NEMA 4 Terminal Box in Class 1 Div 2 3

[roydm]

Hi Guys,
I posted this thread on the code issues forum about a week ago, seems those folks are asleep so pardon me for putting it here as well.
I have a large electrical immersion heater (120kW) in Class 1 Div 2 location. The terminal box is NEMA 4. The manufacturer claims it is suitable for Class 1 Div 2 under NEC Article 500 because "It's considered a npon-sparking device" I suspect it needs to be NEMA 7 or purged.
I need to somehow satisfy Korean KOSHA authority.
Interested to hear what others think.
Thanks
Roy

 

[7anoter4]

Hi Roy
NEC Article 501-3 b(2):
"Resistors, resistance device,… and similar equipment that are used in or in connection with meters, instruments and relays shall comply with (a) above:
"Shall be provided with enclosures approved for Class I, Division 1 locations"
Exception: General-purpose-type enclosure shall be permitted if such equipment is without make-and-break or sliding contacts… and if the maximum operating temperature of any exposed surface will not exceed 80% of the ignition temperature in degrees Celsius of the gas or vapor involved or has been tested and found incapable of igniting the gas or vapor."
So, if the terminal box is far from the liquid surface level and contains only screw or bolt connections the box NEMA 4 is suitable. But the heater has to be provided with enclosure approved for Class I, Division 1 locations [NEMA 7] if the temperature does not meet the above "exception".
My opinion!
Best Regards

 

[itsmoked]

7anoter4;
Class I, Division 1 doesn't this include stuff like hydrogen gas?

What am I missing? Isn't all the conduit rigid, threaded? And lots of adjoining enclosures EXP rated to contain explosions? How can one box be a run-of-the-mill NEMA 4?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[dpc]

Keith,

OP said Class 1, Div 2 - the gas is not normally present. The rules are more lenient than for Div 1.

 

[itsmoked]

Ah Hah!

Thanks.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Senselessticker]

I'm a bit confused about this one... When you say "terminal box"... what exactly are you refering too? My hunch is the NEMA 4 is not complaint for the hazardous location...

 

[itsmoked]

Hi Senselessticker.

That was my thought too but as dpc states since there isn't supposed to be a hazardous atmosphere during normal operations, (Div2), the theory is if there is nothing to 'actually spark' as with a bunch of screw terminals, then there is no expected hazard with the box. If it had, say, a contactor in it, or relays that spark with a high ignition energy then NO not allowed.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[7anoter4]

Thank you dpc and itsmoked!

 

[roydm]

To elaborate, the elememt has about 18 hairpin elements all terminating in the enclosure with jompers and 3 large terminals for each lead.
Roy

 

[itsmoked]

Not sure what YOU mean by 'hairpin'. As long as the wires can't spontaneously connect or disconnect under shaking or thermal cycling I think you're OK.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[roydm]

itsmoked,
The elements are hairpin in shape with both ends in the enclosure. I hear what you are saying about non sparking connections but if you look at a motor rated for class 1 div 2, also non sparking the terminal box is usually much more robust than NEMA 4. The manufacturer claims they have similar heaters installed however they also offer NEMA 7, but in smaller sizes.

7anoter4,
The manufacturer is also quoting NEC Article 501-3 b(2) however I don't think that applies as the heater is not part of a metering circuit.

Thanks for your input.
Regards
Roy

 

[resqcapt19]

Roy,
There is no need to use any special type of motor for Class I, Divison 2 areas. Even an "open" type motor that does not have arc producing contacts is permitted.

501.125(B)... In Class I, Division 2 locations, the installation of open or nonexplosionproof enclosed motors, such as squirrel-cage induction motors without brushes, switching mechanisms, or similar arc-producing devices that are not identified for use in a Class I, Division 2 location, shall be permitted.