Sparking 220v plug

Re: Sparking 220v plug

Mike Brazeau

Is there a switch on the compressor? If so, does it switch both legs of the 220?

Re: Sparking 220v plug

Dale Gillaspy

I would consider putting in a switch on both hot legs of the 220 receptacle.

Sounds like you are using the plug like a switch

Dick Coers

As mentioned, get a switch or get a ball valve and mount it right against the compressor. Shut the valve every time you leave the shop. You will have no line leakage and will have pressure when you return to the shop.

switches and plugs

John K Jordan

David,

I use this 220v disconnect switch on my 5HP IR compressor and another one as a service disconnect for my 5HP cyclone dust collector:

http://www.amazon.com/Leviton-MS302-DS-Disconnect-Industrial-Non-Grounding/dp/B002MPQ51O

Both of these machines are in a sound-insulated closed so I installed the compressor switch outside the closet in the main shop so I can see it and easily turn it off as I leave the shop. I do not leave the compressor powered up over night or when leaving for an extended time for the reason you mentioned.

Leviton also sells this switch with a heavy-duty box/cover plate:

http://www.amazon.com/Leviton-N1302-DS-Double-Pole-Disconnect-Industrial/dp/B003GIS2O4

I'm not a big fan of regularly disconnecting equipment with the corded plug due to the eventual wear on the connectors. Where I have to, for example connecting my welders and plasma cutter to 50 amp outlets, I use a bit of dielectric grease for lubrication and to minimize resistance-increasing oxidation. Dielectric grease is available at any auto parts store. (I use it when installing breakers, light bulbs, almost everything especially for outside and automobile use.)

But your description concerns me. Why is the motor under load when you make the plug connection? Is it because the pressure leaked down and the motor starts up when you plug it in? If so, could you not flip off the pressure-activated switch on the compressor itself before plugging it in? I would not want to plug in a large electrical load into 220v, especially a large motor, for several reasons.

JKJ

Re: Sounds like you are using the plug like a swit

Barry Irby

Good ideas here. Dick's ball valve will work unless the leak is in the compressor itself. Some of the ones I had would leak slowly even with nothing attached to them. I spent a lot of time tracking down and curing the leaks so I could just leave it plugged in and on.

The switch is a good idea. Good ones are designed for many cycles and to not burn up.

If the breaker is handy, you could turn that off, but they are not designed to use as a switch and it may have a limited life, but even then it might be easier to replace the breaker than to add a switch.

Re: Sparking 220v plug

Ellis Walentine

Okay, I'm a mile wide and an inch deep on electrical matters, and I always defer to the professionals when it comes to this sort of question. But, your dilemma reminded me of a rule of thumb, learned the hard way in my case.

We had a big old 5 hp compressor in my old shop and we never turned it off when leaving the shop. One day, back in May of 1999, the unloader valve on the compressor's cylinder head jammed somehow, and when the pressure switch called for air, the motor kept drawing current until it caused a catastrophic failure in my main panel box and sparked my shop fire. Seven alarms. Lost absolutely everything.

The moral of the story is to play it safe with compressors. Turn them off when not in use.

Ellis

leaks and bubbles

John K Jordan

>>...get a ball valve and mount it right against the compressor...

If David's compressor has a significant internal leak a shutoff valve might not help.

I have appropriate valves on my 60 gal 5HP air system, one at the tank and others feeding several plumbing circuits, but although I can detect no leaks downstream from the compressor I still get a VERY slow pressure loss with all valves closed.

After leak testing everything including tank and compressor fittings, I finally put a stethoscope on the (two stage) compressor itself and heard a tiny internal noise indicating some internal leakage, perhaps from a check valve or around one of the pistons, perhaps even from new piston rings not yet seated. It doesn't affect usage and even over a two-week vacation did not drain to below the pressure switch threshold.

BTW, for leak testing I used to mix up soap solution from liquid dishwashing soap. Then I bought a couple of gallons of kids soap bubble solution for a dollar each at Walmart on an end-of-season clearance. Duh. Tires, compressors, air tools, lines... perfect! No mixing, great bubbles.

JKJ

Another thought.....

Barry Irby

After thinking about this for a minute or two and reading John and Ellis' response, it occurred to me that the reason you get the arc is that the compressor is switched "on" by the pressure switch and is putting a load on the circuit and the spark jumps because the compressor is trying to run. If the compressor had a switch on it and you turned it off, you could plug and unplug it without a spark. You unplug it without a spark because the pressure switch is "off". If you unplug it with the compressor running you will get an arc.

When my Grand Daughter is here I turn off the breakers in the shop, but there is never anything running when I do that, so there is little or no arcing inside the breakers. That could be why it does not seem to harm them.

Based on Ellis' experience, a good disconnect switch is in order.

