I’m inspecting my own panel board as part of the pre-licensing course and it’s brought up some questions.
the cable entering the panel board has 2 ungrounded conductors and 1 bare grounded conductor that is bonded to the neutral bus. Then there is an insulated conductor marked with green tape that jumps from the grounding bus to a clamp that is attached to the SE cable’s conduit where it enters the panel. The clamp is similar to the clamp used to bond the GEC to a grounding rod. The only grounding connection in the system is the grounding rod outside just below the meter box. The house is 60 years old so I’m presuming code required only 1 grounding connection.
Is this grounding configuration ok? It’s obviously not up to current code, but is the panel and service equipment sufficiently grounded? How would you right this up in a report? If I wanted or needed to meet current code what needs to be done besides adding a second grounding electrode?
Thanks!
EDIT:
Thanks for the replies so far. I’ve added some pictures below.
Picture 1 below is the jumper from the ground bus connected to the conduit that carries the service cables into the panel.
Afternoon, Andrew. Hope to find you well and welcome to the InterNACHI message board community.
Are you explaining a service panel with cables entering a panelboard with two ungrounded/hot conductors connected to bus lugs typical for a 240-volt circuit?
A few things and some better terminology. The 3 service conductors (two ungrounded and a neutral) is normal for a 120/240 service supply.
As Ryan mentioned a metallic raceway that contains service conductors requires additonal bonding beyond that provided by standard locknuts so what you’re seeing with the reidentified conductor is called a SSBJ or supply side bonding jumper.
The service is required to be connected to a GES (grounding electrode system) which is made up with one or more grounding electrodes. A ground rod electrode can be used to create a GES. The NEC in the past 25+ years has required two ground rods to be considered as a grounding electrode or a single rod that has been tested and is confirmed to have a resistance of 25 ohms or less. Any other electrodes present at the structure like a metal water pipe electrode would also be required to be connected to the GES.
The conductor connecting an electrode to the system is called a GEC or grounding electrode conductor and connects to the neutral.
Lastly the MBJ or main bonding jumper connects the system neutral to the metal enclosure and is typcially a green screw or a metal strap.
I do not like the use of ungrounded conductors because they can carry current under normal operating conditions. Preferably, “hot” or “phase” conductors to describe the conducts would be suitable as to my way of thinking for a service panel.
A 4-wire electrical service feed includes, two hot wires, a neutral wire, and an equipment ground wire. This configuration provides both 120-volt and 240-volt power for appliances and is the standard for subpanels and detached buildings to ensure safety by separating the neutral and equipment ground conductors.
The OP makes no mention of a sub-panel. He’s outlined what sounds like service conductors which would be only 3 conductors for a 120/240 system. Ungrounded is the correct textbook term although there are other suitable terms as well such a hot conductor. Depending on how it’s used the term phase conductor can be tricky. In a 120/240 volt, 1Ø system there is only one phase so other terms are more accurate. In a 3Ø system the term phase conductor can be used.
Good question, Jeff.
Likely its just me but I remember reading somewhere about how ungrounded conductors can become grounded so I Googled it this morning…
“An ungrounded conductor can become a grounded conductor through intentional connection to the electrical system’s ground, such as the neutral point of a delta system, as permitted by code under specific conditions, like a “corner-grounded delta” or when converting from an ungrounded to a grounded supply.”
The term ungrounded throws me off where as live or hot conductors makes the point as to what the conductors are designated for. I guess part of the word ground throws me off.
Like sub panel or auxiliary panel. A sub panel refers to a panel subordinate to the main service panel where as an Auxiliary panel can refer to anything that provides supplementary power or function.
