HVAC/R Glossary

This glossary of HVAC and Refrigeration related abbreviations can help you navigate the most common terms you'll come across during your buying decision.


Acronym What it stands for …
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AC Air Conditioning
AC Alternating Current
ACH Air Changes per Hour
ACM Asbestos Containing Material
AEE Association of Energy Engineers
AFD Adjustable Frequency Drive
AFUE Annual Fuel Efficiency Ratio
AHU Air Handling Unit
AI Analog Input
Anti-Ice Control same as a freeze stat or encapsulated pressure control
AO Analog Output
Aquastat controls the use of a water system. We sell the Honeywell aquastats. You can also use the Ranco ETC series of temp controls.
ASHRAE American Society of Heating Refrigeration and Air Conditioning Engineers
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B Boiler
BACnet A Data Communication Protocol for Building Automation and Control Networks
BAS Building Automation System
Bazooka 636 concentric vent kit
BCA Building Commissioning Association
Bearshit cork tape
BI Backward Incline
BI Binary Input
BO Binary Output
BSLN Baseline
BTU British Thermal Unit
BTUH Brtish Thermal Units / Hour
BY Base Year
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Can a small hermetic compressor
CAV Constant Air Volume
CD Cold Deck
CDD Cooling Degree Days
CEM Certified Energy Manager
CFC ChloroFluoroCarbon
CFM Cubic Feet per Minute
CH Chiller
CHW Chilled Water
CHWP Chilled Water Pump
CHWR Chilled Water Return
CHWRT Chilled Water Return Temperature
CHWS Chilled Water Supply
CHWST Chilled Water Supply Temperature
CLF Cooling Load Factor
CLTD Cooling Load Temperature Difference
COP Coefficient Of Performance
CRAC Computer Room Air Conditioner
CT Cooling Tower
CV Constant Volume
CVRMSE Coefficient of Variation of the Root Mean Square of the Error
CWP Condenser Water Pump
CWR Condenser Water Return
CWRT Condenser Water Return Temperature
CWS Condenser Water Supply
CWST Condenser Water Supply Temperature
CY Current Year
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DA Discharge Air
DB Data Base
DB Dry Bulb
DC Direct Current
DCV Demand Controlled Ventilation
DD Degree Day
DDC Direct Digital Control
DH Duct Heater
DI Digital Input
DO Digital Output
DP Dew Point
DP Differential Pressure
DX Direct Expansion
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EAT Entering Air Temperature
ECM Electronically Commutated Motor
ECM Energy Conservation Measure
ECO Energy Conservation Opportunity
EDH Electric Duct Heater
EEM Energy Efficiency Measure
EER Energy Efficiency Ratio
EF Exhaust Fan
Eggcrate this is a plastic grill material that can replace ceiling tiles. Part Number: 2-4-1/2-ALL
EH Electric Heater
EMS Energy Management System
ESCO Energy Service Company
EUH Electric Unit Heater
EWT Entering Water Temperature
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FC Forward Curve
FCU Fan Coil Unit
FIM Facility Improvement Measure
Firecracker Fan cycling control
FLA Full Load Amps
Flux Used to etch metal for filler (solder) to bold
FMS Facility Management System
FPM Feet Per Minute
Freeze-Stat a switch to stop evaporators from icing up. (eg. AE1C-1-ECO or HH)
FW Feed Water
G Back to Top
GPM Gallons Per Minute
GUI Graphical User Interface
H Back to Top
HCFC Hydrochlorocfuorocarbon
HD Hot Deck
HDD Heating Degree Days
HEPA High Efficiency Particulate Arresting
HFC HydroFluoroCarbon
HHV Higher Heating Value
HHWP Heating Hot Water Pump
HHWR Heating Hot Water Return
HHWS Heating Hot Water Supply
HL High Limit
HPS High Pressure Steam
HR Heat Recovery
HRU Heat Recovery Unit
HRV Heat Recovery Ventilator
HSPF Heating Seasonal Performance Factor
HVAC Heating Ventilation and Air Conditioning
HWP Hot Water Pump
HWR Hot Water Return
HWS Hot Water Supply
HWRT Hot Water Return Temperature
HWST Hot Water Supply Temperature
HX Heat Exchanger
I Back to Top
