Rigid Metal Conduit / Amps

Status
Not open for further replies.
D

domnic

Senior Member
Occupation
Electrical Contractor
I have a 120/240 volt 200 amp service . from the meter base to the main breaker i ran 7' of 2" rmc . if the load on the neutral reads 20 amps . what is the load on the rmc?
 
domnic

domnic

The 2" rmc is bonded at both ends this puts it in parallel with neutral .
 
domnic said:
The 2" rmc is bonded at both ends this puts it in parallel with neutral .
Click to expand...
If its installed properly, The neutral and the egc are connected only at the main switch. There should be no current.
 
domnic said:
The 2" rmc is bonded at both ends this puts it in parallel with neutral .
Click to expand...
It is bonded at both ends to the equipment grounding conductor, not to the neutral conductor. There is no complete path for current to flow in the conduit itself.
 
domnic

domnic

The 2 " rmc is bonded at the meter base to the neutral at the other end it is bonded to the neutral with main bonding jumper. the 2" rmc carries service conductors.
 
This conduit is in parallel with the grounded conductor as the grounded conductor is bonded at the meter and the main bonding jumper is at the service disconnect. The amount of current will be based on the relative impedances of the grounded conductor and the path via the conduit. I would not be surprised to find 25% or more of the grounded conductor current flowing on the raceway.
Don
 
OK, I stand (sit, actually) corrected. And why is it safe to have that much current flowing in a raceway? :confused:
 
charlie b said:
... And why is it safe to have that much current flowing in a raceway? ...
Click to expand...
Come on charlie - you know the answer to this.;) Its on the utility side of the disconnect and therefore safe. If it was our transformer, then it would be an SDS and therefore unsafe.:rolleyes:

carl
 
Charlie,
There are a number of places where the code requires that grounded conductor current flow on things other than the grounded conductor on the line side of the service disconnet. As Carl said, this is only a problem on the load side of the service disconnect....it is not a problem on the line side:rolleyes:
Don
 
If you really want to know the current on the conduit, measure the two phase currents. The difference between those must equal the neutral current plus the conduit current.

A little math should tell you how much current is on the conduit.

Steve
 
Status
Not open for further replies.
Top