Egee test 3 woohoo
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Which of the following indicates the heating requirement at a particular location?
answer
Heating Degree Days
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Most of the energy used at home is used for ____
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Heating
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What is the process in which heat is transferred through electromagnetic radiation?
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Radiation
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How many degree days are accumulated in a seven day period when the average outside temperature is 30 F
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245
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Natural materials like stone and bricks are not good insulation materials.
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TRUE
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When you insulate the attic of a home the R-value of insulation increases at the same rate as its thickness.
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TRUE
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A house in State College, PA (HDD=6000) has 339 ft2 of windows with R value = 2.5, 1843 ft2 of walls with R value = 18, and 1241 ft2 of roof with an R-value = 28. What is the total heat loss from the house for the season (in BTUs)?
answer
40652685.71 BTUs Heat lost through windows = 339 x 6000 x 24 / 2.5 = 19526400 BTUs Heat lost through walls = 1843 x 6000 x 24 / 18 = 14744000 BTUs Heat lost through roof = 1241 x 6000 x 24 / 28 = 6382285.71 BTUs Total heat loss from the house = 19526400 + 14744000 + 6382285.71 = 40652685.71 BTUs
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A wall consists of 0.5\" wood siding (R = 0.81), 0.75\" plywood (R = 0.94), 3.6\" of fiberglass (R = 3.7 per inch) and 0.5\" plasterboard (R = 0.45). What is the composite R-value of the wall?
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15.52
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Heat is lost through walls, windows and roof of a house. What is the primary mechanism of such heat loss?
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Conduction
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In State College, PA the average outside temperature during the month of January was 39 F. Calculate the HDD for the month of January.
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HDD = (65-39) x 31 = 806 degree-days
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A wall consists of 0.5\" wood siding (R = 0.81), 0.75\" plywood (R = 0.94), 1.6\" of fiberglass (R = 3.7 per inch) and 0.5\" plasterboard (R = 0.45). What is the composite R-value of the wall?
answer
8.12 Composite R-value = 0.81 + 0.94 + (1.6 x 3.7) + 0.45 = 8.12
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Dave has a home in Pittsburgh, PA (HDD = 6,000) with a roof area of 1821 ft2. He is considering upgrading the insulation from R-16 to R-28. The estimate for this job from the contractor is $810. Dave's home is heated with natural gas. Last year, the average price he paid for natural gas was $14.5/MCF. Assuming an AFUE of 80.9%, how long will it take Dave to recover his investment (in years)?
answer
6.4 Years Cost of insulation = 810 / 1821 = 0.4448 $/sq.ft Cost of energy = 14.5 / 1,000,000 = 0.0000145 $/BTU Time to recover investment = (0.4448 x 16 x 28 x 0.809) / (0.0000145 x (28 - 16) x 6000 x 24) = 6.43 yrs
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The heat loss through a window (R-1) is 10 MMBTU/year. Calculate the payback period (in years) if Argon is filled in the window to increase the effective R-value of the window to 7. Assume heating price to be $10/MMBTU and the cost for filling Argon is $20.
answer
0.23 years Heat lost through new window per year = (10 x 1) / 7 = 1.42 MMBTUs/yr Reduction in heat lost per year = 10 - 1.42 = 8.58 MMBTUs/yr Savings in energy cost per year = 8.58 x 10 = $85.8 Payback period = 20 / 85.8 = 0.23 yrs
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The time it takes to recover the additional cost through savings is called _____.
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Pay Back Period Payback period is the amount of time it takes to recover the additional cost through savings
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You are warmed by the sun. This is an example of heat transfer by _____.|
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Radiation Radiation is the only mode of heat transfer which does not require a medium. Heat from the sun reaches the earth through space by radiation.
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HDD is used to estimate the amount of energy required for residential space heating during heating season.
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TRUE
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After a house is built, the easiest place to insulate a house is/are _____.
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Attic
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In State College, PA the average outside temperature during the month of January was 51 oF. Calculate the HDD for the month of January.
