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| Subject - Service Calculation 2 | |
| David Hyatt |
This is a contiuation of previous post. Commercial Building. Line Voltage 120/208 (3)phase What size service would you install? Why? These are the motor loads: Pressure washer- name plate= 200 volts, 61 amps, 3phase, 20HP. Demucking pump- name plate= 200 volts, 22 amps, 3phase, 7.5HP. Reclaim system- name plate= 230volts, 19.2 amps, single phase, 1.5HP Compressor- name plate= 200volts, 32.2 amps, 3phase, 10HP The non motor loads are: 1 general purpose outlet. (2) 2 lamp florescent lights. (4) 250watt low bay fixtures. (1) 20 circuit for sump pump. (1) 15 amp cicuit gas heat. |
| Ryan_J | What is the sqaure footage of the building, and what type of building is it? |
| David Hyatt | It is a wash shed 50x30, with a small equipment room 20x20. Total 1,900sq. foot. |
| Ryan_J | I won't be able to answer you for a bit because I am leaving the office in 5 minutes, but your equipment is throwing me off a bit. Why is rated 200V? I think the NEMA standards are 208 or 230 |
| David Hyatt | The motors nameplate says 200/400 volts, I am doing my calculation at 208 volts, that is what we are running to them. |
| David Hyatt | Ryan, this is what I come up with: I will use actual lighting load since I know what that is. (4) 250 low bays 4 x 250w x 125% = 1,250va (2) florescent 2 x 64w x 125%= 160va gas heater 15amps =1800va largest motor 59.4amps x 208 x 1.732= 21,399va x 25%= 5,349va motors 59.4 x 208 x 1.732= 21,399va 30.8 x 208 x 1.732= 11,096va 24.2 x 208 x 1.732= 8,718va single phase 18.7 x 230 x = 4,301va total= 54,073va/208 x 1.732 =150.00amp connected load I am installing 200amp 3phase 120/208 volt service. Will this be adequate? |
| Ryan_J | That will do :) |
| wareagle | David The motors listed do not appear to be a continuous load. Do you know if they are? Not trying to reduce your service but I wanted to check. Bob |
| David Hyatt | The pressure washer could be used for 3 or more hours the others probably not. The architect wanted this to be a 120/240volt 3 phase 400 amp service. I really didn't want that so I did my own calculation with the owners approval. |
| David Hyatt | Ryan, did you See what the architect called for? Sounds like he gets paid on a percentage of what I charge. |
| Ryan_J | Yeah, it wouldn't surprise me. I did a plan review for an electrical engineer one time, and he had a 600 amp service for a new church. One of my review items was that he needed to adjust the ampacity of one of the feeder circuits because the nuetral was non-linear, and I wanted ampacity adjustment as per 310.15(B)(2)(a). His answer...come back with a 1000 amp service!!!! He probably didn't have to do anything at all, but I think just having a gross amount of capacity just makes some people sleep better at night, ya know? :D |
| veganfan | Do you know what % of future use architect was planning? Could he have been plannig for larger future use. |
| JimmyDee | quote: Yep, usually 10%. That sure answers a lot of questions as to why an architect does what they do. I installed a 400 amp service in a church years ago. Load check on a Sunday morning was less than 50 amps each leg. Over kill to say the least. Jim |