changing from a 5hp to 7.5hp compressor

[jwalk2c]

Thanks for such a great forum.
I woke up at about 3 in the morning worrying about my compressor dilemma.
I recently bought a 5hp 60gal IR to replace trusty 30+ yr. old Craftsman/Devilbiss 3hp 30gal.
The IR instructions call for wire size 8 if distance does not exceed 50 ft.
Since my wire run was 65 to 70 ft I used 6-2 nm/vg wire rated at 55 amps connected to a 30 amp breaker.
I used a simple voltmeter for testing and there was no voltage drop at start up that I could tell and the wire is cool to the touch during operation. I get a constant 235 to 236 volts at the switch.
(That’s the limit of my electrical testing knowledge, not sure if this is a test for voltage drop or not)
Everything seems fine except I want to go up to a 7.5hp compressor for sandblasting and SEARS is allowing me to return this compressor. Got to love SEARS, there customer satisfaction guarantee has gave me piece of mind so many times.
Will my wiring be sufficient for a 7.5 hp IR compressor?My garage is unfinished so I can change the wiring if needed. I would rather do that than risk burning up the motor.
I can change the breaker anytime but I like to use the smallest breaker possible.
I will use a disconnect panel (main lug) at the compressor , (right now I have hardwired and soldered from the size 6 wire down to 10 wire to connect to the switch on compressor).
That is my second question. What is the correct wiring to use from a disconnect (main lug) box to the switch box on compressor. I tried to hard wire in the size 6 wire but it is impossible to connect to the small lugs on the 5hp switch. (Dang near impossible to route through the opening in switch box let along connect) That is why I had to solder in 10 gauge wire to the size 6 wires as a reducer for the last 2 feet. And it is not getting warm at this solder connection so I assume its ok for a temporary solution until I wire in the disconnect (main lug).
Thank You So Much.
Johnny Walker

 

[Alchymist]

Thanks for such a great forum.
I woke up at about 3 in the morning worrying about my compressor dilemma.
I recently bought a 5hp 60gal IR to replace trusty 30+ yr. old Craftsman/Devilbiss 3hp 30gal.
The IR instructions call for wire size 8 if distance does not exceed 50 ft.
Since my wire run was 65 to 70 ft I used 6-2 nm/vg wire rated at 55 amps connected to a 30 amp breaker.
I used a simple voltmeter for testing and there was no voltage drop at start up that I could tell and the wire is cool to the touch during operation. I get a constant 235 to 236 volts at the switch.
(That’s the limit of my electrical testing knowledge, not sure if this is a test for voltage drop or not)
Everything seems fine except I want to go up to a 7.5hp compressor for sandblasting and SEARS is allowing me to return this compressor. Got to love SEARS, there customer satisfaction guarantee has gave me piece of mind so many times.
Will my wiring be sufficient for a 7.5 hp IR compressor?My garage is unfinished so I can change the wiring if needed. I would rather do that than risk burning up the motor.
I can change the breaker anytime but I like to use the smallest breaker possible.
I will use a disconnect panel (main lug) at the compressor , (right now I have hardwired and soldered from the size 6 wire down to 10 wire to connect to the switch on compressor).
That is my second question. What is the correct wiring to use from a disconnect (main lug) box to the switch box on compressor. I tried to hard wire in the size 6 wire but it is impossible to connect to the small lugs on the 5hp switch. (Dang near impossible to route through the opening in switch box let along connect) That is why I had to solder in 10 gauge wire to the size 6 wires as a reducer for the last 2 feet. And it is not getting warm at this solder connection so I assume its ok for a temporary solution until I wire in the disconnect (main lug).
Thank You So Much.
Johnny Walker

First off, welcome to the forum
Now, #6 wire might have been a little overkill for the 1st compressor, but it works to your advantage in this situation. The reason you had trouble getting the wire into the lugs was because it normally isn't wired with that heavy of wire.

Best option with something like this is to run #6 - 3 w/g to a small sub panel near the compressor, then breaker and wire size can drop down from the sub panel. It also gives the option of other outlets such as welder from the same sub panel.

As to the larger compressor, post the electrical specs........

 

[PT Doc]

My Condor switch on my 80g5hp is rated for max wire gauge of 10. I spoke with personally and they stated that while you could jam in 8 or 6 wire in there the bend radius would not be good for the larger wire.

I agree with the recommendations to run the wire to as close as possible final location then use lighter gauge wire from the comp to the outlet or hard wired j box. I chose a 50 amp leviton switch and nema 6 50 receptacle. I always flip the disconnect after the comp is done being used.

 

[Charles (in GA)]

http://www.garagejournal.com/forum/showthread.php?t=131410

http://www.garagejournal.com/forum/showthread.php?t=46813

7.5 hp will come with a motor starter that will accept the #6 just fine. This has been discussed in the above threads. Install a 50 amp breaker and hook it up, it will work fine.

Charles