Class 2 Division 1

[dvcraven0522!]

If I have an enclosure in an class II division 1 environment. I believe based on my interpretation of the NEC this enclosure and conduit feeding the multiplexer will also need seal-offs.

I have included a sketch attached to better show the scenario. The system basically operates at 12VDC to the unit and I believe the thermocouple wiring is in millivolts.

Thank you
Dan Craven

 

[petersonra]

I don't know much about class ii. Do you need boundary seals?

 

[don_resqcapt19]

I don't think any seals are needed. Seals are only required where the enclosure is required to be dust-ignitionproof. I don't see why that enclosure would need to be dust-ignitionproof. Also, the drawing looks like an explosionproof enclosure used for Class I installations. That type of enclosure is not required for a Class II installation as there is no requirement to contain an explosion within an enclosure like there is in Class I.

 

[rbalex]

I “endorsed” Don’s post because it is correct but it is an ultimate irony. Section 502.15 describes how and where seals are needed in both Class II, Divisions 1 & 2. What is now absent for the last two Code cycles is where a dust-ignitionproof enclosure is actually necessary. (EDIT ADD: Where the installation is otherwise correct, dust-ignitionproof is usually unnecessary.) See Section 501.10(A)(3) for Division 1 and 501.10(B)(4) for Division 2. None of the Sub-sections in Art 502, Part III. Equipment specify dust-ignitionproof either.

With regard to relationship of Class I, Class II equipment, see Section 502.5.

 

[Julius Right]

NEC Art 502.10 Wiring Methods
(I) General. In Class II, Division 1 locations, the following
wiring methods shall be permitted:
( 1 ) Threaded rigid metal conduit (RMC) or threaded intermediate
metal conduit (IMC), including conduit systems
with supplemental corrosion protection coatings.
A NPT thread is required.No sealing.

 

[dvcraven0522!]

NEC Art 502.10 Wiring Methods
(I) General. In Class II, Division 1 locations, the following
wiring methods shall be permitted:
( 1 ) Threaded rigid metal conduit (RMC) or threaded intermediate
metal conduit (IMC), including conduit systems
with supplemental corrosion protection coatings.
A NPT thread is required.No sealing.

 

[dvcraven0522!]

Thank you all for your responses.

FYI - We have had some explosions relative to the motor starters for the belt conveyors in the space. Basically the starter enclosures where not maintained properly (screws missing or loose on covers etc.,) In essence I am working with an E.C. to relocate all of the starters to an existing MCC building on the roof and only provide start/stop stations at the belt conveyor motors.

So, that forces me to ask another question do the control stations at the motor need seal offs?

Just to be on the save side I am leaning toward providing the seal-off for any voltages. I am concerned where any device or wiring could cause a spark could potentially ignite in this enviroment.

 

[rbalex]

Thank you all for your responses.

FYI - We have had some explosions relative to the motor starters for the belt conveyors in the space. Basically the starter enclosures where not maintained properly (screws missing or loose on covers etc.,) In essence I am working with an E.C. to relocate all of the starters to an existing MCC building on the roof and only provide start/stop stations at the belt conveyor motors.

So, that forces me to ask another question do the control stations at the motor need seal offs?

Just to be on the save side I am leaning toward providing the seal-off for any voltages. I am concerned where any device or wiring could cause a spark could potentially ignite in this enviroment.

To my previous answer above, let me add Section 502.125(B).