Compressed Air Questions

stppinz · Nov 16, 2006

I have a couple of questions on installing a compressed air system.

1 - Do any of you guys have your compressor on a on/off switch? I just don't want my compressor cycling when It is not in use. I guess if my piping is tight, it wouldn't be necessary.

2 - I would like to install a few different air outlets around my shop. What pipe did you use? and did you use a manifold or just Tee of lines?

Thanks for your time

Shane

Charles (in GA) · Nov 16, 2006

Compressed air systems and piping have been beat to death here in the past year or so. You might do some searches to turn up threads on the subject, If I have time I will and post the links.

I leave my compressor on all the time, unless I go out of town. most portable plug in units have switches or levers on the pressure switch to shut them off. If you have a stationary compressor that is hardwired to the building (like mine) then the code requires that you have a disconnect within line of sight from and no more than 50 ft from the equipment. The disconnect can be the circuit breaker in the panel if it meets the requirements.

My disconnect is a sub panel about four feet from the compressor with a circuit breaker in it.

Charles

Charles (in GA) · Nov 16, 2006

stppinz · Nov 16, 2006

Thanks Charles - Yea, I should of just searched first.

When I build my shop, I built a little room off the back to house the compresser. Just the supply and power will come through the wall. It will be a little bit harder to switch off the compresser at the unit. I guess if I make the piping tight enough I won't have to worry about it.

Stuart in MN · Nov 16, 2006

stppinz said:
Thanks Charles - Yea, I should of just searched first.

When I build my shop, I built a little room off the back to house the compresser. Just the supply and power will come through the wall. It will be a little bit harder to switch off the compresser at the unit. I guess if I make the piping tight enough I won't have to worry about it.

Assuming your air compressor will be hard wired, and further assuming it's not powered from a subpanel located in that same little room, a local disconnect switch is required by code. As Charles said, it needs to be within line of sight of the compressor and within 50 feet.

If you install it with a plug on a cord and a receptacle on the wall, that will serve as a disconnect and you don't need a switch.

Charles (in GA) · Nov 16, 2006

Stuart in MN said:
Assuming your air compressor will be hard wired, and further assuming it's not powered from a subpanel located in that same little room, a local disconnect switch is required by code. As Charles said, it needs to be within line of sight of the compressor and within 50 feet.

If you install it with a plug on a cord and a receptacle on the wall, that will serve as a disconnect and you don't need a switch.

That is true, but it might actually turn out to be more expensive than a disconnect. The disconnect doesn't have to be a circuit breaker, just a switch or pull out, in the case of a compressor mounted under a shed roof or a storage room type of location, a weather proof disconnect box like is used for outside aircondiitioning units would work fine, most are rated to 60 amps, and cost $10-$12 at Home Depot or Lowes. If you buy a range/stove cord (50 amp rated) and a receptacle, you will probably spend more than that.

Simply put, weigh all the possibilities, the plug and cord is one I've seen used on water heaters before, and is a good idea.

Pulling the circuit breaker to shut off the compressor is a possibility, but tripping it every day will eventually wear it out, and with most brands (Siemens and GE come to mind) only 15 amp and 20 amp single pole breakers are rated as switches. Other sizes and configurations are not rated as switches and should not be used regularlly as shutoffs for devices or circuits.

Charles

Stuart in MN · Nov 16, 2006

Yes, an air conditioning disconnect would be a good choice, since they're cheap and easy to find.

Pops · Nov 16, 2006

I have read through, skimmed them actually, the threads Charles listed above. There is some great infomration there, however one thing I noted was in the first one the statement was made that the pipes were set up to drain back to the tank, isn't it supposed be the other way around? Aren't you supposed to have the pipes drain away from the tank to an outlet?

J.

Charles (in GA) · Nov 21, 2006

Stuart in MN said:
If you install it with a plug on a cord and a receptacle on the wall, that will serve as a disconnect and you don't need a switch.

Happened on to something in the NEC that was relevant, thought I'd bring it up. This is a technicality, but............

2005 NEC Article 430.109(F) "Cord-and-Plug-Connected Motors" For a cord-and-plug-connected motor, a horsepower-rated attachment plug and receptacle having ratings no less than the motor ratings shall be permitted to serve as the disconnecting means...........

Thus, the plug and receptacle would have to be marked with horsepower ratings on them. Amp ratings would not be sufficient. I'm not sure how common that is, but would eliminate the use of such things as a range/stove cord, plug, and receptacle. Will have to pay special attention to this next time I'm in Lowes, HD, etc.

NEC uses horsepower ratings for a number of things, instead of amperage.

Charles

ZRX61 · Nov 22, 2006

Mine is fed with a 20a/220v ciruit & there's a service disconnect right next to it. I also have a ball valve at the comp to isolate it from the lines.(& theres a breaker box/panel about 7ft from the compressor)

W-Cummins · Nov 23, 2006

Charles (in GA) said:
Happened on to something in the NEC that was relevant, thought I'd bring it up. This is a technicality, but............

