Cord Connectors at Classified Boundary Edge and Wet Well Classification

[bhuey]

I'm reviewing a project that is going to retrofit an existing sewage lift station that is installed at the end of a hallway. The lift station serves a small section of offices and pumps wastewater out to an on-site septic system. The project will be cutting the top off of the old tank and installing a new plastic tank with Class I Div 1 rated submersible grinder pumps. The pumps come with an integrated flexible cord. There is also a set of intrinsically safe floats with integrated flexible cords.

The package came with cord connectors to get the power and control cables through the top of the tank. We will need to tap the plastic top of the tank or install a bulkhead fitting for the cord connectors. The control cable connector is CID2 listed, the power cable connector is not listed but is pressure rated.
Control Connector: https://hubbellcdn.com/specsheet/WIRING_SHC1023CR_spec.pdf
Power Connector: https://www.sealconusa.com/products...relief-fittings/nylon/standard/npt/cd21nr-bk/

A four cable cord seal was included for the float cables: http://www.sjerhombus.com/uploads/SJE_Cord_Seal_Features.pdf

Do cord connectors for flex cable at the boundary of a CID1 space need to be approved for CID1 spaces per 501.10(A)(3)? These fittings will be primarily outside of the boundary but their edge will be touching it. Their purpose it just to support the cable and seal the boundary. If bulkhead fittings are used for connecting the cord connectors would they need to be CID1 approved?


The engineer is looking at classifying the space based on NFPA 820 Figure A.4.2 with the wet well being CID1 and the 'physically separated' room being unclassified. However since there is piping connections an a removable access hatch on the top of the tank this figure doesn't appear to apply to our situation. Reading over NFPA 820 Table 4.2.2 Row 16 'Wastewater Pumping Station Wet Well' or Row 11 'Residential wastewater pumping station wet well' look like the appropriate examples. The upper left diagram in Figure A.4.2(c) looks like the proper diagram even though it doesn't show the wet well being installed in a building. But even this seems over classified for the service. It isn't a residential system but the function is the same. This lift station serves six offices and around 10 people throughout the day. NFPA 4.1.2 states 'this chapter shall not apply to on-site systems' so I think we have some leeway in choosing a fit for purpose classification. Would it be appropriate to classify the space per Table 4.2.2 Row 10 and Figure A.4.2(b) as Class I Div 2?

 

[rbalex]

Sorry for the tardy reply, I don't like to shoot from the hip.

A few comments:

• You haven't mentioned the ventilation so far.​
• Depending on ventilation, with regard to cable terminations, you should be reviewing NEC Sections 501.15(D) and/or (E) and 501.10(B)(4) as well as 501.10(A)(3).
• So far, you have described a non-residential wet well (Table 4.2.2 - Line 16) and not a sewer (Table 4.2.2 - Line 10)

It doesn't take too much for a wet well to become Division 2 (or Division 1 with poor ventilation).

 

[bhuey]

• The tank is vented to atmosphere with no other ventilation.
• Terminations in the tank are part of the listed grinder pumps and the level switches. They came from the factory with the cords attached and sealed.
• 'Row 10' was a typo. I was looking at 'Row 11 Line a' in Table 4.2.2 for 'RESIDENTIAL WASTEWATER PUMPING STATION WET WELL - Pumping station transporting primarily residential wastewater' with less than 12 air changes per hour.

Thanks for looking at this. Quality responses are worth the wait.

 

[rbalex]

• The tank is vented to atmosphere with no other ventilation.
• Terminations in the tank are part of the listed grinder pumps and the level switches. They came from the factory with the cords attached and sealed.
• 'Row 10' was a typo. I was looking at 'Row 11 Line a' in Table 4.2.2 for 'RESIDENTIAL WASTEWATER PUMPING STATION WET WELL - Pumping station transporting primarily residential wastewater' with less than 12 air changes per hour.

Thanks for looking at this. Quality responses are worth the wait.

• Row 11 is still non-residential, I would definitely seek buy-in from the AHJ to secure a Division 2 evaluation. In this particular case, it's a judgment call as to whether the volume of effluent generated is insufficient to create a Division 1 location. (Poor ventilation quickly leads to Division 1.) BTW, how was the original wet well classified?
• There are more to cables than terminations. Also see Sections 501.15(D)(2). If you do secure Division 2 approval, See Sections 501.15(E)(3) instead. In either case, I guarantee you won't get any NRTL certification that the cable is "incapable of transmitting gases or vapors".

 

[bhuey]

• Row 11 is still non-residential, I would definitely seek buy-in from the AHJ to secure a Division 2 evaluation. In this particular case, it's a judgment call as to whether the volume of effluent generated is insufficient to create a Division 1 location. (Poor ventilation quickly leads to Division 1.) BTW, how was the original wet well classified?
• There are more to cables than terminations. Also see Sections 501.15(D)(2). If you do secure Division 2 approval, See Sections 501.15(E)(3) instead. In either case, I guarantee you won't get any NRTL certification that the cable is "incapable of transmitting gases or vapors".

