Best practice for wiring a compressor

[Noltz]

I picked up a HuskyPro 60 gallon compressor that has no cord on it. I have a 12/2 run into the tool room on a 15A double pole breaker. I started mocking it up with BX but I don't see anyone else using BX but SOW or SOOW. I do have SOOW on hand but is there any reason not to use BX? Is vibration an issue?

 

[mm08822]

I would use the cord as it can take the vibration much longer. Bx/ac is best for permanent, fixed, vibration free installs. Not on equipment.

 

[Bert_]

The #12 should be okay. 15 amp breaker isn't going to cut it. You could try a 20 but I would recommend a 30A

 

[sparky 1971]

I have pretty much the same compressor under a different name. I have it on #12 and a 30 amp breaker. I never considered trying it with a 15 or 20. And I used #12 cord, I don't like solid wire for motor connections.

 

[u2slow]

Mine is rated the same. It runs and holds fine on #12 and a 20A breaker. Uses a 6-20R plug actually. Stranded cord would be best.

 

[Noltz]

I'll find myself a 20A and rewire with SOOW. Thanks for the input.

 

[wyliesdiesels]

yeah i wouldnt use BX (you sure its BX? or is it MC?).. get some SOOW cordage

 

[johnre]

I have a 12/2 run into the tool room on a 15A double pole breaker.

If you're going to use this feed from your panel into the tool room and change it from a 120 V feed (hot - neutral - ground) into a 240 V feed (H1 - H2 - ground) by using a new breaker, then wrap the white wire with red tape on both ends. It's now a hot, not a neutral, and should be marked so.

 

[u2slow]

yeah i wouldnt use BX (you sure its BX? or is it MC?).. get some SOOW cordage

Canadian "BX" is AC90.... if manufactured in the last ~40 years.

 

[Noltz]

If you're going to use this feed from your panel into the tool room and change it from a 120 V feed (hot - neutral - ground) into a 240 V feed (H1 - H2 - ground) by using a new breaker, then wrap the white wire with red tape on both ends. It's now a hot, not a neutral, and should be marked so.

I'm fortunate that the tool room was wired in the walls with an 8/3, 12/2 and a spare 15A circuit terminating in an enclosure. The outlets and lighting are on yet more circuits. The prior owner did a lot of epoxy work and this room is heavily insulated, had a gas run (I removed it) and vent ducting to the outside, plus all this power. The 12/2 was 120v 20A for a baseboard heater but I'm not going to be putting it back in so I'll recycle the circuit.

I'm glad you mentioned the tape to reidentify; I did this very thing wiring L6-20 receptacles for my lathe and tire balancer so I'm glad it's still the norm.

 

[Firebrick43]

Mine is rated the same. It runs and holds fine on #12 and a 20A breaker. Uses a 6-20R plug actually. Stranded cord would be best.

6-20 is only rated to 2 hp, the OP motor is 4 hp if we go by the kw number. If you use the amps it’s still over 2hp

Most NEMA plugs are limited to 3 hp on motors.

 

[Cruzan80]

Does the OEM plug rule (OEMs can violate NEMA if original) apply if one sources a NOS plug from the same machine?

 

[johnre]

6-20 is only rated to 2 hp, the OP motor is 4 hp if we go by the kw number. If you use the amps it’s still over 2hp.

My 3 HP table saw came equipped with a 240 V NEMA 6-15P plug on it; the instructions say to use a 20 A power mains with a suitable receptacle (NEMA 6-15R or 6-20R).

My (so called) 4 HP air compressor came equipped the same way with a 240 V NEMA 6-15P. It only delivers 7.7 SCFM @90 PSI so I'm guessing it's about 2.5 HP actual.

Both of these are on separate circuits with 20 A breakers and 12/2G romex feed from my panel about 25 feet away.

It's hard to make hard and fast rules with power mains ratings when the air compressor manufacturers play games like this. I thought they would have learned their lesson a while back with the lawsuit settlement, but apparently not.

 

[u2slow]

6-20 is only rated to 2 hp, the OP motor is 4 hp if we go by the kw number. If you use the amps it’s still over 2hp

Most NEMA plugs are limited to 3 hp on motors.

