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I want to replace all of the wire in my house and in the light fixtures because my house is 36 years old and I think It's time the wire gets updated and upgraded

I currently have 14/2 wire throughout all of the outlets and lighting in the house ( unknown type ), and 18 Gauge running into the fixtures, I'm wanting to upgrade to 12/2 wire so i don't have to worry about high resistance causing high heat with newer technology but I'm lost on what type of wire to use. NM-B, UF-B, THHN, PLTC, THWN I do not want to go cheap, I've heard aluminum wire is bad and it's better to go with copper... I want it to with stand heat, or If any leaks occur throughout the years in an outlet by the window or the wiring in the ceiling

Would UF-B be appropriate for walls and ceilings even though it's rated for underground or outside use?

United States

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    If you have copper wire, and your house was wired with normal practices of the time, there is no reason to "update" your wiring. Have you looked in your electrical panel to see how many circuits are on a 15 A breaker and how many are on 20-A breaker? Do you have circuits on a 20-A breaker that are in #14 wire? If so, that would be a problem, but otherwise your time and money would be better spent elsewhere. – Jim Stewart Nov 6 '18 at 12:44
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    You have a larger risk at damaging the wire in a remodel compared to new construction. The copper wire and insulation is fine and will outlast your children. Whoever gave you the idea that old wire causes high resistance is nuts. I have worked on old knob and tube that was put in in the early 1900's and some of that is still in use after over 100 years. The 18 gauge wire in the light fixtures is good for 7 amps and most fixtures are 60w so you are only drawing .5 amps if LED's half of that. Why do you think you need to update your wiring? – Ed Beal Nov 6 '18 at 13:11
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    No one makes or uses solid aluminum wiring in that size, and as the others said your wiring is fine. Do something useful with your cash. – isherwood Nov 6 '18 at 13:48
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    No, stop now. UF-B wiring is specifically designed for direct burial outdoors - it is entirely the wrong wire to use inside a house. More expensive does not mean better - you must use the correct wire, not the most expensive wire. You have an imaginary problem with a bad solution. Just don't worry about it - your wiring is fine. If you're that concerned, get it professionally inspected. – J... Nov 6 '18 at 16:26
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    Who said aluminium wires are bad? I've seen transformer-houses with blocks of solid aluminium in it... – Mast Nov 6 '18 at 19:11
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NM-B hasn't changed much from then to now

The NM-B cable used in 1982 is little different from today's NM-B cable -- PVC or Nylon-coated PVC insulated copper wires with a kraft paper separator wrapped over them, and a PVC jacket extruded over the top of that -- all of this is impregnated with flame retardants, of course.

Given that, and what is known about PVC insulation, provided the wiring was not damaged by installation or subsequently subject to mechanical abuse, water damage, or prolonged/repeated overload or overheating, there is no reason to be concerned about the state of the wire in your walls.

Your panel is probably a bigger deal than your wires

A 1982-era electrical panel, though, while reasonably modern, could still pose issues. There are three factors I consider when it comes to whether panel replacement is warranted or not, and they are Construction (who built it? is it a conventional/reliable design, or something that hasn't stood the test of time?), Condition (has there been heat damage? water ingress? excess corrosion? loose contacts?), and Capacity (both in terms of amps and more importantly, spaces -- many houses can get by on 100A even in today's world, and even an all-electric house can easily suffice on a 200A service if designed correctly, but running out of panel spaces is a serious and easily-made error in today's world).

If your panel is of a currently made type and has sufficient space, then I would install GFCI and AFCI protection to current Codes at this point -- that will keep you in Code for a long time.

If and only if there are other reasons to rewire

If other reasons to rewire (such as having too few branch circuits, or physical damage to the existing wiring) are in play, then there are a couple options. In any case, going with 12AWG throughout is not a bad idea if you are in the situation -- the additional copper cost is balanced out by the reduction in Bill of Materials line items (i.e. you can get better economies of scale if you don't have to buy so many kinds of wire and cable).

As other answers here indicate, THHN in metal conduit (EMT) is the gold standard of building wiring -- it's largely overkill in a typical house, though, unless you're in Chicago where local codes require the use of conduit wiring methods.

