Learning Center
Glossary: HVAC, Plumbing & Electrical Terms, Explained
The words on your estimate, your rebate form, and your equipment label, defined in plain English for Fraser Valley homes. Each term links to the guide or service page that goes deeper.
How to use this glossary
Look up a term, then follow it into the Learning Center: start with a Learn guide, weigh your options in a Compare guide, and see what happens next when you are ready to act.
Efficiency & Sizing
AFUE
Annual Fuel Utilization Efficiency
The share of the fuel a furnace or boiler burns over a typical year that ends up as usable heat in your home. A 96% AFUE furnace turns about 96 cents of every gas dollar into heat; the rest leaves through the vent. Mid-efficiency furnaces sit around 80%, condensing furnaces above 90%.
BTU
British thermal unit
A unit of heat energy: the amount needed to raise one pound of water by one degree Fahrenheit. Furnace, heat pump, and air conditioner capacity is quoted in BTU per hour (BTU/h).
COP
Coefficient of Performance
How much heat a heat pump delivers for each unit of electricity it uses at a given moment. A COP of 3 means three units of heat for one unit of electricity. COP drops as the outdoor temperature falls, which is why cold-climate models matter in colder pockets of the valley.
Heat Load Calculation
Heat loss and heat gain calculation, CSA F280
A room-by-room calculation of how much heat your home loses on a cold design day and gains on a hot one, based on insulation, windows, air leakage, and orientation. In Canada the recognized standard is CSA F280, and BC heat pump rebate programs expect one.
HSPF2
Heating Seasonal Performance Factor 2
The heating efficiency rating for an air-source heat pump over a typical heating season, measured under the updated 2023 test procedure. Higher is better. Rebate programs often set a minimum HSPF2 for qualifying equipment, so check the rating against the program before you choose a model.
SEER2
Seasonal Energy Efficiency Ratio 2
The cooling efficiency rating for air conditioners and heat pumps under the updated test procedure introduced in 2023, which uses higher duct resistance to better reflect real homes. A higher SEER2 means less electricity for the same cooling. SEER2 numbers read a little lower than old SEER numbers for the same equipment, so compare like with like.
Short Cycling
When a furnace, air conditioner, or heat pump turns on and off far more often than it should. Common causes are an oversized system, a clogged filter, or a safety control tripping. It wears parts out early and leaves rooms uneven and clammy.
Tonnage
Ton of cooling
The capacity size of an air conditioner or heat pump. One ton equals 12,000 BTU per hour, so a 3-ton heat pump is rated for about 36,000 BTU/h. Bigger is not better: the right tonnage comes from a heat loss and heat gain calculation, not square footage.
Heating & Cooling Equipment
Air Handler
The indoor cabinet with the blower that pushes air through your ducts. In an all-electric system it pairs with the outdoor heat pump and often holds the backup heat; in a gas system the furnace does this job.
Auxiliary Heat
Backup heat, heat strips
A second heat source that helps a heat pump on the coldest days or during a defrost cycle, usually electric resistance coils in the air handler or a gas furnace in a dual-fuel system. If auxiliary heat runs constantly in mild weather, something needs a look.
Boiler
Hydronic heating
A heating appliance that heats water and circulates it to radiators, baseboards, or in-floor tubing instead of blowing warm air through ducts. Quiet, even heat, but it does not cool.
Cold-Climate Heat Pump
An air-source heat pump built to keep producing useful heat well below freezing, usually with a variable-speed compressor. Some rebate programs only accept models from a published cold-climate list, so confirm eligibility before you buy.
Condensate Drain
Condensate line and pump
The tubing, trap, and sometimes a small pump that carry water away from a condensing furnace, air conditioner, or heat pump coil. A clog or a failed pump is the most common reason for water around a furnace, and it can shut the system down.
Condensing Furnace
High-efficiency furnace
A gas furnace that captures extra heat by condensing the water vapour in its exhaust, reaching above 90% AFUE. It vents through plastic pipe and makes water, so it needs a working condensate drain.
