Well, this is an area of discussion which has been tossed around over and over, for many years in several Electrical based forums (and in real-time too!).
I find that pointing out the most obvious data, that being the intentions of all parties involved (AHJ and EC), using the basic requirements and reasoning behind them, makes for a real fun time! (read: toss some fuel on the flames)
Nevertheless, I prefer to go this route - mainly to show what is the bottom-line minimum per a Jurisdiction using only a given version of the NEC (NFPA 70) as a guideline.
As usual, if any Jurisdiction has ammended the NEC's Articles in any fashion, which has altered the "Model Code" in one way or another (either by acceptance with ammendments by one, some or all agencies, or has been deleted by one, some or all agencies), this superceeds any of the "Model Code" base articles of the NEC.
Also, keep in mind that not every County in U.S.A. will follow the NEC - a few do not have Code Requirements for some Electrical Installations!
Adding to these Jurisdictional items, there is nothing
HAZARDOUS about installing Electrical stuff to minimum Code articles preferences. As long as the installations will not create threats to life and property, there's no real danger. Inconveniences and annoyances are not lawful reasons of code enforcement (remember the "Fung Suei Code Proposal" a couple years ago in San Francisco? That's a perfect example).
On the same note, this brings in "Design Issues", of which, criteria for performance of electrical installations is "specified" per design, found within contract documents.
These "Issues" may exceed minimal Code Compliance, but may not fall below any minimal compliance (either per article or with engineering exceptions), as this may be a HAZARDOUS Installation.
Exceeding minimal compliance is for the benefit of the Client (Customer), and takes on a whole new set of "Inspections" and "Compliances", which is outside of the realm of the local Building Department - as these are more directed to performance for the Client "All-Around" than minimal conformance for Building Safety.
For now, we will focus on a simple single family dwelling of like 1,000 Sq. Ft., in a Jurisdiction which has accepted to use the NEC "as-is" (with no ammendments). We will not cover any items which may be related to other Building Codes (Mech., Plumb., Building, Energy conservation, etc.), and will be looking at only the BASIC ITEMS of the install (excluding any _SPECIFIC_ electric loads - such as Electric Cooking equipment, Electric water heating equipment, HVAC, Electric Motors, or Swimming Pool / Hot Tub equipment).
The House has the following rooms:
One Kitchen, One Laundry Room, One Living Room, One Family Room, One Dining Room, Three Bedrooms, Two Bathrooms, One Hallway, and a Two-Car Garage.
# 1:: Service Feeder Load Calcs:
General Lighting + Receptacles - 1,000 Sq. Ft. @ 3.0 VA/sq.ft. = 3,000 VA.
Small appliance circuits equal an additional 3,000 VA to the figure.
Laundry circuit adds 1,500 VA to the figure.
(Small Appliance and Laundry may be included with the Gen. Ltg + Recepts. load, using demand factors, or they may be added as there own entries - outside of the Gen. Ltg. values, and be figured without demand factors - it's up to the "Designer").
This results in a Service Load calculation of 31.25 Amperes at 240 Volts - which would be adequately served from a 60 Amp 120/240V 1? 3 Wire Main Service Panelboard, with "Electrical Contractor Installed" feeders of # 6 THHN cu size.
The Utility Company - if were doing the Service Feeders all the way to the Line side of the kWh Meter, may use conductors of 40 amp capacity - sized per the NESC, which might end up being # 8 al., or even #10 al.
# 2: How Many Circuits Is Minimal???
Let's cover the "MINIMAL REQUIRED CIRCUITS" for this installation, per 210.11(A) and (C) of the 2002 NEC:
- Two (2) Small Appliance Circuits,
- One (1) Laundry Circuit,
- One (1) Bathroom Circuit,
- One (1) Bedroom AFCI protected Circuit.
That's it!!!
We need to install at least one Circuit, which is separate from the above listed Circuits, that we can place General Lighting and General use receptacles on - but does the NEC ever state that we MUST install enough circuitry to accomidate the 3VA/sq.ft load calc. figures? Not really!
