Every HVAC quotation is a wall of abbreviations, and most arguments between a distributor and a contractor are really arguments about what one of those abbreviations means. This is the glossary we hand to new sales staff: what each term measures, how it is tested, and where it is misused.
Capacity: BTU and ton
BTU — British thermal unit. The heat required to raise the temperature of one pound of water by one degree Fahrenheit. Strictly, capacity is expressed in Btu/h, and the “/h” is not optional: 36,000 Btu/h is a rate of heat transfer, 36,000 Btu is a quantity of energy. Quotations drop the “/h” and the meaning survives on context.
Ton (of refrigeration) — 12,000 Btu/h. The name comes from the heat absorbed by melting a ton of ice over 24 hours. It is a rate, despite the name.
| Nominal size | Btu/h |
|---|---|
| 1.5 ton | 18,000 |
| 2 ton | 24,000 |
| 2.5 ton | 30,000 |
| 3 ton | 36,000 |
| 4 ton | 48,000 |
| 5 ton | 60,000 |
Nominal tonnage is a bracket, not a measurement. Actual capacity varies with indoor and outdoor conditions and with the matched combination, which is why a “3-ton” system may deliver something other than 36,000 Btu/h on the submittal sheet at design conditions.
Our own ranges use these brackets plainly: the side-discharge outdoor unit is 1.5 to 5 ton, and the furnace family is 2, 3, 4 and 5 ton.
Airflow is the third capacity number that belongs in the same conversation, in CFM (cubic feet per minute). A coil or air handler needs a sensible airflow for the capacity it is asked to carry. Airflow without static pressure is meaningless, so ratings are stated at a pressure — for example 136 CFM at 0.4 in. w.g. Our dehumidifiers, for comparison, move 170 to 315 CFM depending on model.
Efficiency: SEER, SEER2, HSPF, HSPF2, AFUE, EER, COP
Efficiency ratings are ratios. The trap is that each ratio is defined by a specific test procedure, and a number produced under one procedure cannot be compared with a number produced under another.
SEER (Seasonal Energy Efficiency Ratio) — cooling output over a season divided by electrical energy input over the same season, in Btu per watt-hour. It is a seasonal figure: it accounts for part-load operation and temperature variation, not a single steady-state point.
SEER2 — the current generation of the same metric, produced under an updated test procedure with different external static pressure and other conditions. It is not a rescaling of SEER. A SEER 18 unit and a SEER2 18 unit are not the same unit, and you cannot convert one to the other with a multiplier. When a distributor asks us for “SEER2 18”, that is exactly what we quote: up to SEER2 18 on the side-discharge outdoor unit, and up to SEER2 18 on the SEER2 18 mini-split.
EER (Energy Efficiency Ratio) — the steady-state version: cooling output divided by power input at a single defined condition. Less flattering and more useful for comparing how a unit behaves at full load on a design day.
HSPF (Heating Seasonal Performance Factor) — the heating counterpart to SEER for heat pumps, in Btu per watt-hour over a heating season. HSPF2 is the current-generation version under the updated procedure. For a Canadian buyer these matter more than SEER, because a heat pump here spends its life heating.
AFUE (Annual Fuel Utilization Efficiency) — the percentage of the energy in the fuel that a combustion appliance turns into useful heat over a heating season, including cycling and standby losses. Our furnace family is published at 95% AFUE. For context on how such numbers are used in regulation, Canada’s energy efficiency regulations currently require a minimum AFUE for the covered gas furnace categories — 95% for the main category of single-phase gas furnaces without an integrated cooling component, and 90% for space-constrained furnaces with an integrated cooling component. Minimum standards change; check the current regulation text and the model’s energy efficiency report rather than a brochure.
COP (Coefficient of Performance) — a dimensionless ratio of useful heat delivered to energy input at a defined condition. A COP of 3 means three units of heat out per unit of electricity in. Because COP is condition-specific, always ask at what outdoor temperature it was measured.
SRE (Sensible Recovery Efficiency) — used for ventilators, not for air conditioners: the proportion of sensible heat in the exhaust airstream transferred to the incoming supply. See our note on ERV versus HRV.
Static pressure, and why the fourth number matters
in. w.g (inches of water gauge) is the pressure a fan must develop to move air through a system. It is the reason three numbers are never enough. A fan curve shows airflow falling as static pressure rises; ductwork, filters, coils and grilles all consume pressure. A rating of “152 CFM” is one point on that curve and is not comparable with “152 CFM” at a different pressure.
When you compare two products, compare them at the same static pressure, or do not compare them.
Refrigerant designations
R-410A — the HFC blend that dominated residential equipment for two decades. R-32 and R-454B are the two A2L (lower-flammability) refrigerants you will see on new North American equipment, and both appear in our catalogue — for example R-32 on our mini-splits, cassettes and dehumidifiers, and R-454B on our furnaces.
Two rules for a buyer:
- A rating belongs to a refrigerant. A capacity or efficiency number established with R-410A does not transfer to an R-32 or R-454B version of the same cabinet.
- Never blend refrigerant designations in a specification or a nameplate description. It is a compliance matter, and it is also how a shipment gets held at the border.
Certification marks, standards and registrations
Three different things that get called “approval”:
- A certification mark on a nameplate is a safety listing from a certification body accredited by the Standards Council of Canada. In Canada the mark carries the “c” prefix — cCSA, cETL, cUL — or a combined form. A United States-only listing is not equivalent.
- A performance standard such as an AHRI or HVI programme defines how a rating is produced and verified. The result is a published rating, searchable in a public directory, for a defined product or combination.
- An energy efficiency regulation registration with Natural Resources Canada is an import requirement for regulated products, separate from both of the above.
Ask for all three by name, per model. A supplier who answers with a single word — “certified” — has not answered.
The comparison checklist
Before you put two products side by side on a quotation:
- Same metric generation: SEER2 against SEER2, HSPF2 against HSPF2, never SEER against SEER2.
- Same test conditions, including static pressure for airflow and outdoor temperature for capacity and COP.
- Same refrigerant, or an explicit note that the ratings come from different refrigerants.
- Matched combination, not a single box — an outdoor unit rating belongs to the coil and air handler it was tested with.
- Capacity at the outdoor design temperature for the project, not only at rating conditions.
- Nameplate certification mark in its Canadian form.
- NRCan registration status for the models being imported.
- The document behind the number: submittal sheet, rating reference, test standard.
None of these require a competitor’s name or a price to make the decision. They require a document.
Using the glossary
For the equipment these terms describe, start with the side-discharge outdoor unit, the furnace family, and the SEER2 18 mini-split. For the parts inside them — heat exchangers, cabinets, controls — the core components resources hub collects what we publish. And if you want a specification written against a real project rather than a catalogue bracket, send the load calculation and the proposed models through the RFQ form.