Circuit Designing

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BEFORE THE ARCHITECT – HOME DESIGNING BACKGROUND – UNIQUE HOME DESIGN ARTICLES

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HOME ELECTRICAL CIRCUIT DESIGNING

By Before The Architect  Copyright 2002, 2003, 2007 Before The Architect

YOU MAY FREELY QUOTE THE AG WITH PROPER ATTRIBUTION

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INTRODUCTION

    This e-article is about one major matter of crucial interest – home electrical circuit designing...

    Home electricity is a frequent hit on Before The Architect’s website.

    Electrical circuit designing in a home seems to some the willy-nilly running of high-voltage cables between outlets in walls and ceilings. 

    Nothing to it. 

    Right? 

    A custom home builder recently mentioned to this home designer, “House interior lighting?  We move from room to room and slap up some recessed cans."

    Right?

    Wrong, in the opinion of this home designer at Before The Architect. 

    Willy-nilly may be the home electrical circuit designing majority rule, but willy-nilly is not about safety in many senses, not about convenience, and not about durability.

    Let’s take a look at this home designer’s approach to electrical circuit designing in a home.

 

ELECTRICAL CIRCUITS
bullet electrical circuit from its panelboard shall include 
bullet energized conductor, or hot leg
bullet grounding conductor (equipment bonding conductor, etc.) and
bullet grounded conductor (neutral, common)
bullet which the grounded conductor
bullet run throughout that electrical circuit exclusively, that is, with respect to any other electrical circuit
bullet not be crossed-over to
bullet not be interconnected with
bullet not be otherwise shared by
bullet not be split with
bullet no interconnection whatsoever between a grounded conductor and a grounding conductor in a panelboard, subpanel, junction box, device, etc.
bullet no interconnection whatsoever between grounded conductors
bullet regard to or distinction between types of cable 
Comment:  Sorry for all those shall nots; however, this home designer needs to close loopholes.  Interconnecting grounded conductors is especially a condition seen in commercial and industrial wiring, along with several hot legs each relying on the same grounded conductor.  Tragic consequences can come calling from these so-called “dirty neutrals": AFCIs and GFCIs won’t work as designed with interconnected grounded conductors; loading up a grounded conductor with several energized conductors can overheat the grounded conductor.  

bullet electrical circuit load
bullet be judged as to whether it is continuous, i.e., could reasonably operate without interruption for 3 hours or more and
bullet judged continuous, then it shall be derated by 20% (, or the peak load multiplied by 1.25) subsequent to all other deratings  
Comment:  Usually, any given home electrical load is not regarded as continuous.  Continuous loads come into active play in commercial and industrial applications.  However, this home designer knows full well that some loads in a home can operate frequently well beyond 3 hours continuously, e.g., some exterior lighting and some interior lighting, entertainment centers, computer equipment, attic fans, etc.  It’s these loads and those like ‘em that ought to be singled out for special attention when designing and rating an electrical circuit in a home.  This home designer knows, for sure, that he’s in the minority on this one.  He’s unphased (a little electrical pun, there). 

bullet electrical circuit at a time shall be distinguished
bullet dedicated to lighting loads, which loads shall be connected only to that electrical circuit
bullet dedicated to non-lighting loads, which loads shall be connected only to that electrical circuit and
bullet lighting electrical circuit and a non-lighting electrical circuit shall not be interconnected, including as to grounded neutrals 
bullet equipment and entertainment centers shall be supplied by dedicated electrical circuitry at not greater than
bullet separately boxed hard drives and a printer or
bullet printers and boxed hard drive(s) per electrical circuit and
bullet sized Universal Power Supply (a/k/a UPS) with surge protection shall be urged 
Comment:  The home designer and electrical contractor should convey herewith their dedication to applying UPS units of quality between our pricey tools, our precious work and the irregular supply of electricity from our local electric utility. 

     A while back, Before The Architect figured out it lost 3 motherboards and 2 hard-drives to power dips and spikes, many so fast individually that there was no dimming of lighting or loss of digital readout time.  Now, you can sense these extremely brief power blips listening to UPSes click on and off, sometimes in bursts. 

Comment:  Sooner or later this prescript will lurch into distinctions as between linear and nonlinear loads – distinctions which in commercial and industrial applications can be life- and property-protective.  For matters of load linearity, this home designer thinks that in virtually all applications in a residence, so long as a grounded neutral is pulled from the panelboard (whereat it is securely fastened to its bar) separately for each and every electrical circuit run, all should get along safely. 

bullet a kitchen or bar, each of the following electrical appliances shall be connected to an individual electrical circuit at 120 volts, 20 amps (or manufacturer’s specification) with a 20 amp (or manufacturer’s specification) singleplex receptacle or hard-wired to a junction box
bullet
bullet
bullet or, if not a combined unit, then separately to a refrigerator and a freezer
bullet cooler
bullet compactor
bullet drawer
bullet drawer
bullet 
bullet electrical circuit with 15 amp overcurrent protection shall have applied to it only 15 amp rated devices 
bullet electrical circuit with 20 amp overcurrent protection shall have applied to it only 20 amp rated devices 
Comment:  The National Electric Code slices and dices this electrical circuit vs. receptacle match-up sure enough to bunch the shorts of the most serious student.  The home designer’s in no mood to quibble. 

