for the help!

06-29-2013, 04:23 PM	#1
thepunisher Registered User Join Date: Aug 2009 Location: Rochester, MN Posts: 201	Safety Switch Wiring Question I've installed a safety switch for the new air compressor for my garage and I have a question about the ground. The box has a bridge for the neutral and the ground. The bridge is not grounded to the chassis of the box. What's the safest configuration for the ground? Should I also bridge the ground and neutral to the chassis as well or is that not necessary? __________________ Blayne

06-30-2013, 11:42 PM	#2
_Ogre Registered User Join Date: Jan 2012 Location: Motown Posts: 7,680	Re: Safety Switch Wiring Question assuming it is a 220 volt compressor, it will have no neutral only 2 hots and a ground normal hookup would use 8-2 wire to match your 35 amp fuses, those wires look a little smaller than #8 assuming you ran 8-3, just tie the white wire and bare wire together in the equipment ground lug don't double up 2 wires in one lug if your going to be inspected what is the amperage rating of your compressor? __________________ cool, an ogre smiley Ogre's 58 Truk build how to put your truck year and build thread into your signature shop air compressor timer

07-01-2013, 08:18 AM	#3
thepunisher Registered User Join Date: Aug 2009 Location: Rochester, MN Posts: 201	Re: Safety Switch Wiring Question Thanks Ogre for the reply. What's wired to the safety switch is 8-3. The vendor said I needed a 30 amp breaker for the compressor. __________________ Blayne

07-01-2013, 10:00 PM	#4
_Ogre Registered User Join Date: Jan 2012 Location: Motown Posts: 7,680	Re: Safety Switch Wiring Question what amperage is the compressor? this is the deciding factor of wire, breaker and fuse size with a 30 amp breaker you only need to run 10-2 wire, especially with the price of copper where it is a 50 ft roll of 10-2 is $57, while 50 ft of 8-3 runs $104. almost half the price for the correct wire size. you should also have the correct fuses for the motor, bigger is not better __________________ cool, an ogre smiley Ogre's 58 Truk build how to put your truck year and build thread into your signature shop air compressor timer

07-02-2013, 11:09 AM	#5
thepunisher Registered User Join Date: Aug 2009 Location: Rochester, MN Posts: 201	Re: Safety Switch Wiring Question The motor is 22 amps. I wired this with 8 gauge wire in case I ever got to the point of purchasing a different welder that needs a 40 AMP breaker. Obviously I wouldn't be able to run both at the same time but I'm wired to run whatever. The time delay fuses are 35 AMP fuses per Square D's recommendation. Why would the 8 gauge wire be an issue if the breaker is properly sized? I recognize the cost difference, I was able to purchase the wire through a local electrical supply house at $1.22 a foot (considerably less than HomeDepot). I needed 25' so it was ~$30 worth of wire. __________________ Blayne

07-02-2013, 01:49 PM	#6
_Ogre Registered User Join Date: Jan 2012 Location: Motown Posts: 7,680	Re: Safety Switch Wiring Question pre-planning for a welder is a good idea. just making you aware of the wire size and cost. __________________ cool, an ogre smiley Ogre's 58 Truk build how to put your truck year and build thread into your signature shop air compressor timer

07-02-2013, 02:03 PM	#7
thepunisher Registered User Join Date: Aug 2009 Location: Rochester, MN Posts: 201	Re: Safety Switch Wiring Question Awesome, thanks Ogre for the help! __________________ Blayne



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