Handhole between below grade Class 1, Div 1 area and Control Panel

[gust1j]

Question on NEC 501.15 (A)(4) Exception No. 2 and where to install the conduit seal for the Class 1, Div 1 boundary?

I'm adding some level sensors and limit switches to monitor a sluice gate and water level in a below grade sewage control structure considered a Class 1, Div 1 area. The new control equipment is fed from a PLC in an outdoor panel about 75' away, conduit from the control panel will pass through a handhole before penetrating the sewage control structure below grade. I have a few questions for anyone with experience with hazardous areas:

1) Can the Div 1 boundary conduit seal be installed at the outdoor control panel because of NEC 501.15 (A)(4) Exception No. 2?
2) Is the handhole considered a Class 1, Div 1 area if the conduit is not sealed before leaving the sewage control structure Div 1 boundary?
3) Are the conduit stub ups in the hand hole considered still below grade?

Heres a link to an image showing the basic line diagram of the

https://imgur.com/a/iIFYan0

 

[Isaiah]

Question on NEC 501.15 (A)(4) Exception No. 2 and where to install the conduit seal for the Class 1, Div 1 boundary?

I'm adding some level sensors and limit switches to monitor a sluice gate and water level in a below grade sewage control structure considered a Class 1, Div 1 area. The new control equipment is fed from a PLC in an outdoor panel about 75' away, conduit from the control panel will pass through a handhole before penetrating the sewage control structure below grade. I have a few questions for anyone with experience with hazardous areas:

1) Can the Div 1 boundary conduit seal be installed at the outdoor control panel because of NEC 501.15 (A)(4) Exception No. 2?
2) Is the handhole considered a Class 1, Div 1 area if the conduit is not sealed before leaving the sewage control structure Div 1 boundary?
3) Are the conduit stub ups in the hand hole considered still below grade?

Heres a link to an image showing the basic line diagram of the

https://imgur.com/a/iIFYan0

IMO, You’ll need to add 2 more explosion proof conduit seals:
One within 18” of the level sensor since it’s an arcing device - drain seal is suggested for top conduit entry.
And one where the conduit leaves the CID1 sewage control structure OR where it enters the hand hole since philosophically at least, the earth is considered to be ‘unclassified’ therefore a boundary seal is required.
The last conduit seal appears to be correctly shown on the sketch.


Sent from my iPhone using Tapatalk

 

[Dale001289]

Question on NEC 501.15 (A)(4) Exception No. 2 and where to install the conduit seal for the Class 1, Div 1 boundary?

I'm adding some level sensors and limit switches to monitor a sluice gate and water level in a below grade sewage control structure considered a Class 1, Div 1 area. The new control equipment is fed from a PLC in an outdoor panel about 75' away, conduit from the control panel will pass through a handhole before penetrating the sewage control structure below grade. I have a few questions for anyone with experience with hazardous areas:

1) Can the Div 1 boundary conduit seal be installed at the outdoor control panel because of NEC 501.15 (A)(4) Exception No. 2?
2) Is the handhole considered a Class 1, Div 1 area if the conduit is not sealed before leaving the sewage control structure Div 1 boundary?
3) Are the conduit stub ups in the hand hole considered still below grade?

Heres a link to an image showing the basic line diagram of the

https://imgur.com/a/iIFYan0

If the below grade cont structure is considered Class I Division 1 then the above grade area class must be at least Class I Division 2. Is the hand hole located in an unclassified area or Div 2 location?


Sent from my iPhone using Tapatalk

 

[gust1j]

IMO, You’ll need to add 2 more explosion proof conduit seals:
One within 18” of the level sensor since it’s an arcing device - drain seal is suggested for top conduit entry.
And one where the conduit leaves the CID1 sewage control structure OR where it enters the hand hole since philosophically at least, the earth is considered to be ‘unclassified’ therefore a boundary seal is required.
The last conduit seal appears to be correctly shown on the sketch.


Sent from my iPhone using Tapatalk

The level sensor will have a drain seal, that was shown on the level sensor install manual which is why its not shown in the diagram. Could you elaborate why a seal is needed at both the control panel and where conduit enters the sewage control structure? NEC 501.15 (A)(4) says that a seal is permitted on either side of the Class 1, Div 1 boundary.

 

[gust1j]

If the below grade cont structure is considered Class I Division 1 then the above grade area class must be at least Class I Division 2. Is the hand hole located in an unclassified area or Div 2 location?


Sent from my iPhone using Tapatalk

I would call it an unclassified area, but I'm not positive. The control panel, handhole, and sewage control structure are all located in an open field.

 

[Isaiah]

The level sensor will have a drain seal, that was shown on the level sensor install manual which is why its not shown in the diagram. Could you elaborate why a seal is needed at both the control panel and where conduit enters the sewage control structure? NEC 501.15 (A)(4) says that a seal is permitted on either side of the Class 1, Div 1 boundary.

If the area above the hand hole is indeed unclassified, you wouldnt need another conduit seal. If its Division 2 however, the hand hole would default to Division 1 - assuming heavier than air vapors - and you'd need the second seal. Obviously you cant seal underground, so the 10 foot boundary rule becomes a judgement call as to where exactly you install the seal. Also, check to see of the level sensor is "intrinsically safe". if so the 'normal' rules of conduit sealing are no longer applicable. See NEC 504.70.