# High leakage powerstrips



## poppaclutch (Feb 19, 2014)

I have come into possession of a dozen or so High Leakage power strips. Tag says they need to be grounded before power is supplied. With that in mind, can I just use them around the shop as regular power strips? What does high leakage mean?
Thanks,
Rick


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## Walt (Feb 19, 2014)

poppaclutch said:


> I have come into possession of a dozen or so High Leakage power strips. Tag says they need to be grounded before power is supplied. With that in mind, can I just use them around the shop as regular power strips? What does high leakage mean?
> Thanks,
> Rick



Hi Rick,

It appears to be a term of art within the medical devices industry:

http://www.ecnmag.com/articles/2012...excessive-leakage-current-healthcare-industry

In this article, the leakage currents are in the microamp range. If that is the same thing as your power strip is warning about, the concern isn't going to apply in a home shop situation. (If you have a heart condition, or have a pacemaker installed, this may indeed apply to your use of these power strips.)

Note that I can't determine whether this is indeed the same issue as discussed in the linked article. 

Walt


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## pineyfolks (Feb 19, 2014)

That's great, if one of your machines dies you can safely use a defibrillator on it.


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## poppaclutch (Feb 19, 2014)

Thanks. guys.


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## Ray C (Feb 19, 2014)

pineyfolks said:


> That's great, if one of your machines dies you can safely use a defibrillator on it.



LOL...  Good one piney...

Leakage current...  Yes, a very important thing with medical devices.  Whenever you have a powerstrip with surge suppression, it will likely have a higher leakage current.  This just means that the power-strip itself is consuming some power and appears to be a load in parallel along with the items plugged into it.  Stated in other terms, if you unplug a regular power strip and use an Ohm meter to measure the resistance across one of it's outlets, you should see infinite resistance.  In the case of a strip with high leakage current, you will likely read a very high (but non-infinite) resistance.

I'm very curious about these power strips you obtained...  I've never heard of anyone labeling them as "high leakage current".  In the case of medical devices, power strips are highly complex devices and almost always have their own isolation transformer as extra safeguard against "power to the patient".

Ray


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## TOOLMASTER (Feb 19, 2014)

emf maybe


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## poppaclutch (Feb 19, 2014)

OK, here they are. What I am wanting to know is if I have to use the green / yellow ground wire attached to one end or just plug the three prong connector in to my supply and consider it grounded.
Rick


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## JimDawson (Feb 19, 2014)

I think I see why those are labeled like that.  They are metal cases and may be not be internally grounded to the case to isolate the grounds for computer use.  You should be able to use them as they are with out grounding the case.  The only problem would be any internal damage that would cause the hot wire to contact the case internally, that would make the case electrically hot.

By grounding the extra earth wire you would eliminate that possibility by giving the power a path to ground that is not through you.

Recommendation, connect the green/yellow wire the the cover screw on your wall plugs.


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## TOOLMASTER (Feb 19, 2014)

http://www.tlc-direct.co.uk/Book/7.8.2.htm


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## pdentrem (Feb 19, 2014)

These are Rack mount power strips. Not cheap even on the used market.
Computer room racks are usually steel and everything has to be chassis/earth/ground to avoid floating ground loops and energizing the equipment and service personnel. Like Jim stated, connect to ground and be happy. Just check that your wiring is correct, the hot is hot and neutral is neutral. Better safe than zapped!
Pierre


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## awander (Feb 19, 2014)

It's typical of both Dell and APC to have no data available on this unit on their websites. They made it a few years ago, so it is as if it never existed.

Anyway, there is no indication that I can see that the PDU has isolated ground receptacles; I have never seen that in a server PDU.

This link gives some info for a (different) hp rack system that explains about as well as I have found, why the PDU needs to be grounded. Evidently, the amount of leakage current that is allowed to flow through a ground line at a wall receptacle is limited, and because these PDUs have lot's of outlets on them, the amount of leakage from everything that is plugged in to them, added together, might exceed that figure at the wall receptacle. So they mandate a separate ground wire, that will then carry much of the leakage current.


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## Pmedic828 (Feb 20, 2014)

sometimes the "high leakage" of these strips is caused by a stray wire on the stranded power cable coming into contact with the metal case.  Another is that the receptacle in the strip is defective.  These power strips have a 3 wire cord - make sure that the green "ground" of the 3 wire cord connects to the medal box on the power strip and check the resistance from the box to the prong on the plug.  Sometimes, molded connector plugs on these strips break down and the ground opens.  If it has a high resistance, just cut the existing plug off and wire on a new 3 wire plug.
Remember, If you want to defibrillate your lathe, it's 360 joules, then a minute of running it, then shock again! and continue until it quits or it begins to operate smoothly!  As a paramedic, I say, "Let's not meet by accident!"


