Compressor wiring question

[RWD]

Hi guys,
I picked up an old Speedaire 30 gal. compressor with a 2 hp. motor. I want to put it in my garage but don't have 220v in there yet. I will need to run the wire in conduit about 100' from the breaker box in the house basement to the attached garage. Here is the info on the compressor:

mod. #2z499b
Dayton motor mod. #9k324d
2 hp.
3450 rpm
1 phase fr h56 type k (no idea what this is)
ser. fact. spcL (no idea about this either)

115v 24 amp
230v 12 amp

Ok, now for the questions. I assume it would be better to use the compressor with 230 v? If so, what gauge wire would I need to run this safely? At 100' from the breaker box, I'm guessing #10. Or will #12 work? What size breaker should I use?

While I'm pulling the wire, I think I want to add another seperate 110v circuit out to the garage also. I'd like it to be #12 wire. This would be for future tools, maybe a larger 110v. table saw. With #12 wire, what size breaker should this circuit be? I'll be using 1/2" metal conduit. Can I safely put all 4 wires (2 for 220, 2 for 110) in the same conduit? I will add a few junction boxes along the 100' to make the pulling easier.
Thanks guys,
Bob

 

[84TurboBuick]

For a run that long I would use 10/2 or 10/3 for the 220 and 12/2 or 12/3 for the 110.

If you have power that far from the garage, you might consider putting in a small 100amp box in your garage. That way you could have more breakers and it would elimate all those long runs.

 

[markb1]

You could pull #12cu. (30amp breaker) for the motor and not suffer from voltage drop. You could also pull #12 cu. for your 20amp 120volt circuit.

But, as stated above you would be wise to pull 4-#8 cu. in a 3/4" emt conduit to a sub panel (50amp breaker at the main panel) no main breaker needed at the sub panel.

http://www.foxelectricsupply.com/co...l.asp?qsCatID=25839&qsProductNo=GEDTLM1212CCU

Use stranded thhn or thwn wire. Use wire lub when you pull and don't put more than 360degrees of total bends between pull points.

Hope this helps
Mark

 

[Charles (in GA)]

When you go over 3 current carrying wires in a single conduit, code says you must derate the wire's amp capacity. With four wires, you derate to 80% of the wire's original capacity. This would probably be insignificant if you are using all 90C rated wire. as it has a higher amp rating to begin with. As an example, 12 gauge THHN wire, the stuff on reels commonly used in conduit, being 90C rated, is OK for 30 amps up to 86F ambient temperature and not over three current carrying wires in a "raceway" (your conduit)(table 310.16 of the NEC). However, most boxes and breakers and devices that might be connected to the wire are probably only 60C rated and thus the wire itself becomes rated at no higher than the lowest rated device connected to it. At 60C the wire is only good for 25 amps. Since you have to derate to 80%, that 25 amp capacity wire becomes a 20 amp wire, still no issue as you are only going to use a 20 amp breaker anyhow, but...... where is the conduit going to be located? You said metal (the thin stuff, EMT, I suppose) with pull boxes, so are you running it in an attic? If so, the temperature surely exceeds 86F at times, so you again have to derate the wire. Attics easily go to 120F so using this temp we take the 24 amps and mutiply by the derate factor in the same table mentioned above, and we get 11.6 amps. This means you will be using a 10 amp breaker on this circuit!!!! If the attic goes hotter than this, the derate factor is even more. The next problem is the voltage drop. I think that at a 100 ft and a heavy load on the 120V circuit might see voltage drop in excess of the code recommended 3%.

Don't expect to pull Romex house wire thru the conduit, It CAN be done, but you WILL regret ever thinking about it., and the two circuits you want to pull won't fit in the 1/2 conduit if they are romex, as you have fill limits you have to observe.

I tell you all of this to suggest you need to rethink the whole thing and consider running a single, heavy 240V subfeed circuit to a small panel at the garage. Depending on where you are running the cable, and the type of cable you use, you may not even need conduit and the end result may not cost you much more but in the end become a lot more functional.

Charles

 

[PAToyota]

I tell you all of this to suggest you need to rethink the whole thing and consider running a single, heavy 240V subfeed circuit to a small panel at the garage.

Excellent advice right there.

 

[RWD]

Thanks for the quick replies! I thought about a sub-panel but I think it would be overkill in my case. I should have mentioned that I allready have 2 other circuits in the garage and don't really any more other then the 220 for the compressor and MAYBE the extra 110 that I was thinking about adding. BTW, the conduit will be run in the ceiling of the basement with temps no greater then 70.
So if I go with #12 wire, will 20 amp breakers be good for both the 110 and 220 circuits?
Thanks, Bob

 

[PAToyota]

Another advantage of the sub-panel would be that you don't have to run to the basement if you trip a breaker... If it were me, I'd consider running the sub-panel and then run the existing circuits into it as well.

 

[Freejack]

Yet another vote for the subpanel, it makes life so much easier, and gives you much more flexibility in the future.

BTW, on your motor specs, the third line indicates that its a 56H frame, not sure what the Type K means, it could be the manfucturer's nomenclature.

The forth line means the Service Factor is "Special" indicating a definite purpose motor, in this case an Air Compressor.

We (Emerson Motors) had made many of the Dayton motors in the past, but I was having little luck pulling up that model.

Jake

 

[markb1]

2 pole 30a breaker for compressor
1 pole 20 amp " for 120v plug circuit