Yes, it's a compressor wiring question...

[Slowcorrado]

Sorry to post ANOTHER compressor wiring question. But, I'm a firm believer that you can't be too careful and thorough with this type of thing.

I have an old Ingersoll-Rand T30 I'm installing in my small garage and would love some clarification on the proper wiring. I'm located in PA (uses NEC 2012 to my knowledge). I've attached a pic of the motor information plate and compressor





Based on the plate I see it's single phase rated at 230 volts, and I'm guessing 25 amps? My 200A service is 50' away. The motor has its own external "control" box attached that has a reset.

So finally the question: Using copper non-metallic cable (romex), will 10/3 be sufficient and not overkill and what amperage double-pole panel breaker do you suggest? Basic logic says 30A, based on the wire size, but I thought there was some required upsizing based on startup current.

Suggestions and experiences welcomed! Any questions about my setup, please ask. Thanks.

 

[The Cobbler]

not sure on the wire size, but you don't need 3 wire for 240 volt.
you need 2 wire with ground

 

[LS6 Tommy]

Not sure of the code requirements for wire size either, but you can't run NMC on the surface of a block wall. You'll need some sort of conduit, a junction box/disconnect and a whip to the unit.

Tommy

 

[Slowcorrado]

Not sure of the code requirements for wire size either, but you can't run NMC on the surface of a block wall. You'll need some sort of conduit, a junction box/disconnect and a whip to the unit.

Thanks for the response, and shame on me for not posting the details on the connection. Existing whip and junction/control box are pictured below. Will be using PVC conduit to direct the NMC to the control box.

 

[sberry]

You need a number 8 cable or 10 in pipe. Breakers from 30 to 50 but let's pick one in the middle to give a little overhead for starts,,, 40.

 

[sberry]

You need a number 8 cable or 10 in pipe. Breakers from 10 to 50 but let's pick one in the middle to give a little overhead for starts,,, 40.

Can you see the panel from this location, in the same room?

 

[Slowcorrado]

Can you see the panel from this location, in the same room?

Yes, just a large basement. Kind of have to walk around a framed staircase to get to the panel though. How did you arrive at #8 wire In the post above?

 

[sberry]

5hp motor requires 8 cable, its in the big book.

 

[wyliesdiesels]

Why are you running NM in conduit?

Better to run THWN.

For wire size, 5HP needs #8 NM-b or #10 THWN in pipe.

 

[Slowcorrado]

Why are you running NM in conduit? Better to run THWN. For wire size, 5HP needs #8 NM-b or #10 THWN in pipe.

I was going to run the NM through holes in the joists in free air without conduit. Only use the conduit for the short vertical run against the block wall to provide physical protection. I don't have any experience with conduit/single wires. Was worried I couldn't buy it by the foot cheaply like the romex. Also looking for a breaker suggestion.

 

[sberry]

Whoops, phone posts, 40 breaker.

 

[Aceman]

8-2 NM on a 40 amp breaker would be my recommendation as mentioned above by the other posters.

Use a bell end fitting where the cable enters the conduit sleeve.

 

[Slowcorrado]

Thanks to everyone who have given their insight into my issues! Now I just need to find some 8/2 reasonably priced, or THHN 10awg + conduit that's not more expensive!

Either way, it will be nice to get the compressor wired-up and ready for the plumbing part of the project!

 

[wyliesdiesels]

Some other things to keep in mind.

If the panel is not within sight of and further than 50' from the compressor then it needs a disconnect. The disconnect needs to be rated for at least 5HP.

Also, you obviously are already doing it but for future readers, this compressor needs to be hardwired because its rated more than 3HP.

 

[Slowcorrado]

If the panel is not within sight of and further than 50' from the compressor then it needs a disconnect. The disconnect needs to be rated for at least 5HP.

Great point. I am less than (but very close to) 50' from the panel and would need to walk around a framed staircase to access the breaker panel. I'm sure I could argue with an inspector about it, but would my switch/protection box count as a "disconnect"?



If not, what would you suggest? I don't really have a problem installing something to be sure.

 

[wyliesdiesels]

if you have to walk around something to see the breaker panel then that means you cannot see the panel.

no the motor controller doesnt count as a disconnect.

An A/c pullout disconnect would work...

 

[Norcal]

if you have to walk around something to see the breaker panel then that means you cannot see the panel.

no the motor controller doesnt count as a disconnect.

