Explosion proof motors vs XP motors and NEC requirements for CID1 locations

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Dale001289

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I seem to recall motors installed in Class I Division 1 locations need to be Explosion Proof with a service factor of no greater than 1.0 and contain integral thermostats. In addition, T-Leads must be potted and end plates must be fitted with specific tolerances to contain an explosion internally. I understand too, TEFC motors cannot also be rated Explosion proof at the same time.
Yet we're seeing TEFC, 'XP' motors, UL listed, supposedly good for Class I Division 1, Groups C & D with 1.15 SF and T-Leads that are NOT potted - some contain T'Stats and some don't.

Is an 'XP' motor legitimately rated for Class I Division 1 locations?
 
With respect to marking equipment for hazardous locations, neither “XP” nor even “explosionproof” mean very much. See Section 500.8(C)(1) and (2). Only the “Class” and “Division” marks are relevant. Note there is no reference to the term explosionproof in rest of Section500.8(C).

Neither NEMA, UL, nor the NEC place any particular service factor restrictions on motors “...identified for Class I, Division I locations” nor are they required to have integral thermostats. This is may be a client or manufacturers' design preference. If the manufacture does provide them they must be used.

Basically, explosionproof motors are “beefed up” TEFC or TENV. They may not even be beefed up that much; it primarily deals with the bearings.

The motor terminal housing may be integral with the motor enclosure and not “potted”. In this case there must be an external seal. If there exists a factory seal between the motor terminal housing and the motor enclosure then it should say “factory sealed” or something similar.
 
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rbalex said:
With respect to marking equipment for hazardous locations, neither “XP” nor even “explosionproof” mean very much. See Section 500.8(C)(1) and (2). Only the “Class” and “Division” marks are relevant. Note there is no reference to the term explosionproof in rest of Section500.8(C).

Neither NEMA, UL, nor the NEC place any particular service factor restrictions on motors “...identified for Class I, Division I locations” nor are they required to have integral thermostats. This is may be a client or manufacturers' design preference. If the manufacture does provide them they must be used.

Basically, explosionproof motors are “beefed up” TEFC or TENV. They may not even be beefed up that much; it primarily deals with the bearings.

The motor terminal housing may be integral with the motor enclosure and not “potted”. In this case there must be an external seal. If there exists a factory seal between the motor terminal housing and the motor enclosure then it should say “factory sealed” or something similar.
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Thanks again Bob. I don't recall seeing anything stating "factory sealed" on the motor nameplate or motor datasheet. Is the external seal (conduit seal in this case) required if conduit is under 2"?
 
It's the general consensus of CMP14 that arcs can occur between the rotor and stator in "normal" operation.

Technically, if it enclosure doesn't say "factory sealed", it isn't; "potting" isn't necessarily a seal.
 
rbalex said:
It's the general consensus of CMP14 that arcs can occur between the rotor and stator in "normal" operation.
...
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BTW, There is a difference between "can" and "will". There is a difference between, "normal", and "common".

The usual philosophy is Division 2 deals with arcs that will occur under normal conditions, Division 1 deals with both "normal" and "abnormal" arc occurrences. However, "normal" is not defined in the NEC. For an interesting read see Section 500.8(B)(5) where it appears starting a motor isn't "normal". CMP14 has always been aware of this but hasn't quite figured out how to address it without disturbing other issues.

SO - motors are a somewhat special case. They could arc internally under common operating conditions. They aren't usually listed except for explosionproof" [Section 501.125(A)(1)] Then again, identified doesn't necessarily mean listed or labeled. See their definitions in Article 100 - just usually.
 
rbalex said:
With respect to marking equipment for hazardous locations, neither “XP” nor even “explosionproof” mean very much. See Section 500.8(C)(1) and (2). Only the “Class” and “Division” marks are relevant. Note there is no reference to the term explosionproof in rest of Section500.8(C).

Neither NEMA, UL, nor the NEC place any particular service factor restrictions on motors “...identified for Class I, Division I locations” nor are they required to have integral thermostats. This is may be a client or manufacturers' design preference. If the manufacture does provide them they must be used.

Basically, explosionproof motors are “beefed up” TEFC or TENV. They may not even be beefed up that much; it primarily deals with the bearings.

The motor terminal housing may be integral with the motor enclosure and not “potted”. In this case there must be an external seal. If there exists a factory seal between the motor terminal housing and the motor enclosure then it should say “factory sealed” or something similar.
Click to expand...


