COMMUNITY FORUM

rogerrabbit

05:52PM | 05/02/05
Member Since: 12/14/04
8 lifetime posts
Bvelectrical
I am going to be wiring me basement which is unfinished at the time. I was wondering what size of wire I should use? 12-2 or 14-2. It will be just running lights and outlets.. I have the basement broke down into 3 sections. Have enough for the extra breakers. Also, what should I put in for a breaker, 15 amp or 20 amp for all??

Thanks, Roger

Jarrod

05:29PM | 05/03/05
Member Since: 04/12/05
15 lifetime posts
Either wire size is acceptable, but the wire size must match the breaker size. If you use 20 amp breakers, you must use #12 wire. If you use 15 amp breakers, you may use #14 wire.

The choice of one combination or the other is really a matter of preference. 20 amp circuits can obviously carry more load than 15 amp circuits, but this is rarely a concern in a home. On the other hand, since #14 is a smaller gauge wire, it is more flexible and easier to work with.

Either way, you should make sure that the cable you use contains a ground wire (14/2 with ground or 12/2 with ground).

Happy wiring!

Jarrod

MistressEll

06:00AM | 05/04/05
Member Since: 01/30/05
361 lifetime posts
OP: it depends. Check with your local jurisdiction regards to which building codes and electrical codes are effective in your local area, then head off to the library and read up on the subject.

Some codes require limiting residential single family home circuits that contain combination lighting (luminare or light fixtures) and plug and cord receptacles to 1440 VA and 15 amp circuits with exceptions only to dedicated bathroom 20 amp circuits that may also contain a light circuit for that bathroom only and limit its power consumption. The reason for this is that most luminaires (light fixtures) by UL ratings use lesser gauged wiring than can be safely attached to a 20 amp circuit.

strict receptacle ONLY circuits do not have such limitations regards to residental wiring generally, in the codes, excepting certain areas which are specified.

Finally not all areas even ALLOW the use of cabling, so go with the wiring methods that are allowable in YOUR JURISDICTION. (Jarrod some homes and areas are 2-wire GROUNDED with THHN or TW and EMT, SHEESH!).

Determine your wire gauge by the AMPs of your circuit, derated for Ambient temperatures, Ground (EARTH) temperature, length of circuit and derate for conduit/raceways. Also adjust your AWG rating via the rating of your cabling/WIRE temperature VERSUS the rating of your fuse box/circuit breaker box terminals (i.e. if your wire is 90-degree temp rated but your terminals in your circuit breaker box and/or the circuit breakers themselves are rated at 75-degrees or 70-degrees C). you have to derate your wire for heat sink.

The 12 AWG 20 Amp and 14 AWG is a STARTING point. One has to adjust and consider MANY things not just throw in what some poster with a cheat guide and no clear understanding of the codes are. Many jurisdictions in the US use ICC and others use NEC (NFPA Sec 70) for their basis for electrical codes, and they adopt a particular "edition" or Version date for their code authority. Oftentimes local jurisdictions will make modifications to that published code, adding or deleting requirements allowed in their local area. Please check with your AHJ (Authority having jurisdiction) before begining your project and plan accordingly.

Once you know what "code" you need to follow, educated guidance can be offered.

Jarrod's "pat" answer is NOT NECESSARILY CORRECT, as it was not properly "qualified" regards to both NEC and ICC not allowing combination circuits involving luminaires at 20 amps UNLESS EXCEPTED in residential circuits.

Furthermore, if this is other-than a single family dwelling you need to qualify that, as certain attached dwellings (like a 3-flat condo for example where the lower flat includes multi-levels, e.g. basement), a multi-family dwelling, etc. have additional wiring restrictions/considerations.

househelper

07:13AM | 05/04/05
Member Since: 03/31/05
265 lifetime posts
If you think you may eventually finish this area, then go ahead and run two circuits, one for the lights, one for the receptacles. Both can be 14ga or 12ga, I prefer 14ga for the lighting and 12ga for the receptacles, protected by 15A and 20A breakers, respectively. As long as the area is unfinished, the receptacle circuits must be GFCI protected.