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434 HDD HDD = (65-51) x 31 = 434 degree-days
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What is the most common fuel for home heating in the US?
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Natural Gas
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When using a fire place, most of the heated air is lost through the chimney.
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TRUE
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In State College, PA the average outside temperature during the month of January was 28 F. Calculate the HDD for the month of January.
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HDD = (65-28) x 31 = 1147 degree-days
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A room has a wall with an R value of 18 F sq.ft. hr/BTU. The room is 18 feet long and 9 feet wide with walls that are 9 ft high. On a particular day the average outside temperature is 29 degrees F. How much heat is transferred through the walls on that day (in BTUs)?
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23328 BTUs Total area of walls = 2 ((18 x 9) + (9 x 9)) = 486 sq.ft HDD = 65-29 = 36 oF Heat transferred = 486 x 36 x 24 / 18 = 23328 BTUs
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A house in State College, PA (HDD=6000) has 333 ft2 of windows with R value = 2.5, 1840 ft2 of walls with R value = 18, and 1106 ft2 of roof with an R-value = 28. What is the total heat loss from the house for the season (in BTUs)?
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39588800 BTUs Heat lost through windows = 333 x 6000 x 24 / 2.5 = 19180800 BTUs Heat lost through walls = 1840 x 6000 x 24 / 18 = 14720000 BTUs Heat lost through roof = 1106 x 6000 x 24 / 28 = 5688000 BTUs Total heat loss from the house = 19180800 + 14720000 + 5688000 = 39588800 BTUs
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A higher HDD indicates a _____.
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All the above
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Heat in a room from an air register moves from warmer areas to cooler areas of the room due to _____.
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Convection
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A room has a wall with an R value of 16 F sq.ft. hr/BTU. The room is 16 feet long and 8 feet wide, with walls that are 9 ft high. On a particular day the average outside temperature is 34 degrees F. How much heat is transferred through the walls on that day (in BTUs)?
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20088 BTUs Total area of walls = 2 ((16 x 9) + (8 x 9)) = 432 sq.ft HDD = 65-34 = 31 oF Heat transferred = 432 x 31 x 24 / 16 = 20088 BTUs
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A wall consists of 0.5\" wood siding (R = 0.81), 0.75\" plywood (R = 0.94), 2.4\" of fiberglass (R = 3.7 per inch) and 0.5\" plasterboard (R = 0.45). What is the composite R-value of the wall?
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11.08 Composite R-value = 0.81 + 0.94 + (2.4 x 3.7) + 0.45 = 11.08
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Thermal-lined draperies and outdoor awnings can significantly reduce the energy required for air conditioning.
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TRUE
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Katy is planning on adding additional insulation to her roof, which costs $2491. It is estimated that she can save $426/year on energy costs from this modification. What is the pay back period in years?
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5.8 Years Pay back period = 2491/426 = 5.84 yrs
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A room has a wall with an R value of 13 F sq.ft. hr/BTU. The room is 13 feet long and 12 feet wide with walls that are 8 ft high. On a particular day the average outside temperature is 25 degrees F. How much heat is transferred through the walls on that day (in BTUs)?
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29538.5 BTUs Total area of walls = 2 ((13 x 8) + (12 x 8)) = 400 sq.ft HDD = 65-25 = 40 oF Heat transferred = 400 x 40 x 24 / 13 = 29538.46 BTUs
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Because of which two processes do you feel the heat when you are standing next to a wood stove?
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Radiation and convection
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To calculate the heating degree days for a particular day, the day's outside temperature is calculated by _____.
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By adding the high and low temperatures and then dividing by two.
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Home heating is the single highest energy expense for a household.
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TRUE
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In State College, PA the average outside temperature during the month of January was 20 F. Calculate the HDD for the month of January.
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1395 HDD HDD = (65-20) x 31 = 1395 degree-days
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165 CCF of natural gas is equivalent to how many kWh of Electricity?
