14/2 15A circuit length?

[Unregistered]

Is there a maximum length for a 15A circuit (mostly outlets) before code would require a larger guage of wire? I am wiring my unfinished basement and have eight duplex outlets in a 35x15 rec room. By the time the Romex runs from the sub-panel to each outlet, it will be 75+ feet. Should I be using 12/2 for this? Is there a code requirement or general rule of thumb?

Thanks!

[mdshunk]

See the link "Voltage Drop Calc." in the yellow and green boxes at the top of this page. This explains every detail about how far you can run a wire better than any response could. (short answer is, you'll be fine)

[Wgoodrich]

Receptacles for general use in a dwelling are unknown intermittent loads. There is no way to calculate voltage drop accurately concerning unknown connected load of convenience receptacles. Dwellings if wiring remains inside the dwelling has rules specific for dwellings. Voltage drop is not a concern per the NEC rules inside a dwelling.

The above is the rules. However if you run a long distance of 100' or more rule of thumb and you have lights in that branch circuit with receptacles then plug in an iron or other appliance that has electric heat this appliance will cause lights to dim if 14 awg wire. This is not a safety hazard but an annoyance that can be limited by installing 12 awg copper wire instead of 14 awg copper wire for that branch circuit.

Either way your code compliant.

Hope this helps

Wg

[mdshunk]

Yes, but WG, if you had an obnoxious run of #14 or #12 to a far batch of receptacles (like out in flowerbeds in the yard or something), wouldn't you do a voltage drop calculation based on 15 or 20 amps? I think I would.

[Perion]

Yes, but WG, if you had an obnoxious run of #14 or #12 to a far batch of receptacles (like out in flowerbeds in the yard or something), wouldn't you do a voltage drop calculation based on 15 or 20 amps? I think I would.

Just for fun I calculated the voltage drops for a 120 volt branch circuit with a 12 amp and 16 amp load (80% for each of a 15 and 20 amp circuit) at 100 ft and 200 ft cable length (200 and 400 ft combined total length for hot plus neutral conductors).

http://mywebpages.comcast.net/dharp/files/Load.htm

Bottom line - if you're planning on heatin' the flowerbed ya'd better do the calculations ;)

Later,
Perion

[mdshunk]

Point taken... I'll go away now.

[Wgoodrich]

Go back to my reply, I put a limitation of "in" a dwelling. If outside then yes voltage drop is calculated. Most receptacles outside will require a certain purpose concerning an outside branch circuit. Multioutlet general use receptacles inside a dwelling can have a very changing load on that inside general use branch circuit with several receptacles on a circuit.

Outside wiring is normally for specific use. Inside a dwelling any day the load would change. Design of wiring inside a dwelling is very specific in design per NEC rules due to this unknown intermittent loading.

HOpe this helps

Wg

[Unregistered]

Go back to my reply, I put a limitation of "in" a dwelling. If outside then yes voltage drop is calculated. Most receptacles outside will require a certain purpose concerning an outside branch circuit. Multioutlet general use receptacles inside a dwelling can have a very changing load on that inside general use branch circuit with several receptacles on a circuit.

Outside wiring is normally for specific use. Inside a dwelling any day the load would change. Design of wiring inside a dwelling is very specific in design per NEC rules due to this unknown intermittent loading.

HOpe this helps

Wg

Wg,

If load is not known then why not use 80% (or even 50% for continous duty)of circuit rating and calc wire length on the max voltage drop. This would seem "logical" way do calc for an unknown load. In my "new" $330K house I have a computer and monitor in the last plugs on the circuit in a den/office (1 of 3 1/2 rooms on this circuit) and I am having major problems with voltage drop on this circuit. I did some testing and found by using calcs from the NEC 2002 this is a 14/2 circuit and loading the circuit with a 1050 Watt device I get a 12 volt drop, this calcs to a wire length of 235 ft, while this might be within the legal limits as the "unknown load" factor is referenced it is way outside the limits of common sense. With that length of wire I am unable to put more than 2.19 amp load on the circuit before I get a 3% voltage drop. So 1 TV and a 60 Watt light bulb will cause a drop on the circuit of more than 3% of the system voltage.

On another note, is there still a requirement for "All" circuits in a bedroom to be protected by a AFCI, including ceiling lights, fans, smoke alarms. I know this is the way the 2002 code was written but thought something was in the works to remove the ceiling requirements.

Thanks all

Jim

[Wgoodrich]

From the ROPs that I have kept up with I am not seeing a trend to withdraw from all outlets [lighting and receptacles as well as smokes] in a bedroom being required to be AFCI protected.

However many local rules have ammended this NEC rule. Remember the NEC is written to be adopted as law but is often ammended locally before it becomes rule of law in a certain area. Check local ammendments in your area.

Using the 80% or 50% is not viable. Again you may have one house that has 50 receptacles on a certain general lighting circuit but only 1 or 2 receptacles actually used. Then again you may have a house that only has 6 receptacles on a circuit and all 6 are used under load. Then again you spoke of your home and the loads you use calculating the voltage drop beyond reason. Yet sell your home to a different family and that second family may not even use that circuit in normal use in their lifestyle.

To use the 50% or 80% rule which family and what load will apply on what day? There is no way to accurately calculate for voltage drop on a general use circuit. It will change from day to day and hour per hour.

This is why most recommend not to wire per NEC MINIMUM SAFETY STANDARDS but rather to wire all circuits in 12 awg wire. Many advise this larger wire beyond what is required to meet MINIMUMS. However if you built your home did you bid the electrical out to several contractors? Did you take the lowest bid? Did you compare apples to apples in those bids. Did you create a list of bid specs, If not then it would be bid competitively using minimum standards. If a contractor bid 12 awg against another contractor you would hire the lower of the two bids or the best slick talker.

