A central vacuum spec sheet mixes three kinds of lines: performance (air watts, water lift, CFM), construction (motor type, stages, canister, filtration), and installation (amps, intake position, exhaust, clearance, weight). A few lines are marketing and can be skipped. This page goes through every line you are likely to see, says what it means, and says whether it matters for your decision.
How to read a spec sheet in order
- Air watts. The headline. Compare units on this.
- Water lift and CFM. Confirm the balance suits your pipe run and floors.
- Collection method and filtration. Bagged, bagless, hybrid; sealed; HEPA.
- Motor type and count. Bypass vs flow-through; single vs dual; stages.
- Amps and power connection. Does your circuit carry it; plug-in or hardwired.
- Physical and install lines. Intake position, exhaust, clearance, weight.
- Warranty. Length and what is covered.
- Everything else. Convenience features.
Air watts explained covers the first two steps in depth. The rest is here.
Performance lines
| Line | What it means | Does it matter |
|---|---|---|
| Air watts (AW) | Useful vacuum power, calculated from airflow and suction together under ASTM F558 | Yes; the primary comparison |
| Water lift (in of water, sealed suction, static pressure) | Maximum suction with the intake sealed; the force available to overcome pipe and hose resistance | Yes, for long pipe runs |
| CFM (airflow) | Volume of air moved with the intake open | Yes, for carpet; falls under restriction |
| Peak horsepower (HP) | A momentary motor figure with no standard behind it | No; ignore |
| Amps (A) | Current drawn at 120V | For the circuit, not for performance |
| Watts (input) | Electrical power consumed | Same as amps; not output |
| “Rated for up to X sq ft” | Manufacturer’s rough estimate of home size served | Weak guide; size by longest run instead |
| Performance “at the motor” or “motor rating” | Measured on the bare motor before canister losses | Discount; not comparable to unit-rated figures |
Motor and construction lines
| Line | What it means | Does it matter |
|---|---|---|
| Motor type: tangential bypass, peripheral bypass, flow-through (thru-flow) | How the motor is cooled and where exhaust exits | Yes; bypass lasts longer under restriction, tangential supports outdoor venting |
| Motor brand: Ametek Lamb, Domel | The motor supplier | Yes, for replacement part availability |
| Motor diameter (5.7 in, 7.2 in) | Fan housing size; larger moves more air | Quick read on unit class |
| Stages (1, 2, 3) | Number of fans; more stages means more water lift, less CFM | Yes, for matching to pipe run |
| Single or dual motor | One or two motors in parallel | Dual for very large homes only |
| Soft start | Electronic ramp-up on starting | Longevity and comfort; not performance |
| Thermal protection | Motor shuts off when overheated and resets | Expect it; good to have |
| Carbon brushes: replaceable | Whether brushes can be changed without a new motor | Yes, for long-term repairability |
| Motor module: replaceable | Whether the motor is a drop-in part | Yes; this is how units reach 25 years |
| Canister material: steel, powder-coated steel, plastic | Durability and appearance | Steel for a garage; plastic is fine indoors |
| Capacity (gallons or liters) | Dirt bin or bag volume | Convenience; affects height and clearance |
Collection and filtration lines
| Line | What it means | Does it matter |
|---|---|---|
| Bagged, bagless, hybrid | How dirt is collected | Yes; the main lifestyle decision |
| Cyclonic, true cyclonic, filterless | Separation by spin; filterless must vent outdoors | Yes; check the exhaust requirement |
| Inverted bag, self-cleaning filter | Cloth bag that sheds its cake when the motor stops | Yes; defines emptying and maintenance |
| Filter type: pleated, foam, cloth, cartridge | Secondary filter construction | Moderate; pleated and washable is convenient |
| HEPA, HEPA-type, HEPA media | Whether the filter meets the HEPA standard or merely resembles it | Only “HEPA” with a sealed system is meaningful |
| Sealed system | Gaskets so all air passes the filters | Yes, if filtration matters to you |
| Exhaust filter | Filter at the exhaust port for non-vented installs | Only if you cannot vent outdoors |
| Bag-full indicator | Light or gauge showing bag or filter load | Convenience |
| Bag type or part number | Which bags fit | Yes; confirm availability |
Bagged vs bagless and filtration and HEPA explain the trade-offs behind these lines.
