Class 1 Div 2 Motors

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I have 8 motors in a class 1 div 2 location inside a methane gas compressor building. The enclosures are all TEFC. All the motors are rated class1 div 2.THere is gas detectors located above all the compressors/motors. These detectors will turn on a ventilation system and shut down the motors if they detect methane. My question is are sealoffs required for the power feed,RTD's, and space heaters in these motors? I have an electrical inspector saying yes they are if the motors aren't sealed at the point the wires come out of the frame into the motor junction box. But on the other hand they will not be energized if gas is detected.

edited to remove slang word that may be offensive to some
 
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don_resqcapt19

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Don,
In a Division 2 area, those items do not require sealoffs. The only seals that are required are at the boundry, and any enclosure that has an arc producing device. Note, this assumes that the motors do not have any brushes or switches within them.
Don
 

rbalex

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Unless they are installed per one or more of the conditions listed in Sections 500.7(K)(1), (K)(2), or (K)(3), the gas detectors are irrelevant. It appears 500.7(K)(1) may apply ? it?s hard to tell from your description.

Since they are TEFC, the motors are probably suitable for Division 2, but it is highly unlikely they are actually rated for it.

Having said all that, Don is still correct assuming the room is properly classified.
 
Ventilation

Ventilation

There are 4 exhaust fans suitable to purge the building of any gas leaks in the event that one does happen. These fans are controlled by the gas detectors located in the ceiling. Which also shut down all processes of the gas. We do not normally have gas in the atmosphere when in operation. This is why we are Class1 Div 2. :smile: And the building is limited access. There are no manned operations inside.
 

bobgorno

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Colorado
Don,

Not knowing all your particulars, here is my best guess, 1-1/2 cents worth, not that it matters.

You've noted all of the motors are rated Div. 2. Are they truly rated Div. 2 or just applied in a Div. 2 area as allowed by 501.125(B)? Watch out for the space heaters. UL does not currently rate or list Div. 2 motors. CSA does. If they are CSA approved Div. 2 motors, they should have a temperature code. So far so good if you comply. Easier to meet 501.125 if it has a T code.

Ventilation only starts when gas is detected? Hopefully bldg ridge vents are at least always open. If gas detection is considered adequate per recommendations in API RP500, I would think that your building is considered Div.2, inadequately ventilated, with adequate gas detection. (Bob A., am I on right track here?). Div. 2 motors would not have to be S/D on gas detection, but if they are not certified as Div. 2 motors it may be a good idea to be conservative. Are the motors controlled by a VFD?? That can throw a monkey wrench into the whole thing if they are not rated for inverter use and operations are at lower speeds.

No seal-offs would be required at the motor connection box, or the RTD connection box. Since the space heater is not XP, seal-off does you no good there....space heaters still make me nervous, although it probably runs way below the AIT of Methane.

B.G.
 

rbalex

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Yes - you caught my meaning. While gas detection is a recognized protection technique its applications are limited to those listed. The biggest problem is that there is no application Standard similar to NFPA 496 for Purged/Pressurized systems. In the ROC for the 2002 NEC, I suggested the industry that proposed gas detection submit a request to the NFPA Standards Council to create such a document.

Because NFPA rules prohibit mandatory references to outside Standards, those listed in the FPNs to 500.7(K) aren't "code" but API RP500 does address applications for 500.7(K)(1).

Edit Add: UL has begun to list some motors for Division 2. (Item Code "PTHE") Most of them are still "specialty" items and not too likely to be those used in the OP. However, there is one manufacturer that appears to now have a "broad" line of Div 2 listed motors. This could cause havoc in light of some Fed and local OSHA rules. Side Note: The CSA listing in meaningless even though some jurisdictions have erroneously accepted it.
 
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