Div I, Class 2 downgraded with ventilation, per NFPA 820, Chpt 9.

[Todd Foley]

We have an existing sewer pump station that is a Class 1, Div 2 hazardous location, and has been donwgraded to unclassified, with continuous ventillation at 6 air changes per hour, per Chapter 9 of NFPA 820.
If the air flow fails, an alarm signaling system is required per Chapter 7 of NFPA 820.
We are not providing pruge and pressurization because the control room is not sealed, and is open to the outside with several openings in the block walls.
The entire electrical system is connected to an emergency generator.
I do not see where NFPA 70, Article 500.7 allows ventilation as an approved protection method for donwgrading classifications. Will our electrical installation be required to be class 1, Div 2, to meet the accidental condition of a loss of air flow? Or can it remain unclassified?

 

[Smart $]

We have an existing sewer pump station that is a Class 1, Div 2 hazardous location, and has been donwgraded to unclassified, with continuous ventillation at 6 air changes per hour, per Chapter 9 of NFPA 820.
If the air flow fails, an alarm signaling system is required per Chapter 7 of NFPA 820.
We are not providing pruge and pressurization because the control room is not sealed, and is open to the outside with several openings in the block walls.
The entire electrical system is connected to an emergency generator.
I do not see where NFPA 70, Article 500.7 allows ventilation as an approved protection method for donwgrading classifications. Will our electrical installation be required to be class 1, Div 2, to meet the accidental condition of a loss of air flow? Or can it remain unclassified?

IMO HL classification comes before the applicable wiring method. Its either unclassified or C1D2. Can't be both.

But that's JMO...

 

[al]

Classification Detail

Classification Detail

We have an existing sewer pump station that is a Class 1, Div 2 hazardous location, and has been donwgraded to unclassified, with continuous ventillation at 6 air changes per hour, per Chapter 9 of NFPA 820.

Can you identify from NFPA 820 the Table and row where the classification was determined?