501.105 (B)(3) Meters, Instruments, Relays

[fifty60]

To use the exception to 501.105(B)(3) the NFPA 2017 says "...and if the marked maximum operating temperature any exposed surface will not exceed 80 percent of the AIT in degrees C..." What is meant by "MARKED" here. If the general purpose enclosure in question is a single component of a larger piece of Machinery, would the OEM of the larger piece of Machinery be able to test and mark the surface temperature of the component even though they are not the manufacturer of the individual component?

The item in question is a pneumatic solenoid bank that has built in Ethernet. The Solenoid bank itself is explicitly allowed per 501.105(B)(4), but the electronics involved with the ethernet portion lead me to 501.105(B)(3). The AIT is 400 C, so the equipment OBVIOUSLY does not get anywhere near the AIT. The hazardous area is Class I Div 2. To properly use the bank, can I test the exposed surfaces and see then mark the enclosure with this temperature? Is there anyway to use 500.8(C)(5) Special Allowances for General Purpose equipment as reasoning not have to mark the component?

 

[petersonra]

At least some of these solenoid banks are already listed for use in CI D2 areas.

 

[fifty60]

If I could find one that is already listed as CID2 that would certainly be ideal. Do you have any examples off hand that are already listed for CID2? The manufacturers I am looking at have their standard versions, which are not listed, and then they have the intrinsically safe versions. The IS versions are great, but expensive and not necessary for CID2.

I am thinking that they either do not list the normal Solenoid Banks because they are explicitly allowed in CID2 areas, or they no list them because they want to sell more of the IS one, or they simply not got around to listing the ethernet solenoid banks...

The bank meets all the requirements of 501.105(B), except for the temperature "marking" requirement. There is no definition of "Mark" in article 100. Article 500 does define marking, and in 500.8 (C)(4) and 500.8 (C)(6) this definition of marking have exceptions to the requirement of having to mark temperature. Not sure the proper way to look at the marking requirements for 501.105(B)(3), and the requirements in 500.8(C) seem to be the only to go by.

 

[Dale001289]

If I could find one that is already listed as CID2 that would certainly be ideal. Do you have any examples off hand that are already listed for CID2? The manufacturers I am looking at have their standard versions, which are not listed, and then they have the intrinsically safe versions. The IS versions are great, but expensive and not necessary for CID2.

I am thinking that they either do not list the normal Solenoid Banks because they are explicitly allowed in CID2 areas, or they no list them because they want to sell more of the IS one, or they simply not got around to listing the ethernet solenoid banks...

The bank meets all the requirements of 501.105(B), except for the temperature "marking" requirement. There is no definition of "Mark" in article 100. Article 500 does define marking, and in 500.8 (C)(4) and 500.8 (C)(6) this definition of marking have exceptions to the requirement of having to mark temperature. Not sure the proper way to look at the marking requirements for 501.105(B)(3), and the requirements in 500.8(C) seem to be the only to go by.

Is there anyway to relocate the solenoid bank just outside the Division 2 area? My guess is the temp marking refers to T ratings per T500.8(C)

 

[fifty60]

Being able to locate them out of the CID2 area would actual be more ideal than finding a CID2 listed version. However, it is not possible to relocate them. I am not able to find the T code, but I believe the ethernet solenoid bank would have to have one somewhere since it is UL listed. So that information probably exists somewhere. I would like to be able to use the 500.8 references above for not having to mark the temperature on the equipment at all, since it obviously does not reach anywhere close to 80% of 400 C, and is general-purpose fixed equipment.

 

[fifty60]

Reading 501.105 many more times, it occured to me that 501.105(B)(3) is not saying that the temperature has to be marked. It says that the "marked" temperature cannot exceed 80% of the AIT. If the equipment is not marked with the temperature to begin with, then it would meet this requirement. Especially since 500.8 (C)(6) is saying it does not have to be marked to begin with. Does this sound like a sound understanding of the requirements? None of the exposed surfaces are required to be marked. If any where required to be marked, then they would have to be 80% of the AIT.

 

[Dale001289]

Reading 501.105 many more times, it occured to me that 501.105(B)(3) is not saying that the temperature has to be marked. It says that the "marked" temperature cannot exceed 80% of the AIT. If the equipment is not marked with the temperature to begin with, then it would meet this requirement. Especially since 500.8 (C)(6) is saying it does not have to be marked to begin with. Does this sound like a sound understanding of the requirements? None of the exposed surfaces are required to be marked. If any where required to be marked, then they would have to be 80% of the AIT.

You may need to contact the manufacturer directly; See 500.8(A)(3). Even though a listing isn't required, Inspectors may not share your interpretation without some back up paperwork.

 

[IntrinsicSafety]

On first reading, I would think "marked" is referring to 501.105(B)(1):

"Where such an assembly includes any of the equipment
described in 501.105(B)(1), 501.105(B)(2), and
501.105(B)(3), the maximum obtainable surface temperature
of any component of the assembly that exceeds 100°C shall be
clearly and permanently indicated on the outside of the enclosure.
Alternatively, equipment shall be permitted to be marked
to indicate the temperature class for which it is suitable, using
the temperature class (T Code) of Table 500.8(C)."

In this context, the "marking" does not mean an agency marking / listing. It means somebody (i.e. you) did the necessary evaluation and marked the enclosure with the worst-case temperature.

Also, 501.105(B)(1) allows equipment to be "tested". It doesn't say by who. So I'm thinking anyone could do that test as long as you can satisfy your inspector / AHJ that you did it correctly. That fits with the above.

The whole point of 501.105(B) seems to be to allow people to put together assemblies for Div 2 areas without the need to have all of it Div 2 listed. So they're basically asking for verification the bits are non-incendive (i.e. non-sparking, no hot surfaces). As long as somebody does that evaluation, it's OK. All of the above is consistent with that.

If you do such an evaluation, the marked temperature will have to be the worst-case temperature. So full load, worst-case operating conditions, worst-case ambient temperature, etc.

Just my $0.0153987 $USD.

 

[rbalex]

Actually FWIW, in the 2017 NEC, solenoids fall under Section 501.105(B)(4) and aren't included in "... the equipment described in 501.105(B)(1), 501.105(B)(2), and 501.105(B)(3) …".