The vocabulary of measurement-based HVAC.
The terms an NCI-certified technician will use in your System Operation Report. Bookmark this page — your future quote will be written in this vocabulary.
Performance
- Performance
NCI
National Comfort Institute — the industry's measurement-based standard for HVAC system performance. NCI-certified technicians use instruments (manifold gauges, anemometers, combustion analyzers) to test what a system is actually doing, not what it looks like it should be doing.
- Performance
Static Pressure
The pressure inside your duct system, measured in inches of water column. Like blood pressure for HVAC — abnormal readings predict equipment failure and uncomfortable rooms long before the equipment quits.
- Performance
CFM
Cubic feet per minute. The volume of air moving through your system. Manual J (load) and Manual D (duct design) set the target CFM for every room; NCI testing measures whether you actually get it.
- Performance
Manual J
The ACCA load-calculation procedure that determines how much heating and cooling a specific building actually needs, room by room. Rule-of-thumb sizing (square footage × 30 BTU) routinely oversizes equipment by 50%+.
- Performance
Manual D
The ACCA duct-design procedure that translates a Manual J load into ducts sized to deliver the right CFM to each room at acceptable static pressure.
- Performance
Manual S
The ACCA equipment-selection procedure — takes the Manual J load and chooses a specific make/model that matches the load at the design conditions, not just by tonnage.
Equipment
- Equipment
SEER2
Seasonal Energy Efficiency Ratio v2 — the 2023+ federal efficiency rating for air-conditioning equipment. Replaces the older SEER metric with a more realistic test protocol. Northern New Jersey (DOE Region 5) requires a minimum SEER2 of 14.3 for split central AC.
- Equipment
HSPF2
Heating Seasonal Performance Factor v2 — the heat-pump heating-efficiency rating updated for 2023+. The corresponding northern-climate minimum is 7.5 HSPF2.
- Equipment
AFUE
Annual Fuel Utilization Efficiency — how much of a furnace or boiler's fuel becomes useful heat. 80% AFUE is standard; 95+% AFUE is condensing equipment that pays back through lower fuel bills over typical 15-year service life.
- Equipment
BTU
British Thermal Unit. The energy needed to raise one pound of water by one degree Fahrenheit. HVAC equipment is sized in thousands of BTUs per hour (BTU/hr) of heating or cooling capacity.
- Equipment
Heat Pump Balance Point
The outdoor temperature at which a heat pump's capacity equals the home's heat load. Below the balance point, supplemental heat (electric resistance or a backup furnace) is needed.
- Equipment
Defrost Cycle
When outdoor temperatures fall below ~45 degrees Fahrenheit, a heat pump's outdoor coil ices up. A periodic defrost cycle reverses the refrigerant flow briefly to melt the ice; it looks alarming but is normal operation.
- Equipment
Two-Stage Compressor
A compressor that operates at two output levels (typically 67% and 100%). Spends more time at low stage in mild weather — better humidity control, quieter operation, lower bills.
- Equipment
Variable-Speed ECM
Electronically Commutated Motor — the variable-speed motor in modern air handlers. Continuously adjusts blower speed to maintain target static pressure and CFM. Uses ~60% less power than a traditional PSC motor.
- Equipment
Hydronic
Heating or cooling delivered via water (or glycol/water mix) circulated through radiators, baseboards, or radiant tubing — as opposed to air. Older Northern NJ homes are commonly hydronic.
- Equipment
Steam vs Hot Water Boiler
Steam boilers boil water and pipe steam to radiators (older, larger pipes, distinctive radiator hiss). Hot-water boilers circulate hot water with a pump (newer, more efficient). The conversion path depends on the original distribution system.
- Equipment
Condensing Boiler
A boiler that captures heat from exhaust water vapor by condensing it back to liquid before it leaves the unit. Reaches 95%+ AFUE; requires PVC venting (not metal flue) and proper return-water temperatures to actually condense.
Combustion
- Combustion
Combustion Analysis
Measurement of the exhaust gases from a gas furnace or boiler (CO, O2, CO2, stack temperature) using a combustion analyzer. Reveals incomplete combustion that wastes fuel and produces dangerous carbon monoxide.
Refrigerant
- Refrigerant
Refrigerant Charge
The mass of refrigerant in a sealed AC or heat-pump loop. Both undercharge and overcharge degrade efficiency by 20%+; NCI techs verify charge by superheat and subcooling, not by sight glasses.
- Refrigerant
R-22
An ozone-depleting refrigerant phased out under the EPA Clean Air Act. R-22 production stopped in 2020; existing systems can be repaired with reclaimed R-22 but recharges cost hundreds to thousands of dollars per pound.
- Refrigerant
R-410A
The HFC refrigerant that replaced R-22. Still widely installed, but the AIM Act is now phasing R-410A down in favor of A2L (mildly flammable) alternatives like R-454B and R-32.
- Refrigerant
R-454B
A low-GWP A2L refrigerant adopted by most major manufacturers for 2025+ residential equipment under the AIM Act transition. Requires equipment specifically designed for A2L safety.
- Refrigerant
A2L Refrigerant
Refrigerants with low toxicity (A) and mild flammability (2L). The AIM Act transition refrigerants — R-454B, R-32 — are A2L. Requires equipment, charging procedures, and leak-detection designed for the slight flammability.
- Refrigerant
R-32
A single-component A2L refrigerant used in ductless mini-splits and some central systems. Lower GWP than R-410A; one of the AIM Act transition options.
IAQ
- IAQ
MERV
Minimum Efficiency Reporting Value — the standard rating for air-filter particulate capture, 1 to 16. Most residential filtration tops out at MERV 13 (captures viral and bacterial particles); higher MERVs require equipment-engineered duct/blower upgrades.
- IAQ
UV Germicidal
An ultraviolet light installed inside the air handler or duct, used to suppress mold and biological growth on coils. Effective on what it can directly illuminate; not a substitute for filtration.
- IAQ
ERV
Energy Recovery Ventilator. Brings in fresh outdoor air while transferring both heat and moisture to/from the outgoing stale air — maintains indoor air quality without paying full HVAC cost to condition the incoming air.
- IAQ
HRV
Heat Recovery Ventilator. Similar to an ERV but transfers heat only (not moisture). Preferred in dry winter climates; in NJ, ERVs are usually the better choice.
Code
- Code
NEMA Enclosure
National Electrical Manufacturers Association rating for electrical enclosure protection (NEMA 1 indoor, NEMA 3R outdoor weather-resistant, NEMA 4 watertight). Important for AC disconnects and outdoor controls.
- Code
NJ UCC
New Jersey Uniform Construction Code — the statewide construction code enforced through each municipality's construction office. Adopts mechanical, plumbing, electrical, and energy subcodes that govern HVAC permits, inspections, and equipment requirements in every Volpe service area.
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