Gas Appliance Glossary

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Gas Appliance Terminology

• Automatic Cut-off

  A device used on some regulators to close the main valve in the event of pressure deviation outside of a preset range. Must be reopened manually.

• Ceramic Briquettes

  These are used underneath grill plates and above burners to enhance BBQ flavors and ensure an even heat distribution.

• Ceramic Burner

  A ceramic material is used to absorb and reflect heat energy from a gas flame to reinforce and raise the intensity of heat output. This reduces cooking times and reduces energy use.

• Control Valve

  A mechanically, electrically, or hydraulically operated valve, using an external power source to effect its operation, that modifies the fluid flow characteristics in a process. It consists of a valve connected to an actuator mechanism that is capable of changing the position of the flow controlling element or closure member in the valve in response to a signal from the controlling device.

• Diaphragm

  A flexible membrane used in a regulator or relief valve to sense changes in downstream pressure and respond to them, thus moving the restricting element or closure member to which it is attached.

• Drip Tray

  Shallow metal tray located under the burners of a BBQ or Grill to reduce fire risk and improve upkeep of appliance by ensuring any hot oils and fats produced during use are collected ready for disposal. Usually used with a fat absorbing material (such as sand or Fat Absorber).

• Electrode

  An electrode is an electrical conductor used to make contact with a non-metallic part of a circuit. A high voltage discharge can jump (arch) from the end of an electrode (as an anode) across an air space to discharge on a metal surface (cathode) to create an ignition spark (the arch).

• Fat Absorber

  This is a non-caking mineral-based material placed in a drip tray, it is used to absorb fats and reduce smells. Similar texture to cat litter.

• Flame Failure Device

  This is a safety device that reduces the risk of any problems should a flame extinguish. When there is a flame the device senses a high temperature and allows gas to flow. If the flame extinguishes, the device senses a drop in temperature and triggers a valve that stops gas from flowing. Once the flame returns the device allows gas to flow again.

• Flame Tamer

  This device sits between a gas burner and the underside of a grill plate or hotplate. It is used to protect the burner form excess fats and oils falling into the flame and therefore reducing the chance of a flame being created beyond that produced by the burning gas.

• Hot Plate

  This s solid grill plate with no open grooves that sits above a gas-grill burner providing a large cooking surface area. Even heat distribution is needed for fire safety and even cooking temperatures for food quality.

• Infra-Red

  This is a highly intensive radiated heat output, achieved from a short wave heat energy at the highest temperature, with the shortest wave length. Typically the colour of the heating element producing the short heat waves is red/amber/white. The heat wave only heats objects in its path, however these objects can convect heat to surrounding areas once sufficient heat has been absorbed.

• Internal Relief Valve

  A small, spring loaded pressure relief valve contained within the regulator at the center of the diaphragm to prevent outlet pressure from exceeding a predetermined pressure.

• Over Pressure Cut Device

  A mechanical device incorporated in a gas pipework system to shutoff the supply of gas when the pressure at the sensing point rises to a predetermined value.

• Piezo Ignition

  Consists of a small, spring-loaded hammer which, when a button is pressed, hits a crystal of PZT or quartz crystal. Quartz is piezoelectric, which means that it creates a voltage when deformed. This sudden forceful deformation produces a high voltage and subsequent electrical discharge, which ignites the gas. No electric connection is required, though wires are sometimes used to move the sparking location away from the crystal itself. Piezo ignition systems can be operated by either a lever, separate push-button or built into the control knob. Only one spark is generated per turn of the knob or press of the button.

• Pitot Tube

  A hollow tube that connects the area beneath the regulator diaphragm with the vena contracta area of gas flow. The pitot tube causes the diaphragm to sense a pressure lower than that which exists downstream of the regulator, and thus allows the regulator to open more for any given change in downstream pressure. The result is increased regulator accuracy.

• Powder Paint Coating

  A paint process that uses dry powder with no solvents for surface finish. Dry powder can be reused, thereby reducing waste and pollutants. The powder coating over a clean surface provides better corrosion resistance than liquid coat.

• Pressure Relief Valve

  A valve that opens and closes to ensure that pressure does not rise above a predetermined value.