All of this is in general terms of course, your local inspector can provide you with specifics for your area.

Jarrod

04:39PM | 05/04/05
Member Since: 04/12/05
15 lifetime posts
Roger,

The guidelines I listed before are just that. Guidelines. As with every post to this BBS, local codes and rules may supercede the national model codes, such as the NEC and ICC.

The guidelines I gave you will work in most locations, and follow standard installation practices. Ell is correct that there are a number of things (such as derating factors, etc) that should be considered. However, the vast majority of them only apply in very limited circumstances, and/or have minimal affects on the overall design.

Also, if Ell had read the ICC, she would notice that the 2003 edition is only 36 pages long. That's because it adopts the almost 800 page NEC by reference, and only makes minor administrative adjustments. So, jurisdictions that adopt the ICC are still in fact using the NEC.

Again, good luck with your project. It's probably not as complicated as some people would have you believe, and a brief visit with you local building department should clear up any lingering questions.

Jarrod

tshea1

04:04PM | 05/05/05
Member Since: 05/03/05
79 lifetime posts
Roger,

The information you gave us is very limited. What is your intention, future plans for the unfinished basement?

What kind, and how many lights (luminaires) are you intending to use? What are teh dimensions? Generally, wall receptacles are located so no point is more than 6' from a receptacle (receptacles are installed 12' apart). Are you gooing to finish the basement? Is it a shop (unfinished)?

If you can answer a few of these questions, I can give you a general recommendation.

Whatever area you are in, check with the local Building Dept & Electrical Inspector to find out if you as a homeowner are allowed to do your own work. If not, contact a reputible Electrical Contractor.

rogerrabbit

02:05AM | 05/14/05
Member Since: 12/14/04
8 lifetime posts
I plans for the basement are to finish the basement. I will probably just get a 1000' spool of 12-2 w/ground wire.

I plan to have a family room/ rec room with a extra bathroom and bedroom down there. I am going to run the bathroom off a circuit by itself. The lights and receptacle by themselves. Maybe put a refrigerator down there too.

I am putting around 30 can lights down there, the size of 28x62, 1750 sq. ft.

MistressEll

06:32AM | 05/16/05
Member Since: 01/30/05
361 lifetime posts
your lighting circuits will need to be independant of your receptacle circuits in all areas except the bathroom, as your lighting circuits will need to be 15 amp.

The bathroom will require a 20 amp GFCI protected circuit and depending on the overhead lighting and if it is a combination fanvent/heat lamp device there are limitations as to the maximum draw it can use.

any remaining unfinished area can remain lit with the 15 amp overhead lighting circuit, but if you have receptacles in unfinished areas they must be GFCI protected, and more current codes require that they be on an independant 20 amp receptacle circuit. You cannot have an overhead lighting circuit combined EVER with a 20 amp circuit unless its the exception for a dedicated and single luminaire fixture for a bathroom (which is required a 20 amp GFCI protected circuit). Residental lighting circuits are otherwise restricted to 15 amp circuits. Laundry areas and any sink areas (or other water hazards like sump pump pits and the like)have special requirements finished and unfinished as well.

If a jurisdiction has adopted an earlier version of the ICC or the NEC and/or adds their own amendments, that is what the code is, until the AHJ adopts a newer version. Check with your local authority as to what code applies in your area.

deration for length is always to be considered as is the length of the entire circuit not just "outlet to outlet" Number of outlets is also to be considered.

And most important is the rating of your circuit overcurrent protection devices and Box in comparison to the rating of your wire. Most older structures have 70 or 75 degree C rated and when you use 90 degree C rated wire you MUST take that derating into consideration.

A basement can easily contain a circuit that is more than 75 feet in total length. Ambient earth temperatures in Southern States and desert areas can easily be factors in basements. Not knowing where in the world your basement is, can't say whether or not that must be factored in derating.

