Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
What do you think of ChatGBT response?
Derating question
- Thread starter Alwayslearningelec
- Start date
- Location
- Illinois
- Occupation
- retired electrician
I see it as a very dangerous response as it says that the hot wires are USUALLY on different phases or legs. That suggest they can be on the same phase of leg which will overload the neutral.
It also completely ignores 3 phase multiwire branch circuits.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Not sure how you have opposite phases when it's only 1Ø.
Carultch
Senior Member
- Location
- Massachusetts
We've discussed this plenty, on this site. The voltage waveforms on the black and red wires, are mathematically equivalent in the ideal case, to two waveforms that are 180 degrees apart. Yes, I'm aware of the technicality, they are not separate phases, due to how they are produced, but I can understand why someone might call them "phases", despite the technicality.
Split phase is what you might think "2-phase" should be, since they appear to be two phases that are a half cycle apart. Just as a 3-phase wye system is 3 waveforms that are time-shifted by a third of a cycle each, you might expect 2-phase "epsilon" to be two phases that are time-shifted by a half cycle. "Epsilon" is my term, based on how the centertap winding diagram looks similar to the letter epsilon. I call its counterpart "iota" for a 2-wire single phase winding.
In reality, the two apparent out-of-phase waveforms, are produced by centertapping the neutral. At a given snapshot in time when waves are cresting, the black wire may be 170V to neutral (120V nominal), while the red wire is -170V to netutral. A half cycle later, and the signs reverse. The difference is a 340V amplitude (240V nominal), for the voltage across the black and red wires.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
That was my point, the AI that was quoted in this thread is incorrect. IMO for a single phase 120/240 volt system the word leg is more suitable and should be used in lieu of phase.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
I wonder if that was Lake Panasoffkee Elementary School? I have a feeling we may have talked to each other on the phone. I just checked my plans and the Engineer is from Clearwater! When I saw this post I immediately though of the same thing. If it is you, then for others, we were in an existing school with a dedicated HVAC panel, so it also had no neutral. We had to jump through hoops and get a neutral in from 300 feet away in one building. Luckily the conduit was sized large enough. If it is you, then I will just say, it was a pleasure. I am sure most of us here know how adversarial the relationship between and Engineer and an electrician can be. This was an excellent exchange.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
The ChatGPT text is a distillation of the various public discussions on the topic. That is probably why it said 'opposite phase/legs...' People have debated endlessly about what to call the two 'opposite' legs of a single phase center tapped supply. You have a single phase source coil, you have two 'hot' wires with _different_ 'phase angle', but that phase angle is a 180 degree displacement. Part of the issue is that the word 'phase' is used in two different ways.
In the world of 'high phase order electric motors' (motors that use > 3 phases for the stator winding), I've seen the term 'hemiphase' used to describe 2 conductors with a 180 degree phase difference. So a common 3 phase motor would actually have a 6 hemiphase stator. But I don't think this language use ever really caught on.
-Jonathan
In the world of 'high phase order electric motors' (motors that use > 3 phases for the stator winding), I've seen the term 'hemiphase' used to describe 2 conductors with a 180 degree phase difference. So a common 3 phase motor would actually have a 6 hemiphase stator. But I don't think this language use ever really caught on.
-Jonathan
Knightryder12
Senior Member
- Location
- Clearwater, FL - USA
- Occupation
- Sr. Electrical Designer/Project Manager
It was and you must have been talking to my Engineer. Glad it all worked out. First time we have ever had a mechanical piece of equipment like that require a neutral.