Outside of Chicago, if I was considering a rewire and EMT was not in the cards, I would strongly look at the newer MCI-A cables available on the market now. They use a construction that is a hybrid between AC and MC cable, replacing the undersized "bonding strip" in AC with a full-size bare EGC that is in continuous contact with the cable armor, thus providing a type MC cable where the armor is usable as a grounding means.

As a result, MCI-A cables provide some of the advantages of a metal conduit system (such as grounding everywhere) with the speed of cable wiring, especially with the availability of MC box connectors that snap onto the cable and into the box instead of requiring setscrews. This is further underscored by the elimination of grounding conductor makeup, especially when self-grounding device yokes are used.

One handy tip if you do stick with NM

If you are rewiring and do want to stick with NM cable, one tip is to run ENT ("smurf") in places where wiring expansion may be called for (such as between a bathroom fan/light switch and its associated fan, or for traveller runs in complex multiway switching situations), then pull individual THHN wires through it. A 1/2" ENT has room for more THHNs than you'll ever need in a residential environment, and is cheap to acquire and run relative to most other types of conduit.

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In most locations, at least in the US and Canada, houses were wired in 1982 with NM cable (Romex) very similar to the NM used today. That stuff seems to be holding up pretty well, except where it's exposed to excessive heat, sometimes in a light fixture. But I don't know anyone that says that that wire is due for an update.

If you want to replace anything, your panel and breakers would be the first thing I'd consider. Breakers do have a limited life span, and if you're going to replace the breakers, it may or may not be worth replacing the panel too - something to look at.

If you have money to burn and just really want to upgrade your wiring whether you need it or no, without question, I'd go with EMT conduit. That would be a huge job but conduit is forever. If you find a buyer that appreciates a good overbuilt system it may add value to your home. It sounds excessive to anyone from anywhere else, but all homes in Chicago are done in conduit. I have come across a few small apartment buildings / triple-deckers done in conduit. If you want to go even further into eccentric multimillionaire territory, you could do it all in rigid conduit, but that could cost more than the house.

If you're going to overbuild a bit and go with conduit, I bet you'll also want a bolt on panel.

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    I agree, except for the conduit. That's just wasteful in a residence. – isherwood Nov 6 '18 at 13:40
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    I am definitely in the minority but IMO it would not be unreasonable to run anything that extends into a ceiling with a finished floor above it in conduit. For example in a typical two story house, the first floor lights. – batsplatsterson Nov 6 '18 at 14:21
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    In my experience, if anything is reconfigured later it involves new box locations. Conduit actually makes things more challenging in that case. – isherwood Nov 6 '18 at 14:23
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    I don't know about that - you can still branch out of the boxes connected to conduit with cables. But my concern was more maintenance, rodent chewed or water damaged cables, etc. If you're doing major remodeling, drywall / paint work is a given. – batsplatsterson Nov 6 '18 at 14:28
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I'll be honest: UF-B is overkill inside walls. UF-B is designed to do two things NM can't

  1. UV resistant (the outer jacket doesn't break up in sunlight as easily)
  2. Water resistant. The wires are literally coated with the outer jacket (as opposed to merely wrapped like NM) so water cannot penetrate as easily

You're not going to encounter either situation inside your walls (if you do, you've got bigger issues). Even if you do, NM is unlikely to be harmed by short-term exposure to incidental water (i.e. a leak). UF is slightly more expensive than NM for no real gain. If you want to hang the expense and get some real value, go with armor clad and install some metal boxes to boot. This is the closest you can get to conduit without going conduit. It protects the wire against damage (which is a far more common threat to wire than leaks)

I've heard aluminum wire is bad and it's better to go with copper

For branch circuits (i.e. inside your walls), yes. But your electrical service wire is almost certainly aluminum. You cannot buy aluminum wires to go inside your walls (4 gauge and larger is the only way to buy aluminum generally).