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4835.87 KWH We know that, 1 CCF = 100,000 BTU & 1 KWH = 3412 BTU. 165 CCF = 165 CCF x 100,000 BTU / 1 CCF x 1 KWH / 3412 BTU = 4835.873 KWH
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The number of degrees the mean temperature falls below 65 degrees F for a given day is indicated by _____ .
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HDD
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135 CCF of natural gas is equivalent to how many kWh of Electricity?
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3956.62 KWH We know that, 1 CCF = 100,000 BTU & 1 KWH = 3412 BTU ' 135 CCF = 135 CCF x 100,000 BTU / 1 CCF x 1 KWH / 3412 BTU = 3956.623 KWH
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The R-value of thermal insulation depends on _____.
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all the above
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A house in State College, PA (HDD=6000) has 323 ft2 of windows with R value = 2.5, 1970 ft2 of walls with R value = 18, and 1266 ft2 of roof with an R-value = 28. What is the total heat loss from the house for the season (in BTUs)?
answer
40875657.14 BTUs Heat lost through windows = 323 x 6000 x 24 / 2.5 = 18604800 BTUs Heat lost through walls = 1970 x 6000 x 24 / 18 = 15760000 BTUs Heat lost through roof = 1266 x 6000 x 24 / 28 = 6510857.14 BTUs Total heat loss from the house = 18604800 + 15760000 + 6510857.14 = 40875657.14 BTUs
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A house in State College, PA (HDD=6000) has 347 ft2 of windows with R value = 2.5, 1926 ft2 of walls with R value = 18, and 1212 ft2 of roof with an R-value = 28. What is the total heat loss from the house for the season (in BTUs)?
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41628342.86 BTUs Heat lost through windows = 347 x 6000 x 24 / 2.5 = 19987200 BTUs Heat lost through walls = 1926 x 6000 x 24 / 18 = 15408000 BTUs Heat lost through roof = 1212 x 6000 x 24 / 28 = 6333142 BTUs Total heat loss from the house = 19987200 + 15408000 + 6233142.85 = 41628342.85 BTUs
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A thermos bottle has a shiny interior. What type of heat transfer does this prevent?
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Radiation
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The R-value of a composite wall is calculated by _____.
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adding the R-values of all layers
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Most of the synthetic insulation products are very effective insulation materials.
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TRUE
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What is the average cost of electricity in the US?
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$80/MWh
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What is the mechanism by which heat is transferred without the help of any medium (molecules or atoms)?
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Radiation
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The number of degrees the mean outside temperature falls below 65 F for a given day is given by _____.
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HDD
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A process by which energy is transferred as the vibrations of one molecule are passed on to the next, but there is no movement of energetic atoms or molecules themselves is called _____.
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Conduction
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The heat loss through a window (R-2) is 10 MMBTU/year. Calculate the payback period (in years) if Argon is filled in the window to increase the effective R-value of the window to 7. Assume heating price to be $10/MMBTU and the cost for filling Argon is $20.
answer
0.28 years Heat lost through new window per year = (10 x 2) / 7 = 2.84 MMBTUs/yr Reduction in heat lost per year = 10 - 2.84 = 7.16 MMBTUs/yr Savings in energy cost per year = 7.16 x 10 = $71.6 Payback period = 20 / 71.6 = 0.28 yrs
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Warm water rises in a lake and cold water descends. What is this due to?
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Convection
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Dave has a home in Pittsburgh, PA (HDD = 6,000) with a roof area of 1017 ft2. He is considering upgrading the insulation from R-16 to R-28. The estimate for this job from the contractor is $616. Dave's home is heated with natural gas. Last year, the average price he paid for natural gas was $15.6/MCF. Assuming an AFUE of 88.1%, how long will it take Dave to recover his investment (in years)?
answer
8.9 Years Cost of insulation = 616 / 1017 = 0.6057 $/sq.ft Cost of energy = 15.6 / 1,000,000 = 0.0000156 $/BTU Time to recover investment = (0.6057 x 16 x 28 x 0.881) / (0.0000156 x (28 - 16) x 6000 x 24) = 8.86 yrs
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A room has a wall with an R value of 18 F sq.ft. hr/BTU. The room is 15 feet long and 11 feet wide with walls that are 9 ft high. On a particular day the average outside temperature is 40 degrees F. How much heat is transferred through the walls on that day (in BTUs)?