Most "newer codes" also require that BEDROOMS (you mentioned your intent to add a bedroom) be ARC FAULT protected. BEDROOMS are limited to 15 amp circuits. ARC fault protection is quite different than GFCI protection. Whether or not that bedroom will require GFCI being in a basement is a question that can only be determined by which building and fire codes your AHJ has adopted, and how much of this basement is "below grade". There are also issues as to how high from the floor those receptacles must be that is code version and depth from ground level dependant. That BEDROOM will require a separate circuit and will need to be ARC FAULT protected most likely (assuming your AHJ has adopted a code version within the last 10 years). Older bedrooms are grandfathered in but to construct a new one, especially in a basement will envoke that you wire it to your AHJ's current code levels.

12 gauge is fine for your 15 amp circuits but you have already indicated at least ONE location that will require a 20 amp circuit (bathroom addition) so you'll need 10 awg as well at least for THAT circuit.

MistressEll

06:34AM | 05/16/05
Member Since: 01/30/05
361 lifetime posts
that your bathroom needs at least 12 AWG, and your lighting circuits might get away with 14, but that if your bathroom circuit is more than 75 feet and/or other derating factors you MIGHT need a higher gauge for your bathroom, not that you definately did.

Billhart

08:33AM | 05/16/05
Member Since: 04/25/05
1915 lifetime posts
"any remaining unfinished area can remain lit with the 15 amp overhead lighting circuit, but if you have receptacles in unfinished areas they must be GFCI protected, and more current codes require that they be on an independant 20 amp receptacle circuit. You cannot have an overhead lighting circuit combined EVER with a 20 amp circuit unless its the exception for a dedicated and single luminaire fixture for a bathroom (which is required a 20 amp GFCI protected circuit). Residental lighting circuits are otherwise restricted to 15 amp circuits. Laundry areas and any sink areas (or other water hazards like sump pump pits and the like)have special requirements finished and unfinished as well"

The is no general requirment in the NEC that prohibts lighting to be installed on 20 amp circuits. Some 20 amp receptacle circuits (one for multiple bathrooms and the kitcen small appliance circuits) can't also be used to lighting. But that is a limitation those specific types of circuit not on all 20 amp circuits.

However a few localities have adopted such limitations, but it is not in the NEC.

"And most important is the rating of your circuit overcurrent protection devices and Box in comparison to the rating of your wire. Most older structures have 70 or 75 degree C rated and when you use 90 degree C rated wire you MUST take that derating into consideration."

No practical affect since they limited to less than there 60 ampacity anyway.

The only limitation is that some lighting fixtures require 90 degree wiring. But this is NEW so all of the wiring would be 90 anyway.

"A basement can easily contain a circuit that is more than 75 feet in total length. Ambient earth temperatures in Southern States and desert areas can easily be factors in basements. Not knowing where in the world your basement is, can't say whether or not that must be factored in derating."

Where would you find a basement that has an ambient temp over 122?

" BEDROOMS are limited to 15 amp circuits. "

WRONG! There is no general NEC limiting bedroom circuits to 20 amps.

"That BEDROOM will require a separate circuit and will need to be ARC FAULT protected most likely (assuming your AHJ has adopted a code version within the last 10 years)"

There is no requirments for bedrooms to be on separate circuits. There is no prohibition agaisnt powering other parts of the house from a "bedroom" circuit with or without an AFCI.

And "last 10 years" has nothing to do with it. AFCI's did not show up until the 99 NEC and even then did not require them until 2001.

One thing that has not been mentioned is smokes. With remodeling many places require updgrading smoke dectors and more so with a bedroom.

Sometime they will be required hardwired an sometime also tied with hardwired ones in other areas of the house "if practical". That whole area if very subject to local interpretations.

Likewise if you have a hardwired smoke in the bedroom then it is an "outlet" and the 2002 NEC requires that (and lights) to also be AFCI protected. But again many locals have opted out of this.

So if your area requires inspection I would check these out first.


