residential wireing - maximum number of allowable splices

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  #1  
Old 03-19-13, 01:38 PM
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residential wireing - maximum number of allowable splices

given the high cost of wire, is it acceptable to splice/extend wire together in order to reach the needed length (in other words splicing 25' of wire on to 75' to get a total length of 100' rather than purchasing another 100' roll. if so is there a maximum number of allowable splices?

also will this hold true for "home run" circuits like air conditioners microwaves etc?
just wondering if a splice will weaken the integrity of the circuit.

all splices will be properly made in an exposed covered box and are of the same gauge

thanks
 
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Old 03-19-13, 03:46 PM
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is it acceptable to splice/extend wire together in order to reach the needed length (in other words splicing 25' of wire on to 75' to get a total length of 100' rather than purchasing another 100' roll.
Yes.

is there a maximum number of allowable splices?
No.

will this hold true for "home run" circuits like air conditioners microwaves etc?
Yes.

just wondering if a splice will weaken the integrity of the circuit.
Not if properly made.

all splices will be properly made in an exposed covered box and are of the same gauge
If, by properly made, you mean that the stripped portions of insulated conductors will be lined up so that the ends of the insulation are even, the conductors will be twisted together at least three times, clockwise, using pliers, and the end of the splice will be trimmed so that no bare conductor is exposed outside the wire nut after that is installed, then yes. Ideally the boxes should be metal and be bonded to the grounding conductor.
 
  #3  
Old 03-20-13, 12:03 AM
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yes...

it took me quite a few test runs to properly execute a three wire 12ga splice as you had mentioned. the smooth jaw duck bill pliers worked great for this.

any other tips?

thanks
 
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Old 03-20-13, 01:43 AM
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Yeah. Don't use tape. It is a dead giveaway of amateur work that will cause any inspector to scrutinize. If there is exposed copper showing under the wire nut that would pose a threat of fireworks, snip the twisted bundle shorter.
 
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Old 03-20-13, 07:46 AM
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I will throw in that while code-compliant, you should try to avoid splices where possible. It's one additional place that things can go wrong, and the junction box needs to remain accessible.

Sometimes they are necessary and the right answer, but if your basement or attic starts looking like some older houses with junction boxes every 5', you may want to reconsider
 
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Old 03-20-13, 02:32 PM
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Buy a pair of linesman pliers. They're made for this work and have both the best jaw and a built-in wire cutter for trimming the splice.
 
  #7  
Old 03-20-13, 10:32 PM
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thanks

i try to be as through and detailed as possible but over the years i may have left some exposed wire at the bottom of the wire nut, nothing crazy maybe 1/8 - 1/4" absolute max. i have always taped around the wire nut. your comment made me nervous, is that enough to cause "fireworks" ?

i also have the linesman pliers but i found it easier to hold the base of three wire legs neatly together with the duckbill, but ill try the linesman next time

when you say "don't use tape" do you mean tape wrapped around the wire nut as the last step?
i thought this was proper?
 
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Old 03-20-13, 10:54 PM
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There should be no visible copper below the wirenut. A 1/4" is a bit more than allowable

When making your splices....... strip the insulation off the wires. Hold the wires together with your hand so that the ends of the insulation are even. Twist the copper wires clockwise. Trim the wires even and install wire nut.

Installing tape as the last step is not proper. A properly installed wirenut requires no tape.


Proper splices
 
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Old 03-20-13, 11:11 PM
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when you say "don't use tape" do you mean tape wrapped around the wire nut as the last step? i thought this was proper?
The first, last and only thing I do with tape that's been wrapped over a wire nut is throw it away. Not only is it not proper, it is a sure sign of an amateur and a signal to me to check the splice. I wind up undoing the splice and re-doing it almost every time, just because I'm worried about what might have been covered up.

over the years i may have left some exposed wire at the bottom of the wire nut, nothing crazy maybe 1/8 - 1/4" absolute max... is that enough to cause "fireworks"?
Any amount of uninsulated current-carrying conductor exposed beyond the skirt of a wire nut is too much and yes, it can result in fireworks. Anyone on my crew who did that would be "encouraged" to correct it, the first time I found it. I would have to correct it myself if it happened again because that worker would no longer be with the firm. I also walk through my jobs and try to pull a wire out of a completed splice now and then.

i also have the linesman pliers but i found it easier to hold the base of three wire legs neatly together with the duckbill, but ill try the linesman next time
OK, I'll bite. What's a "duckbill"?
 