Bob, what part of the code states the Thermostats must be wired? is this due to manufacturers requirements only, if provided?
Many thanks for all your help.
 
Dale001289 said:
Bob, what part of the code states the Thermostats must be wired? is this due to manufacturers requirements only, if provided?
Many thanks for all your help.
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Section 110.3(B). While most motors aren't listed, explosionproof motors are.
 
rbalex said:
BTW, There is a difference between "can" and "will". There is a difference between, "normal", and "common".

The usual philosophy is Division 2 deals with arcs that will occur under normal conditions, Division 1 deals with both "normal" and "abnormal" arc occurrences. However, "normal" is not defined in the NEC. For an interesting read see Section 500.8(B)(5) where it appears starting a motor isn't "normal". CMP14 has always been aware of this but hasn't quite figured out how to address it without disturbing other issues.

SO - motors are a somewhat special case. They could arc internally under common operating conditions. They aren't usually listed except for explosionproof" [Section 501.125(A)(1)] Then again, identified doesn't necessarily mean listed or labeled. See their definitions in Article 100 - just usually.
Click to expand...

Is this backwards from the usual understanding of the distinction between Div 1 and Div 2? I always thought Div 1 meant the hazard was usually present and Div 2 that the hazard was present intermittently or due to abnormal circumstances (e.g. ruptured tank or leaking pipe).
 
gadfly56 said:
Is this backwards from the usual understanding of the distinction between Div 1 and Div 2? I always thought Div 1 meant the hazard was usually present and Div 2 that the hazard was present intermittently or due to abnormal circumstances (e.g. ruptured tank or leaking pipe).
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No, it's not backwards. In Division 1 fuel is available under "normal" conditions; ignition sources may or may not be. Division 2 means the fuel is not "normal", so only ignition sources need to be dealt with.
 
rbalex said:
It's the general consensus of CMP14 that arcs can occur between the rotor and stator in "normal" operation.

Technically, if it enclosure doesn't say "factory sealed", it isn't; "potting" isn't necessarily a seal.
Click to expand...

Bob, if a decision is reached during a CMP review, does that make it 'official'? If arcs can occur during normal rotor/stator operation, would that mean all motor termination boxes should be sealed, even Division 2? Ref 501.125(B).
 
Dale001289 said:
Bob, if a decision is reached during a CMP review, does that make it 'official'? If arcs can occur during normal rotor/stator operation, would that mean all motor termination boxes should be sealed, even Division 2? Ref 501.125(B).
Click to expand...
Unless the CMP's consensus is documented in the text of the NEC or an Official Interpretation, it isn't "official".

As I mentioned in Post #5, there is a difference between "can" and "will". While arcing may occur, it isn't common just as a short-circuit might occur in the interior of a raceway. Division 1 attemps to address both normal and abnormal sources of ignition. Division 2 only addresses ignition sources that occur as equipment is performing its intended operation.

Sealing a non-explosionproof enclosure is useless if arcs, sparks or high temperatures are a common event.
 
rbalex said:
Unless the CMP's consensus is documented in the text of the NEC or an Official Interpretation, it isn't "official".

As I mentioned in Post #5, there is a difference between "can" and "will". While arcing may occur, it isn't common just as a short-circuit might occur in the interior of a raceway. Division 1 attemps to address both normal and abnormal sources of ignition. Division 2 only addresses ignition sources that occur as equipment is performing its intended operation.

Sealing a non-explosionproof enclosure is useless if arcs, sparks or high temperatures are a common event.
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Thanks Bob. For my immediate scenario at hand - this particular XP i.e, Explosion Proof motor, does not actually state the words "Factory Sealed" anywhere on the nameplate or motor data sheet. Yet the vendor is telling me (have email) its not necessary, since the motor termination box has machined to precise tolerances for fit and has been UL listed for Division 1, therefore the box is by default, factory sealed and no additional seals are required.
I don't feel comfortable with his response. But since non of our standard motor details show conduit seals for Division 1 motors I'm sure there will be plenty of 'push-back' from Construction on this one.
 
"Machining" has nothing to do with factory sealing. It is certainly important to maintain the explosionproof integrity of the enclosure.

At this point I would contact UL directly. I've done it before ( it's one of the reasons I know what I know).
 
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