His motor is rated SPL just like mine. Factory 6-20R cord plug.

There is deliberately no HP rating on the motor, otherwise the HP limit of the plug would apply.

 

[sparky 1971]

His motor is rated SPL just like mine. Factory 6-20R cord plug.

There is deliberately no HP rating on the motor, otherwise the HP limit of the plug would apply.

Mine is also SPL, but it has a sticker on the tank that claims 3.7 HP. All I can say to that is B.S. Just like my 5.5 HP Shop Vac.

 

[u2slow]

Mine is also SPL, but it has a sticker on the tank that claims 3.7 HP. All I can say to that is B.S. Just like my 5.5 HP Shop Vac.

Heh. I know those shop vacs.

I feel the 10cfm@90psi spec is the best measure of the machine. And I know its worked perfectly on #12 and 20A breaker for the past 23 years or so.

 

[nadogail]

Compressor Horse Power ratings were done by the same marketing spokespersons that were employed by the Detroit Automakers.

 

[wyliesdiesels]

My 3 HP table saw came equipped with a 240 V NEMA 6-15P plug on it; the instructions say to use a 20 A power mains with a suitable receptacle (NEMA 6-15R or 6-20R).

My (so called) 4 HP air compressor came equipped the same way with a 240 V NEMA 6-15P. It only delivers 7.7 SCFM @90 PSI so I'm guessing it's about 2 HP actual.

Both of these are on separate circuits with 20 A breakers and 12/2G romex feed from my panel about 25 feet away.

It's hard to make hard and fast rules with power mains ratings when the air compressor manufacturers play games like this. I thought they would have learned their lesson a while back with the lawsuit settlement, but apparently not.

they can do that because their setup gets listed in that manner.

 

[Bert_]

If a manufacturer is allowed to build it I would have no problem doing the same thing. It doesn't magically become a hazard if you put it on yourself.

I'm going to put in (4) 10-50 receptacles on Monday to run a 10hp 1ph motor. Your 20A plug will be fine

 

[Doozer75]

Liquid Tight Flexible Metal Conduit is the only thing I would consider for my air compressor hookup.

 

[Norcal]

Liquid Tight Flexible Metal Conduit is the only thing I would consider for my air compressor hookup.

I prefer the non-metallic version, cheaper, easier to work with, & I pull a grounding conductor anyway, 1/2" metallic sealtight has to have one for circuits rated over 20A.

 

[wyliesdiesels]

If a manufacturer is allowed to build it I would have no problem doing the same thing. It doesn't magically become a hazard if you put it on yourself.

I'm going to put in (4) 10-50 receptacles on Monday to run a 10hp 1ph motor. Your 20A plug will be fine

why wouldnt you use a 6-50r?

 

[Doozer75]

If the wires ever catch fire, I prefer to have them inside the metallic type.
Cheap insurance.

-Doozer

 

[sparky 1971]

why wouldnt you use a 6-50r?

I think I can safely answer that. Every. Single. Farmer. In the state of Iowa thinks that the only receptacle available is a 10-50R. Air compressors, welders, tire machines, twotwenny augers, everything has had the cord end chopped off and a 10-50P stuck on. I even had the local mechanic call me up and ask me to change the end on his new welder. "It came with some fancy damned cord that won't plug in". Of course, I showed up with a 6-50P only to find out he wanted to plug it in to a 10-50R. Back to the supply house for 10-50P because the plasma cutter had a 10-50P on it and they used the same receptacle.

 

[wyliesdiesels]

I think I can safely answer that. Every. Single. Farmer. In the state of Iowa thinks that the only receptacle available is a 10-50R. Air compressors, welders, tire machines, everything has had the cord end chopped off and a 10-50P stuck on. I even had the local mechanic call me up and ask me to change the end on his new welder. "It came with some fancy damned cord that won't plug in". Of course, I showed up with a 6-50P only to find out he wanted to plug it in to a 10-50R. Back to the supply house for 10-50P because the plasma cutter had a 10-50P on it and they used the same receptacle.