Less catastrophic

Dick Coers

Wife came back in one day after heading out for work. "There's something running in the garage". Went out and the belt had broken on the compressor. The motor could have been running all night as far as I knew.

Thanks for the response and suggestions

david

Guess I was using the plug as a switch. My compressor is at one end of my garage shop and the plug is at my lathe on the other end. Its like an obstacle course getting from one to the other, so a shut off valve at the compressor is not practical because of access. Believe a switch as JKJ suggested is the way to go. Appreciate the suggestions and links for purchase. You guys are the greatest.

When is The Tank Drained?

don stephan

All of the suggestions seems to be oriented towards always leaving the tank pressurized. Seems like I've read a number of times that the tank should be drained at the end of each day to remove condensation, or the tank will rust through and fail prematurely.

Re: When is The Tank Drained?

John K Jordan

>>the tank should be drained at the end of each day to remove condensation...

You are correct according to prevailing wisdom and the manufacturer's instructions and everything I've read and learned. Unfortunately, draining the condensation is often ignored. I try to remember to drain my compressor after days where I use it significantly (often I don't use it for extended times) but I often forget.

On recommendation of a wise person, I bought an automatic drain, not yet installed, which will periodically open the condensate valve for a short time on a programmable schedule. Hopefully this will help my tank life.

My compressor is behind heavy walls but that still may not be enough protection if the tank explodes. In the '70s I was a pressure vessel inspector and the training films were compelling. We hydro tested even huge tans in open air (perfectly safe) but when testing with air pressure was called for we tested in an underground bunker.

I notice my compressor mfgr recommends a tank inspection within the first 5 years of use and periodically thereafter. I've had plenty of pressure cylinders visually inspected and hydro tested but I don't know anyone who has had their air compressor tank inspected. Anyone ever had theirs inspected?

JKJ

Depends where you live

Dick Coers

I bet if you live in Phoenix, you never have to drain a compressor. I've not had a tank fail in 40+ years. Other parts have failed, and I've upgraded, but never failed a tank. I've never owned an oil less compressor either. So maybe a little oil vapor gets into the tank? I'd also wager new tanks aren't as thick as the ones I've owned either. Haven't bought a compressor in about 20 years. Drained at the end of every day I used it? Way overkill. I drain my portable about every other year, big stationary maybe less. Central IL location.

Re: Depends where you live

david

We have high humidity a good part of the year. The last time I drained the compressor it had about a cup of water. This was about 6 months ago. Was aware of the potential for rusting out the bottom from the condensate, but still didn't make me more diligent.

So....how does draining

Brian Roberts

the tank dry it?

Seems it would remain wet after draining.

Does draining actually prevent rusting??

Re: When is The Tank Drained?

Stuart Johnson

I read a tank can explode if it is solid and way over pressurized. If under normal pressure and it rusts through it will start leaking and eventually not hold pressure but won't explode.

This was on the internet so it must be true as no false information is allowed.

corrosion and catastrophe

John K Jordan

>>If under normal pressure and it rusts through it will start leaking

>>and eventually not hold pressure but won't explode.

In the pressure vessel inspection field we were taught that any corrosion or small leak is a weak point that could lead to sudden and catastrophic tank failure. I have no idea how likely this is at the low pressures in shop air compressors. Some of the tanks we dealt with were for gas at very high pressure.

Some tanks were tested with sensitive helium leak detectors that could detect even extremely low concentrations of helium gas. (Helium atoms are so small they will get through the smallest pinhole or crack.) Some tanks contained highly corrosive and reactive gasses. A demonstrator showed how pure fluorine gas would cause a strip of bacon to burst into flame - this was a warning against getting too close to even a tiny leak!

BTW, a dive shop in Florida that catered to us cave divers always submerged scuba tanks in a big tank of water for filling with air. It was routine then to over-pressurize aluminum 3000 psi tanks to 5000 psi. I have no idea how protective this submersion would be if a tank exploded.

As for water in air compressor tanks, I read that keeping the water out makes things easier on the downstream dryers and filters in the system. (I read this on the internet too!) I use an industrial desiccant dryer on my lines and the replacement cartridge is not cheap - the manual for the dryer suggested draining the tank often for longer cartridge life. Since the humidity is high here, I wonder if a desiccant dryer on the compressor intake would be useful.

JKJ

Re: corrosion and catastrophe

Dave Paine

Since the humidity is high here, I wonder if a desiccant dryer on the compressor intake would be useful.

Many desiccants are reactivated by heat. I would expect the high heat of the air on the discharge of the compressor would drive out most of the moisture the desiccant attempts to remove.

Re: corrosion and catastrophe

John K Jordan

>>Many desiccants are reactivated by heat. I would expect the high heat of the

>>air on the discharge of the compressor would drive out most of the

>>moisture the desiccant attempts to remove.