Defrost Cycle
In cold, damp weather, frost builds up on a heat pump's outdoor coil. The unit briefly reverses to melt it off, and you may see steam and hear a whoosh. That is normal. A coil that stays iced over is not.
Dual-Fuel System
Hybrid heating
A heat pump paired with a gas furnace in one system. The heat pump handles everyday heating and all of the cooling; the furnace takes over automatically when it gets cold enough that gas becomes the better option.
Ductless Mini-Split
A heat pump with an outdoor unit connected by refrigerant lines to one or more indoor heads mounted on a wall or ceiling, with no ductwork. A good fit for homes heated by baseboards, for additions, and for rooms the main system never quite reaches. One outdoor unit serving several heads is called a multi-zone system.
Flame Sensor
A small safety rod that confirms the burner has lit. If it is dirty, the furnace lights, then shuts off after a few seconds and tries again. Cleaning it is part of a proper tune-up.
Heat Exchanger
The metal chamber in a furnace that passes heat from the burners to your household air while keeping combustion gases sealed off. A cracked heat exchanger is a safety problem because it can let carbon monoxide into the airstream.
Heat Pump
A heating and cooling system that moves heat instead of making it. In winter it pulls heat from the outdoor air and brings it inside; in summer it reverses and works like a central air conditioner. Because moving heat takes less energy than creating it, a heat pump delivers more heat than the electricity it uses.
Heat pump vs. furnace → Heat pump installation → Heat pump repair →
Refrigerant
The fluid that carries heat between the indoor and outdoor parts of an air conditioner or heat pump. The system is sealed, so low refrigerant means a leak, not something that gets used up. Handling it requires certification.
Variable-Speed Compressor
Inverter compressor
A compressor that ramps its output up and down to match what the house needs, instead of running flat out and shutting off. The result is steadier temperatures, quieter operation, and better efficiency at part load, which is most of the year.
Indoor Air Quality
Carbon Monoxide (CO)
A colourless, odourless gas produced when fuel does not burn completely. Every home with a gas furnace, water heater, fireplace, or range should have working CO alarms, and fuel-burning appliances should be inspected yearly.
How often to service a furnace → Furnace not working checklist →
ERV
Energy Recovery Ventilator
Works like an HRV but also transfers some moisture between the airstreams, which can help keep indoor humidity steadier. Which one suits a home depends on the house and how it is used.
HRV
Heat Recovery Ventilator
A ventilation unit that swaps stale indoor air for fresh outdoor air while passing heat between the two airstreams, so you get fresh air without throwing away the heat. During heavy smoke it may need different settings.
Media Filter Cabinet
A deeper filter housing, usually 4 to 5 inches, installed beside the furnace or air handler. The extra surface area lets a high-MERV filter catch fine particles without choking airflow, and filters last longer between changes.
Filter cabinet installation → Wildfire smoke and indoor air →
MERV
Minimum Efficiency Reporting Value
A 1 to 16 rating for how well a furnace filter catches particles. Higher numbers catch finer particles but also restrict more airflow. MERV 13 is a common target for wildfire smoke, as long as a technician confirms your blower can handle it.
PM2.5
Fine particles 2.5 microns across or smaller, small enough to reach deep into the lungs. It is the main health concern in wildfire smoke and the number air quality advisories report.
UV Germicidal Light
An ultraviolet (UV-C) lamp installed inside the air handler or ductwork to limit mould and bacteria growth on the damp cooling coil and in the airstream.
Plumbing & Water Heating
Anode Rod
A metal rod inside a tank water heater that corrodes on purpose so the tank lining does not. Once it is used up, the tank itself starts to rust, so checking it is part of good water heater maintenance.
Descaling
Flushing
Circulating a cleaning solution through a tankless water heater, or flushing a tank, to remove mineral build-up. Scale makes a heater work harder and can shorten its life.
