Class I, Division I Seal-Off Controversy

**GHoffman** · 02-08-19, 02:17 PM

I need your help as soon as possible.
We have a dilemma at our current job site with installation of seal-off’s in a gas production facility at our present job site. The situation is that it is common practice to install a short within 18", a run from the seal-off, to a GUAC conduit body, on to a hazard rated union, and on to an instrument; in all, does not exceed the 18 inch maximum requirement as per NEC Art. 501.15(A)(1)(2) and 501.15(A)(3) See attached picture.
With understanding that in NEC Art. 501.15(A)(3) first states that two or more enclosures basically have to have a seal-off within 18" of each other of not more than 36" in a conduit run and goes on to state "or run of conduit shall be considered sufficient if the seal is located not more than 450 mm (18 in) from the enclosure." Until now, our past customers in the Class I, Division I environment, ruled this installation acceptable and within guidelines.
The reasoning on this is so that if the instrument needs to be replaced, that you can access conductors from the GUAC without damaging them. In addition, the instrument could be easily replaced without shortened or damaging branch circuit conductors, prevent possible seal-off damage and make termination readily accessible. Unfortunately, although this installation is common practice here in the gas and oil fields, the customer wages different to say that this installation is not legal.
Please advise.
Regards, Scooter Hoffman
Name: Class1_Div1 Seal-Off Controversy IMG951746.jpg
Views: 202
Size: 146.3 KB

Name: Class1_Div1 Seal-Off Controversy IMG951746.jpg
Views: 202
Size: 146.3 KB

**petersonra** · 02-08-19, 02:52 PM

read carefully what the last paragraph of 501.15 (A) (2) says.

**oldsparky52** · 02-08-19, 03:06 PM

These are not intrinsically safe circuits?

**Wire-Smith** · 02-08-19, 10:56 PM

Violation if a seal is required, adding the extra volume of guac adds more to the possible explosion pressure on that seal. Its like going over 18". 501.15(A)(1) last paragraph after (1)&(2)

Also, that liquidtight isn't legal, if c1d1 like you say

**don_resqcapt19** · 02-09-19, 05:21 PM

Prior to the 2017 code, conduit bodies of the same trade size as the conduit were permitted between the enclosure that requires sealing and the seal fitting.

2014 501.15(A)(1) ... Only explosionproof unions, couplings, reducers, elbows, capped elbows, and conduit bodies similar to L, T, and Cross types that are not larger than the trade size of the conduit shall be permitted between the sealing fitting and the explosionproof enclosure.

That permission to install conduit bodies between the enclosure and the seal was removed in the 2017 edition of the code.

2017 501.15(A)(1) ...Only explosionproof unions, couplings, reducers, elbows, and capped elbows that are not larger than the trade size of the conduit shall be permitted between the sealing fitting and the explosionproof enclosure.

**GHoffman** · 02-09-19, 09:09 PM

Thanks for your support. I have read several forums relating to this issue and like the other fella's noticed in the 2017 that 'conduit bodies' was omitted compared to 2014 and not sure if it was intentional or error. It is what it is and thanks. Scooter

**don_resqcapt19** · 02-10-19, 04:32 PM

Originally Posted by GHoffman

Thanks for your support. I have read several forums relating to this issue and like the other fella's noticed in the 2017 that 'conduit bodies' was omitted compared to 2014 and not sure if it was intentional or error. It is what it is and thanks. Scooter

It was an intentional change. The panel statement on the revision said:

Conduit bodies were removed from the list in (2) because they should not be allowed in this application due to the increased volume in the raceway system.

**GHoffman** · 02-11-19, 02:47 PM

Pertaining to the attached picture, I received a call from the journeyman who installed the instrument and I need to clarify that the instrument was indeed in a c1d2 area. The problem that he has is that the instrument has external wiring much like a Murphy switch LS200. Problem in the field is most instruments having external wiring which have to have an immediate seal-off will have to require some sort of conduit body for terminating but with that would require a union (optional) and an additional seal-off on towards the raceway.
So would it be: Instrument w/external wiring, seal-off, GUAC conduit body, c1d1 union, and 2nd seal-off?
Am I right? Was hoping for more of a simpler scenario.
Scooter

**gadfly56** · 02-11-19, 03:48 PM

Originally Posted by don_resqcapt19

It was an intentional change. The panel statement on the revision said:

What was the justification, other than it was someone's erroneous application of the precautionary principle? Did someone actually fill the section with an explosive mixture and spark it?

**petersonra** · 02-11-19, 03:53 PM

Originally Posted by GHoffman

Pertaining to the attached picture, I received a call from the journeyman who installed the instrument and I need to clarify that the instrument was indeed in a c1d2 area. The problem that he has is that the instrument has external wiring much like a Murphy switch LS200. Problem in the field is most instruments having external wiring which have to have an immediate seal-off will have to require some sort of conduit body for terminating but with that would require a union (optional) and an additional seal-off on towards the raceway.
So would it be: Instrument w/external wiring, seal-off, GUAC conduit body, c1d1 union, and 2nd seal-off?
Am I right? Was hoping for more of a simpler scenario.
Scooter

why would you need a second seal, unless you are talking about the boundary seal?

eta: and why do you need an XP conduit body to make the splice in?