From AFUE to zoning, here is what the words on your quote, your thermostat and your technician’s report actually mean. Written for Ontario homeowners, not engineers. Search it, browse by topic, or jump straight to a letter.
Know Your System
Understanding the language is the first step to a confident buying decision. Every definition below is written the way we would explain it at your kitchen table, with a link to the service page where it matters most.
Showing all 118 terms
Annual Fuel Utilization Efficiency
The percentage of fuel a furnace or boiler turns into usable heat over a full heating season. A 96% AFUE furnace sends 96 cents of every fuel dollar into your home and loses 4 cents up the flue. Most Ontario homes today install 95% to 98% AFUE condensing furnaces.
Adjusting dampers, registers and blower speed so every room receives the right amount of airflow. Poor balancing is the usual reason one floor is stuffy while another is cold.
A split system that cools an entire home by circulating refrigerant between an outdoor condenser and an indoor evaporator coil, then pushing cooled air through the ductwork.
A general term for an HRV or ERV. It swaps stale indoor air for fresh outdoor air while recovering most of the heat, so ventilation does not drain your heating or cooling budget.
The replaceable media in your return duct or furnace cabinet that traps dust, pollen and pet dander before air reaches the blower and coil. Standard 1-inch filters need changing every 1 to 3 months; 4 to 5 inch media filters last 6 to 12 months.
Cubic Feet per Minute
The volume of air a system moves each minute. A typical rule of thumb is about 400 CFM per ton of cooling. Too little airflow freezes coils and starves rooms; too much is noisy and reduces dehumidification.
The indoor cabinet that houses the blower, evaporator coil and sometimes electric heat strips. It moves conditioned air through the ducts and is the indoor half of a heat pump or ductless-free central AC system.
The temperature of the surrounding air, usually meaning the outdoor temperature a unit is operating in. Heat pump capacity and efficiency are always rated at specific ambient temperatures.
A yearly tune-up in which a technician cleans, inspects and tests your furnace, air conditioner or heat pump. Keeps warranties valid, catches worn parts before they fail and maintains efficiency. Best done in spring for cooling and fall for heating.
A sacrificial magnesium or aluminum rod inside a tank water heater that corrodes so the steel tank does not. Checking and replacing it every few years can double the life of a tank.
When combustion gases from a furnace, boiler or water heater spill back into the home instead of leaving through the vent. Often caused by a blocked chimney or a tightly sealed house with strong exhaust fans. A carbon monoxide risk that needs immediate attention.
The outdoor temperature at which a heat pump's heating output exactly matches the home's heat loss. Below it, supplemental heat runs. Cold-climate models push the balance point far lower than older heat pumps.
The fan inside your furnace or air handler that pushes air through the ductwork. Variable-speed ECM blowers run quieter, use less electricity and hold more even temperatures than older single-speed PSC motors.
A heating appliance that warms water (or makes steam) and circulates it to radiators, baseboards or in-floor tubing. Common in older Toronto homes and in modern radiant-floor installations.
A compact boiler that provides both space heating and on-demand domestic hot water from one unit, eliminating the separate water heater. Popular in condos and smaller homes with hydronic heat.
British Thermal Unit
The energy needed to raise one pound of water by one degree Fahrenheit. HVAC equipment is sized in BTU per hour; a typical Ontario furnace is 60,000 to 100,000 BTU/h and one ton of cooling equals 12,000 BTU/h.
A small cylindrical part that gives the compressor and fan motors a jolt to start and keeps them running smoothly. A failed capacitor is one of the most common reasons an air conditioner hums but will not start.
An odourless, colourless gas produced by incomplete combustion in gas furnaces, water heaters and fireplaces. Ontario law requires CO alarms near sleeping areas in homes with fuel-burning appliances or attached garages.
A heat pump engineered to keep heating efficiently at temperatures well below freezing, typically rated to deliver useful heat at -25°C or colder. The class of equipment that makes heat-pump heating practical in Southern Ontario winters.
A diagnostic test where a technician measures oxygen, carbon monoxide and flue temperature in the exhaust to confirm a furnace or boiler is burning safely and efficiently.