Thus, the plug and receptacle would have to be marked with horsepower ratings on them.
Charles

They are required to be rated, but there is no requirement for them to be marked on the device. I have boxes of them that are HP rated ( hubbell ,S&P, leveton, etc.. ie. HBL2431 L16-20p is rated at 5hp) but have no hp markings on the plugs.

William...

malibu101 · Nov 24, 2006

As everyone above said, have a way to disconnect it and use it. Even if there is a valve at the start of the outgoing line there could be a problem with the air compressor itself causing massive air loss therfore the compressor will either run non-stop or kill itself trying to keep up until you discover it.
When leaving the shop for the night, shut the compressor off. Smart insurance.

Charles (in GA) · Nov 24, 2006

W-Cummins said:
They are required to be rated, but there is no requirement for them to be marked on the device. I have boxes of them that are HP rated ( hubbell ,S&P, leveton, etc.. ie. HBL2431 L16-20p is rated at 5hp) but have no hp markings on the plugs.

William...

OOps, sorry about that misstatement.

Charles

DIGGER_DAVE · Nov 24, 2006

malibu101 said:
As everyone above said, have a way to disconnect it and use it. Even if there is a valve at the start of the outgoing line there could be a problem with the air compressor itself causing massive air loss therfore the compressor will either run non-stop or kill itself trying to keep up until you discover it.

When leaving the shop for the night, shut the compressor off. Smart insurance.

Couldn't agree more!

I lost (destroyed) a compressor a couple of years ago when a hose burst, and it burned up the motor when the compressor siezed. (I was away for a week and the breaker was over-rated)

NOW - At the man door of my shop; is a box with an INDICATOR LAMP (showing that the compressor has power) and a TOGGLE SWITCH that switches low voltage (18 VAC/door bell transformer) to a Heavy Duty DPST 220 VAC RELAY at the compressor. (compressor on second story of my shop)

On the way out the door; the indicator lamp reminds me - Compressor Power STILL On - switch it off!!

Also ... in the same box; an indicator lamp and switch to "kill" power to the overhead door operator. (little extra security)

Another indicator lamp tells me if the shop overhead door is/or isn't, totally closed. (in warm weather I like to leave it open a "crack"; and I tend to forget it's open!!)

kenfath · Nov 26, 2006

(Many) Year ago, when I was in the Army we had the opportunity to acquire a fairly large Gardner Denver air compressor from a closed Nike battery for installation in the motor pool. We were never able to get the piping leak free. The compressor, tank and motor controls shared the utility room with the electric panel, furnace and hot water heater. The utility room which was not readily accessable from inside the motor pool building. We solved the leak problem by installing a globe valve where the pipe entered the motor pool. At the end of the day the valve was closed, the piping bled/leaked off. At the start of the day the valve was opened and the system was charged.

I'm sure someone will ask why did it leak? Midnight scrounging procured the compressor, tank, controls, pipe and fittings. Only the compressor and tank were like new. The leaks were really minor and were of no great concern especially to a bunch of PFCs and SPC4s that were delighted to have compressed air where they needed it. Most likely we needed to rethread some of the pipe in order to get it leak free: however, those tools weren't readily available.

I set up my home shop with a shut off valve between the compressor and the shop piping. I don't have to worry (as much) about a hose blowing out, or someone playing with the blowgun or other tools, when I'm not around.

DIGGER_DAVE · Nov 27, 2006

kenfath said:
I set up my home shop with a shut off valve between the compressor and the shop piping. I don't have to worry (as much)
about a hose blowing out, or someone playing with the blowgun or other tools, when I'm not around.

Have one of those too.
But in my case, the compressor is on the second floor, and the "HOSE" that blew out (was a hydraulic hose with a bad crimp job) was between the compressor and the SHUT OFF valve; and was only 24" long!
(it is used to stop vibration from the compressor and the shop piping)

The REMOTE POWER switching method is just a way to prevent a "run away."
Easy to hook up. Low voltage wiring from the man door to the compressor power relay. (#22 ga. wire)

One other note. MOST compressor makers use the Pressure SHUT OFF switch hooked DIRECTLY to the motor to turn it on and off; and in many cases the pressure switch is "ON the HAIRY EDGE" of it's load carrying capacity!

To reduce the load on it, have it control a secondary HD relay. (mine uses an 18 VAC coil winding) My remote system just turns the 18 VAC transformer ON or OFF. NO POWER to the compressor!!

Compressed Air Questions

stppinz

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Charles (in GA)

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Charles (in GA)

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stppinz

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Stuart in MN

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Charles (in GA)

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Stuart in MN

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Pops

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Charles (in GA)

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ZRX61

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W-Cummins

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malibu101

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Charles (in GA)

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DIGGER_DAVE

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kenfath

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