PPE in MCC

Dec 30, 2016
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#1
Process operators “racking” in/out 480v disconnects in MCC. What level of PPE is required. What level of HRC….What is required please? Thank-You for this forum..
 

Mike M.

New Member
Dec 30, 2016
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#2
Doug,

The level of PPE is going to depend on the incident energy available at the MCC. Our facility only allows “racking” of breakers to be performed by qualified electricians. I hope this helps.

Mike M.
 

Hugh Hoagland

Moderator
Staff member
Dec 30, 2016
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Louisville, KY
www.arcwear.com
#3
Mike is correct but if the MCC meets the tables in upstream protection and fault current calculation the PPE Category is 4 which is 40 cal/cm² gear.

We are not real big fans of racking in starter buckets with the MCC energized since when these fail the whole MCC buss fails and this is usually a large arc flash event due to the clearing time and fault current.

Definitely make sure the MCC’s meet the requirements and the workers are qualified to operate this equipment by training.
 

Hugh Hoagland

Moderator
Staff member
Dec 30, 2016
75
1
8
58
Louisville, KY
www.arcwear.com
#5
Door closed or open has no bearing on energy level from the NFPA 70E or IEEE 1584 perspective. This is an issue of operation.

(4) Normal Operation. Normal operation of electric
equipment shall be permitted where all of the following
conditions are satisfied:

  • (1) The equipment is properly installed.
  • (2) The equipment is properly maintained.
  • (3) The equipment doors are closed and secured.
  • (4) All equipment covers are in place and secured.
  • (5) There is no evidence of impending failure.

Informational Note: The phrase properly installed means
that the equipment is installed in accordance with applicable
industry codes and standards and the manufacturer’s
recommendations. The phrase properly maintained means
that the equipment has been maintained in accordance with
the manufacturer’s recommendations and applicable industry
codes and standards. The phrase evidence of impending
failure means that there is evidence such as arcing, overheating,
loose or bound equipment parts, visible damage, or
deterioration.


We’d add historical failures to this list in the Informational Note.
 
#6
I am busy collecting data for (and performing) an arc flash study today and came across an MCC with the main 480V breaker being greater 40cal/cm2. The plant disconnects fed from the MCC were much lower.

It's best to determine the incident energy. The 70E tables are an option, but the fault current needs to be known before using the tables. The fuse/breaker data/label only provides the max peak asymmetrical fault and overload - never the fault current!

Arc flash studies are not as expensive as most people believe them to be; neither are they that complex. The engineer does most of the work from the data collection to the labelling - It is worth considering.