2020 NEC Optional Method Calculations
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- čas přidán 25. 08. 2024
- Bob teaches you how to do the option method for dwelling unit calculations for both single family and multifamily dwellings. All graphics courtesy of Mike Holt Enterprises. For more information on our test preparation courses for your Master or Journeyman Electrician's License classes visit our website at www.constructio...
Cut and Dried teaching.... love it!!! thank you!
Well, thanks a lot. In the multi-family calculation its suppose to be 65% of the heating, but the number it's different
The 65% percent rule is under 220.82 which is for SINGLE family dwellings. For multi-family you compare the larger of 100% of air conditioning and 100% of the heat according to 220.84(C)(5).
What does it mean the service conductor ampacity 100 or greater? Can we use optional method less than 100A service conductor ampacity?
220.82(A) indicates that this optional method can only be used for 100A or greater. Less than 100 would have to use the standard method.
@constructionseminars4197 thanks a lot. How we know the 100 ampacity for service conductor?
@@opecons I guess you would have to calculate using the standard method first to determine whether the optional method could be used. I have never considered that. That seems like a pain.
code states that dryers are at 5kw (220.54) 2020, I see you used 4kw, I'm just trying to see if it was a typo or is 4kw correct?
4kw is correct because we are using the optional method. One of the most common errors in calculating using the optional method is using rules from the standard method. The 5kw rule is used only when calculating the standard method.
oh man thanks! currently watching this video now, very helpful! @@constructionseminars4197
also, i have my exam coming up soon, how will i know if the optional method would be sufficient for an answer instead of the standard method? im going for SFD.@@constructionseminars4197
Thank you for the video. Clarified a lot of things for me. For the General Loads, the NEC says at least 2 circuits at 1500ea for appliances and 1 for Laundry, is there ever a situation where you use more than just 2 small appliance and 1 laundry?
2 small appliance circuits is the minimum. You are free to add any additional small appliance circuits as well for additional equipment/receptacles. If you add additional, just use 1500 for each.
thanks...btw,at the end on multifamily i came with 36100 VA not 34600VA,probably you added 1500 by accident.
It looks like my graphic was wrong. I just added myself and it is in fact 36100, but the process is still the same. Good catch!
Actually, since 36,100 is greater than 34,600, he forgot to add 1500.
Thanks for the info, is this calculation applicable for appartments in a building as they comes in the same category "Dwelling Units"
For multi-family, see this video czcams.com/video/2-9SWWHHJ1k/video.html
The example in the slideshow is an 1100W microwave but you did your math with a 1000W microwave. I know its only 100w difference but an error like that is extremely important for people who are doing this following along to the video. Be cautious of this mistake in the math, because i spent quite some time trying to figure out why i kept coming up 100W too high when my math was actually correct
Would you add the EV charger into this at 100% of the rated VA, and not add it into the appliances? If added in the appliances we’d effectively be reducing the rating of the EV by 40%.
Although not specifically spelled out in the optional method calculations, I believe that an electric vehicle charging station would meet the definition of an appliance, and would be included in that load.
Interestingly I had an inspection this morning and asked the inspector the same question. He said I should not treat it like an appliance and use its rated VA at 100%. In my load calc I added that to the VA after the 40%. He said that was what he would want to see moving forward.
I can PM my calc sheet or email and we can discuss further
@@LIG_MA24 Since the code does not specify what to do, I would go with what the inspector is asking. He who dies with the green tag wins!
What do you do for gas heater
The gas heater will have less volt-amps than the AC. So you would just use the AC.
88 Toyota Supra I’m studying with mine behind me in the garage
I think the calculation is wrong. Adding all the load for individual should be 36,100 instead of 34,600. If you multiply by 10 unit that would be a big error.
Yes, you are correct. 36,100 x 10 = 361,000. 361,000 x 43% = 155,230. 155,230/240 = 646.79 amperes. That would still require 700A service so the final answer on a test would be the same. Sorry about the mistake, looks like you are the first one to catch it. Good job. Hopefully the math concepts and steps still communicate well.