Class 1, Division 2, Group B

Status
Not open for further replies.
D

derick hoffpauir

Member
The NEC allows the use of a TEFC motor in a class 1, Div. 2 location provide the motor has no arc producing devices such as brushes, 501-8(b). Can you install a TEFC motor in a class 1, div. 2, group B rated area? TEFC motor nameplates do not have a group rating.
 
Re: Class 1, Division 2, Group B

The NEC does not require motors installed in Class 1 Division 2 areas to have Class, Division or Group ratings. The NEC permits the use of standard induction motors in this location.
Don
 
Re: Class 1, Division 2, Group B

Don is correct. See 500.8(B), Exception 3 & 501.8(B)[last sentence].

There is a new "twist" though. I don't know exactly when, but between 4 and 6 months ago, UL began listing motors specifically for Division 2. Previously, they had only listed motors for Division 1 locations. (Explosion proof)

See UL's Online Certification Directory . Do a search on Category Code "PTHE." As of today, three manufacturers are listing Div 2 motors. One lists for all four Class I, Groups. One lists for Class II only. A third lists for Class I, Groups C&D only. FYI, Div 1 motors are Category Code "PTDR."

The significance? It depends on the "listing" requirements of various AHJ's. Check FedOSHA's Definition of "Acceptable"

For general interest's sake, check out who lists motors for "ordinary location" (general purpose)(Cat Code "PRGY")
 
Re: Class 1, Division 2, Group B

Yes, you can install a TEFC motor in a 1-2-B electrical classification, providing there are no arcing devices. The one thing that you will need to be concerned with is temperature. As you are aware the motors today run hotter than the old days, due to the reduction of iron in the stator.
What you need to know is the AIT, (Auto-Ignition Temperature)of the chemical that you are dealing with, and then you cannot have any item have a surface temperature greater than 80 % of the AIT of the chemical that you have in the classified area.
You mention a TEFC motor, you can actually install a open type motor in a Class 1, Division 2 area, provided that their are no arcing devices. I am totally against installing an open type motor in a classified area, and I would not do it, but the code will allow it.
 
Re: Class 1, Division 2, Group B

The basic AIT rule for classified locations is found in 500.8(C):
(C) Temperature. The temperature marking specified in 500.8(B) shall not exceed the ignition temperature of the specific gas or vapor to be encountered.
Click to expand...
Note there is no general 80% of AIT requirement. Nor is there such a rule specifically for motors in Division 2. The 80% reference in Section 501.8(B) refers to the motor space heaters not the motor themselves.

Per 430.7 motors may have either rated temperature rise or the insulation system class and rated ambient temperature. Based on the worst conditions allowed by NEMA, the highest absolute maximum winding temperature any motor is permitted under ?normal? operating conditions is 175C (T3A). Note: Starting a motor is not considered ?normal? in Classified locations [See 500.8(A)(5)]. More typically, the absolute maximum (based on 40C ambient and a ?Class B? temperature rise) is 125C(T4). This is the common operating condition for IEEE 841 type motors. This is the type of motor I generally recommend and specifiy for Division 2.

Unless it's something exotic, Group B is almost exclusively hydrogen (AIT 520C). A few Group C materials have an AIT below 125C.

IEEE conducted some fairly extensive tests and found that, with the flammable material in free flow across a TEFC motor, the minimum ignition energy (MIE) could not be delivered until the winding temperature was at least 100C above the AIT.

The primary concern I have with motors in Division 2 is with VFD applications. NEMA MG-1 recommends motor manufacture consultation. So do I. For Division 1, NEMA requires the motor to be specifically identified for VFD applications as well as Div 1.
 
Re: Class 1, Division 2, Group B

Thanks for all of the input. The chemical thats puts us into the group B rating is Butadiene. 500-5(a)(2)exception 1 allows the use of group D rated equipment provided all conduit runs into explosion proof equipment are provided with seals installed within 18 inches. The problem is that for Class 1, Div. 2 the allowable TEFC is not explosion proof.
 
Re: Class 1, Division 2, Group B

Butadiene (AIT 420C) is one of the "exotics;" the others are found in 500.6(A)(2) Exception 2. I call them "exotics" because their current "Group" is based on their residual identifications from older Codes and standards rather than the current definitions that were introduced in the 1999 NEC.
 
Re: Class 1, Division 2, Group B

To: rbalax, and to any electricians that are dealing with electical classified areas.
Yes, I stated the AIT temperature of a motor shall not exceed 80% of the AIT of the chemical that is in the area. What I should have stated is the following: In a Class 1, Division 2, Group A,B,C,or D, the surface temperature of any electrical equipment shall not exceed 80% of the AIT (auto-ignition-temperature)for the chemical that is in the area. This means lighting fixtures, heaters,etc. The reason that I mentioned motors is because today, three-phase induction motors and transformers do run hotter than they did many years ago.
You can read Section 501.9(B)(1)through(5).
 
Re: Class 1, Division 2, Group B

In Division 2, fixed luminaires, have several interlocking marking and installation requirements. The unique marking requirements are actually exceptions to the general marking requirements found in 500.8(B). [See Exceptions 2 & 3].

The general installation requirement is 501.9(B); the specific requirement is 501.9(B)(2). The last sentence is critical. The 80 percent AIT requirement applies to the lamps ? not the luminaires, per se.

Fixed luminaires (lighting fixtures) in Division 2:

1.) Must have a ?T? rating, and
2.) are not required to have a ?Group? rating, and
3.) if their lamps exceed 80 percent of the AIT they must either be identified for Division 1 or the luminaire?s ?T? rating must have been determined by test ? in which case it may operate at 100 percent AIT.

Ever since "T" rating became a marking requirement in classified locations, Div 2 luminaires have had their ratings determined by test.

In Division 2, there is no general rule of restricting operating temperatures to 80 percent of AIT. Some are similar to luminaires, where testing permits 100 percent AIT if the ?T? rating is determined by tests. Others, such as utilization heaters, are absolute.

In Division 1, the 80 percent rule is absolute [edit add] for exposed surfaces.

[ August 05, 2004, 03:06 PM: Message edited by: rbalex ]
 
Status
Not open for further replies.
Top