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15600 Total area of walls = 2 ((15 x 9) + (11 x 9)) = 468 sq.ft HDD = 65-40 = 25 oF Heat transferred = 468 x 25 x 24 / 18 = 15600 BTUs
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What is the process by which energy is passed as the vibrations of one molecule are passed to the next, but there is no movement of energetic atoms or molecules?
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Conduction
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What is the name of the process by which energy is transferred by the bulk motion of the fluids?
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Convection
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On cloudless nights, heat escapes from our planet and goes into space by _____.
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Radiation
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Katy is planning on adding additional insulation to her roof, which costs $2882. It is estimated that she can save $397/year on energy costs from this modification. What is the pay back period (in years)?
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7.3 Pay back period = 2882/397 = 7.25 yrs
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A room has a wall with an R value of 18 F sq.ft. hr/BTU. The room is 15 feet long and 11 feet wide with walls that are 9 ft high. On a particular day the average outside temperature is 40 degrees F. How much heat is transferred through the walls on that day (in BTUs)? 15600 BTUs
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15600 BTUs Total area of walls = 2 ((15 x 9) + (11 x 9)) = 468 sq.ft ' HDD = 65-40 = 25 oF ' Heat transferred = 468 x 25 x 24 / 18 = 15600 BTUs
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Most of the synthetic insulation products are poor insulation materials
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FALSE
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To calculate the heating degree days for a particular day, the day's average outside temperature is calculated by _____.
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adding the high and low temperatures and then dividing by two.
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Compared to a house built in the 1960's, a house built today has ______.
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A greater R-value
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Katy is planning on adding additional insulation to her roof, which costs $2929. It is estimated that she can save $364/year on energy costs from this modification. What is the pay back period in years?
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8 Years Pay back period = 2929/364 = 8.04 yrs
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Dave has a home in Pittsburgh, PA (HDD = 6,000) with a roof area of 1004 ft2. He is considering upgrading the insulation from R-16 to R-28. The estimate for this job from the contractor is $757. Dave's home is heated with natural gas. Last year, the average price he paid for natural gas was $10.3/MCF. Assuming an AFUE of 87.5%, how long will it take Dave to recover his investment (in years)?
answer
6.6 Cost of insulation = 757 / 1004 = 0.7539 $/sq.ft Cost of energy = 10.3 / 1,000,000 = 0.0000103 $/BTU Time to recover investment = (0.7539 x 16 x 28 x 0.875) / (0.0000103 x (28 - 16) x 6000 x 24) = 16.6 yrs
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106 CCF of natural gas is equivalent to how many kWh of Electricity? 3106.68 KWH
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We know that, 1 CCF = 100,000 BTU & 1 KWH = 3412 BTU ' 106 CCF = 106 CCF x 100,000 BTU / 1 CCF x 1 KWH / 3412 BTU = 3106.68 KWH
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The heat loss through a window (R-3) is 10 MMBTU/year. Calculate the payback period (in years) if Argon is filled in the window to increase the effective R-value of the window to 8. Assume heating price to be $10/MMBTU and the cost for filling Argon is $20.
answer
0.32 years Heat lost through new window per year = (10 x 3) / 8 = 3.75 MMBTUs/yr Reduction in heat lost per year = 10 - 3.75 = 6.25 MMBTUs/yr Savings in energy cost per year = 6.25 x 10 = $62.5 Payback period = 20 / 62.5 = 0.32 yrs
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Dave has a home in Pittsburgh, PA (HDD = 6,000) with a roof area of 1182 ft2. He is considering upgrading the insulation from R-16 to R-28. The estimate for this job from the contractor is $638. Dave's home is heated with natural gas. Last year, the average price he paid for natural gas was $12.9/MCF. Assuming an AFUE of 94.6%, how long will it take Dave to recover his investment (in years)?
answer
10.3 Years Cost of insulation = 638 / 1182 = 0.5397 $/sq.ft Cost of energy = 12.9 / 1,000,000 = 0.0000129 $/BTU Time to recover investment = (0.5397 x 16 x 28 x 0.946) / (0.0000129 x (28 - 16) x 6000 x 24) = 10.26 yrs
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What is the typical cost of natural gas per million BTUs?