The heart of an air conditioner or heat pump. It squeezes refrigerant vapour to high pressure so it can release heat outdoors (in cooling) or indoors (in heating). Inverter compressors vary their speed instead of just switching on and off.
The line that carries away water pulled from the air by the evaporator coil, or produced by a high-efficiency furnace. A clogged condensate drain is a frequent cause of water on the floor around the furnace.
The outdoor unit of a central air conditioner or heat pump, containing the compressor, condenser coil and fan. It releases the heat collected from inside the house to the outdoor air.
A high-efficiency gas furnace (90% AFUE or higher) with a second heat exchanger that pulls extra heat from exhaust gases until the water vapour condenses. Vents through PVC pipe rather than a metal chimney.
The amount of heat that must be removed from a home to hold the set temperature on a design summer day, including heat from sun, occupants and appliances. Determines air conditioner size.
Coefficient of Performance
How many units of heat a heat pump delivers for each unit of electricity it consumes, at a given outdoor temperature. A COP of 3 means 300% efficiency; electric baseboards are always COP 1.
An adjustable plate inside a duct that restricts or redirects airflow. Manual dampers are set once during balancing; motorized dampers open and close automatically in zoned systems.
A short period when a heat pump briefly reverses to melt frost off its outdoor coil in cold, damp weather. Steam rising from the outdoor unit in winter is normal defrost, not a malfunction.
A unit tied into the ductwork that removes moisture from the entire house independently of cooling. Useful in humid Ontario summers and for damp basements where the AC alone cannot keep humidity under 50%.
The temperature difference between supply and return air, used by technicians to check system performance. A central air conditioner typically runs a 16 to 22°F (9 to 12°C) delta T; outside that range points to airflow or refrigerant problems.
The outdoor temperature a system is sized for, based on local climate data: roughly -20°C for heating and 31°C for cooling in the Greater Toronto Area. Equipment is chosen to meet the load at these conditions.
A sealed-combustion appliance that draws combustion air from outdoors and exhausts outdoors through dedicated pipes, never using indoor air. Safer and more efficient than natural-draft venting.
A small fan in a furnace that pulls combustion gases through the heat exchanger and out the vent before the burners light. The furnace will not ignite if the inducer fails to prove airflow.
The tray beneath the evaporator coil that catches condensate and directs it to the drain line. Rusted or overflowing pans cause water damage and are often protected by a float switch that shuts the system off.
A heat pump or air conditioner with one outdoor unit connected to one or more wall-, ceiling- or floor-mounted indoor heads by refrigerant lines, with no ductwork. Ideal for additions, older homes without ducts, and room-by-room control.
The network of supply and return channels that distribute conditioned air through a home. Leaky or undersized ducts can waste 20% to 30% of a system's output before it reaches a room.
Electronically Commutated Motor
A high-efficiency, variable-speed blower motor found in modern furnaces and air handlers. Uses a fraction of the electricity of a conventional motor and allows quiet, continuous low-speed circulation.
Energy Efficiency Ratio
Cooling output divided by electrical input at a single fixed condition (35°C outdoors). Compared with SEER, it shows how an air conditioner performs on the hottest days rather than averaged over a season.
A furnace that heats air with electric resistance elements instead of burning fuel. Simple and safe, but expensive to run in Ontario compared with gas or a heat pump.
A thermostat setting that bypasses the heat pump and runs only the backup heat source (gas furnace or electric strips). Meant for when the heat pump has failed, not for everyday cold weather.
A government-backed certification for products that meet strict energy-efficiency criteria. In Canada, ENERGY STAR certified furnaces, heat pumps and water heaters are often required to qualify for rebates.
Energy Recovery Ventilator
A ventilation unit that exchanges stale indoor air with fresh outdoor air while transferring both heat and moisture between the streams. Preferred where summer humidity control matters, because it keeps some of the muggy outdoor moisture out.
The indoor coil, usually sitting on top of the furnace, where refrigerant absorbs heat and moisture from household air. A dirty or iced-over evaporator coil is a leading cause of weak cooling.
