I have been slowly working on some issues in my basement and came across a junction box this weekend that contained what seemed like 12 gauge stranded wire and 14 gauge solid wire spliced together. The circuit is on 15 amp breaker and contains only a few light fixtures (3). I’m not an electrician but i know it is dangerous to mix two different gauges of wire but I wasn’t sure how big an issue it was given the fact that the breaker is 15 amps and 14 gauge wire is appropriate for that sized circuit. How serious is this and why. It’s just giving me more reason to doubt all the old work buried in this house – not a good feeling.
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Learn more about the benefits and compliance details for the DOE's new water heater energy-efficiency standards.
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
Stranded wire?
I'm wondering more about the stranded aspect of the 12 gage wire. Is this code worthy? I can't recall ever seeing romex with stranded. Is it in a conduit? Perhaps he's got an extension cord running around inside his walls?
Stranded in "Romex"
How many conductors in that "stranded Romex"?
If only 2, black and white, I suspect you are seeing a "creative" use of stranded marine wiring, not Romex. Typically used for low voltage situations (32v DC and lower).
By chance is the jacket gray or white and the stranded wire tinned (silvery in color)?
I am not positive what the maximum voltage of that type cable is -- have only used it on 12 and 24v systems.
Your wire needs further investigation to determine exactly what is there.
If you had #12 AWG THHN stranded connected to 14/2 Romex (solid) and protected by a 15A breaker - that would not be a problem at all....assuming the THHN was protected by a conduit of one type or another.
Jim
The OP said nothing about Romex. He just said that he had what looked like 12ga stranded and 14ga solid wire connected together on a 15A lighting circuit.
Mixing 12 & 14 is OK, if not
Mixing 12 & 14 is OK, if not particularly wise. So long as the circuit is protected by a 15A breaker it's legit. But some people (including some code guys) get worried that someone will see the 12 and figure they can amp the breaker up to 20, especially if it's the 12 that's coming out of the breaker panel.
Stranded is perfectly fine, and in some ways superior to solid. The main problem with it is that it's hard to terminate well on receptacle screw terminals (though this isn't a problem if you use back-wired devices).
You probably have bigger fish to fry than worrying about that wiring.
You may actually have 14ga solid and 14ga stranded wire, not 12ga.
Stranded wire is rated for the total cross-section of its strands, so it appears about one size bigger than solid wire of the same gauge rating. Did you read the gauge printed on the insulation, or did you measure the wire with a wire stripper to determine that the stranded is 12ga and the solid 14ga?
It is dangerous to mix two wire gauges only if the breaker is sized for the larger gauge, making it possible to over-heat the smaller one without tripping the breaker.