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Clever_Proxy
Premium
join:2004-05-14
Villa Park, IL

Turning off Power to a Building

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I have a question for the electricians out there. I have a building that has an industrial 3 phase coming into it. The local utility company out here is going to be performing work on the transformers that feed the building directly. They told us to turn off the power to prevent damage to any of our equipment during the work.

Is there any danger to myself and the building by throwing these switches? I know enough about electricity to be dangerous and that's about it.

garys_2k
Premium
join:2004-05-07
Farmington, MI

1 recommendation

Shouldn't be, just power off as many of the loads in the building as possible via their own switches first. The one lever marked "Main" ought to take care of everything, but may as well kill 'em all once you're ready.



davidg
Good Bye My Friend
Premium,MVM
join:2002-06-15
none
reply to Clever_Proxy

how about getting the maintenance man to do it, as it is his responsibility to know which ones feed what. The one marked "Main" should kill it all but there could potentially be other locations where switches must be thrown.
--
Lack of Preparation on YOUR Part does NOT Constitute an Emergency on Mine!



Clever_Proxy
Premium
join:2004-05-14
Villa Park, IL

No maintenance man. Just me. The building isn't big enough for a maintenance man.

100% positive there are no other places where power is coming in. What you see there is everything off the drop in the alley. There are just panels scattered around labeled "RP-1" "LP-1" etc.



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:8

1 recommendation

reply to Clever_Proxy

What garys_2k See Profile said...

When you turn the big switches on and off, make sure you do so "with authority"...that is, don't do it slowly. You want the mechanisms to snap into place so all three phases cycle properly.

Don't worry, you won't hurt those switches. They're built rather robustly. Don't be timid when operating them.
--
No amount of force can control a free man, a man whose mind is free. You can't conquer a free man; the most you can do is kill him. Well, you can try to...



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:8

1 recommendation

reply to Clever_Proxy

Is this two separate occupancies / tenent spaces? You have two switches marked "main"...



Clever_Proxy
Premium
join:2004-05-14
Villa Park, IL

1 recommendation

No. One building, one meter, one drop.

From my understanding this building used to be some sort of industrial manufacturing building. As the company grew, their need for electricity grew. The second panel was added later to accommodate more 3ph panels for industrial equipment.

Majority of those panels have been replaced by single phase panels to power office and computer equipment. There's only one 3ph panel left that powers RTUs and a handful of garage door openers.



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET

1 recommendation

reply to Clever_Proxy

Nothing should happen if you throw those switches but you can further minimize the risk by having every load individually turned off beforehand.

The other piece of instruction I received was to never stand directly in front of the switch. Stay to the left or to the right whichever side gives you better leverage to move the switch handle (but also consider which side gives a better exit route should things unexpectedly go wrong).

The worst case scenario (not very likely, but something you should know) would be a heavy load still live when you turn the switch and a plasma arc forming across the contacts that doesn't self-extinguish. In that case hot metal vapor will develop inside the switch and it may not stay inside.

Based on the looks of those switches you are not dealing with currents where such a problem would be likely.
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pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast

1 edit

1 recommendation

reply to Clever_Proxy

If you do turn OFF those switches and then of course you will need to turn them back ON in the dark. Unless there is natural light, it will be dark so plan to have a flash light handy.

Here is a quick safety tip:

1.Use your LEFT hand.
2.Stand to the RIGHT of the face of the enclosure.
3.Close your eyes and look to the right when you do the deed.
4.Operate the switch with authority.

This way if in the very unlikely event something bad happens, you will not be standing directly in front of the panel and your face will not be exposed.

It is very unlikely anything will happen, however you only will get one chance!

Tim
--
The difference between genius and stupidity is that genius has its limits.



Clever_Proxy
Premium
join:2004-05-14
Villa Park, IL

Thanks guys. Safety tips noted!

I'll most likely turn off the mains at the remote panels first, then throw the mains.



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET

Since it sounds like you might have 3-phase AC motor loads in the building I would recommend to have an electrician confirm correct phase rotation before you power the mains back on.

A 3-phase AC motor is perfectly happy to turn in either direction (based on the phase rotation) but the mechanical devices attached to the motor (garage door, HVAC compressor, etc.) may not be.

Depending on the nature of the maintenance that is being performed by your utility company that extra caution may not be necessary.
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hdman
Flt Rider
Premium
join:2003-11-25
Appleton, WI

The power company will insure the same phase rotation when they reconnect the building. Shouldn't need to worry about that.
--
The proper way to break in a Harley: Grab a fist full of throttle, and ride it like you stole it!!!



nunya
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
Reviews:
·Charter
·voip.ms
·surpasshosting

1 recommendation

reply to Clever_Proxy

Don't be scared. The disconnects are there to be used. Just shut off all of the mains. Usually, these are spring loaded and fast acting - you probably have to put a little ass behind them.
--
If someone refers to herself / himself as a "guru", they probably aren't.