An A/c pullout disconnect would work...

And pullout discos are cheap.

 

[bczygan]

if you have to walk around something to see the breaker panel then that means you cannot see the panel.

no the motor controller doesnt count as a disconnect.

An A/c pullout disconnect would work...

If the compressor is in it's own room, and the panel is in the shop, is a disconnect required, and does it go in the compressor room?

Bill

 

[mike93lx]

If the compressor is in it's own room, and the panel is in the shop, is a disconnect required, and does it go in the compressor room?

Bill

Seems pretty clear. Can you see the panel from the compressor?

 

[Augus7us]

Why are you running NM in conduit?

Better to run THWN.

For wire size, 5HP needs #8 NM-b or #10 THWN in pipe.

Curious, why does the NM-b have to be 8 and not 10 like the THWN?

 

[wyliesdiesels]

Curious, why does the NM-b have to be 8 and not 10 like the THWN?

because NM-b is limited to 60* c ampacities.

A 5HP motor, by code, needs 35a rated wire and #10 NM-b is limited to 30a in the 60* c column.

 

[Slowcorrado]

Curious, why does the NM-b have to be 8 and not 10 like the THWN?

I believe it's a temperature issue. NM-b is 60deg C while THHN is 75 or 90deg C. Also, the book shows 8/2 NM-b copper as supporting 40A and 10awg THHN as supporting 35A. 10/2 NM-b copper is only 30A. (in my case the conductor needs to be rated for 35A)

Now, on to a disconnect question:

https://www.homedepot.com/p/Square-D-QO-60-Amp-240-Volt-7-4-kW-Non-Fuse-AC-Disconnect-QO200TRCP/202353314



Will this suffice and be a good choice, or should I go cheaper with just a $7 pull-out in a plastic box?

 

[wyliesdiesels]

would need to verify HP rating.

But why complicate things and spend more money?

Just get the pull out D/C. they do come in metal boxes as well

 

[Slowcorrado]

would need to verify HP rating.But why complicate things and spend more money? Just get the pull out D/C. they do come in metal boxes as well

Point taken, the one shown above is $12 instead of the $7 cheapie. Rated to 10HP (60A).

 

[Fisherguy]

...
... would my switch/protection box count as a "disconnect"?



If not, what would you suggest? I don't really have a problem installing something to be sure.

I'm planning the wiring for my shop including my 5 hp Eagle compressor, what is the difference between the switch (or motor controller) shown in this pic and a "disconnect"?

My compressor will be 35 ft from the panel and withing site so I can get away with a switch like in the pic?

 

[wyliesdiesels]

I'm planning the wiring for my shop including my 5 hp Eagle compressor, what is the difference between the switch (or motor controller) shown in this pic and a "disconnect"?

My compressor will be 35 ft from the panel and withing site so I can get away with a switch like in the pic?

A switch does not count as a disconnect needed for servicing.

In your situation no disconnect is needed since the breaker can act as a disconnect.

 

[Fisherguy]

That's what I don't get, doesn't a switch disconnect the compressor from power?
Just trying to understand...

 

[Toothaker]

That's what I don't get, doesn't a switch disconnect the compressor from power?
Just trying to understand...

The NEC specifically calls out the switch as not being a disconnect, and it requires a disconnect if not within 50 feet or not visible from the location of the compressor.

Take the cover off the switch, and the wires are energized on one side of the switch.

 

[teamextreme]

Part of the confusion is that is not a "switch" as everyone is calling it, it's a motor starter. Yes, putting the HOA in OFF mode will shut it off, but there isn't a means to lock out the switch and I suspect that's the reason it's not considered a disconnecting means.

 

[Fisherguy]

OK thanks guys.

 

[Norcal]

Part of the confusion is that is not a "switch" as everyone is calling it, it's a motor starter. Yes, putting the HOA in OFF mode will shut it off, but there isn't a means to lock out the switch and I suspect that's the reason it's not considered a disconnecting means.

While it is code compliant to switch 1 leg of a 240V 1Ø circuit, or 2 legs of a 3Ø circuit, a disconnect must break all conductors, a selector switch does not comply as a disconnect.

 

[teamextreme]

While it is code compliant to switch 1 leg of a 240V 1Ø circuit, or 2 legs of a 3Ø circuit, a disconnect must break all conductors, a selector switch does not comply as a disconnect.