WTF

 

[Bert_]

WTF

Yes, in the ag world the 10-50 is standard. You buy a portable auger and the dealer will automatically install a 10-50. If I put anything else on I will get complaints, "won't fit my other plugs"

I just looked at the online inventory at my local electrical supplier. They have (33) 10-50's, and (5) 6-50's. So that pretty much shows what everyone is using.

 

[Bert_]

Got a little inverter welder earlier this summer and one of the first things I did was to "fix" the plug.

Could have made an adapter but when 90% of the receptacles are already a 10-50 why not just go with the flow.

 

[wyliesdiesels]

I guess some people just don’t care about standards

 

[Bert_]

I think I can safely answer that. Every. Single. Farmer. In the state of Iowa thinks that the only receptacle available is a 10-50R. Air compressors, welders, tire machines, twotwenny augers, everything has had the cord end chopped off and a 10-50P stuck on. I even had the local mechanic call me up and ask me to change the end on his new welder. "It came with some fancy damned cord that won't plug in". Of course, I showed up with a 6-50P only to find out he wanted to plug it in to a 10-50R. Back to the supply house for 10-50P because the plasma cutter had a 10-50P on it and they used the same receptacle.

I'm surprised you don't keep a 10-50 plug and receptacle on the truck

 

[LS6 Tommy]

Generally speaking, when equipment doesn't come with a cord it's meant to be hard wired. Just looking at it from a purely technical point of view, if it's not "portable", it shouldn't be wired with any cord, it should be hard wired.

Tommy

 

[sparky 1971]

I'm surprised you don't keep a 10-50 plug and receptacle on the truck

I keep a couple at home now, but to be honest, I do very little work around where I live and that's by choice. I don't want to, everything is **** and nobody want's to spend the money to make it remotely close to being right so I just make the 30 mile drive to the city every day where I can charge more. Also, the drive home helps me get wound down and shift gears in order to be ready for the commotion of the home life.

 

[Firebrick43]

His motor is rated SPL just like mine. Factory 6-20R cord plug.

There is deliberately no HP rating on the motor, otherwise the HP limit of the plug would apply.

SPL means nothing to the NEC. Its just an attempt to fool people into buying substandard ****. And it works apparently.

If it does not have horsepower listed on the nameplate, you would have to follow

430-6(A)(1)

"where the motor is marked in amperes, but not horsepower, the horsepower rating shall be assumed to be the corresponding to the value given in Table 430-248"

According to the table the motor is over 2 hp.

Now if the cord and plug comes on the compressor from the factory wyliesdiesels in post 18 would be correct. Although I still wonder about the receptacle side motor hp being exceeded?

But you are suggesting that the OP use a plug that is not factory installed and isn't rated for the HP per NEC 430-6(A)(1) and the manufacture of an installed on cord 6-20P just because yours is.

That would be non code compliant advise.

 

[u2slow]

SPL means nothing to the NEC.
...
But you are suggesting that the OP use a plug that is not factory installed and isn't rated for the HP per NEC 430-6(A)(1) and the manufacture of an installed on cord 6-20P just because yours is.

That would be non code compliant advise.

Interesting contradiction.

Modifying a consumer product (adding a cord plug) is up to the consumer. Code has no say in that.

His motor has the identical nameplate specs as mine. If my motor burnt out, i would replace it with another (also same as his), and attach the 6-20p cord again. No difference whether its my old motor, new motor, or his motor. Replacing motors with like-for-like is a common job for me as an electrician.

 

[Firebrick43]

Interesting contradiction.

Modifying a consumer product (adding a cord plug) is up to the consumer. Code has no say in that.

His motor has the identical nameplate specs as mine. If my motor burnt out, i would replace it with another (also same as his), and attach the 6-20p cord again. No difference whether its my old motor, new motor, or his motor. Replacing motors with like-for-like is a common job for me as an electrician.

Its no contradiction.

The code does not allow the consumer to do whatever the hell they want. Many get away with doing what ever they want but that doesn't make it right.

And if you are not using factory parts, then no its not listed and you shouldn't be doing that. Its common for any electrician to replace with similar motors but you still have to follow code when doing so.