Billhart

08:33AM | 05/16/05
Member Since: 04/25/05
1915 lifetime posts
"any remaining unfinished area can remain lit with the 15 amp overhead lighting circuit, but if you have receptacles in unfinished areas they must be GFCI protected, and more current codes require that they be on an independant 20 amp receptacle circuit. You cannot have an overhead lighting circuit combined EVER with a 20 amp circuit unless its the exception for a dedicated and single luminaire fixture for a bathroom (which is required a 20 amp GFCI protected circuit). Residental lighting circuits are otherwise restricted to 15 amp circuits. Laundry areas and any sink areas (or other water hazards like sump pump pits and the like)have special requirements finished and unfinished as well"

The is no general requirment in the NEC that prohibts lighting to be installed on 20 amp circuits. Some 20 amp receptacle circuits (one for multiple bathrooms and the kitcen small appliance circuits) can't also be used to lighting. But that is a limitation those specific types of circuit not on all 20 amp circuits.

However a few localities have adopted such limitations, but it is not in the NEC.

"And most important is the rating of your circuit overcurrent protection devices and Box in comparison to the rating of your wire. Most older structures have 70 or 75 degree C rated and when you use 90 degree C rated wire you MUST take that derating into consideration."

No practical affect since they limited to less than there 60 ampacity anyway.

The only limitation is that some lighting fixtures require 90 degree wiring. But this is NEW so all of the wiring would be 90 anyway.

"A basement can easily contain a circuit that is more than 75 feet in total length. Ambient earth temperatures in Southern States and desert areas can easily be factors in basements. Not knowing where in the world your basement is, can't say whether or not that must be factored in derating."

Where would you find a basement that has an ambient temp over 122?

" BEDROOMS are limited to 15 amp circuits. "

WRONG! There is no general NEC limiting bedroom circuits to 20 amps.

"That BEDROOM will require a separate circuit and will need to be ARC FAULT protected most likely (assuming your AHJ has adopted a code version within the last 10 years)"

There is no requirments for bedrooms to be on separate circuits. There is no prohibition agaisnt powering other parts of the house from a "bedroom" circuit with or without an AFCI.

And "last 10 years" has nothing to do with it. AFCI's did not show up until the 99 NEC and even then did not require them until 2001.

One thing that has not been mentioned is smokes. With remodeling many places require updgrading smoke dectors and more so with a bedroom.

Sometime they will be required hardwired an sometime also tied with hardwired ones in other areas of the house "if practical". That whole area if very subject to local interpretations.

Likewise if you have a hardwired smoke in the bedroom then it is an "outlet" and the 2002 NEC requires that (and lights) to also be AFCI protected. But again many locals have opted out of this.

So if your area requires inspection I would check these out first.


tshea1

08:58AM | 05/16/05
Member Since: 05/03/05
79 lifetime posts
Check with your AHJ and Building Dept to find out if you are allowed to do your own wiring and what additional requirements they have. Are you allowed to use non-metallic sheathed cable (sheathed electrical cable), or must the wiring be in conduit or metal clad cable. Also when in doubt hire a qualified licensed electrician.

30 can lights is a large amount of fixtures. You can wire either with #14 or #12 AWG. The #14 must be on a 15Amp breaker. You will probably have several switches to control different lights. Assuming you are using 150W lamps you will need at least 3 15 Amp circuits

The bathroom will be on a 20 Amp circuit including a GFI receptacle. The NEC allows the lights in the bathroom to also be on the same circuit as the GFI.

I would also install a vent fan. It can be wired to the light or to an independent switch.

The receptacle spacing should be so that no point along the wall is more than 6’ from an outlet.

The unfinished basement will require a GFI receptacle—somewhere.

The bedroom will need to be on an AFCI circuit, including the smoke alarm. Check with the AHJ to find out what code cycle your municipality is on and if the AFCI circuits are required. If not, it’s still a good idea to install.

You can wire up to 13 receptacles on a 20Amp circuit, but I would limit it to 9. Based on 28x62, you will need at least 15 receptacles.

Hope this helps.


househelper

05:22PM | 05/17/05
Member Since: 03/31/05
265 lifetime posts
Tshea, but for the NEC at least, there is no restriction on the number of receptacles on a circuit in a dwelling.

