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#81387 - 08/06/02 07:19 AM NFPA70E
cornbread Offline
Junior Member

Registered: 08/01/02
Posts: 4
Loc: carrollton, kentucky, usa
Reference NFPA 70E Table 3-3.9.1 Hazard Risk Category Classifications.

600V Class MCCs

Work on energized parts, including voltage testing has a Hazard/Risk of 2*

2* means that a double-layered switching hood and hearing protection are required for this task in addition to other ….requirements of Table 3-3.9.2 of part II.

Is this indicating a hood must be worn to take voltage reading in a MCC bucket??
Thanx CB

2014 / 2011 NEC & Related Books and Study Guides
#81388 - 08/06/02 12:11 PM Re: NFPA70E
Redsy Offline

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
That would be my understanding.

Our company considers testing for the presence of, or measuring the level of voltage at the MCC to be classified as "Testing" or "Diagnostic". In which case we reduce the PPE requirement to :
Calorie-rated Arc-shield.
6 ounce Nomex clothing.
Safety glasses.
Heavy-duty leather gloves.

Anything beyond that reguires:
Switchmans hood.
Switchmans jacket.
6 ounce Nomex clothing.
Safety glasses.
Voltage-rated gloves.

#81389 - 08/06/02 01:26 PM Re: NFPA70E
Bjarney Offline

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
Redsy — Is that voltmeter IEC/EN 61010-1 "category" rating [UL3111 comparable, supposedly] being given any consideration where you work?

#81390 - 08/07/02 04:34 AM Re: NFPA70E
Redsy Offline

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA

The only consideration given to the type of voltmeter is that it be "single function". This way you can not have it on the wrong function.
I have a Tegam 125 Voltman, and interestingly, it shows no category rating.
I'll check the paperwork.

#81391 - 08/07/02 01:42 PM Re: NFPA70E
gpowellpec Offline

Registered: 12/06/00
Posts: 128
Loc: Irving, Tx USA
Hate to throw this in, but feel I have to.

If there is any 480 exposed in the bucket you are working "on or near" 480 and the hood is required. If you short out the 480 to ground or phase to phase with the probes the combustion by-products will likely be inhaled. This is the main cause of death or severe injuries in this scenario.

Gerald POwell

#81392 - 08/08/02 01:13 PM Re: NFPA70E
Dan Neeser Offline

Registered: 03/12/02
Posts: 29
Loc: St. Louis, MO, USA
Start with 2- to see how to identify the required PPE. This section details the two ways to identify the required PPE for a task.

The first is as you suggested, find the task in Table 3-3.9.1 of NFPA 70E-2000 and note the hazard/risk catagory. Then go to Table 3-3.9.2 of NFPA 70E-2000 to find the PPE required for that task. This is a general table and I can see where some instances are conservative and others may be inadequate. It all depends upon the available fault current and the overcurrent device and operating time that is protecting the circuit.

The other way is to calculate the incident energy available based upon a selected working distance. The FR clothing and PPE used must be rated for this amount or higher value of incident energy.


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