Thermostatic Expansion Valve
A metering device that controls how much refrigerant flows into the evaporator coil, adjusting to the cooling load. More precise and efficient than fixed orifices used in older systems.
Minimum Efficiency Reporting Value
A 1 to 16 scale for how well a filter captures particles. MERV 8 handles dust and pollen; MERV 11 to 13 captures finer smoke and allergens. Higher is not always better: a dense filter in a system not designed for it restricts airflow.
A thin metal rod that confirms the burners have lit. When coated with residue it cannot sense the flame, so the furnace lights, shuts off after a few seconds and tries again. Cleaning it is a routine maintenance task.
A safety sensor in the condensate drain pan or line that shuts down the air conditioner if water rises too high, preventing overflow and ceiling or floor damage.
The pipe or chimney passage that carries combustion gases from a furnace, boiler or water heater safely out of the home.
A forced-air appliance that heats air with gas, propane, oil or electricity and pushes it through ducts. The most common heating system in Ontario homes, and the usual partner for a central air conditioner or a hybrid heat pump.
A metal housing installed on the return side of the furnace that holds a thicker media filter and seals better than a slot in the blower compartment.
The electrically controlled valve that meters natural gas or propane to the burners when the control board calls for heat, and shuts it off instantly if any safety opens.
A ground-source heat pump that exchanges heat with the earth through buried loops instead of outdoor air. Extremely efficient year-round but requires significant excavation or drilling, so best suited to new builds and larger properties.
The metal chambers inside a furnace where burning fuel heats the air passing over them, keeping combustion gases separate from your breathing air. A cracked heat exchanger can leak carbon monoxide and usually means the furnace must be replaced.
An engineering calculation (often called a Manual J or CSA F280 calculation in Canada) of how much heating and cooling a home actually needs, based on size, insulation, windows and orientation. Proper sizing depends on it; guessing by square footage does not.
A system that moves heat rather than generating it: it pulls heat from outdoor air into the home in winter and reverses to act as an air conditioner in summer. One appliance for both heating and cooling, and the most efficient electric heating available.
A tank water heater that uses a small heat pump on top to pull heat from the surrounding air into the water, using roughly a third of the electricity of a standard electric tank.
Electric resistance elements inside an air handler that provide backup or supplemental heat when a heat pump alone cannot keep up or is in defrost.
High-Efficiency Particulate Air
A filter that captures 99.97% of particles down to 0.3 microns. True HEPA is too restrictive for most residential furnaces, so it is usually installed as a bypass air cleaner or in standalone units.
A central air system using small 2-inch flexible ducts and higher air speeds, allowing air conditioning to be retrofitted into older homes without conventional ductwork.
Heat Recovery Ventilator
A ventilation unit that brings in fresh outdoor air and exhausts stale indoor air, transferring heat between the two streams. Required in most new Ontario homes and the standard fix for stuffy, over-humid winter air in tightly sealed houses.
Heating Seasonal Performance Factor 2
The seasonal heating efficiency rating for heat pumps under the 2023 test standard. Higher is better; ENERGY STAR cold-climate models typically exceed HSPF2 8.1. Replaced the older HSPF figure, which read about 15% higher for the same unit.
A unit mounted on the furnace or ductwork that adds moisture to the air during the dry heating season. Reduces static, dry skin and cracked woodwork; ideal indoor humidity in winter is around 30% to 40%.
Heating, Ventilation and Air Conditioning
The umbrella term for every system that heats, cools, ventilates, filters and controls humidity in a building.
A heat pump paired with a gas furnace. The heat pump handles most of the season efficiently and the furnace takes over only during the coldest snaps. A popular Ontario upgrade path that keeps gas as a safety net.
A ceramic element that glows red-hot to light the gas burners in a modern furnace, replacing the old standing pilot light. Brittle and a common wear item.
The overall cleanliness and comfort of the air inside a home: particulates, humidity, ventilation, carbon dioxide and volatile organic compounds. Improved with filtration, ventilation (HRV/ERV), humidity control and UV or air-purification add-ons.