MistressEll

08:21AM | 05/19/05
Member Since: 01/30/05
361 lifetime posts
there is no limitation on the number of receptacles in a residental circuit, except

1) combination lighting (now called luminaire) and receptacle circuits are and HAVE been limited to 15 amp and 1440 va for a LONG TIME by the NEC. It is the introduction of a LIGHTING fixture that envokes the limit. This is why most lighting circuits in homes are DEDICATED to that purpose and receptacles are often served from a different branch circuit with its own overcurrent protection. Luminaires in residential applications ARE limited to 15 amp branch circuits EXCEPT where OTHERWISE noted.

2) NEC has for SOME TIME required a dedicated 20 amp gfci receptacle for bathroom, and LIMITS the luminaire/fan/overhead to a power limit and provides for ONE such feature/outlet for that DEDICATED circuit.

3) The future bathroom and future bedroom CAN NOT SHARE THE SAME CIRCUIT. The unfinished area receptacles and the bedroom area CANNOT SHARE THE SAME receptacle CIRCUIT. The finished non-bathroom areas can share the same circuit with the bedroom, IF LOCAL CODES permit.

4) I referred to the arc fault protection and KNOWING that MOST AHJ have adopted SOME CODE VERSION THAT IS AT MOST 10 years old, and that both of the more well known code authorities have included that requirement (arc fault protection for bedrooms)within that time period (NEC went back and forth on the requirement in its specifications twice in the 90s).

Funny that "jarrod" and "tshea1" here both offer advice, yet in another post on a pond pump tshea1 is asking the questions and jarrod is the "authority" berrating and answering questions.

I think you need to get your screen names in order Jarrod, as its obvious you're the same person!

househelper

08:29AM | 05/19/05
Member Since: 03/31/05
265 lifetime posts
Ell: Please provide the code sections for your claims of NEC limits on combination lighting/receptacle circuits.

I would suggest you keep your opinions of other posters to yourself.

tshea1

08:33AM | 05/19/05
Member Since: 05/03/05
79 lifetime posts
Whoever you are you seem to be misinformed.

I am not Jarrod.

I have been doing electrical work for 30 yrs.

Your item 1

The NEC does not restrict lighting circuits to 15Amp. SHow your proof!

Item #2

You are actually agreeing with me! Let me clarify-"The bathroom will be on a 20 Amp circuit including a GFI receptacle. The NEC allows the lights in the bathroom to also be on the same circuit as the GFI." ONLY for that bathroom.

#3 No one said that except you.

#4 "And "last 10 years" has nothing to do with it. AFCI's did not show up until the 99 NEC and even then did not require them until 2001." 2005-2001=4 yrs. EZ math.

MistressEll go to the thread Who are you and post if you dare!!


Billhart

02:27PM | 05/19/05
Member Since: 04/25/05
1915 lifetime posts
"The unfinished area receptacles and the bedroom area CANNOT SHARE THE SAME receptacle CIRCUIT."

The circuit that serves the bedroom can also serive the unfinished area of the basement, garage, outdoor, hall, living room, and any other location in the house except those few areas that require dedicated circuits (bathroom, kitchen/dinning room, laundry).

PS, I am not Jarrold, tseah1, househelper or anyone other than, Just Plain Old Bill.

But of course you knew that from FHB.


tshea1

06:48PM | 05/19/05
Member Since: 05/03/05
79 lifetime posts
"PS, I am not Jarrold, tseah1, househelper or anyone other than, Just Plain Old Bill."

Bill, I'm tshea1 not tseah1!

Have a nice day! See ya on another thread since we are not the same guy!!


piewicket

08:29AM | 05/26/05
Member Since: 05/24/05
6 lifetime posts
It looks like you will need a minimum of five circuits. This depends on wether or not you will have a heat, vent, light in bathroom. if so that would be 6. 2 ckts for the lighting minimum since you will have 30 Can lights if they are 75r40 lamps that would be about 18A worth of load exceeding the 80% rule of the overcurrent device. 1 or 2 ckts for the bath (one for heat vent light, one for receptacle). One dedicated for the refer 20A. Then 1 or 2 for the recepts depending how many there are. The loads placed on houses anymore I would run all the circuits on 20A breakers.

