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ARE 346N Building Environmental Systems
Midterm Exam II November 29, 2007
Write your name on every page including this one. Closed book, closed notes. Formulae/Information: P = √3 × I × V (3) Area of a circle = πrr^2 P = I × V (1) Perimeter of a circle = 2πrr V = I × R 1 W = 3.413 BTU/hr E = Iws = F × LLF × CU/A 1 ton AC requires 1 kW CR = 2.5 × PAR × h 10 lux ≈ 1 fc NEC – nothing smaller than 12 AWG in commercial buildings
1 _____________ / 8
2 _____________ / 4
3 _____________ / 4
4 _____________ / 4
5 _____________ / 8
6 _____________ / 6
7 _____________ / 16
Total _____________ / 50
Write your name on every page as well as this one. If you use any additional
sheets, make sure that your work is easy to follow. Do not write on the backs
of any sheets of paper. If you use any of the assumed data (i.e. you can’t get
part of a question), make sure that you make it clear that you are doing so.
NOTE THAT ASSUMED DATA IS NOT NECESSARILY CORRECT.
SHOW ALL OF YOUR WORK AND CLEARLY REFERENCE WHAT
TABLES/FIGURES YOU ARE USING.
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1. You are designing a 277/480 3 panel with the following loads: 8 pts Phase 1 Phase 2 Phase 3 1 – pole loads 5 kW 2 kW 2 kW 2 – pole loads 2 kW 4 kW 4 kW 3 – pole loads ___ kW 10 kW 10 kW a) What is the value for the blank 3-pole load on Phase 1? Justify your answer? 1 pt If you can’t get a), assume 9 kW. b) What size panel would you recommend? 3 pt If you can’t get b), assume 200A. c) What size of copper feeders would you recommend? 2 pts If you can’t get c), assume #6. d) What size conduit would you recommend? 1 pt e) What, if anything, would you change about the distribution of loads? Why? 1 pt 2. A branch circuit on the panel above needs to supply an 8 kW 480V load: 4 pts a) How much power does this contribute to Phase 1 on the panel? 1 pt b) What size circuit breaker, conductor, and conduit do you recommend? 3 pts
Page 4 of 8 5 (continued). Briefly define each of the following terms: c)Lamp lifetime d)Conduit
7. For each of the following, pick the lamp with the higher value of the stated parameter. 6 pts total – ¾ pt each CFL = 13 W compact fluorescent, FLT = 32W fluorescent tube INC = 60 W incandescent, HAL = 60 W halogen SOX = low pressure sodium, HPS = high pressure sodium DAY = daylight LED = light emitting diode Parameter Lamp 1 Lamp 2 Heat Generation CFL SOX Efficacy INC HAL CRI DAY LED Lifetime CFL HPS Degradation with age SOX FLT Efficacy CFL LED Lifetime CFL HAL Lifetime HAL INC
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6. Consider the fixture below and assume that each fixture has 3 2900 lumen tubes. 16 pts Assume that the fixture(s) are suspended 3 feet from the ceiling and are being used to light a 60 ft long, 20 ft wide, and 20 ft high (indoor) Class II racquetball court at a University. Assume 50% reflective walls, a 25% reflective floor, and a 65% reflective ceiling JUSTIFY ALL OF YOUR ANSWERS. Assume answers (and make it clear if you are doing so) if you need an answer to a previous part and can not get it. a) What level of horizontal illumination do you recommend for this space? 1 pt b) Is vertical or horizontal illumination more important? 1 pt c) Is the floor an appropriate work surface? Explain. 1 pt d) What is the ceiling cavity effective reflectance? 3 pts e) If the work surface is on the floor, what is the floor cavity effective reflectance? 1 pt f) What is the CU? 3 pts g) Assume an LLF of 1.1, how many fixtures would you need? 2 pts h) Is this fixture a good choice for this use? Be specific about quality and other issues in your answer. 4 pts
Page 8 of 8 TABLE 12. Panels and Switchboards _______________________________________________________________________________________________________________________________________________________ Capacity in amperes for mains and mugs (MLO), and number of spaces or poles. _Single _____________________________________________________________________________________________________________________________________________- Phase 120/ 208 or 120/ 240 ___________ 40 or 70 2 or 4 100 8 - 12 - 16 - 20 - 24 125 2 - 4 - 6 - 8 - 12 - 16 - 20 - 24 150 12 - 16 - 20 - 24 - 30 200 4 - 8 - 12 - 16 - 20 - 24 - 30 - 40 - 42 225 24 - 30 - 42 400 24 - 30 - 42 600 24 - 30 - 42 _Three- Phase 120/ 240 or 120/ 208 ________________________________________________________________________________________________________________________________________________________ 60 3 100 12 - 18 - 24 - 30 125 12 - 20 - 30 150 18 - 24 - 30 - 40 - 42 200 12 - 18 - 24 - 30 - 40 - 42 225 30 - 40 - 42 400 24 - 30 - 42 600 24 - 30 - 42 Three _______________________________________________________________________________________________________________________________________________________- Phase 277/ 480 125 12 - 18 - 30 225 30 - 42 400 30 - 42 600 42 Switchboar ___________________________________________________________________________________________________________________________________________ d Amperes ___________ 480 volts 400 600 800 600 volts 1,000 1,200 1,600 2, 2, This is a partial listing of manufactured panels and switchboards. Verify availability and check capacity when multi- pole breakers are installed. Compact tandem breakers are available. They pack two single- pole breakers in the space of a standard single- pole breaker. Panels are manufactured 14” or 20” wide, depths range from 3” to 6”, and heights vary with capacity up to 60”.