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Old 03-20-13, 11:46 PM
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duckbill / flat-nose pliers

please-
another question related to this thread rather than start another.
i am building a work bench 16' long and would like 4 or 5 outlets placed along its length. i will be using 12-2 NM wire and its a straight run so i can chain the outlets. whats the maximum number of outlets that can be chained? i would like at least 3 but 4 or 5 would be preferred. there is a single dedicated 12ga 20a outlet in the basement that i can take off from, the max would be 5 including that.

also-
i am ultra careful when doing any sort of wiring and never cut corners, that said i am not a professional. although i have confidence in my splices i am a bit nervous and concerned after reading some of the good advice i have received. mechanically speaking whats the theory behind 1/4" of exposed wire at the bottom of the nut being a hazard, and is the tape i have been applying around the nut all these years itself a hazard?

thanks
 
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Old 03-21-13, 12:09 AM
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duckbill / flat-nose pliers
Linesmans pliers have a flat nose. What's the difference?

i am building a work bench 16' long and would like 4 or 5 outlets placed along its length. i will be using 12-2 NM wire and its a straight run so i can chain the outlets. whats the maximum number of outlets that can be chained? i would like at least 3 but 4 or 5 would be preferred.
There is no limit to the number of receptacles you can feed with a single circuit. The limit is the load attached.

What will you be plugging in here?

Is your workbench in an unfinished basement or in your garage?

mechanically speaking whats the theory behind 1/4" of exposed wire at the bottom of the nut being a hazard, and is the tape i have been applying around the nut all these years itself a hazard?
It's not a mechanical hazard, it's an electrical hazard. No exposed live parts of a system means no exposed live parts of a system. An exposed live conductor is a potential source of ground faults, arc faults, and personal injury or death.

The tape is not a hazard. It is a nuisance and a mess.
 
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Old 03-21-13, 12:13 AM
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No.....don't get all worried now. YOU know how your connections are made. They're solid. The tape on your wirenuts will not present a problem. From now on.....you'll make connections with no tape.

As far as the outlets......there is no limit. I have 12 receptacles on a bench shorter than yours. Most of the things plugged in are very low current draw.





wow......ol' lightning fingers Nash got me
 
  #13  
Old 03-21-13, 06:16 AM
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The jaws on some duckbill pliers have no serrations. I have a small pair too light for twisting wire. I don't like using linesman's pliers because the serrated jaws can scar the conductors.

With the price of wire the way it is I can see why someone would want to splice rather than buy another 100'.

I don't want to hijack the thread, but why the metal box?
 
  #14  
Old 03-21-13, 08:24 AM
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Nash said......."ideally metal"...... but plastic boxes can also be used.
 
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Old 03-21-13, 10:01 AM
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I don't like using linesman's pliers because the serrated jaws can scar the conductors.
The face of the jaw on a good pair of linesman's pliers is finely serrated to help grip the wire and lessen the chance of slipping. When a workday can include making more than 200 splices, it makes a difference. Until and unless my linesman's start removing some conductor, they'll remain the first tool in my hip pocket in the morning. If they ever do that, I'll return them for a new pair under their lifetime warranty.

I don't want to hijack the thread, but why the metal box?
No problem. I thought I had explained this earlier, but it may have been in a different thread.

A metal box can, and should, be bonded to the equipment grounding conductor. Once that is done, that box becomes part of the low-impedance path to ground that is an important life safety provision. A plastic box eliminates that opportunity.

Why are there no plastic panelboard boxes?
 
  #16  
Old 03-21-13, 04:26 PM
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NashKat - I'm not an electrician and I must be missing something here. Tlaking residential, NM wiring, how does a metal box nailed to a wooden stud provide a lower impedance path than a ground wire attached directly to the device. Actually, I'm not even sure where impedance enters into it.

I always thought that the ground requirement for a metal box was a safety feature in case of an inadvertant contact between a hot wire and the box, something that can't happen in a plastic box.
 
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Old 03-21-13, 04:37 PM
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Why are there no plastic panelboard boxes?
Actually, there are. Mostly smaller and I wouldn't use one, but they do exist.

Concerning tape on wire nuts, while I agree that it is unnecessary and such a friend and coworker was doing some work in his home and when the electrical inspector asked him why he was taping the wire nuts Tom replied that it was because the wires sometimes would not be securely held by the nut and fall out. Tom told me the inspector nodded and told him he didn't need to see anymore, he was doing fine work.

Now knowing the electrical inspector for this jurisdiction was an absolute by-the-book stickler for almost anything and everything I was a bit amazed at that story. I guess it just goes to show that you can never second-guess what might set off an inspector.
 
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Old 03-21-13, 04:52 PM
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Tlaking residential, NM wiring, how does a metal box nailed to a wooden stud provide a lower impedance path than a ground wire attached directly to the device.
It doesn't, and I didn't say it did. What I said was
Originally Posted by Nashkat1
that box becomes part of the low-impedance path to ground that is an important life safety provision.
Actually, I'm not even sure where impedance enters into it.
OK. Would you prefer low-resistance?