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5
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When you place a spoon into a cup of cocoa it gets hot over time. What is this due to?
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Conduction
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140 CCF of natural gas is equivalent to how many kWh of Electricity?
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4103.17 KWH We know that, 1 CCF = 100,000 BTU & 1 KWH = 3412 BTU ' 140 CCF = 140 CCF x 100,000 BTU / 1 CCF x 1 KWH / 3412 BTU = 4103.165 KWH
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Of the following sources, where does the most heat loss occur for a typical home?
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Cracks in walls, windows and doors
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A wall consists of 0.5\" wood siding (R = 0.81), 0.75\" plywood (R = 0.94), 1.2\" of fiberglass (R = 3.7 per inch) and 0.5\" plasterboard (R = 0.45). What is the composite R-value of the wall?
answer
6.64 Composite R-value = 0.81 + 0.94 + (1.2 x 3.7) + 0.45 = 6.64
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The R-value of a composite wall is calculated by _____.
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adding the R-values of all layers
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In State College, PA the average outside temperature during the month of January was 42 F. Calculate the HDD for the month of January.
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713 HDD HDD = (65-42) x 31 = 713 degree-days
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What does the R-value of thermal insulation depend on?
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all the above
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Which mechanism of heat transfer does not need any medium (molecules or atoms)?
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Radiation
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117 CCF of natural gas is equivalent to how many kWh of Electricity?
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3429.07 We know that, 1 CCF = 100,000 BTU & 1 KWH = 3412 BTU 117 CCF = 117 CCF x 100,000 BTU / 1 CCF x 1 KWH / 3412 BTU = 3429.073 KWH
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Which one of the following provides the most insulation?
answer
6 inches of Cellulose
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he heat loss through a window (R-2) is 10 MMBTU/year. Calculate the payback period (in years) if Argon is filled in the window to increase the effective R-value of the window to 10. Assume heating price to be $10/MMBTU and the cost for filling Argon is $20.
answer
0.25 years Heat lost through new window per year = (10 x 2) / 10 = 2 MMBTUs/yr Reduction in heat lost per year = 10 - 2 = 8 MMBTUs/yr Savings in energy cost per year = 8 x 10 = $80 Payback period = 20 / 80 = 0.25 yrs
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What is the process by which energy is transferred by the bulk motion of the fluids?
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Convection
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On cloudless nights, heat escapes from our planet and goes into space. What is this due to?
answer
Radiation
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Natural gas is sold in the US at $1.50 per CCF. What is the cost of heating per MMBTU? Recall that 1 MCF = 1,000 Cu. Ft and has 1,000,000 BTU; 1 CCF = 100 Cu. Ft and has 100,000 BTU.
answer
$ 15.00/MMBTU ($1.50/CCF) x (1 CCF/100 cu.ft) x (100 cu.ft/100,000 BTU) x (1,000,000 BTU/ 1 MMBTU) = $15.00/MMBTU
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The higher the R-value, the greater the insulating effectiveness.
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TRUE
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Most of the synthetic insulation products are poor insulation materials.
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False
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A wall consists of 0.5\" wood siding (R = 0.81), 0.75\" plywood (R = 0.94), 3.1\" of fiberglass (R = 3.7 per inch) and 0.5\" plasterboard (R = 0.45). What is the composite R-value of the wall?
answer
Composite R-value = 0.81 + 0.94 + (3.1 x 3.7) + 0.45 = 13.67
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Warm water rises in a lake and cold water descends. What is the name given to this process?
answer
Convection is a process by which energy is transferred by the bulk motion of the fluids (gases or liquids).
