We are installing conduits between quazite hand holes and need to bond the rigid metal conduits. Some boxes are designated for AC power which will have their bonding jumpers sized in accordance with Table 250.122. However, other boxes are designated strictly for 24VDC instrument cables/conduits, others for fiber optic only cables/conduits. There are also several spare conduits with no assigned cables. This is where I'm stumped. I know we need to install bonding jumpers in these locations as well, but how would I size them?
Bonding Discontinuous Raceways
- Thread starter quantum
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Are they required to be bonded?
What is the application/location of these conduits? (Other than in the ground)
They presumably emerge somewhere and go back to some type of equipment.
Just trying to get all the info
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Bonding jumpers are in T. 250 102(C)(1)
250.122 is for equipment grounding conductor.
250.122 is for equipment grounding conductor.
It's a customer spec and I'm referring to 300.10. In general, DC conduits extend from the Station Control Panel to instrument end devices. AC conduits extend from power panels or the MCC to their loads. Spare conduits exist between quazite boxes.
But I'm not dealing with main or supply side bonding jumpers?
250.102(D)
"A single common continuous equipment bonding jumper shall be permitted to connect two or more raceways or cables if the bonding jumper is sized in accordance with 250.122 for the largest overcurrent device supplying circuits therein."
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If metallic raceways are entering non-metallic quazite boxes what are you bonding them to, other than each other? 300.10
If the customer specd it, ask for a bonding jumper size?
That's certainly the final solution, but I always like code guidance/reference before entering the RFI process.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Right you said bonding but as I see it a piece of metal conduit is an equipment grounding conductor. Thus 250.132 is applicable I believe and the jumper between raceways should be sized by 250.122
- Location
- Bremerton, Washington
Bonding is typically not required, but for hazardous locations it may be. At a minimum size the jumper for the power supply branch circuit, so probably a #12.
But a 12 THHN has fine stranding, and easy to damage. I would run a 6 AWG BCS
But a 12 THHN has fine stranding, and easy to damage. I would run a 6 AWG BCS
kwired
Electron manager
- Location
- NE Nebraska
That was a little of my thoughts, for something that doesn't necessarily need bonding yet you choose to do so for whatever reasons I'd probably go with at least 8 AWG solid or as you mention 6 AWG more for mechanical durability reasons even though 12 AWG should have sufficient electrical continuity.
What about compliance with 300.10? I'm assuming that a discontinuous RGS conduit needs electrical continuity even if it only contains fiber optics.
kwired
Electron manager
- Location
- NE Nebraska
raceways are also to be continuous from box/enclosure to box/enclosure.
When used for mechanical protection for communications and such they aren't always run that way. Or even when used for protection of power cables that otherwise don't need to be in raceway.
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