Smaller EGC on 30A circuit

Status
Not open for further replies.
M

mwr

Member
Location
IL
Coworker was ill advised in my opinion and ran a #14 to a 30A dryer for the EGC from panel to outlet. (4 wire - 3#10's and the smaller ground). I too thought this was compliant until I got home and checked.

I was wondering if this is something I now need to correct after the fact?
and would pigtailing the #12 with a #10 from the box and a #10 to the outlet be code compliant?

Trying to avoid returning to fix this. Or at least not having to yank the #14 and repull another EGC.
 
qcroanoke

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
mwr said:
Coworker was ill advised in my opinion and ran a #14 to a 30A dryer for the EGC from panel to outlet. (4 wire - 3#10's and the smaller ground). I too thought this was compliant until I got home and checked.

I was wondering if this is something I now need to correct after the fact?
and would pigtailing the #12 with a #10 from the box and a #10 to the outlet be code compliant?

Trying to avoid returning to fix this. Or at least not having to yank the #14 and repull another EGC.
Click to expand...

2008 NEC
Table 250.122 requires a #10 equipment ground on a 30 amp to 60 amp circuit.
Pig tailing a #10 to #14 will not make it right.
 
M

mwr

Member
Location
IL
qcroanoke said:
2008 NEC
Table 250.122 requires a #10 equipment ground on a 30 amp to 60 amp circuit.
Pig tailing a #10 to #14 will not make it right.
Click to expand...

My rationale is that the conduit will now serve as the ground and the #14 is an additional bond. Not acceptable?
 
M

mwr

Member
Location
IL
sparkyrick said:
Is this all in metal conduit? Then omit the 14 altogether and run a #10 from the back of the outlet box to the receptacle.
Click to expand...

Yes I should have been clear... this is in all emt and rigid system. That was my next question, cap the #14 and just bond to box. However, what is wrong or non-compliant about pigtailing the #14 as well?
 
qcroanoke

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
mwr said:
My rationale is that the conduit will now serve as the ground and the #14 is an additional bond. Not acceptable?
Click to expand...

Only if you pull the #14 out and use the conduit as the ground. NEC doesn't take into account it being in conduit. if you run a ground it has to be what 250.122 calls for.
 
M

mwr

Member
Location
IL
Only if you pull the #14 out and use the conduit as the ground.
Click to expand...

Pulling it would be a waste of time and labor no?

Don't you think having the added 14 as an additional bonding wire would be going beyond code minimum? Unless there is some issue about a faults return path and the smaller conductor that I am missing..... please explain. Leave the quirkey inspector out of this... im curious from a safety functionality standpoint.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
mwr said:
Pulling it would be a waste of time and labor no?

Don't you think having the added 14 as an additional bonding wire would be going beyond code minimum? Unless there is some issue about a faults return path and the smaller conductor that I am missing..... please explain. Leave the quirkey inspector out of this... im curious from a safety functionality standpoint.
Click to expand...

From a safety standpoint you are 100% correct. It will only decrease the impedance during a fault condition.

From a code standpoint it is a violation of 250.122. There are no exceptions to allow the use of a smaller copper grounding conductor in a metal raceway.
 
M

mwr

Member
Location
IL
That's where I am confused, excuse my ignorance, but what would be a faults quickest return path... the conduit or the #14? And if the 14egc then that would mean it would burn correct?