• "Row 11 is still non-residential," - I don't understand. Row 11 is for residential wastewater pumping station wet wells. Are you saying that my installation is still non-residential or something else?
• The original wet well doesn't appear to have any classification. It's from 1974 and the motors are installed outside of the wet well.
• The cables came already sealed at the termination. The jacket will be kept continuous to the control box. Cords are not installed in conduit in the wet well. The boundary transition is planned to be made with the cord passing through the cord connectors and cable seal I linked to in my original post.
• Can these cord connectors I linked to be used at the top of the tank / classification boundary? They are not approved for Class I Division 1 as required by 501.10(A)(3) but they will be primarily outside of the classified area. What approval / listing is required for cable fittings that are at the boundary of a classified area? Can these connectors be used if the wet well is classified Class I Division 1 with a Class I Division 2 bubble around where the cables cross the boundary?

 

[rbalex]

I apologize, I may have misunderstood - are you saying it is definitely a residential application? If so, then Division 2 seems applicable and you're home free. "Offices" does not generally lend itself to "residential", but as I said, the volume of effluent is what makes the distinction.

You really don't need a boundary seal for cables that are sealed at the terminations under Section 501.15(E)(3) and the "unclassified" end doesn't need a seal either. Judiciously selecting the "boundary" as being outside the jacket may help. (Need to make that clear in your documentation though) That's one of the reasons UL will certify certain cable jackets as having a "gas/vaportight continuous sheath" even if they are "capable of transmitting gases or vapors through the cable core." In other words, if gases or vapors can't enter the cable through the "sealed" end how will they be transmitted to the unclassified end - especially where they weren't supposed to be gases or vapors in the Division 2 location under "normal" operating conditionsin the first place?

 

[bhuey]

It is definitely office space. The sewage is treated on-site so per NFPA 820 4.1.2 "This chapter shall not apply to on-site systems, force mains, or those sewers that principally convey industrial wastes." So Table 4.2.2 doesn't apply but it is still the best resource I have to evaluate this installation. There is typically 10 workers in the office space.

I agree with your assessment on the boundary seal requirements if the area can be classified as a Class I Division 2 area.

If the area is classified as Class I Division 1 how do we bring the cable through the bulkhead and meet code? From what I've read in the code a cable seal still won't be required at the boundary but we do want to limit passage of gas in the hole that the cable passes through. The design calls for these cord connectors and cable seals to provide this function but they aren't listed for Class I Division 1. Can the classified boundary be defined as going right up to the cord connector but not include the cord connector? That makes sense but it also seems a bit peculiar. Could this boundary edge definition also work are bulkhead fittings used at the top of the tank so that we had something to screw our cable connectors to?

 

[rbalex]

As I’ve mentioned before, the volume of effluent is the key to the real distinction between “residential” and “industrial”; in that light, I suggest looking at Table 4.2.2, Line 9. (We were so close.)

That said, if for some reason it is determined that the wet well is still Class I, Division1, the situation is more complex than Division 2. Again, carefully clarifying and documenting that the “boundary” is the exterior of the cable, I would not terminate the cable at the bulkhead, but rather extend it completely through a connector similar to either the Hubbell or Sealcon. Then accept there will be a small classified envelope similar to that shown around the vents in NFPA 820, Figure A.4.2(c) [Left side]. As long as the cable end is sealed in the well, there is no need for a "boundary" seal or one on the unclassified end for a cable that extends completely through the resultant envelope, IMO, the connector only needs to be listed for supporting the cable as its function is mechanical only and not electrical since it would not produce any ignitions on its own.

 

[bhuey]

Thanks, Bob.

I was also looking at Table 4.2.2, Row 9 when I was considering the installation in the residential class. That location and function permits no more than 1500 gallons per day. With the toilets we have that permits each person around 100 flushes per day.

What you propose for handling the Class I Division 1 situation also makes sense. My hang up has been the 501.10(A)(3) Boxes and Fittings statement 'All boxes and fittings shall be approved for Class I, Division 1. Article 100 defines fittings as 'An accessory such as a locknut, bushing, or other part of a wiring system that is intended primarily to perform a mechanical rather than an electrical function.'

I will pass this information along to the engineer putting together the installation package.

 

[rbalex]

Approved is also a defined term and it doesn’t necssarily mean listed or labeled or even identified (all are Article 100 defined terms - you should check and be intimately familiar with all of them if you do any great deal of HazLoc work)

There was an attempt during the 1999 and 2002 NEC cycles to require all material and equipment in Classified locations to, in fact, be specifically listed or labeled ​for the locations. It failed, but the end result was what became Section 500.8(A). This was to give AHJs a basis for “approval” in absence of a listed or labeled product.

If you read Section 500.8(A) carefully, you Will find it closely parallels FedOSHA's definition of acceptable in Part 29 CFR 1910.399. Also check the definitions of accepted and approved.

Personally, I would have no problem standing by NEC Section 500.8(A)(3) as the basis for my recommendations. Remember: the goal in this case is to prevent the cable(s) from channeling flammable materials from the classified location to a source of ignition.