Connecting to Power - Single Phase 230v 5 hp Air Compressor - Ingersoll Rand

bulletpruf · 2026-05-21T10:08:09-0400

Electrical stuff generally makes my head hurt, but I just got a new IR air compressor from Tractor Supply - https://www.tractorsupply.com/tsc/p...OPygWrEEKNKHvKCxlkIflG8CoJsP9jMxoCecoQAvD_BwE - it's single phase, two stage, 5 hp.

The specs state: 21.5 Full Load Amps, Recommended Breaker Amp Size 40, Recommended Wire Gauge <50 ft. 8 Gauge (8 AWG).

I have 230v connected to a 30 amp (i.e., smaller than recommended) breaker traveling about 30' to a box on the wall next to the compressor.

I do have the instructions, but they're generic for several different models of compressor.

I'm inclined to hard-wire the compressor, but I would be ok with a plug, too.

I guess my first step is to confirm that I have 8 gauge wire going from the panel to the box on the wall.

Scott

I don't have a recent picture of the panel since the compressor breaker was added, but I'll get one.

mm08822 · 2026-05-21T10:28:50-0400

To be certain, you should post a pic of the motor nameplate (not the compressor nameplate.)

If the motor nameplate states 5 Hp @21.5A, I would use the #10s you already have in place. The disconnect needs to be verified that it is rated for at least 5HP at 240vac. Replace if not. ( A new installation would base numbers off of 28A and not your 21.5A for current code requirements.)

The 2pole 30a cb may be able to handle the start-up current. If not, replace it with a 2 pole 40a cb.

Hardwire straight to the disconnect otherwise a plug and receptacle needs to be rated for 5 hp also. (Those are expensive and are rarely needed.)

ETA: I'm assuming you have 10's in place already.

bulletpruf · 2026-05-21T10:43:05-0400

mm08822 said:
To be certain, you should post a pic of the motor nameplate (not the compressor nameplate.)

If the motor nameplate states 5 Hp @21.5A, I would use the #10s you already have in place. The disconnect needs to be verified that it is rated for at least 5HP at 240vac. Replace if not. ( A new installation would base numbers off of 28A and not your 21.5A for current code requirements.)

The 2pole 30a cb may be able to handle the start-up current. If not, replace it with a 2 pole 40a cb.

Hardwire straight to the disconnect otherwise a plug and receptacle needs to be rated for 5 hp also. (Those are expensive and are rarely needed.)

I'll get a picture of the motor nameplate when I confirm wire size.

Gotcha on the disconnect.

micromind · 2026-05-21T11:00:55-0400

Odd as it may seem, #10s and a 40 amp breaker would be code compliant for that motor.

Motors are different than normal stuff in the code.

wyliesdiesels · 2026-05-21T14:18:53-0400

motor circuits are easy

wire sized 125% of NEC FLC table amps (28a for 5HP as listed on nameplate not compressor label). This means 35a rated wire for 5hp

disconnect needed if more than 50' from and not within sight of panel

must be hardwired unless you can find plug and receptacle rated for 5 or more HP

Firebrick43 · 2026-05-21T14:31:44-0400

wyliesdiesels said:
motor circuits are easy

wire sized 125% of NEC FLC table amps (28a for 5HP as listed on nameplate not compressor label). This means 35a rated wire for 5hp

disconnect needed if more than 50' from and not within sight of panel

must be hardwired unless you can find plug and receptacle rated for 5 or more HP

To add to this, there are no inexpensive plugs and receptacles that are rated over 3 hp. All the NEMA ones are limited to 3 hp. Pin and socket plugs/receptacles get really salty if its actually listed.

micromind · 2026-05-21T18:31:11-0400

wyliesdiesels said:
motor circuits are easy

wire sized 125% of NEC FLC table amps (28a for 5HP as listed on nameplate not compressor label). This means 35a rated wire for 5hp

disconnect needed if more than 50' from and not within sight of panel

must be hardwired unless you can find plug and receptacle rated for 5 or more HP

This is true however, it should be noted that the #14/15A #12/20A #10/30A rules do not apply to motors. Use the 75C column in the NEC.

#14=20 amps, #12 = 25 amps and #10 = 35 amps.

bulletpruf · 2026-05-21T19:05:19-0400

wyliesdiesels said:
motor circuits are easy

wire sized 125% of NEC FLC table amps (28a for 5HP as listed on nameplate not compressor label). This means 35a rated wire for 5hp

disconnect needed if more than 50' from and not within sight of panel

must be hardwired unless you can find plug and receptacle rated for 5 or more HP

Panel is about 30' from the compressor and within eyesight, so I'm ok if I don't need the disconnect.

thanks

bulletpruf · 2026-05-21T19:19:26-0400

Went to the shop. Here's the label on the motor. Looks like 19 amps but with a max of 22.5 amps, right? 30A breaker and #10 AWG sufficient for this?

