Always using gray 14/2 outdoor electric cable... indoors and out

Question

I know that gray, UF-B outdoor 14/2 electrical cable can be used both outdoors and indoors for permanent installations in Michigan. Why isn't the outdoor cable ALWAYS used for ALL 15amp indoor wiring then?

The outdoor cable can do so many more things than the indoor.

Outdoor cable:

• Is 25%-50% cheaper.
• Is highly resistant to acids, alkalis, corrosives, chemicals, lubricants, fungus, water, UV
• Can be directly buried underground for sheds, garages, barns, etc.

Both in/out door 100' reels are copper. 100' of the indoor weighs 6.1#. The outdoor weighs 6.5#.

I don't see the downside. Just the drastic lower price is enough to use it everywhere indoors and out. What am I missing? Why would the far better/safer/durable cable be so much cheaper... and NOT used everywhere 14/2 15amp is needed?

Update: 3 different DIY store employees didn't have an answer. But they found their manager that "knows all about wiring". He said you CAN use the outdoor wiring, indoors... but the building inspector would immediately raise a red flag due to the gray coloring... and give you a headache about it.

(I would think the inspector would only say "wow, you guys used the far better product than needed. Excellent job.")

Answer 1

I haven't found UF to be cheaper than NM-B, but UF is a total pain to work with. It's hard to strip and is stiffer than NM so makes it hard to pull.

Answer 2

UF-B doesn't come in some configurations

Good luck finding /4 or /2/2 UF-B -- it simply isn't made! On the other hand, there is nothing wrong with using some spare UF of the correct gauge and wire-count for an indoor run, and this might be desirable in a crudely roofed shed or utility space that's only barely "indoors".

Pricing varies

Your experience with UF being vastly cheaper than NM sounds like a local anomaly, otherwise people would do as you say. Normally, NM is somewhat cheaper as it uses somewhat less material for the jacketing, and is also easier to work with due to the ability to use a paper separator between the jacket and the insulated wires inside.

Answer 3

It's not just about the "per-foot" cost

Yes, anywhere NM-B is required, UF-B is allowed. So, "#14 NM" is a size you don't need to buy.

The way I see it, it's not just about the material cost per foot. It's also about the capital you have tied up in the fractional spools of material. And part of the problem here is that pricing is setup to be significantly cheaper when you buy larger spools, so you have to buy 250' spools of everything just to pay a non-outrageous per-foot price.

"Perfect world" you have 12 spools: 14/2, 14/3, 12/2, 12/3, 10/2, 10/3, all in both NM and UF. And since buying them in <250' spools is not cost effective, go price those 12 spools in 250' lengths. That's a lot of capital to tie up!

So buying the perfect wire for every task is just not cost effective unless you're wiring a house a week.

I actually take it a step further. Anywhere #14 is required, #12 is allowed. I don't stock any #14 wire.

But that's a pricing glitch

It's either a discount-store fluke, or a temporary "run on" building materials, or an error in your source data. UF is more expensive because the insulation and sheathing is more complicated. If anything, shortages and the building craze is drying up NM, since people aren't wise to the fact that UF will suffice.

Answer 4

From my experience, underground UF-B is generally more expensive as the jacket material is more expensive to make. Currently, many big box stores have the UF-B marked less than the NM-B cable. That's because the price is not as inflated from demand like NM-B. NM-B is also used more frequently because it is WAY easier to work with. Wire prep 50 outlets with some good romex cable then try to do the same with equivalent size UF-B and it will be easy to see why underground cable is not typically used indoors. However, I am tempted to buy some myself for a 100ft run from my panel to an RV outlet on the outside of my house. 50ft of it will be indoors so my previous plan was to buy romex 50' NM-B for around $50 and use individual wires in conduit for the outdoor portion. Now, the indoor NM-B is nearly 3 times the cost it was when I first priced it and I can do it cheaper with underground cable.

Answer 5

Aloysius Defenestrate wins it for his suggestion (but in a comment). It does indeed look like the lower price was due to higher copper prices (Home Depot even had a makeshift sign taped to their shelf). Perhaps the lesser used "outdoor cable" was store inventory from months before the price increases. While the much used "indoor cable" was newer stock, at its newer higher prices.

And a thank you to George Anderson for the stripping suggestion. Outdoor may be harder to strip. I've never tried it... but it looks like part of the difference between the 2 cables are:

• Indoor has its white outer insulation bundled loosely around all 3 conductors.
• Outdoor has its gray outer insulation bundled tightly around EACH of the 3 conductors, individually. (Probably to avoid an airspace where water could gather.)

Wrong answers: It's not "an extension cord". It's not due to being the wrong gauge, nor aluminum wire, nor the wrong amp rating. It wasn't a pricing error, not a huge sale.

100' copper 14/2 indoor white: $86
100' copper 14/2 outdoor gray: $56

Answer 6

I know I'm a bit late to the dance here, but here's the reason you shouldn't....NEC says you cannot run more than 50 ft of UF or Direct Burial cable indoors. Beyond 50 ft you need to run it in RIGID conduit (insane) or transition it to indoor cable. Why? Because UF jacket is often polyethylene or gel-filled and is highly toxic when it burns. The material that makes it resistant to so many things and acceptable to run in the dirt, makes it a hazard when it burns.