"Dennis Spexet" wrote in message
...
I've got a 200A GE loadcenter in my basement that has almost all of its
spaces used up (with 1/2" breakers), and so I want to install a subpanel.
In my installation, I would install a 100A subpanel, right next to the
main
panel (about a foot away). The subpanel would be connected to a 100A
double-pole breaker in the main panel.
I've been able to answer most of my questions from reading past messages,
as
well as books I have on electrical wiring. However, there are a couple
questions that I've been wondering about:
1. Is a main lug panel actually required for the subpanel? Or can a
main
breaker panel be used instead? From what I understand so far, either
kind can be used. I've also read that a disconnect mechanism of some kind
(main breaker) must be used if the subpanel contains more than 6 circuits.
You can put a 100 amp breaker in your main panel to protect the subpanel. A
hundred amp main in the sub is not required, but it does offer a little bit
more protection. A circuit breaker trips when it gets hot. The heat can be
caused from an overloaded circuit or from a loose connection within the
panel. A loose connection will arc when there is a load on the circuit and
generate heat. That heat from arcing could cause permanent damage to your
subpanel. If you have a main breaker in the subpanel in will sense the heat
sooner than the circuit breaker in the main panel and trip.
2. What kind of wiring should be used between the two panels? I was
planning on using four lengths of shielded #2 copper -- two for the hots,
and one each for ground and neutral. I'm not sure if the shielded cable
is
OK for the ground, though. Also, is there any requirement for solid vs.
stranded cable, etc.?
Number 2 is good for the current carrying conductors. You only need a
number 6 for your grounding conductor. As far as I know number 2 solid is n
ot available. It would be too difficult to work with. You could make the
neutral conductor number 1 since it does carry the load for both hots. This
is becoming more and more prevalent in commercial and industrial
installations as a result of neural conductors overheating from harmonics
caused by computers and other electronic equipment.
3. Is a conduit required, given the short distance (1 foot) between the
two panels? If the subpanel was farther away, then I'd think that a
conduit
is required. But since it's only a foot, I'm not sure.
You can buy 1'' x 12'' (Or 1 1/4'' x 12'') galvanized nipples at an
electrical supply house (DO NOT use one from a plumbing supply). Get 4
locknuts and 2 bushings and install it between the two panels. It will look
neater and less subject to abuse. Conduit is not required. You could use
BX, MC, Romex, or Service Entrance cable. Use the correct connectors at
each end and use bushings on the connector.
Safety first.
John Grabowski
http://www.mrelectrician.tv
Thanks much in advance for your help!
-Dennis Spexet,