A variable-speed compressor drive that ramps output up and down to match demand instead of cycling fully on and off. Delivers steadier temperatures, quieter operation and much higher efficiency. Standard on modern heat pumps and premium air conditioners.
A safety device that shuts off the furnace burners if the air inside gets too hot, usually because of restricted airflow from a dirty filter or a failing blower.
The pair of insulated copper pipes that carry refrigerant between the outdoor and indoor units of an air conditioner or heat pump.
The amount of heating or cooling a space needs at a given moment. Equipment should be sized to the calculated load; oversized systems short-cycle, undersized systems never catch up.
An accessory that lets an air conditioner run safely in cold outdoor temperatures, used for server rooms or spaces with year-round cooling needs.
Outdoor air deliberately brought into a home to replace air removed by exhaust fans, range hoods and dryers. Without it, a tight house can go negative and pull combustion gases back down the flue.
The recognized methods for calculating a home's heating and cooling load, room by room. F280-12 is the Canadian standard referenced in the Ontario Building Code; a reputable installer sizes equipment from one of these, not from the old unit's nameplate.
A thick (4 to 5 inch) pleated filter in a dedicated cabinet. Far more surface area than a 1-inch filter, so it captures more while restricting airflow less and lasting 6 to 12 months.
A furnace whose burner adjusts in small steps (often 40% to 100% of capacity) to match the exact heat needed, rather than running only at full blast. The quietest and most even-heating type, usually paired with a variable-speed blower.
A ductless heat pump with one outdoor unit serving two to eight indoor heads, each controlled independently. Lets you heat or cool only the rooms in use.
The manufacturer's label on equipment listing model, serial number, capacity, electrical requirements and refrigerant type. Have it handy when booking a service call.
The fuel most Ontario furnaces, boilers and water heaters burn, delivered by pipeline. Enbridge Gas is the primary distributor across Southern Ontario.
A home built or retrofitted so efficiently that adding solar panels would produce as much energy as it uses over a year. Heat pumps, HRVs and airtight envelopes are the core HVAC ingredients.
The large sheet-metal box attached directly to the furnace or air handler where air is collected before entering the supply ducts (supply plenum) or after arriving from the returns (return plenum).
A gas tank water heater with a built-in fan that pushes exhaust through PVC pipe out a side wall, so it does not need a chimney. The standard replacement in homes where the furnace no longer uses the chimney.
A furnace safety that confirms the draft inducer is moving exhaust gases before allowing ignition. Blocked vents or condensate backups commonly trip it.
A thermostat that follows a schedule you set, lowering temperature overnight or while away. Smart thermostats add learning, remote app control and utility rebate eligibility.
A bottled fuel alternative to natural gas for homes beyond the pipeline network. Propane furnaces and water heaters are the same appliances as their gas counterparts with a conversion kit.
The refrigerant used in most air conditioners and heat pumps installed from about 2010 to 2024. Being phased down in Canada in favour of lower-global-warming refrigerants such as R-454B and R-32.
The new generation of lower-global-warming-potential refrigerants adopted in equipment sold from 2025 onward. Mildly flammable (A2L class), so installation and service require updated training and tools.
Heat delivered through warm surfaces (floors, panels or radiators) rather than blown air. Even, silent and dust-free; in-floor hydronic systems are usually fed by a boiler or a hydronic heat pump.
A wall-mounted or freestanding unit that releases heat from hot water or steam supplied by a boiler. Cast-iron radiators are common in Toronto's older housing stock.
Money back from a utility or government program for installing qualifying high-efficiency equipment such as cold-climate heat pumps, smart thermostats or heat pump water heaters. Programs change often; ask us what is currently available before choosing equipment.
The working fluid that absorbs heat as it evaporates indoors and releases it as it condenses outdoors. Sealed systems should never need topping up; a low charge means there is a leak to find and fix.
The precise amount of refrigerant a system is designed to hold. Both undercharge and overcharge reduce efficiency and can damage the compressor, which is why proper installation includes weighing and verifying the charge.
The grille covering a supply duct opening in a floor, wall or ceiling, usually with adjustable louvres to direct or partly close airflow.
