MA HVAC case studies
MA HVAC · Put your knowledge to work in context.
The Massachusetts HVAC contractor credential is a state-issued license that allows a business to contract for refrigeration, air conditioning, and related sheet metal work in Massachusetts. It is aimed at owners and qualifying individuals who intend to bid, install, and service comfort-cooling and refrigeration systems for the public rather than work only as employees under someone else's license. The MA HVAC case studies are 5 cases and about 3,226 words.
1Walk-in cooler retrofit: bubbles, superheat, and vertical lift
A 2-ton remote condensing unit serving an 8 ft by 10 ft walk-in cooler was retrofitted from R-404A to R-448A. The line set is 55 ft total, with a 24 ft vertical rise from the condensing unit to the evaporator; the liquid line is 3/8 in.
700 words, about 4 min2Second-floor hot bedrooms: oversized equipment versus undersized ducts
A homeowner in Worcester complains that the second-floor bedrooms are 5°F warmer than the first floor in July. The existing system is a 3-ton, 13 SEER split with a PSC blower, a 16 x 8 in.
641 words, about 3 min3Condensing boiler replacement with an orphaned water heater
A contractor is replacing a failed 140,000 Btu/h atmospheric gas boiler in a 10 ft by 12 ft basement mechanical room with a 120,000 Btu/h condensing boiler. The new boiler will be direct-vented through the sidewall with 3-in.
636 words, about 3 min4Rooftop unit branch circuit: MCA, MOP, and ambient derating
A contractor is replacing a 5-ton rooftop package unit on a 208/230 V, three-phase, 60 Hz building. The new unit nameplate lists a minimum circuit ampacity of 32 A and maximum overcurrent protection of 40 A.
639 words, about 3 min5Fire damper omission and a disputed change order
A mechanical contractor is installing a new 12 x 8 in. galvanized supply duct in a 4-story office building.
610 words, about 3 min