# Entering Live MDP Panels



## RePhase277 (Feb 5, 2008)

I'm just going to be honest with you here, this IS IN NO WAY ADVICE ON HOW YOU SHOULD DO IT!

I might pull a cover and see what I'm up against. If I have good working space and it hasn't been just jacklegged full of conductors, I'll do my thing. I use a piece of cardboard to catch the shavings and direct them out of the can. This is at 208/120... 480 is a different story....:shifty:


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## MTW (Aug 28, 2013)

A 208/120 high amperage service will still have significant fault current, especially if it's close to the transformer. The bigger issue is if something does go wrong, who is on the hook to replace the gear and breakers you melt down? You are, of course.


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## drewsserviceco (Aug 1, 2014)

Rackatiers makes a couple of magnetic debris catchers for drilling like you describe. 

I would definitely have insulating blankets on hand (and use them). I came into the trade using cardboard, but now it's my name, health and insurance on the line...blankets are cheap compared to damaging any one of those, let alone replacing damaged equipment. 1000V rated blankets are pretty inexpensive really. 

It all depends on the situation and my comfort level.


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## 6 shooter (Feb 4, 2008)

drewsserviceco said:


> Rackatiers makes a couple of magnetic debris catchers for drilling like you describe.
> 
> I would definitely have insulating blankets on hand (and use them). I came into the trade using cardboard, but now it's my name, health and insurance on the line...blankets are cheap compared to damaging any one of those, let alone replacing damaged equipment. 1000V rated blankets are pretty inexpensive really.
> 
> It all depends on the situation and my comfort level.


What are those insulating blankets you talk about? I don't think I have seen them.


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## RePhase277 (Feb 5, 2008)

6 shooter said:


> What are those insulating blankets you talk about? I don't think I have seen them.


They're used so the people nearby can put you out after the explosion.


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## drewsserviceco (Aug 1, 2014)

RePhase277 said:


> They're used so the people nearby can put you out after the explosion.



I can't remember off the top of my head this late in the day. 

I believe they're class 1 and rated for 1000V insulating value. Much thinner and more flexible than a higher rated blanket you've probably seen before. 

I would typically use them to insulate the energized parts from my work area and then use cardboard or similar means to provide more of a physical barrier (so that something like the cutter from the knock out doesn't fall and puncture the blanket defeating the whole purpose). 

Really handy.


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## Moonshot180 (Apr 1, 2012)

Engineering safeguard would have to be in place to completely isolate craft from the energized gear. Some say the insulating blankets are the safeguard. I don't they are really meant for that purpose. 

So without a blanket, if the work would expose craft to energized components then work with the POCO to shut it off.


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## emtnut (Mar 1, 2015)

6 shooter said:


> Do you guys that do a lot of commercial services shut the main off on larger MDP panels? Say 800 amp and larger. It would be for adding a panel board off the main service.
> 
> I would have to come out the top of the service to the new panel. The metal shavings falling down from the top would be a concern falling down on the buss bars while cutting the knock outs. So I was wondering what some of you guys do? The service is a 120/208 system.


I see this question come up a lot.
I can see a plant, running 24/7 not wanting to shut down. They will push to work around live equipment.
Correct me if I'm wrong here ... but commercial ? Can't it be done on a weekend ?
What are the consequences of a shut down ?

Do a planned shut down ... safe, and everyone goes home.


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## 6 shooter (Feb 4, 2008)

This service was a 800 amp. It had a main breaker in it. If you shut that breaker off to work in there are there proper steps to shut the 800 amp breaker off. Like wise to re energize it?


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## backstay (Feb 3, 2011)

6 shooter said:


> This service was a 800 amp. It had a main breaker in it. If you shut that breaker off to work in there are there proper steps to shut the 800 amp breaker off. Like wise to re energize it?


I'll be really honest here, if you are asking this kind of question, you shouldn't be doing the work. I'm not being an ass. Long before I was rooting around in large panels by myself, I had a couple of thousand hours in with someone else. This is not the place to make a mistake because you've never done this before.


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## MechanicalDVR (Dec 29, 2007)

6 shooter said:


> What are those insulating blankets you talk about? I don't think I have seen them.


http://www.highvoltagesupplies.com/store/product/class-4-blanket-22x22-orange-1307.cfm


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## MechanicalDVR (Dec 29, 2007)

drewsserviceco said:


> I can't remember off the top of my head this late in the day.
> 
> I believe they're class 1 and rated for 1000V insulating value. Much thinner and more flexible than a higher rated blanket you've probably seen before.
> 
> ...



