Upon a reread of the original post, you are correct. That 50A breaker isn't remotely guaranteed to trip even with a continuous 48A load. If it really is installed with 8 gauge wire, the installer should be retrained(assuming they ever got training in the first place).
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Breaker tripping
- Thread starter JoelCool
- Start date
Well, I don't see that as a training problem if he thought it was a 50A circuit (since that's what the breaker is). 8 gauge THHN wire in conduit at 75 degrees does meet exactly a 50A circuit rating. It's just the wall connector that's the problem if it's configured for a 60A circuit (48A continuous supply).
I didn’t follow this whole sub-thread
But… in theory what you saying is mostly true. 2nd wire doubles the area needed but 3rd does not take double but doesn’t exactly fill the gap either. Probably adds 65%. Good math problem
But in PRACTICE a 3rd wire does not stay perfectly nestled in a triangle. And the increases the diameter needed as much as the 2nd (worst case when they all twist around each other).
They do stay nicely packed in Romex.
Tesla declined warranty replacement when Son-in-Law returned the unit - charring around the terminals could only be due to poor installation. The HPWC was mounted on a post yards from their house so there was low risk. Electrician said it was working when they completed the installation, and the payment check had cleared.
Our daughter and son-in-law claimed the referral credit Elon Musk signature v2 HPWC on a shelf in my garage.
<Start TMI> I agreed because:
- They have three hostages (grandchildren). Forcing a young family to purchase an unbudgeted HPWC when there’s one available in the family isn’t good for anyone.
- They had purchased the original HPWC and excavated the power line trench as part of a car-share agreement my wife and I offered.
In 2017 I gave her a Model S 100D (Long Range) as a birthday gift since she didn’t want to buy gas anymore. She loved it except for the size (hard to park downtown) and lousy interior storage.
When the dual-motor Model 3 became available in mid-2018 she took a test drive and fell in love. We got her a Model 3 Stealth Performance (acceleration and track mode, no visible “bling” (spoiler, red brakes, lower suspension…).
I got the S, which was my favorite. Except I telecommuted most days, so it usually sat in our driveway, next to the Hyundai Sonota (so-NOT-a Tesla) that it replaced.
My wife and I saw that our daughter’s family had a minivan and an aging, increasingly expensive SAAB 9-3. Our daughter had a long commute several days a week, and they frequently ferried the grandchildren that would carry our DNA into the future.
A car-share would give them access to Tesla Model S reliability, safety and low energy cost. Daughter and son-in-law sold their SAAB and paid (in installments) the Sonata’s $10k KBB value.
Each family then put an “S” car into the share. We split insurance, maintenance and repairs. Our insurance agent set up a policy that covered our scenario. As mentioned, our daughter’s family paid for HPWC which was one of our non-negotiable conditions.
The car-share worked well. After a month or so, our daughter and her husband defined “share” as, “Model S is at our house. Grandpa is welcome to admire it through the dining room window during dinner at our house. He can borrow it and leave the Sonata here whenever we don’t have plans to use it.”
The share ended when my retirement approached. I explained that the first thing I planned to do after putting down my pencil ( keyboard) was to jump in the S (Free Unlimited Supercharging as long as we own it) and drive around the country visiting old friends.
They wouldn’t be stuck since the Sonata they bought to contribute to the car-share would be in their driveway full-time. Immediate response - “That’s unacceptable!” I helped them configure and order a 7-seat Model Y. I paid for FSD to continue safeguarding our DNA.
We eventually sold the Sonata for about $9,300 when used car prices were strong. We signed the check over to our daughter.
It’s all in the shape of two circle in another circle versus 3 circles in a circle. You have a lot of extra space, when you have two circles in a circle.I didn’t follow this whole sub-thread
But… in theory what you saying is mostly true. 2nd wire doubles the area needed but 3rd does not take double but doesn’t exactly fill the gap either. Probably adds 65%. Good math problem
But in PRACTICE a 3rd wire does not stay perfectly nestled in a triangle. And the increases the diameter needed as much as the 2nd (worst case when they all twist around each other).
They do stay nicely packed in Romex.
Probably the most important thing in your comment was this is “in theory.”
Just because you can use a smaller diameter raceway doesn’t mean you should. 1” EMT works well.
Mrbrock
Active Member
So if the two wires are deemed too large to be too tight to pull (2x 6ga thhn in 1/2 EMT), how does adding a third wire (1x 10ga thhn) make the two larger wires that are too tight to pull now not too tight to pull if they continue to take up the same space (plus the added space of the 3rd wire)?
And why shouldn't you do something if it meets code? If you shouldn't do it, it shouldn't meet code. That's why there is code.
It’s a safety code. You go bigger so you don’t have a hard time pulling the wires through.
Mrbrock
Active Member
So you’re saying the code that allows 2x 6ga a 1x 10ga in 1/2 EMT is wrong? Or are there different codes for practical use and safety that you have to follow that are conflicting with different standards? By your logic, everyone should run 0ga wiring in 4” conduit for every circuit because “it’s a safety code”.
NEC are the standards to ensure safety.
They are not the standards to ensure ease of installation.
NEC allowable fill may be safe, but may also be a pain to pull. A jam factor of 3 is not against code, but one might regret not upsizing the conduit.
Mrbrock
Active Member
Thank you for explaining in that matter. The other answer of “it’s safer” doesn’t fly. If an electrician told me he was upsizing everything above code for safety, I’d show him the door. If you can’t do it, that’s one thing, but if you want me to spend more money to make your life easier then you need to be honest about that and not hide behind safety. And you’ll be making less money because it’ll take less time. Pick your poison.
I also know every situation is different. 15ft straight line with my example, no need to upsize unless you possibly think you’ll need a neutral later. Putting in 1” Emt is just silly in that instance.
Upsized conduit would theoretically save more labor time than its incremental cost.
3/4": $0.96/ft
1": $1.76/ft
Couplings, $0.49 vs $1.02
50 foot run cost difference:
$.80 * 50 + $0.53*4 = $42.12
<15 minutes of labor equivalent
15 foot run:
15*$0.80 + $0.53 = $12.53, a rounding error on typical installation cost.
Mrbrock
Active Member
So you’re suggesting $200/hr labor cost? Otherwise you are paying a lot more in parts to save not much in labor cost. At $100/hr, your less than 15 minute savings is worth less than $25. And if $12.53 is a rounding error on a 15ft run, the electrician is wasting a whole bunch of time and therefore my money and won’t be getting the job. This is why people skip the electrician most of the time.
Eric33432
Member
Depending on the complexity of a conduit run, sometimes it is best practice to upsize the conduit for ease of installation but it does not make the installation any safer. I would not ask an electrician why he or she ran 2 #8 and 1 #10 in a 1/2" conduit since that meets code, but if he ran those wires in 1" I might ask him why he thought that necessary.
I use 3/4" conduit and run 2 or 3 #6 and 1 #10 for 6-50 and 14-50 receptacles and for hard wiring wall connectors or sometimes run #6 MC when conduit is not appropriate, and install 50 amp breaker for such 50 amp receptacles and 60 amp breaker for wall connectors assuming the load calculation allows for such ampacity.
Some DYIers might be more comfortable using larger conduit.
I use 3/4" conduit and run 2 or 3 #6 and 1 #10 for 6-50 and 14-50 receptacles and for hard wiring wall connectors or sometimes run #6 MC when conduit is not appropriate, and install 50 amp breaker for such 50 amp receptacles and 60 amp breaker for wall connectors assuming the load calculation allows for such ampacity.
Some DYIers might be more comfortable using larger conduit.
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