One-Family Standard Service Calculation - Deep Dive
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- Опубликовано: 8 сен 2024
- This video shows a detailed, step-by-step approach to an electrical service calculation. The use of a handy table format makes it easy to understand and implement into real-world applications, and likewise is very useful for study and exam prep.
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Electrical, NEC, Exam, Test, Load, 2020, Table, Feeder, Master, Journeyman, Apprentice, Electrician, Calc, Calculation, Service
Thank You so much for simplifying this demand factor.
You bet. It can certainly get confusing.
Great work. Very clear no stone left unturned. Appreciate that. Would love to also see transformer and motor calcs. Thanks for sharing
Thanks for the comments! I would really like to make some motor and transformer calc videos. Due to time contraints, I'm not sure how soon that will be, unfortunately. But I will certainly prioritize those if I get multiple requests for them.
Thanks again for the kind words!
I understand 220.60 to say, add 125% of whichever motor load is larger to your noncoincident load. say your condenser fan is 3.5 amps,
3.5 x 1.25 =4.375 added to your 220.60 calculation. 120 x 4.375= 525 va.
Due to its phrasing, it's a very tough section to get a clear meaning from. There are two main ways the second sentence of 220.60 can be taken: either as complementary, or as exceptional to the first sentence.
The wording specifies that you take 125% if it is NOT the largest of the noncoincident loads. And note that it doesn't say to do so IN LIEU OF the first sentence. It is written as an additional statement, not as an exception to the first statement. So this 125% of the smaller load would be in addition to the largest noncoincident load. In this case, that would be 12,000VA + 8125VA = 20,125VA. A monstrously huge value.
If this were the case, what is the point of discussing noncoincident loads if they are simply going to be added together? So, I don't believe that is their intent, but that is how they worded it.
However, let's say for a moment that they meant the second sentence to be an exception to the first. Then in this example, we would take ONLY the heat pump load at 125% (8125VA) and eliminate the larger furnace load (12,000VA) from the calc. I certainly don't think that is what they intended either. We'd be leaving the largest (by far) load of the whole service out of the calculation altogether.
Anyways, I hope I didn't just add more confusion to the mix! The code-making panel has some more work to do before the next NEC gets printed, IMO.
nice explanation... Seems like you have a good start to a relitavly new chanel - Liked and subscribed!
Thanks Dave, I really appreciate the support!
Thanks for the work you've put in. Is your table available to purchase or download?
Glad you found it helpful. Unfortunately, I'm still working on making the tables available for download. I'll hopefully have that done soon!
Good Morning Why is the AC/Heat pump the largest motor??? Im a bit confused...
In most residences, the AC/HP compressor motor will be the largest in the occupancy. So that is the assumption in these calcs. On a test, they will tell you which is the largest motor if it's part of the calc.
The Best video. What if I have heat pump for swimming pool heating. Is it appliances or Heating and cooling? Thanks!
Thanks! Glad you found it helpful.
It would have to go under Appliances, like any water heater.
220.51 is for Fixed Electric SPACE Heating only. Refer to 424.1 for the scope of FESH equipment. Remember, a heat pump or AC is placed in the heating column only because it is usually a noncoincident load with the heat. Without electric heat, an AC or HP would be calculated at 100%.
if you had a gas heater and a AC that is 5520W do you still hit the AC with 125% Largest Motor?
Yes, as long as you don't have any other larger motors elsewhere, of course.
In most cases for residential, the AC or heat pump will be the largest motor load of the building - even with an electric furnace (because the heat strips are the lion's share of the load, not the motor).
Thanks. What if you have an EV?
EV chargers would fall under appliances in 2020.
However, in 2023, a new section was added - 220.57. This changes two things:
1) It requires a minimum rating of 7200VA (or nameplate, if higher).
2) Also, it no longer allows the 75% demand factor to apply (4 or more appliances) in 220.53.