Haven't used the 1000v type.

The ones I have are rated for 36,000v. 

http://www.highvoltagesupplies.com/store/product/class-4-blanket-22x22-orange-1307.cfm


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## 6 shooter (Feb 4, 2008)

backstay said:


> I'll be really honest here, if you are asking this kind of question, you shouldn't be doing the work. I'm not being an ass. Long before I was rooting around in large panels by myself, I had a couple of thousand hours in with someone else. This is not the place to make a mistake because you've never done this before.


Yea that's fine, I wouldn't feel comfortable in there unless in was turned off. But to my question about the large breakers, is there a certain way to shut them down besides throwing the switch down?


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## backstay (Feb 3, 2011)

6 shooter said:


> Yea that's fine, I wouldn't feel comfortable in there unless in was turned off. But to my question about the large breakers, is there a certain way to shut them down besides throwing the switch down?


If they are standard CB, then you can just shut them down. I would drop loads if the thing was carrying 50% load or something. As far as going back on. Anytime you do work in a panel like that, you should megger it with all breakers off. You never know, sometimes a tool will get left across something or you've introduced a short with the work you did.


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## frenchelectrican (Mar 15, 2007)

backstay said:


> If they are standard CB, then you can just shut them down. I would drop loads if the thing was carrying 50% load or something. As far as going back on. Anytime you do work in a panel like that, you should megger it with all breakers off. You never know, sometimes a tool will get left across something or you've introduced a short with the work you did.


That is pretty much the SOP I do with MDP's and it is good way to check all other breakers to make sure they are cycling properly ( turn it off and on with out power source is on ) that way you know it is safe to heat it up after you verify it with megger.

the Megger is the safest way to verify the MDP is in safe manner before you turn the main breaker back on.

Whatever you do with those breaker .,, DO NOT stand front of them when you heat them up. in case if something go wrong it can get ya hard. 

I got hit few time with that. so I know how strong the blast it is. it dont matter what voltage it is 208 240 480 or whatever ya got there just play it safe.,,


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## MechanicalDVR (Dec 29, 2007)

backstay said:


> If they are standard CB, then you can just shut them down. I would drop loads if the thing was carrying 50% load or something. As far as going back on. *Anytime you do work in a panel like that, you should megger it with all breakers off.* You never know, sometimes a tool will get left across something or you've introduced a short with the work you did.



:thumbsup:

Good way of handling it!


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## active1 (Dec 29, 2009)

There is a difference between an insulating blanket and an ark flash blanket.
The insulating blanket does not migrate the ark flash energy.
Insulating blankets cost $100's.
Ark flash blankets cost $1,000's.

An insulating blanket may protect you about as good as a piece of cardboard in a flash situation.

Both would be blown toward you if not secured.

If you don't have the proper PPE, know how to access the AF category, and training including ark flash, don't do this.

Here is a test example of an ark flash blanket.
In the test it looks set up about 2' from the gear and the dummy is another 3' from the blanket (5' total). Even with the ARK FLASH blanket secured to poles, 5' away the dummy's head is engulfed in flames. Point being an Ark Flash blanket is not enough PPE.


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## active1 (Dec 29, 2009)

One company I worked for provided to PPE or training. No safety rules or policies. They were working at a night time warehouse club remodel (store open daytime). The company did everything wrong.

One worker was tasked with running something into the main gear.
Foreman didn't know when he was going to do it except sometime that night.
The worker was working alone.
Being due for a remodel all the EM light heads had bad batteries.
Herd the explosion and lights went out on all the people working.
Large store 100% dark.
Had to search for flash lights / use cell phone display light (before flashlight app).
Once they found a flash light they went back in to look for the missing person.
Found him next to the gear burnt and skin dripping off.
He was working in the gear with uninstalled tools bolting in something and got between phases.
Had 0 PPE on.
Only thing right was they called for an ambulance.
He survived after skin graphs months in the hospital.
They didn't want to do a scheduled shut down, cause you know, they got a computer in the office they didn't want turned off.
Ended up loosing power all night till they could replace the fuses the next morning.
I didn't work that night. I got hired the next day to take his place.


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## active1 (Dec 29, 2009)

Had a friend working at a smaller casino by the strip.
Went to pull off the cover on the main gear.
He didn't see there was holes left open in the top and old hardware laying there.
It fell inside and blew up.
He said the only thing that saved him and his apprentice was him holding the cover blocking the blast.

Many don't understand whats involved in an ark blast.
When copper starts to vaporize all hell breaks loose.


