New compressor question

[CaseyJones]

I got a 6hp, 30gal Campbell Hausfeld air compressor from Mrs Claus. My barn is approximately 150' feet from my house. It has 30amps of power run in 10ga UF off my pool power supply. I have found there is just not enough power out in the barn for the compressor.

I have 2 options. One, install a sub-panel at the house and run 60amps to the barn in 6ga UF. Two, put the compressor in the garage (where is works perfectly) and run air line out to the barn. Option 2 would be, I think, cheaper and easier. What do y'all think would be the preferred solition?

I just thought of a third option. Put 150' of air hose on a hose reel and roll it out and in as needed. Hmmm...

[ 12-28-2003, 06:06 PM: Message edited by: CaseyJones ]

[Donn]

You have to make sure you have enough pressure at the end of a 150' air run, first. If you do, run a rigid line underground.

[capt jake]

Like Donn said, there is a surprising amount of pressure loss given the distance. One other concern will be the cold lone that you have buried will condense moisture, not so good. :(

I had a simular situation with my shop, as it was wired with 10awg (30 amp)over 400 plus feet. :eek: needless to say, I ended up abandoning this run and running 90 amp service on a new run, with a new panel in the shop (only 145 feet). Expensive, but well worth it in the end.

While you have a trench opened up, put another run of conduit for future?? stuff!! Easier now than later!!!!

Oh, and if you have a way of providing warm air to the compressor, you will vertually eliminate the moisture issue (as long as it doesn't get cold on tehat buried run). My old shop had the compressor in the furnace room and what a difference from it's former location in the garage. smile.gif

[ 12-28-2003, 06:33 PM: Message edited by: capt jake ]

[CaseyJones]

Here's a follow up question. Don't laugh.

Does doubled-up 12ga equal 6ga? I found 250' of 12/2 UF for $39. Was wondering if I could lay a pair of 12ga wires.

[capt jake]

Uh...No. I can't remember the mathematics, but it won't have the capacity to carry enough amperage.

Only correlation I have is if you had to hoses (2 1/2"), they won't flow even close to the amount that a single 3 1/2" will. Total GPM (lets say that is amperage)flowing is reduced by 75% with parallel lines vs a single. Thus a larger line (wire) is prefered over several smaller ones.

(The above may be wrong, it might be 50%, been a while on that subject). Suffice it to say it is the cross sectional are is not the same in the two.

Hope that made sense to you.

[ 12-28-2003, 07:18 PM: Message edited by: capt jake ]

[CaseyJones]

Glad I asked. ;)

And thanks for expanding on your answer. That makes sense. Two 2 1/2" pipes carry 117 cu inches of water per foot of pipe and one 5" pipe carries 235 cu inches per foot.

[ 12-28-2003, 07:21 PM: Message edited by: CaseyJones ]

[capt jake]

Bingo!!! I did make sense after all!! smile.gif

[CaseyJones]

capt jake

posted 12-28-2003 07:22 PM
Bingo!!! I did make sense after all!! Is that a first? ;)

[ 12-28-2003, 07:30 PM: Message edited by: CaseyJones ]

[capt jake]

Maybe not a first, but it seldom happens this quickly. smile.gif smile.gif smile.gif

[Tom Lathrop]

Normal engineering practice is to limit the loss in the feed line to no more than 2% of the line voltage. I have a 7hp (they call it "peak" hp) CH compressor that draws 15amps on a 240V line and I assume that you have the motor wired for 240.

The wire tables call for AWG 8 at 150 feet and 16 amps to limit voltage drop to a maximum of 2% of the line voltage. I would think that you are OK if you are coming directly off the main but since you are working off the Pool supply, there is obviously more loss. Paralleling the line with another AWG 10 line should solve your problem.

Before you do anything drastic, I suggest you measure the voltage at the motor at the end of 150 feet and at the pool to see how much drop you are getting at each location, when the motor is running, of course. If you are more than about 4.5V (less than the 240V at the main box), then something has to be done. It may be that the pool supply line is the main problem.

[capt jake]

Yup, see, we have an electrical engineer who will help you out!! smile.gif smile.gif I don't know any of the particulars nearly as well as Tom. smile.gif

Tom can help steer you straight, and I hope to gleen some knowledge as well. smile.gif

[Ken Hutchins]

I ran a 3/4 inch air line underground to my barn, about 110 feet. No problem, I made sure to have a down pitch to the barn and put a tee at the end with a short nipple and plug at the low point for a place to occasionally drain the condensate. My compressor is in the heated house basement therefore I am compressing drier air than what would be if the compressor was in the barn.

[CaseyJones]

Thanks, Tom. I forgot about the pool supply. I'm sure it isn't 10ga. I think I'll go with a 60amp sub-panel off my main, then run 6/2 UF out to the barn. I have an existing panel in the barn with 2 15amp breakers that I'll switch out.

[CaseyJones]

Hmmm....Ken. What did you use for the air line? Galvanized pipe?

[Tom Lathrop]

Casey,

A sub panel is definitely the best way to go. You will always want more circuits than you think you'll need.

I'm building a boat shed that I will want some power in but there is no more room on either the main or my shop sub panel. Have to put in another sub and most likely a new feed from the meter.

It's only money.