I/O Input Output
Inducer Motor also known as a venter motor. It vents harmful gas out of the furnace through 636 pipe to the outside of the house or building
IAQ Indoor Air Quality
IPMVP International Performance Measurement and Verification Protocol
IR Infra-Red
J Back to Top
Jellybean specific style of crimp connector
K Back to Top
King Valve The shut off valve on a condensing unit. This where refrigerant is charged and where the line set piping connects to
L Back to Top
LAT Leaving Air Temperature
LHV Lower Heating Value
Line Voltage Thermostat Used for electrical baseboards or anything using 120/208v to match amperage. Look for these Honeywell items
LL Low Limit
LON Local Operating Network
LP Low Pressure
LPS Low Pressure Steam
LRA Locked Rotor Amps
LWBT Leaving Wet Bulb Temperature
LWT Leaving Water Temperature
M Back to Top
M&V Measurement and Verification
MA Mixed Air
MAT Mixed Air Temperature
MCC Motor Control Center
MUA Make-up Air Unit
Muffin Motor 3.3" unit bearing motor eg. R-5411
MX Metrix Utility Accounting System
MZ Multi-Zone
N Back to Top
NC Normally Closed
NEMA National Electrical Manufacturers Association
NO Normally Open
NPSH Net Positive Suction Head
O Back to Top
OA Outside Air
OAP Outside Air Percentage
OAT Outside Air Temperature
OCS this stands for “Our Compressor Shop”. It is referring to internal purchases used for the business. It was called this when RSL operated their own compressor rebuild shop decades ago
ODP Open Drip Proof
OWS Operator Work Station
P Back to Top
Pancake 636 low profile vent termination kit (1HT
Pancake Drier stout suction line filter driers. ie C-145-S-TT-HH
PC Performance Contracting
PE Professional Engineer
Penthouse Unit they are likely referring to a self-contained refrigeration system that is mounted on the top of a walk-in box. We stock the Bohn Pro3
PH Pre-Heat
PID Proportional Integral Derivative
PRV Pressure Relief Valve
PRV Pressure Reducing Valve
PTAC Packaged Terminal Air Conditioner
Q Back to Top
R Back to Top
RA Return Air
Rezpack/Respack this is short for “Residential Packaged Unit”. They are a rooftop square in shape that are typically 2-5 tons. In some parts of North America they are used in residential applications.
RF Return Fan
RH Reheat
RH Relative Humidity
RPM Revolutions Per Minute
RTD Resistance Temperature Detector
RTU Roof Top Unit
S Back to Top
SA Supply Air
SAT Supply Air Temperature
SC Shading Coefficient
SEER Seasonal Energy Efficiency Ratio
SF Supply Fan
SHFG Solar Heat Gain Factor
SHR Sensible Heat Ratio
Silfos comes in 5 and 15% silver and is used to bond copper to copper. No flux required
Silver Solder Silver solder required flux or comes pre fluxed and is used for bonding dissimilar metals
Skeleton Motor specific style of motor used in small refrigeration applications.
SP Set Point
SP Static Pressure
Super Hose Also known as High Pressure Control Hose. We stock the Ritchie yellow jacket product. Part #: 78712, 78718, 78724, 78730, 78736, 78748, 78760, 78772
SWP Steam Working Pressure
T Back to Top
T Temperature
T Thermostat
TEV Thermostatic Expansion Valve
TOD Time Of Day
TORR Millimeter of Mercury (mmHg)
Trax/Traxx Oil/Traxx Oil Control Trax is an old brand name. The customer is likely looking for a Copeland oil level control – Part #: OMB-JB1
TXV Thermostatic Expansion Valve
U Back to Top
UH Unit Heater
UV UltraViolet
UV Unit Ventilator
V Back to Top
VAV Variable Air Volume
VD Volume Damper
Venter Motor also known as an inducer motor. It vents harmful gas out of the furnace through pipes to the outside of the house or building
VFD Variable Frequency Drive
VSD Variable Speed Drive
VSP Variable Speed Pump(ing)
W Back to Top
WB Wet Bulb
WC Water Column
Window Shaker refers to the window mounted air conditioners. We stock Friedrich, and have access to Comfort-aire and Amana
X Back to Top
Y Back to Top
YTD Year To Date
Z Back to Top