bullet electrical motor-driven or electrical heater-driven loads shall be on individual electrical circuits dedicated to that single load and either hard-wired or singleplexed, e.g.
bullet
bullet washer
bullet space heater
bullet dryer
bullet kitchen appliance that’s built-in
bullet other appliance or heater that’s built-in or required by residents
bullet bathroom lavatory individually and
bullet 
Comment:  This means, among others, no splits or branches to or from a microwave electrical circuit. 

bullet two-pole electrical circuit
bullet be individual [new word for ‘dedicated’]
bullet be applied only to a unique, two-pole load
bullet not be interconnected with any other electrical circuit 
            Comment:  This prescript must be followed absolutely.  Of note in a two-pole electrical circuit to supply a motor, the grounded conductor regularly carries bits of electrical energy back to its seat on the panelboard.  Interconnecting the grounded conductor in a two-pole cable or harness with other grounded conductors can be a lethal mistake. 

bullet grounding neutral (often bare or with green insulation) shall be connected in parallel and not in series to each device, i.e., one grounding conductor to each device wherein each grounding conductor is securely tied to the line’s grounding conductor
bullet an outlet of ganged switches and
bullet an outlet of ganged receptacles, that is,
bullet device shall be pigtailed to its line 
bullet less than 2-2 linear inch diameter solid, smooth, straight conduits
bullet extend from lowest level of a residence, including but not limited to a crawlspace or basement or on L1 on a slab-on-grade up to and into the attic of the residence
bullet be located
bullet closely as possible to the panelboard
bullet accessible to conduit interior from the panelboard on finish
bullet be clearly identified at each terminus with bright coloring or other visually distinctive means
bullet serve as post-finish raceways for cable between levels 
bullet in not less than one
bullet in not less than one.
bullet be temporarily sealed to air flow at each opening to abate flame spread between levels 
bullet any electrical circuit with more than one device or appliance or similar, cable connections shall be by pigtail in parallel, i.e., sequential electrical circuitry shall be prohibited
bullet a bathroom, each lavatory shall have its own dedicated 120V/20A electrical circuit for a GFCI-protected duplex receptacle 
bullet shall be no less than 2 utility receptacle electrical circuits in a kitchen and bar (whether or not the bar is adult) 
bullet receptacle electrical circuits shall be dedicated 
bullet smoke alarm electrical circuit
bullet land separately to electrical circuit breaker of an actively used lighting electrical circuit, which breaker shall be designated for a double tap or
bullet be the first branch on that actively used lighting electrical circuit, before any switch device connection 
bullet electrical circuits shall not serve the same receptacle device. i.e., a receptacle shall not be split-wired
bullet circuits serving kitchen loads shall serve only kitchen loads 
ELECTRICAL CIRCUIT DESIGNING DIAGRAM

bullet look at a small chunk of a recent Electrical and Lighting Plan by Before The Architect
bullet in plan view of a Masters Bath suite with electrical circuitry drawn right on the plan set’s floor plan 
Electrical Circuitry Designing, Plan View

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Key: CLO = closet; D = dimmer; G = ground fault interrupter; H = height; HR = home run; L = lighted switch; lm = lumens; MIR = mirror; PS = pressure switch; S = single pole switch; S3 = three-way switch; S4 = four-way switch 
bullet how several points of electrical circuitry designing guidance play out (along with points elsewhere herein under on receptacle designing and switch designing)
bullet can reckon illumination levels in each space as between ambient and task site, remembering that all this is much further identified in a Lighting Schedule and Lighting Notes, again, elsewhere on this website
bullet one area of further limit to lighting pros works and that’s the height and spread of sconces in both HIS and HERS
bullet the squared electrical circuit lines as opposed to the looping, curvy style.  Imagine the mess all those curves would have made in this tight, complexly electrical circuited space.  Straight lines mean a lot herewith to convey meaning.
bullet how Before The Architect handles almost all aspects of luminaires after establishing electrical circuitry siting, e.g.,  “TO SHOWER LIGHTING AND FAN" and “TO HALL LIGHTING."  Lighting pros are only proscribed by Before The Architect generally in two aspects of lighting: illumination level and type.  The rest – luminaire choices, numbers, and sites are up to them; that their day job.
bullet should be made of the dedicated receptacles to each of the lavatories which are symbolized by the HR designation, along with outlet height over finish floor level.  HERS, you’ll recognize, gets 2 dedicated receptacles along her counter.  Missing in this version of the floor plan is designing of a seating area open below-counter in HERS.
bullet at all the dimmers
bullet at all the lighted switches
bullet pressure switches are applied in each smaller closet.  So convenient – as long as you close the closet doors
bullet note the many switches throughout these spaces, in order to ensure convenient control of lighting and appliances
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