SnapsProvolone
Well-Known Member
Did your electrician a load calc to account for preexisting loads and anticipated loads?
120 amp sub panel question
- Thread starter ODanksta
- Start date
ODanksta
Well-Known Member
Really swim does not know but the rest of the house is pretty much not used. Really the only power being used is basically just the grow room, 2 central AC's, and a fridge for beer. Everything else is gas. The house is also super energy efficient, swim has the best of everything in insulation. So swim is not worried about overloading the main. But then again swim is not a electrician. Swim is more worried about 1000 electric bills then overloading.
SnapsProvolone
Well-Known Member
Wow that swim feller sure gets around. 
Yes I can understand that learning when and where the neutral wires get bonded to the grounding wires, and learning when and where the neutral wires does not get bonded to the grounding wires can be confusing and difficult to the novice DIY. Hey it gets even more confusing when the NEC uses a language of it own with a different definition for the word "grounded conductor", a different definition for the word "grounding conductor", and a different definition for "earth ground"...so be aware of the spelling difference between the words ground, grounded, and grounding. To eliminate confusion to readers in my posts on RIU, I chose to refrain from using the words "grounded conductor" to describe a neutral conductor.
On the secondary side of the pole mounted step down transformer serving that resident, the center tap of the transformer winding (which now becomes refer to as the "neutral" connection on the transformer) gets grounded to earth ground. The neutral wire feeding to your home gets grounded again to earth ground at what NEC refer to as the panel with the "service disconnect means" (in layman's terms that would be the panel with the "first disconnect"). Based on what he have described about that main circuit breaker panel having the neutral wires, earth ground connection and equipment grounding conductors bonded inside that panel and to the enclosure, the electrician who install that panel and the inspector who approved it is telling me that the main circuit breaker in that panel is being the " first disconnect". That being said, only that panel can have the neutral wires bonded to the equipment grounding wires. From that point on when the wires leave that panel, under no circumstances can the neutral be bonded to the grounding wires. The neutral wires will now be refer to as "current carrying conductors", and the grounding wires will be refer to as "normally non-current carrying conductors". The purpose is to eliminate current from flowing through the grounding wires until there is a fault. In a sub-panel the neutral wires are mounted on one bar that is mounted on plastic insulators so that it will not bond with the enclosure. This is refer to as "floating the neutral wires". This step alone has created only one pathway for neutral currents to travel to the main panel (we want only one pathway for neutral currents). When a short circuit fault occurs between a hot wire and a enclosure, the fault current must have a separate low impedance pathway to the main panel in order for the circuit breaker to remove the fault current on the enclosure quickly. The equipment grounding conductor provides this low impedance pathway. The equipment grounding conductor is connected on a separate bar in the sub-panel that is not insulated from the enclosure. As noted in the YouTube video, he had to purchase and install the grounding bar separately in his sub-panel.