MistressEll

06:48AM | 06/18/05
Member Since: 01/30/05
361 lifetime posts
210.52(C)(1) throught (C)(5)

Exception No. 1 to 210.52(B)(1) is meant for example a separate switched

lighting circuit for that UC lighting in which the switch controls the receptacle that feeds the lighting

i.e. transformer supplied low voltage under cab lighting. These are limited to 15 amp circuits.

as are all luminaries, and are rated as demand loads and limited to 1440 va.

Demand Load (luminare/lighting fixtures) designed at 80% (converse of 125%).

Simple math, VA = volts times Amps. To determine the "amp" portion, divide VA by Volts.

1440 divided by 120 volts equals 12 amps. 12 amps just happens to be exactly 80% of 15 amps. Hence the restriction for any combination circuit in residential wiring that includes a recepticle AND a luminaire (light fixture) to 15 amps, UNLESS OTHERWISE EXCEPTED...i.e. dedicated bathroom circuit allowing overhead "outlet" to include fan/light. This restriction has been in the codes a LONG TIME. So sorry you missed it.


MistressEll

07:03AM | 06/18/05
Member Since: 01/30/05
361 lifetime posts
The National Electrical Code (NEC) addresses current carrying capacities of both conductors and components. Unfortunately, some designers fail to recognize the limited SCCR of some lighting contactors. They may mistakenly place this equipment in a circuit with higher fault currents than the product listing allows. Electrical design safety of the lighting control system is instrumental in developing the foundation of the system before details of the control scheme are established.

Receptacles NEW 2002 NEC 406.

Luminaire. A complete lighting unit that consists of a lamp or lamps together with the parts designed to distribute the light.

Intent: “Luminaire” replaces the terms “fixture” and “lighting fixture,” which were used throughout the 1999 NEC but never defined. The Illuminating Engineering Society of North America and most manufacturers use this new term.

Art. 210 - Branch Circuits

210.7 Branch Circuit Receptacle Requirements

(A) Receptacle Requirements. Receptacle outlets must be located on branch circuits in accordance with the requirements listed in Part III of Article 210.

(B) Receptacle Requirements. Specific receptacle requirements are covered in Article 406.

Intent: Usability of the Code has become important to the Code-making panels. They believed relocating the installation requirements for receptacles and cord connectors to Art. 406 would make the Code easier to use. Art. 406 also includes the installation requirements for receptacles and cord connectors that were located in Art. 410, Part L of the 1999 Code.

210.7 Branch Circuit Receptacle Requirements

(C) Multiple Branch Circuits. Where more than one branch circuit supplies more than one receptacle on the same yoke, a means at the branch circuit panelboard must be provided to simultaneously disconnect the ungrounded (hot) circuit conductors supplying the receptacles.

Intent: The change makes it necessary for all ungrounded (hot) circuit conductors terminating on multiple receptacles (duplex) on the same yoke to be disconnected simultaneously regardless of type of occupancy. The rule prevents persons from working on energized circuits they thought were disconnected. The 1999 NEC only required the circuit disconnect to simultaneously interrupt the multiwire circuit to multiple receptacles on the same yoke if the receptacle was located in a dwelling unit.

Luminaire. A complete lighting unit that consists of a lamp or lamps together with the parts designed to distribute the light.

Intent: “Luminaire” replaces the terms “fixture” and “lighting fixture,” which were used throughout the 1999 NEC but never defined. The Illuminating Engineering Society of North America and most manufacturers use this new term.

Qualified Person. A person who has the skill and knowledge related to the construction and operation of the electrical equipment and its installation. This person has received safety training on the hazards involved with electrical systems.

Intent: The 1999 NEC used the term “Qualified Person(s)” in about 65 sections, and the revision clarifies that a qualified person must have received safety training on the hazards involved. No longer is a person considered qualified simply by being familiar with the construction and operation of the equipment and the hazards involved.

