Is stranded wire inferior to solid core wire in this situation?

[MiniMe4Eng]

I have to run 2x20A and 1x15A circuits on the outside of the house for like 9m (27') -that is RW90 in conduit.

I have been trying without success to find solid core wire (individual wires) cut by meter. I would have to buy a 300m spool. Even if I use the same color for all the wires and use tape to mark the ground/neutral and hot I am still under 100m.

From what I am seeing it would be maybe easier to get stranded core.
My plan is to get with exterior rated cable to inside of the house and there to connect using a junction box with NMD cables which will be easier to push pull through the finished ceiling (there is insulation there)

From what the vendors told me this wire is more popular because it is easier to pull but from what I am reading technically it is less performant.

Are there any major problems that I should be aware of when using stranded wire ?

 

[3DDave]

Corrosion would be the most likely problem and slightly more likely to have problems at terminations unless ferrules are used.

Any moisture that enters the wire at the ends or small punctures will wick, carrying any corrosives with it.

Stranded wire was used between the anchors for the power at my house and the breaker panel - I would get water dripping into the panel as it ran down those strands during heavy rains.

 

[LionelHutz]

Electricians almost exclusively use stranded for conduit pulls. Can't be many downsides to it that aren't relatively easy to overcome.

 

[3DDave]

I am sure that many electricians do whatever is most convenient for them. No need to "overcome" anything if it's building in future repair work.

 

[Gr8blu]

Pulling 15 or 20 A for house wiring means using either AWG #10 or AWG #8, depending on the "safety" factor.
For both of these sizes (in North America), the commercially available standard is a 7-strand construction, not single strand.
This could be why you are being stuck with a "minimum purchase" amount when opting for single strand conductor.

You should be able to find the stranded version direct off the roll - at whatever length you need - at the local hardware store or electrical supply store.

 

[TugboatEng]

Stranded wire is preferred for every application except homebuilding where cheap is a condition of primary importance.

Stranded wire does not work as well in push in type connections. Those should be avoided regardless of wire type used.

 

[LionelHutz]

No need to "overcome" anything if it's building in future repair work.

Right... they use it so it fails all the time. Good grief.

 

[3DDave]

They use it because they don't care if it fails sometime in the future. Good grief.

Isn't Romex type wire solid? Doesn't that get pulled in conduit? If individual wires are wanted there are jacket strippers and it is available in short lengths.

What was the original question - Is stranded wire inferior to solid core wire in this situation?

Is stranded wire the superior option with no drawbacks?

 

[waross]

Electricians almost exclusively use stranded for conduit pulls. Can't be many downsides to it that aren't relatively easy to overcome.

That may be because building wires in AWG #8 and larger are not available in solid construction.
I have been retired for some time now, and things change but:
For over 60 years on the construction side, the standard was;
AWG 14, and AWG 12, solid wire.
AWG 10, solid or stranded.
All larger sizes stranded.
UNTIL THE INTRODUCTION OF THHN.
THHN became popular for conduit work, not because of the stranding, but because of the slippery and compact nature of the insulation.

Pulling 15 or 20 A for house wiring means using either AWG #10 or AWG #8, depending on the "safety" factor.

????
I started working as a helper, wiring houses on weekends while I was still in school, in 1956.
Some of the work was re-wires of houses built and wired in the '20s. 30's and 40's.
"either AWG #10 or AWG #8"
I seem to have missed that one.
Copper AWG #14 or AWG #12.
Aluminum AWG #12 or AWG #10
Have electricians wired millions of houses over the last 100 years and been doing it wrong?
Wait;
Have I made a mistake?
Am I not on Eng-Tips but on FaceBook by mistake?
#8 AWG is OK on FaceBook.

 

[Gr8blu]

I apologize, Bill.
I am so used to rating ampacities for high temp environments I automatically derate everything ... you are correct. AWG 12 and 10 are FAR more common in residential construction at these current levels ...

