Unit 14 DIVISION OF DECIMAL FRACTIONS 79 23. Find the wall thickness of this rigid polyvinylchloride (PVC) tube. 2.181 ft- 2.375 ft 24. A 1-ton HVAC unit will remove up to 12,000 Btu/h. What size unit is needed for a house with a heat load of 28,576 Btu/h? (Round up to the next higher either half or whole number.) 25. A circulating fan can supply 9,525.6 cu ft of air in 1 hour. What is the largest volume room that will have its air exchanged 4.5 times each hour?