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## Cow (Jan 16, 2008)

Thanks for the reality check active.

Seems a lot simpler to just skip all the extra safety precautions and shut it down instead, right 6 shooter?


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## backstay (Feb 3, 2011)

Molten copper headed your way at 600 psi.


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## active1 (Dec 29, 2009)

backstay said:


> Molten copper headed your way at 600 psi.


I read 700 MPH at 140-160db.

There is a reason copper is used in explosive devices.
The explosive vaporizes the copper and the copper does the damage.

Even with the proper space suit on some are killed by the blast energy or at least the blast pushing them into or off of something.

OSHA claims over 7,000 AF injuries per year or 1-2 deaths per day.

Some don't realize there are actually 2 dangers in gear.
Electric shock and the ark blast.


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## backstay (Feb 3, 2011)

active1 said:


> I read 700 MPH at 140-160db.
> 
> There is a reason copper is used in explosive devices.
> The explosive vaporizes the copper and the copper does the damage.
> ...


We had a blue suit for racking in 6600 volt breakers. You had to stand right in the open door to run the motor that lifted the switch into position. No chicken switch. I asked if the suit would save us. The rep that sold it said, " it's so you can have a open casket, maybe". We had a tremendous amount of fault current. Steam turbines, hydro turbines and a butt load of motors. I sure miss doing that job.


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## frenchelectrican (Mar 15, 2007)

backstay said:


> Molten copper headed your way at 600 psi.


600 PSI .,,basically it is the same pressure you find in alot of diesel engines even my personal diesel truck is 575 PSI ( i verifed with compression gauge so that is serious amount of pressure ) 

the other good example is large EMD diesel anytime we bar over the engine with test port is open we do NOT stand front of the test port basically anything in the cylinder will spit out over 500 psi pressure ., basically a shotgun there. 


Ya molten copper can infect alot of damage. plus shockwave too.


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## TGGT (Oct 28, 2012)

active1 said:


> There is a difference between an insulating blanket and an ark flash blanket.
> The insulating blanket does not migrate the ark flash energy.
> Insulating blankets cost $100's.
> Ark flash blankets cost $1,000's.
> ...


That's a cool blanket.

Not sure how you're supposed to anticipate the arc flash to take the time to step behind it.

Sent from my SM-G360T using Tapatalk


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## active1 (Dec 29, 2009)

The blanket is to protect you while your toolie works in the gear.


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## TGGT (Oct 28, 2012)

active1 said:


> The blanket is to protect you while your toolie works in the gear.


Oh good, so the blanket will be supplemented by the roasting body of your pal. Should box him in on both sides to make sure he takes the brunt of it.


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## active1 (Dec 29, 2009)

TGGT said:


> active1 said:
> 
> 
> > The blanket is to protect you while your toolie works in the gear.
> ...


The intent of the posts is to provide enlightenment in the difference between an insulating blanket and a AF blanket and the dangers of an AF.

This is no means any suggestion to buy, use, or not use. As I said get training.

Anyone including TGGT or the OP that doesn't comprehend, care to listen, or thinks they know better then have at it.
I could careless.


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## TGGT (Oct 28, 2012)

active1 said:


> The intent of the posts is to provide enlightenment in the difference between an insulating blanket and a AF blanket and the dangers of an AF.
> 
> This is no means any suggestion to buy, use, or not use. As I said get training.
> 
> ...


I'm arc flash trained. I just find that video humorous.

Sent from my SM-G360T using Tapatalk


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## mitch65 (Mar 26, 2015)

Around these parts even the mills that run 24 hours have stopped installing buckets in hot MCCs all that sort of thing has to be planned for shutdown. 5 years ago we thought that it was overkill, now it's normal. That being said, commercial safety standards don't seem to be the same, pretty much anything short of installing buss hardware is done hot in lots of places. Much easier and safer to pull a short night shift and de-energize the equipment. We have shut down hotels for a couple of hours and they run 24-7.


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## MechanicalDVR (Dec 29, 2007)

mitch65 said:


> Around these parts even the mills that run 24 hours have stopped installing buckets in hot MCCs all that sort of thing has to be planned for shutdown. 5 years ago we thought that it was overkill, now it's normal. That being said, commercial safety standards don't seem to be the same, pretty much anything short of installing buss hardware is done hot in lots of places. Much easier and safer to pull a short night shift and de-energize the equipment. We have shut down hotels for a couple of hours and they run 24-7.


Couldn't agree more. 

There is no installation or repair job so important that it's worth getting fried over.:no:


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