Electrical and control lines
| Line | What it means | Does it matter |
|---|---|---|
| Voltage (120V, 240V) | Supply voltage | Yes; 240V units need a dedicated circuit and an electrician |
| Amps | Draw at the rated voltage | Yes; check against the circuit, especially dual motor |
| Plug-in or hardwired | Whether the unit has a cord and plug or is wired in | Hardwired is an electrician’s job |
| Dedicated circuit required | Manufacturer requires its own breaker | Yes; a licensed electrician installs it |
| Low-voltage terminals (24V) | Where the inlet control wire connects | Standard on all units; nothing to decide |
| Low-voltage transformer, relay, or circuit board | The control electronics | Repairability; are they sold as parts |
| Utility inlet on unit | An inlet on the canister for a hose in the garage | Convenience for garage and car |
| Run-time delay | Unit runs a few seconds after the hose is removed to clear the pipe | Minor convenience |
| Diagnostic lights | Indicate power, bag full, service due | Convenience |
Installation and physical lines
| Line | What it means | Does it matter |
|---|---|---|
| Intake position (left, right, both, top) | Where the 2-inch pipe connects | Yes; must meet your pipe stub, or plan an elbow |
| Intake size (2 in OD) | Pipe standard | Expect 2 in; anything else is non-standard |
| Exhaust port position and size | Where the exhaust pipe or muffler connects | Yes; plan the run to outdoors |
| Dimensions (height, diameter or width, depth) | Overall size | Yes; fit in the space |
| Clearance below | Room needed to remove the bag or bin | Yes; often a foot or more |
| Weight | For the bracket and the wall | Mount to studs; matters for drywall |
| Mounting bracket included | Whether you need to buy one | Check |
| Muffler included | Exhaust silencer | Check; usually worth adding |
| Operating temperature range | Where it can be mounted | Avoid unheated spaces in cold climates |
| Noise (dB) | Sound level, with or without a stated distance | Rough guide only; not comparable across brands |
Warranty and support lines
| Line | What it means | Does it matter |
|---|---|---|
| Motor warranty (years) | Coverage on the motor specifically | Yes; the main failure point |
| Unit or canister warranty | Coverage on the housing, board, and other parts | Yes; often different from the motor |
| Lifetime warranty | Usually limited and defined narrowly; read the terms | Read the exclusions |
| Authorized installer required | Warranty valid only with dealer installation | Yes, if you plan to buy online or DIY |
| Parts availability | Whether bags, filters, motors are sold separately | Yes; decides whether the unit is repairable at year 12 |
Lines that do not matter
- Peak horsepower. No standard, no correlation with cleaning. Air watts explained covers why.
- “Commercial grade” or “professional” without a spec behind it. Marketing.
- Square-footage ratings without a pipe-run basis. Use the system sizer.
- Bare-motor ratings presented as unit ratings. Measured before the canister, bag, and filter reduce them.
- Color and finish. It lives in the garage.
- Gallon capacity as a performance line. It is a convenience line.
- Decibels without a distance. Not comparable.
Glossary of terms on spec sheets
| Term | Meaning |
|---|---|
| Air watts | Useful vacuum power; airflow times suction, scaled |
| ASTM F558 | The test standard most air watt ratings follow |
| Bypass motor | Motor cooled by a separate fan, not by the working air |
| CFM | Cubic feet per minute of airflow |
| Cyclonic | Separation of dirt by spinning the air |
| Direct-connect | Inlet and hose that carry 120V through the connection |
| Flow-through (thru-flow) | Motor cooled by the working air |
| HEPA | Filter standard: 99.97 percent of 0.3 micron particles |
| Hybrid | Unit that runs bagged or bagless |
| Inverted bag | Cloth filter bag hanging open-end-up that sheds dust when the motor stops |
| Low-voltage | The 24V control circuit that starts the unit from the inlets |
| Pigtail | Electric hose powered by a cord to a wall outlet |
| Sealed suction | Water lift; suction with the intake blocked |
| Sealed system | Gasketed air path so all air passes the filters |
| Soft start | Electronic ramp-up to reduce inrush current |
| Stages | Number of fans on the motor shaft |
| Tangential discharge | Exhaust directed out a horn; allows piping outdoors |
| Thermal protector | Overheat cutoff that resets when cool |
| Utility inlet | Hose inlet on the canister itself |
| Water lift | Sealed suction measured in inches of water |
What to do next
With the spec sheet decoded, compare two or three candidate units on air watts, then on water lift or CFM for your situation, then on collection method and warranty. Motor types explains the construction lines in more depth, and the buying guide puts the spec comparison in its place in the decision order.
Frequently asked questions
What specs matter most on a central vacuum?
Air watts first, as the single measure of cleaning power. Then water lift if your pipe run is long, and CFM if you have deep carpet. After that, the collection method and filtration, then amperage and intake position for installation. Peak horsepower and square-footage claims are the least useful lines.
What does 'rated for up to 8,000 sq ft' mean on a central vacuum?
It is the manufacturer's estimate of the largest home the unit will serve, usually assuming a reasonable pipe run and a 30 ft hose. It is a rough guide, not a measurement. A sprawling 4,000 sq ft home with the unit at one end can load a motor harder than a compact 8,000 sq ft one. Size by your longest run.
What is the difference between air watts and amps?
Air watts measure the useful vacuum power the unit produces. Amps measure the electrical current the motor draws. A more efficient motor produces more air watts for the same amps. Compare on air watts; use amps only to check the circuit.
How loud is a central vacuum in decibels?
Manufacturers rarely publish a decibel figure, and when they do the measurement distance and conditions vary, so the numbers are not comparable across brands. Treat a published dB figure as a rough guide. The unit is in the garage or basement; what you hear in the room is the hose and the powerhead.
What does 'gallon capacity' mean on a central vacuum?
The volume of the dirt canister or bag. Larger means fewer emptyings and a taller unit that needs more clearance below. Typical residential capacities are several gallons. It is a convenience spec; it does not affect cleaning.
Why do some spec sheets list water lift in inches and others in kPa or mm?
Different units for the same measurement of sealed suction. North American sheets use inches of water; European and some Canadian sheets use kilopascals or millimeters of water. Convert before comparing, or compare on air watts, which is reported the same way everywhere.