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ekstra   ara
 Post subject: Just Learning
PostPosted: Mon Jan 23, 2012 11:10 am 

Joined: Mon Jan 23, 2012 10:42 am
Posts: 1
Our company just recently made the requirement for following NFPA 2012. We are now required to wear the following when powering on and off a Power Distribution Unit...

• Cotton Undergarments
• Long Sleeved Shirt (natural fiber)
• Long Pants (natural fiber)
• Safety Glasses or Goggles
• Hearing Protection (inserts)
• Leather Gloves (as needed) or Insulating Gloves with Protectors.

Until we have these protections our we cannot perform our normal work.

Our normal operating procedure for deenergizing this PDU is (1) power down all equipment being powered by the PDU, (2) open all 20 amp 120VAC breakers to kill all power outlets, and (3) open the two 255 amp panel breakers that split the power load, (4) open the main 200 amp breaker. We reverse the procedure when powering up.

Our PDU is rated as follows..

480 V 127.5 KVA 3 PH 60 Hz.

208/120 V 125 KVA

I've been working with electronics with the US Navy and NASA for over 30 thirty years and never have experienced a breaker explosion or flash. Are exploding breakers a new trend? From what I've seen from videos of breaker flash overs now on the internet, the examples shown show that only as asbestos fire suit could save you.

What happened to regulatory safety test and standards of manufature of electrical equipment?

Are my company requirements too high for the operation of our PDU?


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PostPosted: Wed Feb 22, 2012 8:19 am 

Joined: Thu Oct 27, 2011 9:34 am
Posts: 14
I can't give you exact answers for your questions but may provide some insight.

On testing, manufacturers do have to meet a particular criteria to meet standards BUT this does not mean that 100% of breakers will work properly.

When implementing 70E, you have a few options which you can analyze the level of arc flash energy. It seems as if your company has not completed a detailed analysis and are using the tables in 70E to provide the level of PPE required.

According to your example-you fall into the 240-600 section of the tables. If you leave the covers on, then if a breaker is operated you will have to have Cat 0 PPE donned (which you stated above).

So, in being very brief and not reviewing many other parts of your maintenance program etc., your company requirements are correct for your example.

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