Frankly, what would you suggest be done to avoid having to yank the #14?.... there is no inspection here, its just for safety and practicality I am inquiring. Although I am told by my foreman to leave it be but I am back in the morning hanging fixtures and I think I am going to pigtail the #14 with 2 #10 (one to outlet, one to 1900 box) for my own piece of mind unless I am totally missing something here about the quickest path to ground.
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
mwr said:
That's where I am confused, excuse my ignorance, but what would be a faults quickest return path... the conduit or the #14? And if the 14egc then that would mean it would burn correct?
Click to expand...
In most cases the conduit is the better fault return path, even where a code sized EGC of the wire type has been installed in the conduit. While not code compliant, I would expect in most cases a #14 would flow enough current on a ground fault to cause the 30 amp breaker to open the circuit.
Frankly, what would you suggest be done to avoid having to yank the #14?.... there is no inspection here, its just for safety and practicality I am inquiring. Although I am told by my foreman to leave it be but I am back in the morning hanging fixtures and I think I am going to pigtail the #14 with 2 #10 (one to outlet, one to 1900 box) for my own piece of mind unless I am totally missing something here about the quickest path to ground.
Click to expand...
There is no hazard caused by connecting the #14 EGC...just a code violation.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
mwr said:
Right, but I am confused about the parallel paths back to the panel. If that even applies to egc's.
Click to expand...

EGCs are often electrically parallel. Had the correct 10 AWG EGC been run in this circuit it too would be in parallel with the conduit.

Consider a steel framed building like a warehouse, office or school. All the wire EGCs get bonded to the electrical boxes which are mounted to the steel structure tying almost all grounding paths together.



and I was thinking #14 would burn before opening the circuit.
Click to expand...

I doubt that very much, consider that a 10 AWG EGC is allowed to be used with a 60 amp circuit.
 
G

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
don_resqcapt19 said:
There is no hazard caused by connecting the #14 EGC...just a code violation.
Click to expand...
I would agree that there is no direct immediate hazard caused by either connecting the #14 or leaving it unconnected in the raceway.

But here are two hypotheticals:
Connect the #14 and now someone working on the installation later will not realize that it is critical to maintain the integrity of the raceway EGC path. (OK, the code requires that the raceway EGC be properly bonded if it is continuous, but if a nonconductive raceway section is present, code requires a wire EGC.) And if the raceway continuity is somehow compromised, a quick EGC connectivity check will still come out OK because of the presence of the #14. But the effective EGC will not be adequate.

If the #14 is present but not connected, someone doing work at an intermediate j-box may not realize that the #14 is doing nothing and rely on it when making a new EGC connection.
 
S

SceneryDriver

Senior Member
Location
NJ
Occupation
Electrical and Automation Designer
Just go replace it with a #10. How much wire are we talking about? Do it right, even when no one's looking.


SceneryDriver
 
kwired

kwired

Electron manager
Location
NE Nebraska
mwr said:
That's where I am confused, excuse my ignorance, but what would be a faults quickest return path... the conduit or the #14? And if the 14egc then that would mean it would burn correct?
Click to expand...

When a fault occurs you have multiple current paths for a section of the circuit, the raceway, the EGC, and any other items that are inherently bonded to either in more then one location also become parallel components. Current will divide proportionally to the resistance of each path. If the raceway and the EGC were the same resistance they each would be carrying equal amount of current, but chances are the raceway is lower resistance and will carry more current. Metal conduit racks bolted to steel building structure will likely be even less resistance and if they exist ver likely carries more fault current then the raceway or the internal EGC. They still want that EGC fully sized (if it is present), and the raceway as intact as possible as they are the primary paths we want the fault to flow should the metal building not be a continuous path.

mwr said:
Right, but I am confused about the parallel paths back to the panel. If that even applies to egc's. and I was thinking #14 would burn before opening the circuit.
Click to expand...
#14 can carry a lot of current before it will "burn". But at same time the proper sized 10AWG can carry even more and will have less resistance. Less resistance means more fault current will flow, which means even faster response time from the overcurrent device. Depending on the circuit characteristics a 14 AWG instead of a 10 AWG where required could reduce the amount of current flowing during the fault by hundreds or even thousands of amps. That will mean the duration of the fault will last longer before the overcurrent device opens - exact time all depends on the trip curve of the device, but in general we want as low of an impedance possible to make that trip happen faster.

Your ungrounded conductor will have some impedance as well so you need to factor that into the fault circuit to get a total impedance of the fault circuit, and how it effects the amount of fault current.
 
Status
Not open for further replies.
Top