Class 1 Div 2, Flexible Conduit, and Low Voltage.

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
OK; it was just a misimpression on my part. HOWEVER you definitely need a careful review of Section 500.7(K) Combustible Gas Detection System. The details of design requirements aren't in the NEC; they are referenced in the Informational Notes especially IN No. 3.
 

Dan LV

Member
Location
Tennessee
So are you referring to this document?
"ANSI/ISA-60079-29-2009"

Because everything I have found is fairly expensive, in order to see what it says. As for system design and proper installation we are in compliance with the approved design and layout of the manufacturer. Not that what they say goes, but they did provide the recommended material list/system layout and have verified our compliance during site visits. Is this the type of thing you are thinking of? There isn't much design to do other than proper coverage area.

 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
I don't have a personal copy of nor ready access to ANSI/ISA-60079-29-1. I am generally familiar with its contents though. I highlighted the basic issues of Section 501.7(K) main text in red. ANSI/ISA-60079-29-1 is the reference standard to achieve compliance with Section 501.7(K). ANSI/ISA-60079-29-1 requires a significant amount of regular maintenance, testing and documentation. Technically, Informational Notes are not enforceable; however, you would be hard put to defend a design that wasn't compliant with it.

501.7(K) Combustible Gas Detection System. A combustible
gas detection system shall be permitted as a means of protection
in industrial establishments with restricted public
access and where the conditions of maintenance and supervision
ensure that only qualified persons service the installation.
Where such a system is installed, equipment specified
in 500.7(K)(l), (K)(2), or (K)(3) shall be permitted.
The type of detection equipment, its listing, installation
location(s), alarm and shutdown criteria, and calibration
frequency shall be documented when combustible gas detectors
are used as a protection technique.
ADDITIONAL NOTE: Your reasoning behind using a gas detection system appears to be an application of 500.7(K)(1); i.e., if you didn't use gas detection, it would be a Division 1 location. Otherwise, there's no real reason to use gas detection at all.
 

Dan LV

Member
Location
Tennessee
Okay, so we need to verify design. To clarify, the gas detection system is in no way needed to create an allowance for any other system or for the space in general. This is an additional space of a facility that has been classified Class I Div 2 without any gas detection for years. The winds of change in greater safety consciousness are causing more and more the implementation of systems and practices that aren't required by any other decisive group than "the coporate office". At least that's what I've been seeing at places like this site as well as within my own company. An "above the standard" approach to safety. It's probably a good practice, although sometimes excessively tedius. The definition of a Class I Div 1 space is overkill for this space. It definitely is rightly categorized as a Div 2.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
One of the more common scenarios with classified locations is over-classifying "just to be safe". Once the cost of compliance with over-classifying raises its ugly head, many try to justify downgrading the installation by pointing out it didn't really need to be classified that way.

This is NOT the case in your proposed installation. In fact, it's just the opposite. However, in this case, over-installing "just to be safer" is a serious waste of money that won't add any significant amount of safety to the installation.

That said - go for it.
 
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Dan LV

Member
Location
Tennessee
My assumption is that you meant they were throwing detection on top of an already acceptable building when you said:

"This is NOT the case in your proposed installation. In fact it's just the opposite...."

And not that the building is borderline Div 1. Either way, my thoughts on the matter may lean toward yours regarding waste. Thankfully I have no real stake in this site except for business...and of course doing a proper job is included in that. One other area of benefit they will have, and will be using, is to monitor, trend, and study the changes in alcohol level. Along with multiple building temps, even non concerning levels of alcohol can be used to create a "model" for a good product over a not as good product. We are using analog signals to monitor an alcohol range 0-100% LFL. If there was very gradual, low level seepage I guess it can fit into a pattern that is helpful. The only "alarmable" levels are up in the industry standard range of 25-50% LFL.

Bob, I appreciate your patience and I am sorry if there has been too much back and forth. As I said before, all of the information I've received here has equated to a huge learning experience of which I am grateful for. What is learning if not filled with questions along with an ear to listen?! Anything else you wish to add is welcome. The 5 hour drive I've gotta make in a few hours is gonna pull me away for a while though. Thanks everyone.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
I've said in other threads that dealing with hazardous locations isn't rocket science, but it isn't a trivial exercise either.

This thread started with a "simple" query about using LFMC in Division 2 - it's OK to use when the grounding/bonding requirements of Section 501.30 are observed. You had already covered that so we could have stopped there. But you added the information that the devices were "...at least class 1 div 2 rated".

That raised a flag about potential sealing and listing/labeling issues. We worked through that but discovered the devices were gas detectors.

New flag. What was the basis for classifying the location in the first place? We were assured it wasn't actually necessary to classify above Division 2; the gas detectors weren't necessary but just for 'warm/fuzzies'. No problem. We could stop there.

I'm not familiar with the processes involved, it's not my design and it's not my money. So I'll leave you with this thought to consider Most alcohols have LFLs of 2% or less. (Ethyl and Methyl are exceptions) Even a "slow leak" wouldn't take long to reach 25% LFL. Nevertheless, I wouldn't be too concerned if proper ventilation were constant rather than turned on at some alarm level.
 

Dan LV

Member
Location
Tennessee
It's been a very long week and I have been unable to respond, but I did want to add something. First off, thanks for summing things up. And to your point, yes there is adequate ventilation in the way of open air louvers every so many feet around the building and the mechanical units circulate air 24/7 also. Reaching an "alarmable level" LFL% would take quite an abnormal situation. Your input will be passed on to those actually responsible for the conduit work. We will do what we can to make an informed and acceptable installation plan that results in what is considered proper for the site. Thanks again!
 
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