 

[MiniMe4Eng]

I need to run:
-1x15A for hair dryer
-1x15A for smart toilet
-1x15A for an adjacent room (kitchen, the current circuit is tripping any time I have the hair dryer and a kettle on or kettle and a small convection oven)
-1x15A for lights (this is optional)

I need to run 27' in a PVC conduit (1") on the exterior of the house and then I can either switch to regular cable or continue with the same
I also have QBR15A that will go into a commander bc40200r1 panel (200A)

Here is chatgpt's solution for this

Overview of Your Setup​

Circuit	Load Type	Breaker	Approx. Load	Length
Hair dryer	15A circuit	QBR15A	~12.5 A	27' exterior + 24' interior
Smart toilet	15A circuit	QBR15A	~8–9 A	Same
Kitchen branch (oven/kettle)	15A circuit	QBR15A	~13–14 A	Same
Lights (optional)	15A circuit	QBR15A	Low (<5 A)	Same

• All 15 A circuits
• 3 or 4 circuits total
• Exterior run = 27′ in 1″ PVC conduit
• Want to use stranded RW90
• One common ground
• Panel: Commander BC40200R1 with QBR15 breakers

---

Step-by-Step Wire Sizing​

1. Conductor Type​

• RW90 stranded copper, 90 °C rated, outdoor-suitable
• CSA-approved for wet/outdoor use when in conduit

---

2. Conduit Fill & Derating​

Scenario	CCCs (Hot + Neutral)	Derating (%)	Resulting Ampacity (14 AWG RW90)
3 circuits	6 CCCs	80%	25 A × 0.80 = 20 A OK
4 circuits	8 CCCs	70%	25 A × 0.70 = 17.5 A OK

→ 14 AWG RW90 is sufficient for all 15 A circuits, even if you include the optional lighting circuit.

---

3. Ground Wire Size​

• Shared #14 AWG copper RW90 is sufficient for up to 15 A per circuit
• Must be green or re-identified with green tape

---

4. Conduit Fill (1″ PVC Schedule 40)​

• 14 AWG RW90 stranded ≈ 4.8 mm²
• 9 conductors (8 CCC + 1 ground) = 43.2 mm²
• 1″ PVC allows 40% fill = ~215 mm²

You're well within the fill limit

---

5. Voltage Drop Check (27′ exterior + 24′ interior = 51′ total)​

• For 15 A on #14 copper: voltage drop ≈ 2.6%
• Well below the 5% typical limit → No upsizing needed

---

Final Wire List (If You Include 4 Circuits)​

Wire Type	Qty	Use	Color
#14 RW90 Cu	4	Hot wires	Black, Red, Blue, Yellow (or mark with tape)
#14 RW90 Cu	4	Neutrals	White (mark with tape to match circuit)
#14 RW90 Cu	1	Ground (shared)	Green or green tape

→ Total: 9 conductors in 1″ PVC conduit = code compliant
If you drop the lights circuit:

• Only 6 CCCs → better derating (80%), easier pulling

---

Breaker Compatibility​

Your QBR15 breakers in the Commander BC40200R1 panel are:

• Bolt-on
• Rated for solid copper
• Do not accept stranded wire directly

Solution:​

• Splice stranded to solid pigtail in a junction box near the panel (fully code-compliant, as discussed earlier)

---

Summary​

Element	Recommendation
Conductor type	#14 AWG RW90 stranded copper
Ground wire	#14 AWG RW90, 1 shared, green
Circuits allowed	4 (15 A) in 1″ PVC with full compliance
Breaker type	QBR15 — use solid copper pigtails
Voltage drop	Acceptable (≤ 3% over 51′)
Junction boxes	Required at transition to solid pigtail

---

 

[MiniMe4Eng]

The problem is: where do I find solid pig tails )

I suspect this can be done with regular cable, not RW90

 

[MiniMe4Eng]

From what I am reading I have the option to buy a spool of 300M of white and mark it with colored tape

 

[waross]

-1x15A for an adjacent room (kitchen, the current circuit is tripping any time I have the

hair dryer and a kettle on or kettle and a small convection oven.

