1 / 22

Residential and Commercial Electrical System Sizing Guide

Learn how to size residential and commercial electrical systems, compare differences, identify loads, and calculate panel sizing following NEC article 220 guidelines. Includes examples, data collection, and conductor sizing.

feeney
Download Presentation

Residential and Commercial Electrical System Sizing Guide

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Objectives • Finish residential electrical systems • Solve some example • Compare electrical systems for residential and commercial building

  2. Residential system sizing Typically 3 wire 1 phase system 120/240 V • Procedure defined by NEC article 220: • Identify characteristic electrical loads • Add lighting (3W/ft2) • Add two 20 Amps circuits for kitchen • Add one 20 Amps circuit for laundry • Electricity for HVAC equipment based on requirement for heating or cooling

  3. Homework 5 - problem 2 • Sizing the residential electrical system • Defined by NEC article 220-30 • Similar to the example we worked out • You need to collect the data for several characteristic consumers • Includes conductor sizing

  4. Summary of Power Sizing • Include enough capacity for heating and cooling • Work through kitchen and then other rooms • Include any items that are unusual • Take first 10 kVA and then 40% of remaining load

  5. Panel Sizing • Find panel power usage and neutral usage • Size panel conductors and associated conduit and switches

  6. Electric panel - 3 wire 1 phase 120/240

  7. Commercial buildings-Differences Defined by NEC and local electric code! For example: No NMC (non metallic sheeted cables) wiring allowed

  8. Other differences? • Three phase • Multiple panels • More attention to expansion possibilities • More voltage levels available • For example: 277/480 and 120/208

  9. Typical Building Electrical Services

  10. Building Needs: Lighting and Duplexes • Lighting • Typically use lighting power densities for building type • Sometimes actual lighting load • Requires neutral • Duplexes • NEC/local electrical code specifies number that are required for different applications • Requires a transformer • Requires neutral wire

  11. Building Needs: HVAC/Other/Auxiliary • HVAC from system sizing • Don’t forget fans, reheat coils, etc. • Building equipment • Transportation (elevators etc.) • Food service • Specialty uses • No neutral conductor on power panel typically • Auxiliary • Energy management, security and safety, data transfer, telecommunications

  12. Electrical Systems for Commercial • Example:

  13. Panel D • Duplexes (receptacles) • Phase total 60 kVA, 14kVA (neutral) • 30 poles

  14. Transformer capacity • 200∙208∙√3 = 72 kVA ~ 75 kVA • 200∙208 / 480 = 86 A • 100 A switch • Neutral 117*208/480 = 50 A • Three #1 and one #6 aluminum (could use #4) • 100A fuse - could use 90, but likely same price

  15. Building Needs: Lighting and Duplexes • Lighting • Typically use lighting power densities for building type • Sometimes actual lighting load • Requires neutral • Duplexes • NEC/local electrical code specifies number that are required for different applications • Requires a transformer • Requires neutral wire

  16. Panel D • Duplexes (receptacles) • Main lugs only (remote protection) • 3 Phase total 60 kVA, 14kVA (neutral) • 30 poles • 60 kVA / (208V √3 ) = 167A • Select: 200 A panel • Neutral 14 kVA /120V = 117A (or if not specified 167A) • Table 11-2 for (200A, aluminum 75C, 117 neutral, but we expand to 130A like phase) • Hot wires should be 250 MCM, Neutral #2/0 aluminum • 2½ inch conduit

  17. Transformer capacity • P = I V ∙√3 =200∙208∙√3 = 72 kVA ~ 75 kVA SD switch selection: • For transformer: I1E1=I2E2 • I2 = I1E1/E2 = 200∙208 / 480 = 86 A • Select switch rated for 100 A • For 100 A rated switch select: Three #1 (aluminum) and one #1 for neutral (aluminum) • 90A fuse for phases

  18. Lighting Panel • 100A - 20 pole spaces • Hot: 65kVA/(480V∙√3) = 78 A - #2 Aluminum • Neutral: 22 kVA /277V = 79 A - #2 Aluminum • 100 A three pole fused switch • 1½ inch conduit

  19. Power Panel • No neutral? – all three pole circuits • 33 poles required – chose 42 standard size and allows for expansion • 165kVA/(480 √3) = 198 A • Choose 225A switch (could use 200 A, but you count on expansion) • 3 300 MCM aluminum wires – 2 inch conduit (in the book table you don’t have MCM 300, however it exist)

  20. Wireway • 198A + 86 A + 78 A = 362A • 400A would allow for some expansion, some would probably go to 600A • 400A three-pole switch • Six 250 MCM (unlikely to find conductors big enough to just have 3) and one #2/0 aluminum • Neutral current: maximum = 117 A, you can expand neutral too (130 A)

  21. Summary Panel Sizing • Find panel power usage and neutral usage • Size panel conductors and associated conduit and switches

More Related