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET
reply to hdman

Mistakes happen.

Perhaps phase rotation swaps are more of an issue here since in PG&E territory phase rotation is counter-clockwise (ACB or L1-L3-L2) while most of the US uses clockwise rotation (ABC or L1-L2-L3).
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nunya
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
Reviews:
·Charter
·voip.ms
·surpasshosting

I've seen several scroll compressors (RTUs) fried because the poco restored the phases improperly. I've seen blowers, mixers, and other manufacturing equipment left running backwards by the poco. It happens.
Their typical response: "Not my problem".
Which makes it my problem. And I guess that's good because I could always use more money.
--
If someone refers to herself / himself as a "guru", they probably aren't.



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:8

1 edit

1 recommendation

reply to Clever_Proxy

Just a couple of things for people not used to seeing that kind of equipment...

-Those are fused disconnects rather than circuit breakers. They use bladed fuses and feed the distribution panels in the building where the 'normal' branch wiring circuits terminate.

- That kind of switchgear of that vintage can have covers that slide down when the screws are removed so it is imperative to be very careful when removing the covers that they do not slide down and severely injure your toes/feet (even through your boots), or that they do not fall into the gear unexpectedly.

- Most reasonably modern (last ~20 years) RTUs have phase-loss and reverse rotation protection devices in the control circuitry. Additionally, one more thing to look out for on building restarts after a prolonged outage is the sudden load of all the units being called at the same time on hot days, or even cold days when the system has electric supplemental/emergency heat. This can drive demand charges up if the units all come on at the same time. Again, most units have staggered on-delay timers to alleviate this problem during power outages of the normal kind (i.e., storm-related, etc) so it shouldn't be too much of an issue.

As was pointed out by others, reverse rotation can be an issue, so it would be best if someone contacts the power crew foreman prior to their beginning work to make sure that the crew addresses the phase sequence issues appropriately. Most utilities are aware of the issue, and endeavor to address it, but you never can be too sure unless you ask. Be polite and diplomatic, of course, when doing so.
--
No amount of force can control a free man, a man whose mind is free. You can't conquer a free man; the most you can do is kill him. Well, you can try to...



LazMan
Premium
join:2003-03-26
canada
reply to nunya

Just to duck out on a bit of a tangent - are you guys not jumping on the Arc-Flash bandwagon down there?

I now have to have exclusion zone's marked on the floor, and need to wear a suit to operate anything 600v or higher; or 100A or larger.



Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom

1 recommendation

said by LazMan:

Just to duck out on a bit of a tangent - are you guys not jumping on the Arc-Flash bandwagon down there?

I now have to have exclusion zone's marked on the floor, and need to wear a suit to operate anything 600v or higher; or 100A or larger.

More Big Brother. I worked in industry for 35 years before retiring and the thousands of MCC starter buckets, 2300 v starters, 4160 v starters and 15 kv switchgear and transformers never once did we ever have an "arc-flash" and we worked a lot of the 480 volt gear hot. The key is to have qualified trained Electricians to do the work.

The damn suits are a sick joke mandated by a government agency whose inept employees are clueless but have unaccountable power.


LazMan
Premium
join:2003-03-26
canada

No disagreement - I think it's overkill, as well...

I used to change breakers in live panels all the time (production environment, killing power was a pain in the ass) - now, that's a big no-no...

I have been involved in two arc-flash incidents (a minor one first hand; when a 2000A disconnect was operated under load, and failed, one part of the aftermath, when a 3000A breaker cell blew while racking in the breaker) - so I know the hazards. There's a time and place to wear the suit, but I think they've gone crazy with how restrictive it's become up here...

Anyways - so, I assume it's become an issue for you guys down there, too, then...



Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom

said by LazMan:

No disagreement - I think it's overkill, as well...

I used to change breakers in live panels all the time (production environment, killing power was a pain in the ass) - now, that's a big no-no...

I have been involved in two arc-flash incidents (a minor one first hand; when a 2000A disconnect was operated under load, and failed, one part of the aftermath, when a 3000A breaker cell blew while racking in the breaker) - so I know the hazards. There's a time and place to wear the suit, but I think they've gone crazy with how restrictive it's become up here...

Anyways - so, I assume it's become an issue for you guys down there, too, then...

Yes it had just started when I retired in 1998. My replacement had to deal with it and from what I heard the suits and requirements were a royal PITA and effected employee effectiveness and productivity. Not to mention the additional cost of the "suits"


nunya
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
reply to LazMan

I think you replied to the wrong person. I didn't say anything about arc flash.
--
If someone refers to herself / himself as a "guru", they probably aren't.



LazMan
Premium
join:2003-03-26
canada

I know you didn't bring it up - I was asking if it's becoming an issue for you guys; the same way it's become a pain in the ass up here.



