HI HVAC case studies
HI HVAC · Put your knowledge to work in context.
The HI HVAC credential is a professional certification for heating, ventilation, and air conditioning practitioners who want formal recognition of their technical knowledge. It is aimed at technicians, installers, service personnel, and maintenance staff who work on residential and light commercial systems, as well as those preparing to move into more senior or supervisory roles. The HI HVAC case studies are 5 cases and about 4,289 words.
1Condensing Furnace Lockout on an 8°F Morning
A 2009 two-story house has a 100,000 BTU/h, 92% AFUE condensing furnace in a second-floor closet, vented with 2-inch PVC intake and exhaust that pass through the rim joist and terminate side by side under a 3-foot roof overhang. Each pipe ends in a downward-facing 90-degree elbow about 14 inches above the patio slab.
857 words, about 4 min2Two Bath Fans, a Tight House, and a Spilling Water Heater
A 1,800-square-foot, three-bedroom ranch built in 1978 has two bathrooms and a recirculating range hood. A blower door test measures 2.8 ACH50.
900 words, about 5 min3Low Delta-T on an R-410A Split System
A 3-ton R-410A split system with a thermostatic expansion valve, installed in 2014, is checked on a 95°F afternoon after the house has been cooling continuously for an hour. Return air at the air handler is 76°F dry bulb and 63°F wet bulb; supply air is 63°F, a 13°F temperature difference.
808 words, about 4 min4High Static Pressure on a 3-Ton Retrofit
A 1,950-square-foot single-story house has a 3-ton (1,200 CFM) split system installed during a 2019 remodel. The return is a single 14-inch flex duct from one hallway grille.
839 words, about 4 min5Auxiliary Heat That Trips the Breaker
A 2016 heat pump with a 15 kW electric heat kit in the air handler serves a 2,200-square-foot house. The heat kit nameplate reads: 15 kW at 240 V, 62.5 A, minimum circuit ampacity 78 A, maximum overcurrent protection 80 A.
885 words, about 4 min