The amount of moisture in the air compared with the maximum it could hold at that temperature. Comfortable indoor range is 30% to 50%; too high breeds mould, too low dries skin and woodwork.
Air drawn from the rooms back to the furnace or air handler to be filtered and reconditioned. Undersized returns are one of the most common design flaws in older homes.
The component that lets a heat pump switch between heating and cooling by changing the direction of refrigerant flow.
A self-contained packaged heating and cooling system installed on a commercial roof and connected to the building's ductwork. The workhorse of retail, office and light-industrial HVAC.
Seasonal Energy Efficiency Ratio 2
The seasonal cooling efficiency rating for air conditioners and heat pumps under the 2023 test standard. Higher means lower summer electricity bills. Minimum in Canada is around 13.4 to 14.3 SEER2 depending on size; premium inverter systems reach 20 or more.
The step-by-step order in which a furnace or heat pump starts up, runs and shuts down. Technicians follow it to pinpoint exactly where a system is failing.
Lowering the thermostat (or raising it in summer) for periods when the home is empty or everyone is asleep. Worthwhile with furnaces; with heat pumps, smaller setbacks are usually better because deep recoveries trigger backup heat.
When a furnace or air conditioner starts and stops in rapid, short bursts instead of completing normal run cycles. Causes include oversizing, a clogged filter, a faulty thermostat or low refrigerant. Wears out equipment quickly.
Single-stage equipment runs at full capacity or off. Two-stage runs at a lower output (around 65%) most of the time and steps up only when needed, giving quieter operation, fewer temperature swings and better humidity control.
A Wi-Fi connected thermostat controllable from a phone, with scheduling, learning, occupancy sensing and energy reports. Many Ontario utility rebate programs include smart thermostats.
Any system with separate indoor and outdoor components connected by refrigerant lines, which describes almost every central air conditioner, heat pump and ductless unit in residential use.
The resistance to airflow inside a duct system, measured in inches of water column. High static pressure means the ducts, filter or coil are choking the system, which raises noise and energy use and shortens blower life.
Any secondary heat source that assists a heat pump on the coldest days: a gas furnace in a hybrid system, or electric heat strips in an all-electric one.
Conditioned air leaving the furnace or air handler on its way to the rooms through the supply ducts and registers.
An on-demand unit that heats water only as it flows through, with no storage tank. Provides endless hot water, saves space and cuts standby losses, but needs periodic descaling in hard-water areas like much of Southern Ontario.
The control that senses room temperature and tells the heating or cooling equipment when to run. Its placement matters: a thermostat in direct sun or near a supply register will misread the whole house.
A unit of cooling capacity equal to 12,000 BTU per hour, the heat needed to melt one ton of ice in a day. Most Ontario homes need 2 to 4 tons; correct sizing comes from a load calculation, not square footage alone.
Technical Standards and Safety Authority
Ontario's regulator for fuel-burning equipment. Anyone installing or servicing gas furnaces, boilers or water heaters in Ontario must hold a TSSA gas technician licence (G1, G2 or G3).
Equipment whose motors or compressors can run across a wide range of speeds rather than one or two fixed settings. Delivers the best comfort, lowest noise and highest efficiency of any equipment tier.
How combustion gases leave an appliance. Natural draft relies on a chimney; power-vent and direct-vent systems use fans and PVC or stainless pipe. Venting must match the appliance efficiency, which is why a new furnace can orphan an old water heater on the chimney.
Manufacturers typically cover parts for 10 years when equipment is registered, but labour is separate and usually 1 to 2 years from the installer. Annual maintenance is often a condition of keeping the parts warranty valid.
A storage tank (typically 40 to 60 gallons) heated by gas or electricity that keeps hot water ready at all times. Expected life is about 10 to 15 years; rusty water or a wet floor usually signal it is time to replace.
A filtration or purification device installed in the ductwork that treats all the air in the home on every cycle, unlike portable units that clean one room. Includes high-MERV media cabinets, electronic air cleaners and UV systems.
Try a shorter word or a different spelling, or ask one of our technicians directly. We are happy to explain anything about your system.
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