Clever_Proxy
Premium
join:2004-05-14
Villa Park, IL
reply to nunya

Okay, now you guys have me curious

After doing a little bit of Googleing, basically 3 phase power is wired in 2 general configurations. Delta and Wye (forgive me if I'm mistaken). Delta has a "high leg" where the power is of higher voltage than the other two legs. Is this what you're referring to when you speak of phase rotation? Is there any way to confirm what the transformer configuration is? The transformers here are pole mounted. I can post pictures.


nonymous
Premium
join:2003-09-08
Glendale, AZ
reply to Jack_in_VA

said by Jack_in_VA:

said by LazMan:

Just to duck out on a bit of a tangent - are you guys not jumping on the Arc-Flash bandwagon down there?

I now have to have exclusion zone's marked on the floor, and need to wear a suit to operate anything 600v or higher; or 100A or larger.

More Big Brother. I worked in industry for 35 years before retiring and the thousands of MCC starter buckets, 2300 v starters, 4160 v starters and 15 kv switchgear and transformers never once did we ever have an "arc-flash" and we worked a lot of the 480 volt gear hot. The key is to have qualified trained Electricians to do the work.

The damn suits are a sick joke mandated by a government agency whose inept employees are clueless but have unaccountable power.

maybe no arc flash suits but probably say cotton work clothes not nylon or polyesters leisure suit to melt into skin even with a small error.


PSWired

join:2006-03-26
Annapolis, MD

2 recommendations

reply to Clever_Proxy

Delta and wye wiring schemes for 3 phase power are not relevant to phase rotation. AC power is characterized by a voltage that varies continuously in a sinusoidal pattern. 3 phase AC power presents 3 separate voltages, each with the same sinusoidal pattern, but delayed in time with respect to each other:




Phase rotation refers to which of the sinusoids is assigned to each wire in the 3 phase system. When a motor is attached to 3 phase power, the order of these sine waves determines which way the motor spins. So if they're mixed up, the motor will turn the wrong way.

Another common problem is that one of the phases will be disconnected. Equipment like motors will continue to work, but the components for the remaining two phases will be overloaded and could overheat.


Clever_Proxy
Premium
join:2004-05-14
Villa Park, IL

So with that being said, there's no real way for me to check rotation without some decent knowledge and testing equipment?

I guess the easiest and least damage inducing way to test is to power on a device that wouldn't be severely affected by a wrong phase rotation (like one of the 3 phase garage door openers?)



Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
reply to nonymous

said by nonymous:

said by Jack_in_VA:

said by LazMan:

Just to duck out on a bit of a tangent - are you guys not jumping on the Arc-Flash bandwagon down there?

I now have to have exclusion zone's marked on the floor, and need to wear a suit to operate anything 600v or higher; or 100A or larger.

More Big Brother. I worked in industry for 35 years before retiring and the thousands of MCC starter buckets, 2300 v starters, 4160 v starters and 15 kv switchgear and transformers never once did we ever have an "arc-flash" and we worked a lot of the 480 volt gear hot. The key is to have qualified trained Electricians to do the work.

The damn suits are a sick joke mandated by a government agency whose inept employees are clueless but have unaccountable power.

maybe no arc flash suits but probably say cotton work clothes not nylon or polyesters leisure suit to melt into skin even with a small error.

We required cotton work uniforms and safety glasses


jjoshua
Premium
join:2001-06-01
Scotch Plains, NJ
kudos:3
Reviews:
·Verizon FiOS

1 recommendation

reply to Clever_Proxy

said by Clever_Proxy:

So with that being said, there's no real way for me to check rotation without some decent knowledge and testing equipment?

More like a $25 meter.

»www.ebay.com/itm/T471-Phase-Sequ···91745841


leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET
reply to Clever_Proxy

said by Clever_Proxy:

I guess the easiest and least damage inducing way to test is to power on a device that wouldn't be severely affected by a wrong phase rotation (like one of the 3 phase garage door openers?)

If that garage door opener has a properly working overload cutoff then that is an easy and perfectly valid test. It should be pretty obvious when the garage door moves (or tries to move) in the wrong direction.

Edit: before testing the garage door, test a large variety of the single phase loads. It should be obvious if one of the phases is missing because 1/3 of the loads in the building won't work.
--
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nonymous
Premium
join:2003-09-08
Glendale, AZ
reply to jjoshua

said by jjoshua:

said by Clever_Proxy:

So with that being said, there's no real way for me to check rotation without some decent knowledge and testing equipment?

More like a $25 meter.

»www.ebay.com/itm/T471-Phase-Sequ···91745841

Sure? Someone is worried about how to throw a breaker and you are suggesting they hook up a meter?

Now a question to some of the other posters. Why would the utility return power with a different phase. One poster even said a utility said not their problem and they made cash fixing things.

Ok I was only a utility helper years ago mostly new construction dead plant. But we still did outages for cutovers etc. We hooked everything back up the same as we found it after cutting in the new plant. No random phase shifts etc.