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Katy is planning on adding additional insulation to her roof, which costs $2651. It is estimated that she can save $330/year on energy costs from this modification. What is the pay back period in years?
answer
8 Years Pay back period = 2651/330 = 8.03 yrs
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Mr. and Mrs. Martin's home is heated by a natural gas furnace and has an Annual Heat Loss of 79,081,683.91 BTUS. Natural gas in their area costs $1.269/CCF and has a Heating Value of 100,000 BTUs/CCF. The Martins recently purchased a furnace for their home that will result in an Annual Heating Cost of $1080. What is the efficiency of the Martin's new furnace?
answer
0.929 Amount of Natural gas that was burnt in new furnace = 1080/1.269 = 851.0638298 CCF = 851.0638298 x 100,000 BTU = 85,106,382.98 BTU ' Efficiency = 79,081,683.91 / 85,106,382.98 x 100 = 92.92%
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A spoon that is placed in a cup of hot coffee gets hot over time due to _____.
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Conduction
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The circulation of air due to temperature differences in a room is called a _____.
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convective loop
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Most of the synthetic insulation products are very effective insulation materials.
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TRUE
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Oil is sold in a particular region at $1.10/gal and natural gas at $11.47 per MCF. Given that the oil has a heating value of 140,000 Btus/gal and natural gas of 1 MMBtu/MCF, which fuel is cheaper to use?
answer
Oil Oil: (1.10/gal) / (140,000 BTU/gal) = (1.10 / 140,000) BTU (1.10 / 140,000) BTU x (1 MMBTU / 1,000,000 BTU) = $7.86/MMBTU Natural Gas: ($11.47/MCF) x (1 MMBTU/1 MCF) = $11.47/MMBTU
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You feel the heat of a wood stove when you stand next to it. What is this due to?
answer
Radiation and convection
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Heat in the room moves with the warm currents from warmer areas to cooler areas due to _____.
answer
Convection
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Brownies bake in a glass pan using these 2 methods.
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Radiation and conduction
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HDD is used to estimate the amount of energy required for residential space heating during a cool season.
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TRUE
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There is no reason to ventilate the attic in the summer if it is well insulated.
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FALSE
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When a heat pump is used to heat a house in winter, how is the Coefficient of Performance affected as the outside temperature drops?
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it decreases
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All of the following are examples of ways to improve energy efficiency of heating systems, except _______.
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Opening the front door in winter to filter and clean warm air.
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Which of the following is not true about a geothermal heat pump?
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Its cost is a hindrance for their development
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Radiant floor systems heat _____.
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the entire floor
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A heat mover speeds up a natural heating process.
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FALSE
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In a baseboard radiator, _________increase(s) the surface area, which in turn leads to more efficient heat transfer.
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Fins
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An active system emits more SO2 directly into the environment than a passive system.
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FALSE
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A freezer maintains a temperature of 30ºF while the outside temperature is 75ºF. What is the COP of the freezer cooling system?
answer
11.8 COP = Thot/(Thot-Tcold) Tcold = 30 F = (30-32)x5/9 C = -1.11 C = -1.11 + 273 K = 271.89 K Thot = 75 F = (75-32)x5/9 C = 23.89 C = 23.89 + 273 K = 296.89 K COP = 296.89/(296.89-271.89) = 11.87
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Insolation is a combination of the following words _____.