I always thought that the ground requirement for a metal box was a safety feature in case of an inadvertant contact between a hot wire and the box, something that can't happen in a plastic box.
The box must be grounded so that any power that gets loose inside it can use that path to get to ground (and probably trip a breaker or blow a fuse as it does so). That's an emergency overflow drain (what the EGC really is) working at its best. And that can't be done if the box is non-conductive.

BTW, devices mounted in grounded metal boxes are not required to be bonded to ground. Only devices mounted in plastic boxes are. I always do it anyway, and we advise it here, but the code regards it as belt-and-suspenders.
 
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Old 03-22-13, 03:44 PM
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I thought that devices (switch, receptacle etc) connected in a metal box were connected to ground through the device framework. That's probably why there is no code requirement for additional grounding.

I still can't figure out why a grounded box is a better option than a grounded device. It seems as if a failure in a metal box, where a hot wire might contact the box, might be more dangerous than a failure in a plastic box where the same contact wouldn't be a short/safety issue.

My last post - I hijacked the thread and that wasn't my intent.
 
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Old 03-22-13, 03:47 PM
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Furd - I had a similar situation, only the inspector wanted me to put green spaghetti on every ground pigtail. I was using metal boxes. I asked him to show me where that was code. He asked me if I wanted to pass the inspection. We know how that worked out.
 
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Old 03-22-13, 04:23 PM
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Inspectors like that should be called for the abuse of their power.
 
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Old 03-22-13, 06:16 PM
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Inspectors like that should be called for the abuse of their power.
Just don't call them to their face!

I have seen the gamut of inspectors, in all fields. The ones that nitpick the tiniest detail and the ones that won't even get out of their vehicle. Sometimes both in the same individual.

I've seen electrical inspectors that okayed re-identifying #8 conductors but dinged the use of IMC stub-ups from the ground stating the EMT was not acceptable. Then a week later okaying EMT stub-ups twenty feet away because the contractor had already poured concrete.

I had an inspector that okayed a new service without ever leaving his automobile. When I called and asked him to please sign off the permit he then became an ogre and revoked his own approval. He insisted that the GEC connection to the water piping be within five feet of the crawlspace entry, ignoring the NEC requirement that it be within five feet of the water pipe entering the premises.

I've had boiler inspectors that never even stuck their head inside a manhole, let alone tap the rivets or stays with a hammer. I've had different inspectors that wanted 40 some tubes removed so they could inspect deeper into the boiler.

Some inspectors are very good, some are very bad. Most are adequate for catching gross errors. A few are just plain power-hungry jerks. The best advice I ever received on the subject of inspectors was to make certain that I inspected the job and was satisfied because I was there every day versus the inspector being there only once a year.
 
  #23  
Old 03-24-13, 11:47 AM
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thanks for all the good advice

i need clarification on a few points please

1) concerning the ground, i will be using nm 12-2 wire, the boxes will be metal with one duplex outlet mounted to a wooden surface, there will be a total of 5 boxes. i assumed that the ground wires (feed/supply in each chained box) would be pigtailed together with a green ground wire (three total) and the green ground wire would go to ground on the receptical. as i read the replies i see nashcat indicated that the box should also be grounded. so am i understanding correct that each ground pigtail should be 4 wires consisting of the 2 bare copper and 2 green wires, one to ground on receptical and one to metal box? and is this true as well for outdoor GFI outlets? the house was wired in BX years ago and i know that the metal jacket acts as it own ground so this is new territory to me.

2)concerning another possible circut..
i might have to pass the NM wire through a tight spot containing the bathroom plumbing, it will be nearly touching the trap for the tub and pass within inches of the supply pipes. i was planning on running the NM through a short length of EMT for this section. is this OK? or is it too close to the pipes?

3)when chaining outlets the "line" is the feed in and the "load" goes out to the next. Correct?

4)when chaining outlets as is there any way / or is it not advisable to put 2 duplex (4 outlets) in each square box. this is easy for the last on the chain but how about the middle ones.

thanks
 
  #24  
Old 03-24-13, 12:43 PM
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1) When you bring the romex into the box.....you can wrap the ground wire once around the green screw and then it will become a tail.

2) if there is no other way to run the wire then sleeve should be ok. Keep future plumbing repairs in mind since you don't want to use a torch near the romex.

3) On a standard receptacle there is no load or line. With GFI receptacles..... the feed "in" is the line and the feed "out" is the load.

4 ) absolutely no problem using a 1900 type 4" square box for two receptacles. Use a deep box for added room.

I splice all wiring in the box and leave three taps for the device. White, black, and ground.
I didn't go back to re-read thread but if these receptacles need GFI protection then just use one in the first location and the rest can be standard receptacles connected to the load of the GFI receptacle.
 
  #25  
Old 03-24-13, 12:57 PM
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You don't even need the sleeve where the cable gets near the drain or plumbing lines. You would be better off with PVC if you do sleeve the cable. Otherwise the EMT should be bonded to the grounding conductor.
 
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