I recently replaced a small 100A residential panel with a larger 100A panel. The panel is located several feet from the meter therefore a service disconnect is mounted next to the meter socket and joined via a nipple. The service wires to the panel are from the service disconnect are run inside a length of IMC. The neutral in the panel is not bonded to the panel and a ground bar is used for equipment grounding. When I looked at the service disconnect I didn?t notice a ground rod or wire suggesting that the service was grounded. I opened the service disconnect and the meter socket and found that the neutral was not bonded inside the disconnect but rather inside the meter socket and a ground wire inside ran from the neutral down the incoming pipe (underground feed) to ground. Does the neutral in the service disconnect still need to be bonded and a ground rod driven? Also, the original panel had the neutral bonded to the panel and being that the service disconnect was bonded to the panel through the conduit could this potentially create objectionable current by supplying more than one path for neutral current to ground?
Bonding & Objectionable Current
- Thread starter lyonpj
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
Re: Bonding & Objectionable Current
250.24(A) permits the grounding electrode conductor to be connected to the grounded conductor at any "accessible point from the load end of the service drop or service lateral to and including the terminal or bus to which the grounded service conductor is connected at the service disconnecting means". 250.24(B) requires that the grounded conductor be bonded to each service disconnet enclosure. If the grounded conductor is bonded in the meter and metallic conduit is used between the meter and the service disconnect, the conduit will be in parallel with the grounded conductor.
Don
250.24(A) permits the grounding electrode conductor to be connected to the grounded conductor at any "accessible point from the load end of the service drop or service lateral to and including the terminal or bus to which the grounded service conductor is connected at the service disconnecting means". 250.24(B) requires that the grounded conductor be bonded to each service disconnet enclosure. If the grounded conductor is bonded in the meter and metallic conduit is used between the meter and the service disconnect, the conduit will be in parallel with the grounded conductor.
Don
Re: Bonding & Objectionable Current
This paralleling of the conductors is not a problem because the neutral conductor is sized to handle the entire load, and any current that would flow through the metal piping would reduce the current in the neutral to no deleterious effect. Paralleling of conductors elsewhere is done to allow smaller conductors to carry larger loads by sharing the load between them. If there is a bad connection, or one parallel conductor is lost, then the other conductors must carry the extra load. If they are not sized large enough to to handle the full load (and they are usually not)they may overheat.
[ September 22, 2003, 07:21 PM: Message edited by: earlydean ]
This paralleling of the conductors is not a problem because the neutral conductor is sized to handle the entire load, and any current that would flow through the metal piping would reduce the current in the neutral to no deleterious effect. Paralleling of conductors elsewhere is done to allow smaller conductors to carry larger loads by sharing the load between them. If there is a bad connection, or one parallel conductor is lost, then the other conductors must carry the extra load. If they are not sized large enough to to handle the full load (and they are usually not)they may overheat.
[ September 22, 2003, 07:21 PM: Message edited by: earlydean ]
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