Here's a current shot of the panel.

There's 10 gauge solid core wire at the junction box next to the compressor.

At the panel, there's 10 gauge braided core wire coming off the 30 amp breaker for the air compressor circuit. The braided core and solid core wires are spliced together at a junction box about halfway down the run.

And here's the junction box that's halfway down the run. This is where I was doing to potentially get power for my Bridgeport clone mill (single phase 230v or potentially 3 phase). This is where the braided 10 gauge wire is connected to the solid core 10 gauge wire with wire nuts.

Any thoughts on how I should do this? If I have to run 8 gauge wire, I can live with that, but if 10 gauge is sufficient, I'm ok with sticking with that, of course.

I did a quick search and it appears that connecting solid to braided wires isn't unsafe.

PCustoms · 2026-05-21T19:26:52-0400

bulletpruf said:
Any thoughts on how I should do this? If I have to run 8 gauge wire, I can live with that, but if 10 gauge is sufficient, I'm ok with sticking with that, of course.

Anyone care to comment on the box fill?

micromind · 2026-05-21T19:28:17-0400

#10 is fine.

Solid and stranded are spliced together all the time, no problem.

Firebrick43 · 2026-05-21T19:30:56-0400

That looks like the 4" junction box has already far exceeded its fill rating but on the junction box next to the compressor knock a knockout out and get a premade armored whip from home cheepo or lowes. They are 30 dollars or so for a 10/3

https://www.homedepot.com/p/Southwire-1-2-in-x-4-ft-10-3-Ultra-Whip-Liquidtight-Flexible-Non-Metallic-PVC-Conduit-Cable-Whip-55311201/203009404

Screenshot_21-5-2026_19329_www.homedepot.com.jpeg

Chuckster in NJ · 2026-05-21T19:31:35-0400

PCustoms said:
Anyone care to comment on the box fill?

mm08822 · 2026-05-21T19:45:52-0400

PCustoms said:
Anyone care to comment on the box fill?

Nothing a 3# lump hammer couldn't make more room for.
And there's always extension boxes.

mike93lx · 2026-05-21T20:55:16-0400

PCustoms said:
Anyone care to comment on the box fill?

It's full

wyliesdiesels · 2026-05-22T00:13:11-0400

micromind said:
This is true however, it should be noted that the #14/15A #12/20A #10/30A rules do not apply to motors. Use the 75C column in the NEC.

#14=20 amps, #12 = 25 amps and #10 = 35 amps.

correct, have to read past 240.4(D) however the ampacity of NM-b doesnt change regardless if its feeding a motor. for 5HP, 35a rated wire is required. this means #10 THWN or #8 NM-b because #10 NM-b is limited to 30a

wyliesdiesels · 2026-05-22T10:17:07-0400

bulletpruf said:
Went to the shop. Here's the label on the motor. Looks like 19 amps but with a max of 22.5 amps, right? 30A breaker and #10 AWG sufficient for this?

wire size is based on nameplate HP NOT nameplate FLA....

bulletpruf said:
Here's a current shot of the panel.

Do you have 3Ø Delta? because skipping every 3rd breaker space indicates this And here's the junction box that's halfway down the run. This is where I was doing to potentially get power for my Bridgeport clone mill (single phase 230v or potentially 3 phase). This is where the braided 10 gauge wire is connected to the solid core 10 gauge wire with wire nuts.

bulletpruf said:

That box is way too full

bulletpruf said:
Any thoughts on how I should do this? If I have to run 8 gauge wire, I can live with that, but if 10 gauge is sufficient, I'm ok with sticking with that, of course.

I did a quick search and it appears that connecting solid to braided wires isn't unsafe.

#10 THWN is fine

bulletpruf · 2026-05-22T11:25:44-0400

wyliesdiesels said:
wire size is based on nameplate HP NOT nameplate FLA....

Gotcha. It's 5 hp.

wyliesdiesels said:
Do you have 3Ø Delta? because skipping every 3rd breaker space indicates this

The shop is wired for 3 phase, but the third leg has not been energized yet, if that makes sense. The electrician said he needs to add one more component before it's live.

wyliesdiesels said:
That box is way too full

Agreed. Is there a simple way to address this?

wyliesdiesels said:
#10 THWN is fine

Thanks

wyliesdiesels · 2026-05-22T11:45:10-0400

bulletpruf said:
Agreed. Is there a simple way to address this?

bigger can but it wont be quick...

Connecting to Power - Single Phase 230v 5 hp Air Compressor - Ingersoll Rand

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