Art. 110 - Requirements for Electrical Installations

210.12 Arc-Fault Circuit-Interrupter (AFCI) Protection

(A) AFCI Definition. An AFCI protection device provides protection from an arc fault by recognizing the characteristics unique to an arcing fault and by functioning to de-energize the circuit when an arc fault is detected.

(B) Dwelling Unit Bedrooms. All branch circuits supplying 15 or 20A, single-phase 125V outlets installed in dwelling unit bedrooms must be AFCI protected by a listed device that protects the entire branch circuit.

Intent: The change extends AFCI protection to all 125V outlets in dwelling unit bedrooms, whereas the 1999 NEC only required AFCI protection for all branch circuits that supply 15A or 20A, single-phase 125V receptacle outlets in dwelling unit bedrooms. The Code defines an outlet as “a point on the wiring system at which current is taken to supply utilization equipment” [Art. 100]. This includes openings for receptacles, luminaires, or smoke detectors.

The practice of separating the lighting from the receptacle circuits in dwelling unit bedrooms will now require two AFCI circuit breakers. The 125V limitation to the requirement means AFCI protection would not be required for a 240V baseboard electric heater.

Made of Insulating Material: Sec. 410-18(b), Ex. -- new. This new exception allows you to install a luminaire (lighting fixture) with exposed conductive parts at an existing outlet where the wiring method does not provide an equipment-grounding conductor. In such cases, this rule allows you to install and use a separate equipment-grounding conductor in accordance with Sec. 250-130(c). This rule change provides a legal means for installing a luminaire (fixture) with exposed metal parts on existing branch-circuits without the existing wiring method having an equipment-grounding conductor means.

There are other restrictions in the NEC that may appear to disallow this, however, principally Sec. 210-23. For example, Sec. 210-23(a) reads as follows (pay particular attention to the second sentence):

(a) 15- and 20-Ampere Branch Circuits. A 15- or 20-ampere branch circuit shall be permitted to supply lighting units, other utilization equipment, or a combination of both. The rating of any one cord- and plug-connected utilization equipment shall not exceed 80 percent of the branch-circuit ampere rating. The total rating of utilization equipment fastened in place shall not exceed 50 percent of the branch-circuit ampere rating where lighting units, cord-and plug-connected utilization equipment not fastened in place, or both, are also supplied.

Be careful with the second sentence. It refers to the rating of any one utilization equipment. It applies to applications where there are multiple receptacles or multiple outlets. The idea is to reserve some branch-circuit capacity for the vacant half of a duplex receptacle, for example, or for other receptacles on the circuit. Then, if equipment is permanently installed, the rules reserve even more capacity (50%) for the other outlets or receptacles. The result is a logical progression from a 100% loading allowance for an individual branch circuit, to an 80% limit on any one cord- and plug-connected appliance, to not over 50% for permanent equipment.

The parent language in Sec. 210-23, which governs all subsections that follow, supports this argument:

210-23. Permissible Loads. In no case shall the load exceed the branch-circuit ampere rating. An individual branch circuit shall be permitted to supply any load for which it is rated. A branch circuit supplying two or more outlets shall supply only the loads specified according to its size in (a) through (d) below and summarized in Section 21024 and Table 210-24.

The second and third sentences of this section must be read in concert. The second sentence clearly allows, as in this case, a 20A individual branch circuit to supply a 19A microwave oven, and a 30A branch circuit to supply a 29A coffee maker. The third sentence has the effect of removing the receptacle restrictions from the individual branch circuits described here. The subsections that follow only apply where there are "two or more outlets."

This will be further clarified in the 1996 NEC. The words "or receptacles" will

Branch-circuit protection

This analysis assumes noncontinuous loading. The branch-circuit overcurrent protection must properly protect the plugs and receptacles as installed, and Sec. 210-21(b)(1) requires the branch-circuit protection to not exceed the receptacle configuration ratings in these cases. If the load were effectively continuous, the branch-circuit overcurrent protection would need to be increased to cover the additional 25 % load allowance required by Sec. 220-3(a), and that would, in turn, increase the required receptacle (and therefore, the required plug) ratings. This in turn is why the UL standard (see Par. 10.5.5 above) normally requires a 125% allowance and only permits the 100% sizing with actual continuous loading not over 80% of the branch circuit rating.

http://ecmweb.com/mag/electric_art_overcurrent_protection/index.html

Dwelling units.

