Class I, Div II installation

[overkill94]

I'm doing a third-party inspection in a cl I, div II location and they're using installation techniques I'm not familiar with.

1. Instead of a normal pressurized purge or an explosion-proof panel, they have external air constantly blowing through the panel and some sort of moisture gauge

2. Some motors are rated for cl I, div II but others are TEFC, and some motors are regular Design B, insulation class F

3. Another panel isn't purged or explosion-proof but all components inside (mostly 120 VAC and 24 VDC) are rated for cl I, div II except for some fuseholders and a low voltage counter (motor hours I think)

The customer seems pretty confident that these are all acceptable practices except for maybe the Design B motor and the fuseholders/counter. When I looked through NEC articles 500/501 I ended up with more questions than answers. What say you, experts?

 

[rbalex]

I'm doing a third-party inspection in a cl I, div II location and they're using installation techniques I'm not familiar with.

1. Instead of a normal pressurized purge or an explosion-proof panel, they have external air constantly blowing through the panel and some sort of moisture gauge

2. Some motors are rated for cl I, div II but others are TEFC, and some motors are regular Design B, insulation class F

3. Another panel isn't purged or explosion-proof but all components inside (mostly 120 VAC and 24 VDC) are rated for cl I, div II except for some fuseholders and a low voltage counter (motor hours I think)

The customer seems pretty confident that these are all acceptable practices except for maybe the Design B motor and the fuseholders/counter. When I looked through NEC articles 500/501 I ended up with more questions than answers. What say you, experts?

1. What is inside the panel that would require it to be explosionproof or purged/pressurized in absence of simple ventilation? Is the moisture gauge an arc-making device?

2. Are the motors three-phase? How do you know some of them are rated for Division 2? Why would Design B be an issue?

3. Is there a disconnect ahead of the fuses that is suitable for the area classification? Is the counter an arc-making device?; how do you know?

 

[overkill94]

1. What is inside the panel that would require it to be explosionproof or purged/pressurized in absence of simple ventilation? Is the moisture gauge an arc-making device?

2. Are the motors three-phase? How do you know some of them are rated for Division 2? Why would Design B be an issue?

3. Is there a disconnect ahead of the fuses that is suitable for the area classification? Is the counter an arc-making device?; how do you know?

1. It's a normal control panel with circuit breakers, contactors, etc. I don't believe the gauge is arc making

2. Yes, 3-phase; some have a class I div II certification on them; Wasn't sure if the design would have any effect on whether it would be acceptable or not

3. No disconnect in the panel - this is a subpanel that is fed from a circuit breaker in a non-classified location

 

[rbalex]

1. It's a normal control panel with circuit breakers, contactors, etc. I don't believe the gauge is arc making

2. Yes, 3-phase; some have a class I div II certification on them; Wasn't sure if the design would have any effect on whether it would be acceptable or not

3. No disconnect in the panel - this is a subpanel that is fed from a circuit breaker in a non-classified location

1. Unless the customer can show the installation is consistent with NFPA 496, Type Z pressurization, it would not appear to be suitable for Class I, Division 2.

2. If the motor certification is only CSA, it is technically not acceptable. That said, TEFC is generally acceptable in Division 2.[501.125(B)]

3. For the fuses, see 501.105(B)(5) or 501.115(B)(3).

 

[srinivasan]

The customer seems pretty confident that these are all acceptable practices[/QUOTE] If it is a specification based project, ask them to show the specification where it is mentioned to use such a equipments/instruments. If it Ex 'p' panel, passing air into the panel without purge/ pressurized is not acceptable.