In this case the desiccant dryer is some distance from the compressor. This is recommended to allow the air to cool so moisture can condense before it hits the dryer. (A typical recom end action is about 20ft of line IIRC.) Condensed moisture on my system is collected by a trap and a water separator immediately before the dryer. So far this has worked well.

The desiccant dryer might be overkill for some shops but my air also feeds my plasma cutter and occasional spray finishing which both benefit from dry air. (I still use secondary dryers at the point of use.)

I'm considering rigging up some way to pump warm air through the desiccant dryer cartridge to see if I can reactivate it. Or maybe devise a cartridge I can fill with loose desiccant beads.

JKJ

Re: corrosion and catastrophe

Dave Paine

In the industrial gas plants, we needed to remove moisture and CO2 prior to sending the air to the cryogenic separation. A two vessel arrangement with each vessel filled with perlite to remove moisture and a molecular sieve material to remove the CO2.

One vessel on-line for e.g., 45 mins, then valves switch to reactivate this vessel and have the other vessel go on-line.

Two different methods to reactivate, thermal swing which used hot waste nitrogen and an electrical heater, and pressure swing which released the pressure from the vessel and used warm waste nitrogen which was warmed by heat exchange with hot gas from a compressor discharge.

You will likely be looking at a thermal regeneration. Easy to set up a two vessel system with manual switching.

A hot air gun plumbed into a vessel for regeneration may work. A number of potential options.

Filling tanks

Bill Howatt

When i was a teenager many years ago I used to work at a place that filled scuba tanks. I was told the tank of water was for cooling the tanks, no mention of any safety usage. We didn't over-pressure.

Bill

Re: corrosion and catastrophe

John K Jordan

>>A hot air gun plumbed into a vessel for regeneration may work. A

>> number of potential options.

I looked at the used cartridge this morning while it was fresh on my mind. Turns out it comes apart easily and will be easy to refill with either new or dried desiccant. I'll probably use the blue/red indicator type to make it easier to see when it is dry in the oven. The old cartridge had 81 grams of water in about 350 grams of desiccant!

I had about 1/4 cup of water in the bottom of my 60 gal compressor tank. It's been a couple of months since I drained it and that was with very little use.

JKJ

JKJ

Re: corrosion and catastrophe

Dick Coers

I use a Salvation Army toaster oven to dry desiccant. Works great! I had a lot of moisture trouble when I had my custom furniture shop. Air sanders and spray guns used a lot of air. When both of us were sanding, the tank on the compressor was almost hot to the touch, so we were sending a lot of moisture down the line. I used a filter, then a desiccant filter and then finally a paper roll filter to capture the final moisture in front of the pressure pot in the booth. They used to call those toilet paper filters, but just because of the similar look of the replacement filter to the nickname.

Electrical standards

Geoff Whaling

"Short circuits and arc faults are extremely dangerous and potentially fatal."

Fix the problem before you injure yourself or burn down your shop!

I'm very happy that we have Australian/New Zealand Standard for Wiring Rules (AS/NZS 3000:2007) and the Electrical Safety Act in Australia which mandate many aspects of electrical installations and installation by licensed tradespersons only.

One aspect of the wiring rules covers "protection against arcing faults." In this instance the compressor or another device after the plug is drawing a load current which is capable of bridging the air gap (generating an arc) between the plug and outlet/socket before physical contact is made between the components of the plug and outlet - a serial arc fault, - highly undesirable.

The circuit is live when the compressor is both plugged in or unplugged. The reason the circuit is live most likely is that it is not a switched supply to the compressor (or another device) everything is live all the time. The compressor is drawing a current at the time the circuit is being made or broken OR there is another fault resulting in a current being drawn.

The plug is effectively being used as a “switch / isolator” and is not designed for that application, as the arcing clearly demonstrates.

The arc itself is caused by uncontrolled conduction of electrical current. The arc fault current and voltage generates a massive release of energy. This ionises the surrounding air and is capable of vaporizing the conductive metal which can expand something like 67,000 times its solid volume, generating heat and intense light (arc flash).

The erosion of the plug components is a direct result of the arc and will only serve to increase the risk of this hazard causing harm.

The resulting arc can be hazardous to the installation, building and persons as the arc can cause personal injury (eyes, intense burns etc), damage to other electrical devices connected to the installation, the wiring and may cause fire.

Arcing of electrical installations, circuits at plugs / outlets, in switches etc is neither normal nor safe and is an undesirable electrical safety and fire hazard.

Our Australian and most world wide wiring rules are written to prevent those hazards through good design, sound installation practice and wiring, switches and associated devices etc that meet electrical standards approvals.

Install a switched outlet! Turn off the compressor before unplugging the power cord/lead.