Each of these needs a 15 Amp circuit.
Split the receptacle into two 15 Amp circuits.
2 pole, 240 Volt breaker, three wire circuit.
Wire? Stop obsessing. Use the wire that is available.

I suspect this can be done with regular cable, not RW90

RW90 is pretty regular.

Have you heard the expression;
"Will you trust anonymous advice from a stranger on the internet?"
That chatgpt advice is even much worse.
I won't even begin to list the code violations.
chatgpt doesn't know the codes, doesn't know the code interpretation and doesn't know code enforcement.

If you are really worried about water wicking down the conductors, try this, ON THE WET END.
Strip about 3/8" or 1/2" of your stranded wire and a short stranded pigtail.
Straighten the strands on both conductors.
Cover each wire end with RTV silicon.
Fill a wire nut with RTV silicon.
Use the wire nut to join the pigtail to the main conductor.
Wipe off the excess RTV silicon.
Be aware that some grades of RTV are conductive until they set and dry.

 

[TugboatEng]

Black is the standard color choice monochromatic installs. Tape doesn't necessarily stay on during conduit pulls so have a plan to identify conductors after the pull.

I'm not a fan of PVC conduit. It gets brittle after a few years in sunlight and breaks. Metallic conduit doesn't require a ground conductor (check local codes) and can that can offset the cost difference. Exterior should be RMC but it's easy to transition to EMT once protected inside.

I also feel that grounded metallic enclosures are safer than plastic. I supplied all metallic plugs for our 480 volt shore power due to the wet environment. This is contrary to most other similar installations in my industry.

Wire nuts? We're in the age of lever nuts now. Don't forget to give them a tug after you drop the lever.

If you're so terrified of corrosion due to wicking, tin plated conductors are available. I see them a lot in maritime. Most water problems occur when NEMA 4 enclosures are used where a NEMA 3R would suffice (NEMA 4 doesn't drain if there is leakage).

 

[waross]

Black is the standard color choice monochromatic installs

Stick to tugboats.
Colours are an issue with the codes that you are not familiar with.
Tape is not code acceptable for identifying grounds or neutrals.
There are two types of wire nuts; Solid (Conical spring) and Resilient (Variable volume spring). The resilient wire nuts are excellent and readily withstand thermal cycling. I was with one contractor who standardized on the slightly more expensive Variable Volume Spring wire nuts on the basis of the higher reliability.
The saving of one avoided call-back a year more than covered the slight extra cost of the variable volume spring type wire nuts..

 

[TugboatEng]

Sure, there are multiple types of wire nuts but the lever type is currently there best option. For less skilled installers it eliminates the challenge of selecting the correct wire nut size.

OP said they were going to buy a spool of white and I wanted to correct that. Every shoreside install I have seen uses black conductors with tape identifiers. I usually only work with 480V shoreside so there is no neutral.

I looked a little bit and now I'm not so sure color coding is even mandatory in the USA. NEC/NFPA 70 don't seem very firm on it though that may have changed recently? Regional rules vary.

On the boats I work with IEEE 45. We have no color code. Taping is not required. Grounds usually end up being red. DC positive usually ends up white. Colors only correlate to a number, most of the time.

 

[waross]

Every shoreside install I have seen uses black conductors with tape identifiers

Larger sizes of conductors, such as you will have seen when connecting shore power, are not bound by the "no colour tape" rule as are smaller wire sizes.
You have obviously never seen a code compliant, shoreside, lighting panel.
Your shipboard advice is generally sound.
For on shore installations?
Take it to FaceBook.
There are codes and practices that you have obviously never seen.

 

[mparenteau]

Grounded conductor, #6AWG and smaller: NEC 200.6
Ungrounded conductors: NEC 235.5
Grounding conductor: NEC 250.119

There are code requirements for insulation colors, esp. for grounded conductors and grounding conductors in terms of continuous, colored insulation.

Mike

 

[MiniMe4Eng]

If this helps you I am in Ontario Canada