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Incident solar radiation
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Which of the following items is used in a passive solar heating system?
answer
Deciduous Trees
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Which one of the following devices can be used to both heat and cool a house?
answer
A Heat Pump
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When using a fire place, most of the heated air is lost through the chimney.
answer
TRUE
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Which one of the following devices may heat as well as cool a house?
answer
A Heat Pump
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One of the heating systems we talked about in this course comprises of a system of ducts. What is the process by which heat is transferred in this system?
answer
Convection
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The temperature inside a home remains at 70°F. If on Tuesday the temperature outside is 55°F, but then on Wednesday the temperature outside is 35°F, what is the percent change in COP? (Round your answer to the nearest whole number)
answer
57% decrease 57% decrease. By plugging the numbers into the COP equation, it is found that an outside temperature of 55°F produces a COP of 35.3 and an outside temperature of 35°F produces a COP of 15.13. Then finding the percent change from the first to the second results in -59%.
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Electrical resistance heating systems approach an efficiency of 97%. This makes electrical baseboard heating more efficient than a heat pump.
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FALSE
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A house that effectively uses passive solar heating and cooling will_____.
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Face south and have deciduous trees growing on the south side to block heat in the summer and allow sunlight in the winter.
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Bleeding air from the pipes of a hydronic radiant baseboard heating system will _____.
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Increase efficiency
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High temperature, high pressure refrigerant comes out of the compressor and _____.
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condenses, giving off heat to the inside
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The collector's efficiency increases as ______.
answer
useful energy delivered increases (insolation remains constant) Collector's Efficiency = Useful energy deliverd/insolation on collector*100, and therefore if the useful energy delivered increases, the collector's efficiency will increase.
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What is the process by which forced-air furnace systems distribute heat?
answer
Convection
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Which one of the following items is used in a passive solar heating system?
answer
South facing windows South facing windows are used in a passive solar heating system
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A heat pump (heating) with a COP of 3.0 maintains an indoor temperature of 67 degrees F. What is the outside temperature (in F)?
answer
-108 F 67 oF = (67 - 32) 5 / 9 oC = 19.44oC = 19.44 + 273 K= 292.44 K ' 3 = 292.44 / (292.44 - tcold) ' tcold = 292.44 - 292.44 / 3 = 194.96 K = 194.96 - 273 oC = -78.04 oC = (-78.04 x 9 / 5) + 32 oF = -108.48 oF
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A heat pump with a COP of 5 maintains an indoor temperature of 65ºF. What is the temperature outside?
answer
COP = Thot/(Thot-Tcold) Thot = 65 F = (65-32)x5/9 C = 18.33 C = 18.33 + 273 K = 291.33 K 5 = 291.33/(291.33-Tcold) Tcold = 233 K = 233 - 273 C = -40 C = (-40x9/5)+32 F = -40 F
question
Compared to a house built in the 1960's, a house built today has _____.
answer
A greater R-value
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What is the physical meaning of coefficient of performance?
answer
It is the amount of heat moved between the reservoirs for every unit of work done
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The word insolation is a combination of which of the following words:
answer
Incident solar radiation
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The home heating and cooling system is the major residential user of energy
answer
TRUE
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Which one of the following is not an advantage of forced air heating systems?
answer
They usually have a very high efficiency (80-90%)
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Which one of the following is true about a geothermal heat pump?
answer
It saves energy and the environment
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Due to convection, a house with an electric radiant system and floors with a high thermal mass, can reduce heating costs if the electric company offers \"time-of-use\" rates.
answer
FALSE
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What is the most commonly used fuel for residential heating?
answer
Gas Natural Gas, 55% of households use natural gas.
question
A solar collector's efficiency increases as ______
answer
useful energy delivered increases (insolation remains constant) Useful energy delivered increases. Based on the equation: Collector's Efficiency = Useful energy delivered/insolation on collector*100, and there fore if the useful energy delivered increases, the collector's efficiency will increase
question
Solar and GHP heating systems have absolutely no impact on the environment.
answer
FALSE
question
Flat plate collectors are usually placed on the roof or on the ground where there is sunlight. Such collectors are classified as _______.
answer
Active Systems
question
A heat pump (heating) with a COP of 2.2 maintains an indoor temperature of 67 degrees F. What is the outside temperature (in oF)?
