It is currently Thu Feb 22, 2018 3:38 am



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: HRC on labels
PostPosted: Fri Jun 27, 2014 2:16 pm 
Offline

Joined: Fri Jun 27, 2014 1:51 pm
Posts: 4
Hi, I am new here. Apologies if this has already been asked.

Regarding labeling - the 2009 version of 70E contained table 130.7(C)(11) which cross-referenced incident energy levels with an HRC. The 2012 version of 70E removed this table.

The 2009 version allowed the engineer to indicate the incident energy level on the arc flash label. The contractor could presumably go to table 130.7(C)(11) to find the HRC and PPE required.

The 2012 version allows the engineer to indicate the highest HRC for the equipment, or the incident energy level. The highest HRC comes from the tables dictating HRC based on what type of work is performed. If incident energy level is used on the label, the contractor can no longer cross-reference to get the HRC. Instead (s)he must go to table H.3(b) to understand what PPE is required.

Am I missing something? I seems like the HRC 'method' isn't as meaningful as the incident energy level 'method.'

Thanks in advance,


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: HRC on labels
PostPosted: Fri Jun 27, 2014 4:17 pm 
Offline
Sparks Level
User avatar

Joined: Tue Nov 12, 2013 6:31 am
Posts: 238
Location: Port Huron, Michigan
If you are using the tables you use what is, for a short time longer, known as the HRC level. If you are calculating values using a study, you list the incident energy. The 2015 code does not allow you to list both values on the label, you choose based on the method you are using.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: HRC on labels
PostPosted: Fri Jun 27, 2014 6:38 pm 
Offline
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 1878
Location: North Carolina
H/RC stands for hazard/risk category. It includes both a likelihood and severity (incident energy) consideration. If you do your own risk analysis then you need your own system. The H/RC table is specific to the equipment/task tables in 70E. In the draft 2015 edition, the likelihood analysis is broken out so we have 3 tables (task, equipment, and PPE). Likelihood is interpreted as whether or not any PPE is required. Thus the PPE table will use the term PPE level and H/RC is retired. Incident energy is more flexible. The specific types of PPE required show up in the text but the combination of clothing used to get there is open. It is even possible to do layering IF it is tested.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: HRC on labels
PostPosted: Tue Jul 08, 2014 6:20 pm 
Offline

Joined: Fri Jun 27, 2014 1:51 pm
Posts: 4
Thanks guys, this helps a lot.

I have a follow up question I was hoping you might be able to help with. Section 130.5(C) Equipment Labeling states "Electrical equipment such as switchboards, panelboards, industrial control panels, meter socket enclosures, and motor control centers ... and are likely to require examination, adjustment, servicing or maintenance while energized, shall be field marked with a label containing all of the following information:"

My questions:
1. What is considered an 'industrial control panel?' Would this be a motor controller located on a skid? Its my understanding much of the equipment in these panels operate at 12 or 24V DC.
2. Where do enclosed circuit breakers and disconnect switches fit in? They aren't technically in the list of equipment but I often see them labeled.

Thanks again,


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: HRC on labels
PostPosted: Wed Jul 09, 2014 4:31 am 
Offline
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 711
Location: Rutland, VT
mattgron wrote:
My questions:
1. What is considered an 'industrial control panel?' Would this be a motor controller located on a skid? Its my understanding much of the equipment in these panels operate at 12 or 24V DC.
2. Where do enclosed circuit breakers and disconnect switches fit in? They aren't technically in the list of equipment but I often see them labeled.


1. NEC 70 Article 409.2 defines an Industrial Control Panel. To paraphrase, basically it is assembly of two or more components consisting of power circuit components only or control circuit components only or a combination of the two mounted within an enclosure. There is also a UL document, UL 508A, Standard of Safety for Industrial Control Panels which may contain more detailed definition if needed.

2. Note that the definition is not all inclusive since the term "Electrical equipment such as...." is used. If the enclosed CB and disconnect switches are such that they are adjusted (open or closed) for operation or LOTO, I label them. Additionally, fused disconnect switches may require a fuse replacement while still energized. Some facilities will verify the absence of voltage on the load side for LOTO. These activities would require the proper PPE.


Last edited by wbd on Wed Jul 09, 2014 4:32 am, edited 1 time in total.
added missing word


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: HRC on labels
PostPosted: Wed Jul 09, 2014 11:19 am 
Offline
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 1878
Location: North Carolina
UL 508A came out about 10 years ago and standardized what had already existed.

Regardless of whether UL 508A exists, there are basically two prevalent construction techniques for self-contained machine-builder type equipment such as a skid mounted chemical system. The first type is more typical of a "field construction" method. It consists of a set of unistrut rails and/or a large steel panel with several combination starters and junction boxes with electronics housed in them. The starters usually have a trough above or below them containing the bulk of the power wiring. The individual components are UL Listed.

A typical design for the same applicaiton that you would see from a panel builder shop or more commonly on European equipment is that it comes with a single large panel. Inside that panel are all the starters (individual open frame style starters bolted to a panel), protection circuits, relays, electronics, etc., all in one large enclosure. That is what UL 508A (and NEC) are referring to. UL 508A allows this to be a Listed application while mixing different equipment from different manufacturers within the panel.

Voltages in both designs are typically 480, 240, 208, 120, or 24 VDC and frequently there are multiple voltages such as 480 V power for starting, 120 V for signalling, and 24 VDC for analog instruments, within the exact same panel.

As you can imagine with the "industrial control panel" design, arc flash rating is essentially the same throughout the panel. Working distance is somewhat difficult to quantify. The "field assembled" combination starter design does not have this problem as each enclosure stands on its ow. But this is also a considerably more expensive product.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 6 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2017 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883