  • Al THHN and XHHW-2 singles are available in 8AWG and larger, but you are right insofar that the mineral costs don't pay until you get to things larger than 6AWG copper can handle. – ThreePhaseEel Nov 7 '18 at 3:01
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Upgrade the Breakers and/or the Panel

As others have said, copper wiring installed properly doesn't "go bad". What goes bad are connections, outlets, fixtures and breakers. The way to protect all of that - and protect against any true wiring faults as well - is to upgrade your panel. Current code requires GFCI and/or AFCI in many locations. GFCI is for protecting against ground faults and therefore is required in wet areas like kitchens and bathrooms. AFCI is for protecting against arc faults which theoretically can occur anywhere. AFCI is properly done at or near the panel. GFCI just needs to be someplace before the humans it is protecting, so it can be at the panel or at the outlets in the kitchen, bathroom, etc.

My recommendation would be to check/upgrade:

  • If you have existing GFCI outlets or breakers, test them and replace any that don't trip properly when tested.
  • If you have any circuits that should have GFCI (this generally means counter receptacles in the kitchen and any receptacles in the bathroom, but there are other areas like the garage that may need them too under current code) then either put a GFCI in the first receptacle in each chain or replace regular panel breakers with GFCI.
  • For most other circuits (e.g., bedrooms), AFCI is part of the current code requirement and ideally should be added at the panel (in place of regular breakers). That will help protect against many types of potential wire faults.
  • If your panel currently has "double stuff" breakers then making these GFCI and/or AFCI replacements may not be practical. If so, it may be time for a panel replacement or adding on a subpanel in order to have more spaces for full size breakers.
  • If your dryer and/or stove is currently on a 3-wire (bootleg ground to neutral) connection then upgrading that to a code-compliant 4-wire connection is a priority.
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You need to factor the risk vs reward.

You do not mention electrical issues. So the only thing you could do is introduce them, given you will not have as much access to the wires as during the building phase. On the other side appliances and everything in general is made using less and less power. You are upgrading wiring while you should be using less power. This really doesn't make sense as your first reaction.

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How I wish our house was wired in #12 copper! My sister bought a new house in a tract development outside Gulfport MS and all her receptacles and lights were on 20 A circuits in #12 copper. No #14 wire in the house. I admired that, but really it is overkill.

The receptacles and lights in our 48-year-old house in Dallas TX are wired in aluminum: #12 for 15 A circuits and #10 for 20 A circuits. I have pig-tailed all the terminations, but have not replaced any aluminum conductor. I have never tied into any of the original aluminum wiring. I have added two 20 A circuits in #12 copper, but I have no plans to ever replace the original wiring unless we would be doing an extensive renovation.

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    You don't say why you wish and admire. #12 contains roughly twice the copper, which means twice the mining and processing and the pollution and energy wasted that involves, for no benefit. – isherwood Nov 6 '18 at 13:46
  • @isherwood I agree completely. It can't be justified, it is heavydutyitis. I suppose I thought that one would never have to wonder if there was #14 on some 20 A circuit. I may be reacting to the fact that our house is substandard-- both bathrooms are on the same 15 A GFCI breaker with #12 aluminum (prolly not as good as #14 copper). Each bathroom has one receptacle, lights, exhaust fan, heat lamp with fan. The breaker never trips even when my wife uses a 1600 W hair dryer, but I wonder if that #12 aluminum is sometimes getting warm. – Jim Stewart Nov 6 '18 at 15:57
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    This isn't an answer - you're just telling us a story about yourself. – J... Nov 6 '18 at 16:28
  • I was pointing out an example of a tract development in which no #14 was used, so others than the OP think it's desirable to have all #12 copper in branch circuits, and I said that it was really overkill. That is an answer, albeit a long winded one. In a properly wired house is it OK for the lights to dim when a vacuum cleaner is plugged into a receptacle on a 15 A breaker which also has lights on it? Is it even OK to have lights and receptacles on the same 15 A circuit? Maybe with all #12 one can put more receptacles on a breaker ? – Jim Stewart Nov 6 '18 at 17:41
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    @JimStewart No, it's not OK for the lights to significantly dim. This is an indication that either the circuit is overloaded (possibly with a faulty or incorrectly sized breaker) OR an indication that there are bad connections along the feed that are contributing to voltage drop under load. With aluminum wire I would be extremely suspicious of bad connections in the first instance. It is OK to have lights and receptacles on the same branch circuit, generally. There are exceptions depending on the location and intended use of the outlets, of course. – J... Nov 16 '18 at 17:00

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