Heating and Cooling Systems Glossary Flashcards

Vocabulary flashcards covering fundamental terminology, metrics, and components from the Heating and Cooling Systems course text.

Air scoop

A device installed in the hot water supply main at or near the heating source to separate and direct the air to a cushion tank or automatic air vent.

Airtrol tank fitting

A device installed on the bottom of a cushion tank with a tube or tubes extending up into the tank to simultaneously allow expanded and contracted water flow while discouraging air escape.

Aquastat

An automatic switching device operated by temperature change that can act as a high limit protector or burner control on a hot water boiler.

Boiler horsepower

The evaporation of $34.5\,lb$ ($15.7\,kg$) of water per hour from a temperature of $212^\circ F$ ($100^\circ C$) into dry saturated steam at the same temperature, equivalent to $33,475\,Btu$ ($9.81\,kW$).

British thermal unit

The amount of energy required to raise the temperature of one pound of water through $1^\circ F$, which is $1/180$ of the heat required to raise one pound mass of water from ice point to steam point under constant pressure of one atmosphere.

Condensing Boiler

A high-efficiency boiler ($90\%$ plus) with an additional heat exchanger that extracts sensible and latent heat by condensing combustion water vapor into acidic condensate.

Cushion / expansion tank

A completely closed tank containing water and air (or inert gas) placed upstream of the circulator that allows water in a closed system to expand and contract without appreciable pressure change.

Degree days

A unit measurement based on temperature difference and time; for any day with a temperature below $65^\circ F$, it is the difference between $65^\circ F$ and the daily mean temperature.

Direct return system

A piping system described as "first supplied, first returned" where return water is piped to the boiler by the shortest feasible route.

Reverse return system

A piping system described as "first supplied, last returned" where heat transfer unit return paths are arranged so all circuits are of approximately equal length.

Draft hood

A device built into an appliance or vent connector to ensure combustion product escape during no-draft or back-draft conditions, prevent back draft, and neutralize chimney stack action.

Flow switch

A device installed in piping that opens a circuit if no flow is present to protect the boiler in the event of circulator failure.

Force Flow Heater

A convector unit equipped with an added blower to move greater quantities of heated air, specifically suited for large entrance ways.

Latent Heat

The change in heat content of a substance when its physical state is changed without a change in temperature.

Lock Shield Valve

A radiator valve covered with a metallic cap that shields the spindle from accidental adjustments after being set with a spanner.

Low - temperature boiler

A boiler limited to a maximum operating temperature of $121^\circ C$ ($250^\circ F$).

Low-pressure boiler

A boiler connected to a system limited to a maximum working pressure of $30\,PSIG$ for water or $15\,PSIG$ for steam.

Low water cut-off

A float-operated or electronic probe device used to shut down fuel to the burner when boiler water drops below its operating level.

Monoflow or venturi tee

A tee used on one-pipe forced hot water heating systems to create an obstruction in the pipeline and an inspiration effect on the downstream side.

Passive Air

Natural exchange of fresh air through non-airtight building structures driven by wind, temperature differentials, and thermal buoyancy.

PSIA

Pounds per square inch absolute, which is the sum of gauge pressure and atmospheric pressure.

PSIG

Pounds per square inch gauge, representing pressure above atmospheric pressure.

Sensible Heat

Heat that, when added or subtracted, results in a change of temperature without changing the physical state of the substance.

Thermostatic Radiator Valve

A self-actuating valve controlling flow to a heat transmission unit using a liquid-filled capillary tube that expands and contracts with ambient temperature changes.

Vent damper

A device installed on the vent immediately above the boiler that closes to prevent warm air escape when not firing and opens upon a call for heat.

Wild Loop

An uncontrolled piping loop connecting supply to return piping (such as wall fin in a crawl space) that maintains continuous flow for freeze protection.

Wiredrawing

The knife-like cuts or cutting away erosion effect on a valve disc, plug, or seat.