The 3VA/sq. ft. figure is NOT A CONNECTED LOAD VALUE!!! It's a minimal figure for Service Ampacity (more correctly, Service Capacity).
If you had this 1,000 Sq. Ft. House, would you ever have 3,000 VA of Lighting going at the same time?
Queue the song "I Wear My Sunglasses At Night"
Even with Receptacle loads - most of which would likely be Portable Lamps, how often would this 3 KVA figure be reality?
So, according to article 210.52, we need to install Receptacle Outlets in these following locations in dwelling units:
Kitchen areas (anything in the areas for preparing food), Bathrooms, Outdoors (at least one), Laundry Rooms, Basement , Garages, Hallways, Family Rooms, Dining Rooms, Living Rooms, Parlors, Libraries, Dens, Sun Rooms, Bed Rooms, and Recreation Rooms.
Additionally, 210.70 explains we need to provide Lighting Outlets in every Habitable Room and Bath Room (at least One Wall-Switch Controlled Lighting Outlet in these rooms), and at least one wall-switch controlled Lighting Outlet in Hallways, Stairways, Garages (attached or detached garages with electric power), outside of these Garages, attics, Underfloor spaces, Utility Rooms, and Basements.
We do need to design the Lighting Circuit to the _CONNECTED LOAD_ we have placed on it, and once again, we are free to design ourselves, as there is no NEC required LIGHTING POWER LEVEL specified in the Code Book.
In the Bedrooms, we choose to use "1/2 Hot Receptacles" for Lighting, which places the Bedroom Lighting Outlets on the AFCI Protected Bedroom Circuit.
We also plan to use "1/2 Hots" in the Living Room and Family Room.
The remaining rooms / areas will use "Fixed Lighting Outlets", which total up to be a MINIMUM of 8 Lighting Outlets for these remaining areas.
If we plan to use Lighting Outlets of 150 Watt rating (maximum), this will be a _CONNECTED LOAD_ of 1,200 VA - which may easilly be supplied by a single 20 amp circuit.
We even have the capacity to include General Purpose Receptacles on this Lighting Circuit - and still conform to _BASIC NEC_, but to be nice, we will give these General Purpose Receptacles there own Circuit.
So how many _BASIC_ Circuits do we need in this Scenario?
Seven (7)
Will it work??
Yes!!!
Will it be _MINIMAL_ Code Compliant???
Yes!!!
Will it be a Hazardous Installation - if installed "Correctly"???
No!!!
Will it pass Inspection by the DBS???
Yes!!!
Will the Installing Electrical Contractor be "Cutting Corners" or "Making A Bundle Of $$$"???
Most likely- No!!!
If there are no specifications to require above-minimal circuitry, and the project was "bid" that way, the EC is not doing anything wrong, and is barely making any profit on the project.
Think over these basic examples in this scenario, then it becomes apparent what the _UNDERLYING INTENT_ is!
This Scenario would be prototypical of nearly any project, which falls under the NEC.
This statement is the most "To-The-Point" and concise thing I have ever heard, and it was stated by an Electrical Inspector:
"Inspectors May Not Exceed Their Authority (only enforce via the rules governed by the documents accepted by the agencies involved - typically, the NEC "NFPA 70"),
And,
Installers May Not Fall Below The Minimums (minimum Code Compliance).
If This Is Not Comprimised, All Is OK"
I see the views from all 3 angles daily in my career:
* From the view of the DBS Inspectors - enforcing the minimal compliancy, but having a "wish" that the minimals were a bit beefier,
* From the view of the Designer - designing an Electrical System which works, yet every Client Meeting results in more and more "Value Engineering",
* From the view of the Electrical Contractor - Proposal price is just enough to cover all overhead expenses, with a small profit - unless something goes wrong.
Look at each project in this aspect, and things become mind numbingly confusing! But this is the way things are in the Industry.
We all need to understand each others' role - and most importantly... TALK TO EACH OTHER!!!
OK, off my soapbox now!
Feel free to fire away!!!
Scott 35
edited tew cour-reckt sphelleengh
