HVAC Exam (Refined)questions and answers

Rate of Cooling: Want to cool 11,000 CFM of Air. V = 13.8. What is the rate of cooling? 11,000/13.8 = 797.1 lb/min Heat Transfer, Water: The flow through a hot water heat exchanger is 15 gpm, EWT is 160 and LWT is 140. What is Q? Q = (500)(15)(160-140) = 150,000 BTUH 01:06 01:31 Heat Transfer, Air: 2,000 CFM, EAT is 72, LAT is 55. What is Q? Q = (1.1)(2,000)(72-55) = 37,400 BTUH Infiltration: Building built in 1971, size is 100' x 250' with 12' ceiling heights. What is the infiltration rate for summer and winter? Summer = ((100x250x12) x 1(From Chart))/60 mins = 5,000 CFM Winter = ((100x250x12) x 1.5 (From Chart))/60 mins = 7,500 CFM Ventilation: New style beauty shop intended for 23 occupants. 23 ppl x 25 cfm/person (from chart) = 575 CFM R & U Value For Wall: Use tables 2.5 for film, 2-3A for components, 2-4 for air space. If R value is given per inch, multiply that by the component's thickness for your R. If the R is for thickness listed, use that number. Add all numbers for R. U value = 1/R Building Heat Loss: 1,400 sq ft wall, U value = 0.1, Indoor temp is 70, Outdoor temp is 0. Q = (0.1) x (1,400) x (70-0) = 9,800 BTUH Outdoor Air Heat Loss: Infiltration rate of 4,000 CFM, Ventilation rate of 6,000 CFM, Indoor temp = 70, Outdoor temp = 0. Q = (6,000)(1.1)(70-0) = 462,000 BTUH Calculating TETD for Walls: 4" face brick + 2" insulation + 8" common brick. Total SF = 20,000. 4PM, Dark Color. 1. Find Group from wall components using chart (K) 2. Find weight/sf from chart (130) 3. Find U Value from chart (0.10) 4. TETD is value from chart using time of day, group, and color. (22) 5. (0.10)(20,000)(22) = 44,000 BTUH Calculating TETD for Roofs: 1' Insulation+ 2" HW Concrete. 4pm, 0.04 U value, roof size = 30,000 sf, Dark Color. 1. Find TETD in table using roof components (81) 2. (0.04)(30,000)(81) = 97,200 BTUH What ASHRAE Standard is 55 2013? Thermal Environmental Conditions What ASHRAE Standard is 62.1? Ventilation for Accurate Indoor Air Quality What ASHRAE Standard is 90.1? Energy Standards for Buildings except low rise residential What ASHRAE Standard is 189.1? Standard for the design of high performance green buildings What are the 4 components of a refrigerator? 1. Compressor 2. Condenser 3. Evaporator 4. Expansion Valve What are the 4 factors of comfort? 1. Personal Parameters 2. Humidity 3. Air Speed 4. Temperature Slab Edge Problem: Given temp and R. Multiply Linear ft x R Slab Problem: Given ground water temp, R/SF. Multiply SF x R Value Baseboard Heater: Room needs 8,500 BTUH of heat. Standard density (250 Watts/ft). How many boards? 250 x 3.41 = 852.5 8,500 / 852.5 = 9.97' So you need 2 5' Units What does SEER stand for and what is the minimum rating? Sustainable Energy Efficiency Ratio 14 What is the minimum % efficiency for a new gas furnace? 80-90% How many CFM per ton? 400 CFM How many BTU per ton? 12,000 BTU What layer of the atmosphere does refrigerant affect? O-Zone