Electrical contractors are well aware when bidding they have to bid MINIMUM to compete or they will lose the job. If that contractor went to you and said I bid 12 awg wire then you would then ask the lower bid did he bid 12 awg wire. His answer of coarse would be yes to keep the job. Yet if you had not asked you would have seen dimming of lights due to voltage drop of 14 awg wire on a heavily loaded circuit. To say this is unsafe would be untrue. To say you would wish to have hired the other contractor that tried to bid proper heavier wiring, that is an after fact. You have no idea how many people talked to me after the job was done by a competitor telling me they wished they had picked me. After fact didn't put food in my family's mouth.

Yes you are correct. 12 awg wire is better to address voltage drop.

Yes you are correct it is better to stay about 10 receptacles on a circuit for 20 amp and 7 receptacles on a circuit for 15 amp but reality says it ain't going to happen unless you wire the home yourself. Then when you sell that house do you believe you will get more money because it was wired in 12? NO.

Yes you are correct but in reality it does not normally happen on 80% of the homes.

Safe 14 awg as Code says. Better 12 awg as most contractors wish they could wire.

Never install larger than 12 awg wire to a receptacle or switch screw. These devices are not designed for that larger wire.

YOu have no reliable factor to calculate voltage drop or use 80% or 50% rule. This is why there is specific rules for dwelling branch circuit designs found in 210.11 and 210.52 of the NEC. Also be aware that if you have a piece of equipment fastened in place and if that load if 50% of that branch circuit the NEC requires that circuit to be dedicated.

Hope this helps

Wg

[Unregistered]

Wg,

Thanks for the reply.

This house is a "tract" home and was not built by a homeowner, but the builder did represent one room as a den/office and this room is the last on a 15amp 14/2 235ft wire circuit. One would have thought to run seperate circuit since it would be used as an office and have more load than a bedroom circuit, but that is between me and the builder.

Would it be legal and safe to rewire in this way. Leave the 15amp AFCI breaker in place and run 12/2 or 10/1 from breaker panel to top of wall in office where 14/2 wire enters wall from attic, mount a junction box, tie the 12/2 or 10/2 into the 14/2 going down the wall. Doing this will eliminate the other 200ft of 14/2 wire from this circuit and get rid of my voltage drop problem from 1 computer and 1 monitor and 1 printer. I know taping a 14/2 into a 12/2 or 10/2 is a no-no when there is a 20 or 30 amp breaker but how about with a 15 amp breaker.

Thanks for the info

Jim

[Wgoodrich]

Legally you would have no issue in my opinion with the buider. The wiring you discribe is all general receptacles are placed evenly on all general lighting branch circiuts then he met minimum safety rules.

It is common to run a 12/2wGrnd wire from panel to area of a room then connect to 14/2wGrnd wiring the room to address voltage drop concerns. Easy fix if you had an electrician that ran the cables from each receptacle to the attic then down to the receptacles. Many electricians that wire production style use stilts and wire in this manner up and down instead of through studs. If not then you can fish a wire down an inside wall with no problem to one receptacle in that room and power from a new 12/2wGrnd cable that has a marking tape in the panel telling 14 awg wire is involved in the circuit for future electricians to know a reduced size it there then using the original 14/2wGrnd cables wiring the room. Rememeber to disconnect the power feed entering that room from the original circuit. Also be aware electricians often power receptacles on opposite sides of the wall from receptacle to receptacles. If this is the case in your wiring style and the opposite side of the wall is a bedroom then don't forget to add in the AFCI breaker to meet Code. Just remember to size the breaker to the smallest wire ampacity on that certain circuit. This would address the voltage drop concern you have in your home splitting the circuit in half and eliminating the voltage drop.

Wiring production such as your type home it is all about money. Many times an electrician loses a bid for a $50 dollar difference in their competitive bids. This is the difference between a custom built home and production homes in quality. Problem is the custom built home often sells for the same price as the production home. Women seem to pick the home they buy and they look for pretty faucets and cute design. Sound structural patters usually have little to do with price of house or how it sells.

Welcome to the world of production !

Wg

[Unregistered]

Wg,

Thanks for the info, I'm meeting with the builder customer care manager on Monday and they have already said they would run a seperate circuit to the office if that will solve the problem. I think I will suggest they run a line of 10/2wGnd from panel to all rooms and tie into the 14/2wGnd going down the wall to the outlets. Since it is a long run I think 10/2 would be best and still keep the voltage reasonable at the last plug on the line.

Thanks again for the info/opinions

Jim

[Wgoodrich]

You are fine with your plan if you do two things for current and future concerns. Code requires that the breaker be sized in amps to the smallest ampacity rated wire on each circuit. I advise you to tag those larger wires with a flag stating the smallest wire on each circuit inside the panel to ensure someone later on does not unknowingly install too high amp rating breaker creating a fire hazard if that tags are not there to advise future electricians of smaller wire on that circuit.

Good LUck

Wg

[Unregistered]

You are fine with your plan if you do two things for current and future concerns. Code requires that the breaker be sized in amps to the smallest ampacity rated wire on each circuit. I advise you to tag those larger wires with a flag stating the smallest wire on each circuit inside the panel to ensure someone later on does not unknowingly install too high amp rating breaker creating a fire hazard if that tags are not there to advise future electricians of smaller wire on that circuit.

Good LUck

Wg

Wg,

First thing on my list was a warning tag for the 2 circuits stating just that.

Thanks again for the info...

Jim