answer
-172 F 67 oF = (67 - 32) 5 / 9 oC = 19.44oC = 19.44 + 273 K= 292.44 K ' 2.2 = 292.44 / (292.44 - tcold) ' tcold = 292.44 - 292.44 / 2.2 = 159.51 K = 159.51 - 273 oC = -113.49 oC = (-113.49 x 9 / 5) + 32 oF = -172.29 oF
question
If a heat pump is used to heat a house in the winter, how will the Coefficient of Performance be affected if the inside set temperature is changed from 70 F to 65 F?
answer
it increases
question
In home heating, if the outside temperature increases, holding the inside temperature constant, the Coefficient of Performance of a heat pump decreases.
answer
FALSE
question
In heating mode when the refrigerant liquid moves past the expansion valve it_____.
answer
evaporates, absorbing heat from the outside
question
On a summer afternoon you should keep the draperies closed on all west-facing windows to block out the hot sun
answer
TRUE
question
When looking at a graph of BTUs/h and outdoor temperature, the amount of supplemental heat (in BTUs) can be determined by_____.
answer
subtracting home heating requirement BTU point for a specific temperature by the heat pump output BTU point for the same temperature, to the left of the balance point
question
Which of the following sources of energy is the most efficient for heating systems?
answer
Electricity
question
The coefficient of performance for a single heat pump in heating mode is greatest at which temperature?
answer
50 F
question
If a heat pump is used to heat a house in the winter, how will the Coefficient of Performance be affected as the outside temperature drops?
answer
it decreases COP = Thot/(Thot-Tcold) When Tcold is reduced, COP decreases
question
Which term is used to describe the efficiency of a Central Air Conditioner?
answer
SEER
question
Opening the drapes of windows on which side of a house helps in heating?
answer
South
question
What is nearly half of the energy used at home used for?
answer
Space heating and cooling
question
A heat mover
answer
uses work to move heat from a low temperature reservoir to a high temperature reservoir
question
A heat pump (heating) with a COP of 3.8 maintains an indoor temperature of 64 degrees F. What is the outside temperature (in F)?
answer
-74 F 64 oF = (64 - 32) 5 / 9 oC = 17.77oC = 17.77 + 273 K= 290.77 K ' 3.8 = 290.77 / (290.77 - tcold) ' tcold = 290.77 - 290.77 / 3.8 = 214.25 K = 214.25 - 273 oC = -58.75 oC = (-58.75 x 9 / 5) + 32 oF = -73.75 oF
question
Horizontal loop geothermal heat pumps are used when there is less space available.
answer
FALSE
question
What is the physical meaning of the coefficient of performance?
answer
It is the amount of heat moved between the reservoirs for every unit of work done
question
Which one of the following is an example of thermal mass?
answer
Stone
question
AFUE stands for _____.
answer
Annual Fuel Utilization Efficiency
question
What is the typical range for the COP for heat pumps?
answer
1.5-3.5
question
When a heat pump is used to heat a house in the winter, how will the coefficient of performance be affected if the inside set temperature is changed from 65 F to 70 F?
answer
it decreases
question
Which of the following is recommended to look at when purchasing a furnace
answer
Annual Fuel Utilization Efficiency
question
Using kitchen and bath exhaust fans may adversely affect the heating and cooling requirements.
answer
TRUE
question
What kind of efficiency rating do gas and oil heating systems use?
answer
AFUE
question
Balance point for a heat pump occurs when _____.
answer
the heat pump output equals the home heating requirement
question
Which one of the following will have a negative impact on the home heating efficiency?
answer
Open front door in winter to filter and clean warm air.
question
A \"desuperheater\" can provide a homeowner with _____.
answer
free or reduced cost hot water
question
The compressor of a heat pump system ___________ the pressure of the refrigerant, ________ its temperature.
answer
increases, raising
question
The furnace/air conditioner will run for longer periods of time when the air filter is dirty.
answer
TRUE
question
Most of the energy used at home is used for _____.
answer
Heating
question
What happens when the outside temperature falls below the 'Balance Point'?
answer
the heat pump output falls below the home heating requirement
