Class and Division boundaries

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Mike McDonald

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Hello,
I am struggling to find any quickreferences to the actual physical dimensions of the D1 and D2 area of a Class 1 location. I found one reference that said a D1 location is only 5 feet from a source, but a D2 is 10 feet from a source. Huh?
This would pertain to an above-ground fuel oil tank, and its supply and return piping, and having been installed in a location where previous non-rated equipment is located. Also this tank has a transfer station installed in a basement mechanical room...again near previously non-hazardous classified items such as lighting fixtures and motor starters, even though it used to contain gas fired boilers!!!
Thanks for any input folks.
 
Let me rephrase my entire statement. What are the boundary limits in feet or meters from equipment such as above ground storage tanks and associated flammable liquid piping leaving and returning from that tank? There are bolted flanges on that piping as well. Is the most distant flange considered to be the edge of the equipment, and therefore the beginning of the Class/Div boundary? I see no references to boundaries in the NEC in article 500, with the exception of requirements "within 10 feet of the boundary" phrases used for sealoffs. I do NOT have the handbook, which in previous years ( 80's and 90's etc), there were small pictograms showing things like grounding systems, bonding, and similar concepts throughout the Code. All of the following articles from 501 on only describe wiring methods and specific equipment, but never any reference to WHERE that equipment is required in feet or meters from something like the tank or piping I referred to. Thanks.
 
I don't believe fuel oil (presume you are talking about kerosene or other similar fuels) ordinarily creates an art 500 classified location when used/stored at general atmosphere conditions.

Unlike gasoline it doesn't give off flammable vapors with low ignition temp.

Even if it did your description of usage indicates it is all contained either in the tank or piping and that still wouldn't create a classified location, other than near tank ventilation openings or if there were open transition methods - like you might have for filling portable containers
 
this diagram may be helpful

c1d1 level switch in a c1d2 rated area

i am packaging a pump system for customer with their supplied instrumentation. the area classification is c1, d2, group c/d per the supplied documentation. the sticky situation is they have supplied a level switch that is c1, d1 rated. i have added a rated elbow and seal directly out of the...
forums.mikeholt.com
 
The most applicable tables and diagrams in the NEC for the OP are in Article 515. However, as kwired pointed out most fuel oils won't usually create a classified location.

Some additional thoughts. Unless you refer to an applicable standard found in Section 500.4(B) IN No. 2 or Articles 511 to 516, if they are applicable, (Read their Scopes) attempting to classify from the NEC directly from Article 500 is the equivalent of design DIY. You should get a qualified person to properly document classifications as required by Section 500.4(A). BTW this is Fed and State OSHA enforceable. The NEC Handbook is not authoritative in itself and it says so in its introduction. This not to say it isn't valuable, but recognizes it is not a mandatory interpretation for AHJs.
 
kwired said:
I don't believe fuel oil (presume you are talking about kerosene or other similar fuels) ordinarily creates an art 500 classified location when used/stored at general atmosphere conditions.

Unlike gasoline it doesn't give off flammable vapors with low ignition temp.

Even if it did your description of usage indicates it is all contained either in the tank or piping and that still wouldn't create a classified location, other than near tank ventilation openings or if there were open transition methods - like you might have for filling portable containers
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Hi and thanks. From what I read it’s “under normal conditions”, true. But if a repair needs to be performed on the tank or flange, then the installation becomes different. I didn’t catch if fuel oil was in the substance list. It is a petrochemical combustible. Until I get a chance to read what substances are considered , I’m just flappin gums.
 
So of course here is the real issue for me with the installation. There are conduit‘s which were installed to supply this equipment which are explosionproof seal offs and capped ells and enclosures. As I stated in my OP this was placed next to non-hazardous or classified equipment already in place. So as I had asked my supervisor and one of the engineers, does that now make my equipment unsafe? So I will do a little more digging and find out who classified the location. Because if it is Then my equipment needs to be replaced. If it is not then obviously we wasted a lot of money paying the contractor to install those components.
 
kwired said:
I don't believe fuel oil (presume you are talking about kerosene or other similar fuels)...
Click to expand...
Fuel Oil, commonly stored in 250-gallon tanks in residential basements, is burned in furnaces to heat homes.

It is basically diesel fuel that's been dyed with a purplish color so the rev'nooers can tell if you're buying 'cheap' fuel oil for your diesel automobile (or semi) instead of 'motor fuel' that's had the taxes paid.
 
Mike McDonald said:
Hi and thanks. From what I read it’s “under normal conditions”, true. But if a repair needs to be performed on the tank or flange, then the installation becomes different. I didn’t catch if fuel oil was in the substance list. It is a petrochemical combustible. Until I get a chance to read what substances are considered , I’m just flappin gums.
Click to expand...

The hazards for that repair becomes more of an issue if you need to do some welding, drilling, grinding, etc. and not so much of an issue for your electrical installation.
 
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