As noted above, GFCI protection has been required for all 15A and 20A, 125V receptacles in the bathroom area of a dwelling unit for more than 20 yr.

GFCI protection devices are also required for all 15A and 20A, 125V receptacles located in garages and grade-level portions of unfinished or finished accessory buildings used for storage or work areas of a dwelling unit [210.8(A)(2)]. However, there are a couple of exceptions to this rule. GFCI protection is not required for receptacles that are not readily accessible, such as a ceiling-mounted receptacle for a garage door opener. Nor are they required for a receptacle on a dedicated branch circuit located and identified for a cord-and-plug-connected appliance, such as a refrigerator or freezer.What about crawl spaces and unfinished areas of the basement? Once again, all 15A and 20A, 125V receptacles installed within a dwelling unit crawl space [210.8(4)] or in each unfinished portion of a basement not intended as a habitable room but used for storage or as a work area [210.8(5)], must be GFCI-protected. However, the Code does note a few exceptions to these rules: GFCI protection is not required for receptacles that are not readily accessible or are located on a dedicated branch circuit and identified for a specific cord-and-plug-connected appliance, such as a sump pump.

Circuit breakers are designed to carry 100% of their rated current while the NEC dictates an 80% application. Why the difference?

One of the most often asked questions is, "How do I size a circuit breaker?" A commonly misunderstood fact about circuit breakers (CBs) is related to the percentage of loading permitted by the NEC and the CB design, and why the two may be different. Let's investigate both aspects.

CB design

A CB is designed and evaluated to carry 100% of its rated current for an indefinite period of time under standard test conditions. These conditions, per UL 489, Underwriters Laboratories Standard for Safety for Molded-Case Circuit Breakers and Circuit Breaker Enclosures, include mounting the CB in free air (i.e.: with no enclosure) where the ambient temperature is held at 40 [degrees] C (approximately 104 [degrees] F). Under these conditions, molded-case CBs are required not to trip at rated current.

However, a CB most frequently is applied in equipment at 80% of its rated current under NEC Sec. 384-16(c). If you understand why this requirement is in place, you'll be able to apply CBs correctly.

CB characteristic trip curves

CB characteristic trip curves document how long it takes for specific CBs to trip depending upon the level of current. Fig. 1 shows a typical curve for a thermal-magnetic CB. The curved portion at the top represents the time it takes for the CB to trip on overload. An overload condition will cause heat buildup around the current path, within the CB as well as along the power conductors. This heat, which is generated by the current flow, is actually what causes the CB to trip in this region not simply the magnitude of the current flow. This portion of the curve is said to have an inverse time characteristic, which means that the CB will trip in less time at higher levels of current flow.

Since the current path (including both the CB and the conductor) reacts to heat, the overall operating temperature of the equipment becomes a factor in sizing a CB in an enclosure.

Other factors that may affect this equipment operating temperature include:

* Size and location of the enclosure;

* More than one current carrying device housed in the same enclosure;

* Level of current each device is carrying; and

* Environmental conditions in the area of the equipment.

Consequently, simply designing a CB to hold 100% of its rated current only addresses a portion of the concern. The equipment must be able to safely sustain the heat generated by all sources without exceeding the temperature limits in the product test standard. Both of these factors are accounted for by the sizing rules imposed by the NEC.


Click to reply button Inspiration banner

INSPIRATION GALLERY



Post a reply as Anonymous

Photo must be in JPG, GIF or PNG format and less than 5MB.

Reply choose button

Anonymous

Post new button or Login button
Register

Follow banner a
Newsletter icon Flipboard glossy Facebook Twitter Pinterest Youtube Rss icon