[Gord May]

Per your posted info', you are already experiencing a significant Voltage Drop in using #10AWG Cu. to feed a 30A Load. Suggest you consider using:
Paralell #10 for 30A (as Tom suggested)
-or-
At least #4 AWG Cu for 60A.
BTW:
I would expect that A 6HP Motor (a little unusual) might draw on the order of 35 Amps @ 230Volt (Nominal), so check your nameplate for FLA.
Paralell #12 AWG Cu is rated at [(2 x 20A) x 0.80] = 32 Amps if both conductors exactly the same length.
Paralell #10 rated 48 Amps as above.
Regards,
Gord

[ 12-30-2003, 06:41 AM: Message edited by: Gord May ]

[TimothyB]

Originally posted by CaseyJones:
Here's a follow up question. Don't laugh.

Does doubled-up 12ga equal 6ga? I found 250' of 12/2 UF for $39. Was wondering if I could lay a pair of 12ga wires.The Math isn't that hard, but basically current capacity goes up with sectional area of a conductor. So, assuming we have two wires, they are disk shaped in cross section.

So Area = PI*Radius^2

two wires of 1" diamater vs one wire of 2" diameter...

A = 3.14159 * (0.5)^2 = .78 Sq in

Total area = (0.78) * 2 = 1.57 Sq In

a 2" wire would be..

A = 3.14159 * (1)^2 = 3.14 Sq In

Since current capacity is roughly linearly related to cross sectional area, that means one 2" wire can carry something like twice the current as two 1" wires. So to get equal current volume you would need to use 4 1" wires, not 2.

--T

PS:

(a) Current = number of electrons/cubic metre x cross sectional area of the wire x speed of the electrons x electron charge
(b) Resistance = [resistivity x length of wire]/cross sectional area

[ 12-30-2003, 09:28 AM: Message edited by: TimothyB ]

[Alan D. Hyde]

Can't he just bump the line up to 240 volts for the run out, and then drop it down to 120 at the far end???

Won't need wires as big (or costly) that way.

OR (electrical experts here) am I wrong??? My knowledge of these matters doesn't go too far beyond the practical, and the fairly basic A= W/V... :D

Alan

[ 12-30-2003, 11:03 AM: Message edited by: Alan D. Hyde ]

[Dale R. Hamilton]

I had same problem 150 feet away- The ultimate, and I believe BEST solution was to call the electric company and have them run another 200 amp service to the shop/barn. Then you have unlimited power-'course you have 2 electric bills-but you're going to use the same amount of electricity. BTW- now that my shop is a businesss, I can take all the charges from the 2nd meter off my income tax.

[CaseyJones]

You know, Dale, I hadn't really thought of that. I think the only expense I'd have is burying the feeder line. That may be the way to go.

[CaseyJones]

Alrighty then. Entergy is scheduled to drop a new pole & run 200amp service out to the barn. all I have to do is bury the cable & do the service panel in the barn. What a great solution. :D

[Ron Williamson]

Alan
to get 240 volts,they use two 120 volt lines,that's why there are two hots(generally red and black)
Some utilities won't run two services to the same address(two meters to read,two bills to collect).
A sub-panel and the right-sized wire should be much cheaper anyway.
R

[Dale R. Hamilton]

utility companies are hungary for new customers-especially if you tell them your going to put in a business. They may not have to put in a new pole for 100 feet.

[Alan D. Hyde]

Ron, I understand that, but when I was in England they ran 240 (or 220) and could get more amps through smaller wires longer distances.

Or was I seeing things?

My understanding is that voltage may be analogized to water pressure in a line...

Alan

[Dale Genther]

Alan, you can put the same number of amps thru a particular wire no matter if it is 110 or 220 volts. The difference is, with say 15 amps thru a 14 gauge wire you can get more power with 220 volts than you can with 120 volts. 110 volts X 15 amps = 1650 watts vs. 220 volts x 15 = 3300 watts. BTW this figures are accurate for DC only there are other factors to take into accounts when using AC voltage, but it is close enought to being correct for this purpose. AC theory with lead/lag/ cos theta, etc. is a different animal than simple DC theory.

[CaseyJones]

Ma haid hurts after reading Dale's reply. :confused:

[Ken Hutchins]

I used 3/4 copper.

[capt jake]

Ma haid hurts after reading Dale's reply You don't need 200 amps!! 200 feeds most houses at present, do you need that much in a shop/barn?? I don't think so... IMHO! smile.gif

[warthog5]

Casey your doing the right thing, putting the new service in.
In my case I had 200amp service to the main outside the house, and the house only needed 100amps. [small house w/ natural gas everything]
I ran a line to the shop and supplyed 100amps to the shop. I then put a 125amp sub panel in the shop.
The only thing I can't run at the same time is the AC and the mig welder. It's not a big deal.

[CaseyJones]

CaptJake, no the barn doesn't need 200amps, but we have been seriously contemplating a detatched 3 car garage with an in-law suite attached. Between the barn and the 1 bedroom apt, we will have all the power we need.

[CaseyJones]

Well, rats.....

Engineer came out & told me it was going to be close to $2000 for the new pole & 400' run to the barn. He looked at my house main panel & told me we actually have 400 amps coming in off the street. My main panel is actually only using 150 of those 400 amps, so I have more than enough capacity for a sub-panel out to my barn.

[warthog5]

Darn Around here you call Gulf Power and tell them you need some power and they come right out and stick a pole in the ground and run power to it.
The last time I had it done, they came on a holiday and did it. No Charge.