Gas Line
Gas piping
The piping that carries natural gas from the meter to each appliance. Adding a range, barbecue, fireplace, or tankless heater often means a new or larger line, and gas piping work in BC must be done by a licensed gas fitter under a permit.
Storage Tank Water Heater
The familiar cylinder that keeps a set amount of water hot and ready. Lower upfront cost and simple to replace, but it can run out during back-to-back showers and loses some heat while it sits.
Tankless Water Heater
On-demand water heater
A wall-mounted heater that heats water as it flows instead of keeping a tank hot. It saves space and never runs out mid-shower, but it needs enough gas supply and proper venting, and yearly descaling keeps it efficient.
Electrical
Level 2 EV Charger
A 240-volt charger on its own circuit that charges an electric vehicle several times faster than a standard wall outlet. Whether your panel can take it is the first question.
Panel Upgrade
Electrical service upgrade
Replacing or enlarging your main electrical panel, often from 100 amps to 200 amps, so the house can carry new loads like a heat pump, EV charger, or hot tub. It involves an electrical permit and coordination with the utility.
Standby Generator
A permanently installed generator that starts on its own when the power goes out and switches the house over through a transfer switch, keeping heat, the fridge, and the sump pump running.
Whole-Home Surge Protection
A surge protective device installed at the main panel that limits voltage spikes before they reach the electronics in your furnace, heat pump, appliances, and devices.
Permits, Rebates & Trades
CleanBC
The Province of British Columbia's climate plan. Its home programs offer rebates for switching to heat pumps and other efficiency upgrades, including a larger income-qualified stream. Rules and amounts change, so check the current program before you commit.
CleanBC rebates and your upgrade → Heat pump rebates in BC →
Comfort Advisor
The person who visits to assess your home and equipment when you are considering a new system, then walks you through options, sizing, and rebates in a written estimate.
What to expect from a comfort advisor visit → Get a free quote →
FortisBC Rebates
Utility rebates from FortisBC on qualifying high-efficiency heating and water heating equipment. Each offer has its own equipment list, contractor requirements, and deadlines, and some can be combined with CleanBC rebates.
Gas Fitter
A tradesperson certified in BC to install, connect, and service gas appliances and piping. Gas fitters hold a Class A or Class B certificate; Class B covers typical home appliances, Class A also covers larger systems.
Gas Permit
Installation permit
The permit a licensed contractor takes out before installing or replacing a gas furnace, boiler, water heater, or gas line. It puts the work on record and makes it subject to inspection. Unpermitted work can cause trouble with insurance, resale, and rebates.
HPCN
Home Performance Contractor Network
The BC network of contractors registered to install equipment under CleanBC home rebate programs. If your installer is not a member, a CleanBC rebate application can be refused, so ask before you sign.
Maintenance Plan
A yearly service agreement that schedules tune-ups for your furnace, heat pump, air conditioner, or water heater so they are checked before the season that works them hardest. Many manufacturer warranties expect documented annual maintenance.
Red Seal
The Interprovincial Standard Red Seal, a national endorsement showing a tradesperson has met the Canada-wide standard for their trade. Rep-Air's owner, Justin McIntyre, is a Red Seal HVACR technician.
Service Call Fee
Diagnostic fee
A flat charge that covers a technician's visit and diagnosis. At Rep-Air it is $189, waived when you go ahead with the repair or installation we quote. Estimates on new systems are free.
What to expect at your service appointment → Get a free quote →
Technical Safety BC
TSBC
The provincial safety regulator that licenses gas and electrical contractors and issues permits for regulated gas and electrical work across most of BC. Some municipalities run their own permit programs, so the permit authority depends on where you live.
Definitions are general guidance for homeowners, not legal or code advice. Rebate rules and permit requirements change, so confirm current details with the program or your local permit authority. Browse every guide in our Learning Center, get quick answers in our FAQ library, or see our heating, cooling, plumbing, and electrical services.
Still not sure what your estimate means? Ask us.
Free estimates on new systems across the Fraser Valley, with every line explained before any work starts.