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## poppaclutch (Feb 21, 2014)

Remember, If you want to defibrillate your lathe, it's 360 joules, then a minute of running it, then shock again! and continue until it quits or it begins to operate smoothly!  As a paramedic, I say, "Let's not meet by accident!"[/QUOTE]

I might try that on my Harbor Freight mini lathe... know what I mean, Vern?


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## Joe0121 (Feb 22, 2014)

Others beat me to it. Those are rack mounted power supplies for servers. I repair said server for a living and have had quite a shock when the UPS was faulty and static current had built up. Computer equipment has A LOT of power running through a lot of metal so excellent grounding is a must have.


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## mws (Feb 22, 2014)

"High leakage" is the norm for most consumer electronic equipment which utilizes any sort of noise/high-frequency suppression on the power leads by means of capacitive/inductive filters.  The capacitance shunts the high frequencies to ground very readily. The labeling of such devices as "high leakage" seems fairly new to me, and I've been in electronic design most of my life. Medical equipment requiring high isolation usually utilizes highly insulated (several 1,000 volts) transformers to magnetically couple any required power to the device. 

The power strips you have obtained are not unusual or different from any other consumer power strips not so labeled. Provided they are grounded, they will not present any additional hazard or concern. If you do connect them without the ground connected you will be able to measure (with an average volt/ohm meter of about 20,000 ohms per volt, not a "wiggly") about 60 volts AC (1/2 the line voltage) between the power strips (open) ground lead and either the line or neutral feeding it. This is the leakage voltage being divided across the two suppression capacitors and the strip's ground. The current will be VERY low however, as the caps are selected to pass much higher frequencies than 60 cycles. But even at 60 cycles, some small amount will "leak" if there's no load (ground) to drain it off.   If you were to complete the circuit from the open ground to earth with your body you might feel it, but it would not likely hurt an average healthy person. On the other hand, if you have a pacemaker, or defibrilator, it would certainly be enough current to set off some serious "bells". 

If you look at any old (pre-1960 or so) radio, TV and audio equipment it was common to have quite a bit of capacitance from line to chassis, with a separate screw on the chassis labeled "Ground".  Naturally, many people ignored, or mis-wired, the "ground" terminal and were rudely shocked by their error. No pun intended. Hence the advent of three wire cords.  

One last word, another device commonly found in these "power strips" are MOVs, "Metal Oxide Varistors". These devices are designed to break down and pass HUGE amounts of energy to ground, or line to neutral, in the event of high voltage surges. Most 120 volt "surge protectors" use MOVs set to conduct around 350 volts.  These MOVs can become dangerously leaky if subjected to small surges repeatedly. Such a leaky MOV could hurt you if the power strip were ungrounded. Most of the time the damn things just blowup and short out, and the power strip has to be thrown away. 

Personally, I hate the damn things. IMHO if the voltage surge gets to the point where the MOV conducts the damage has, more often than not, been done already and the so called "surge protector" is yet one more device to be replaced.  I'm not saying they don't have their place, just not in cheesy AC power strips (unfiltered) plugged into the wall.  Since your strips are likely filtered, that's a far better device, but still not quite what they're marketed to be in terms of device protection.  Mostly, these filtered power strips are employed to help meet FCC Part 15 regulations on radiated electronic interference. 

They would be a nice thing to have on say VF Motor Drives, or brushed universal motors, in your shop if you listen to AM radio, etc.  


Guess that's all I can remember, hope that helps satisfy your curiosity.  

Mark


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## Wireaddict (Feb 23, 2014)

It's hard to know exactly what's inside these power strips without having one apart on my bench but the fact that these have 2 ground leads suggest that the MOVs may be connected to the metal case & that's where the leakage to ground would occur & create a shock hazard if it weren't grounded.  The manufacturers _could've_ connected the metal case to the ground wire in the power strip cord but they usually don't with medical & sensitive electronic instrumentation mainly to prevent ground loops & resultant AC hum.  This concept is called isolated grounding &, even though both grounds are required to originate at the building, earth & cold water ground point in the main panel, they are run separately with metallic conduit being one conductor & a ground wire inside being the other.  At the outlet/load/device end of the power strip leakage or fault current from the MOVs is ideally carried off by the case ground & the receptacle grounds are connected separately to the equipment that's plugged in.  As mentioned earlier, for our purposes, just connect the separate green/yellow ground wire to the wall outlet cover screw & use a metal, not a plastic outlet cover.


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## poppaclutch (Feb 23, 2014)

Thanks for all the replies. Very informative. I will take a pic of the innards and post tomorrow.
I sure do appreciate and enjoy this forum.
Thanks,
Rick


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