• Reflector

  This a metal reflective device that allows radiant heat to be reflected to desired directions, and in some cases used to reduce overheating of materials behind the reflector.

• Regulator (Valve)

  The device which governs the flow of gas to a gas appliance.

• Roasting Rack

  Used to lift meats above the base of a cooking dish when a roast is to be cooked under a hooded gas grill.

• Rotisserie

  This device is positioned across a gas grill, raised above the grill plates so that food (normally a meat joint) can be turned automatically around on a pole (spit) ensuring even cooking and distribution of any juices/fats from the food.

• Sear Zone

  Using infra-red heating and ceramic technology, this is a zone that will generate intense and responsive heating to seal foods (even burning outer skins for effect). The zone is often used with a moving rotisserie to avoid food staying in one place and risk being unintentionally burnt.

• Side Burner

  On some gas grills there is a separate horizontal ring burner, similar to those on a gas hob, used to heat pans and trays for cooking food. These are used as additional heating surfaces to the grill and various pan and tray shapes can be used.

• Teflon Coated

  This is a special non-stick coating applied to a cooking surface. Careful use with non-metal utensils and non-scratch cleaning of the surface is in needed to avoid scratching and eventual erosion of the non-stick properties.

• Thermostat

  A device that automatically maintains a predetermined temperature in an appliance or component.

• Tilt Switch

  This is a safety device that reduces the risk of any problems should a heater fall over. When a heater is sitting on the floor the switch provides a connection and allows electricity to flow. If the heater falls over, the switch becomes an open circuit and electricity no longer flows, hence disabling the device. Once the heater is set upright again the switch connects the circuit and the heater operates again.

• Timer

  A timer is used to preset the heater's hours of operation. 24 hour timers can set on/off times over one 24 hour period, then need to be reset. A 7 day/24 hour timers can set on/off times over a week and a 24 hour period (example: you can have an appliance switching on/off every Tuesday and Thursday between 7am and noon).

• Trivet

  This also known as a hot plate, and is placed between a serving dish/bowl and the heated surface, to protect the serving dish/bowl.

• Valve

  A device used for the control of fluid or gas. It consists of a fluid retaining assembly, one or more parts between end openings, and a movable closure member which opens, restricts, or closes the parts.

• Venturi Tube

  This tube is located between a burner and a control valve (operated by the control knob of a gas appliance). This must be kept clean to allow gas to flow from the valve through to the burner. A Venturi is fitted with aeration holes to allow air to be pulled into the fuel air mixture required for combustion.

• Vitreous Enamel

  Heat treated enamel paint that is cured while drying to provide hard wearing surface protection.

• Warming Rack

  A wire rack that extends over the width of a hooded gas grill so that food can be kept warm, this removes the need for food to be kept on the flat grilling plates.

Energy Measurements

• BTU (British Thermal Unit)

  Energy required to raise the temperature of 1 lb of water from 60°F to 61°F at 1 atmosphere pressure.

• Demand

  The rate at which fluid is delivered to or required by a system, part of a system, or a piece of equipment, usually expressed in terms of volume per unit of time.

• Differential Pressure

  The difference in pressure between two points in a system.

• Flow Capacity

  The rated flow through a regulator under stated in let, outlet, and droop pressures.

• Gauge Pressure

  Pressure reading as shown on a gauge (psig or bar g). The difference between atmospheric pressure and the pressure the gauge is measuring.

• Inlet Pressure

  The pressure at the inlet opening of a valve (PI).

• Kilowatt (kW)

  The SI unit of power. It is used to specify the thermal performance of a heater (kW Heat Produced) as well as the power energy it consumes (kW Energy Consumed). Kilowatts are used as energy measurement for heat output in gas appliances such as storage water heaters. Kilowatts are typically used in relation to electricity and have limited use within gas appliances although they are accepted as an additional marking for use on applicable gas appliances.

• Kilowatt Hour (kWh)

  The standard unit of sale of electricity; it is the equivalent power consumed by a purely resistive load of 1000 Watts (1kW) for 1 hour. Your electricity supplier will specify the price in your supply contract. This measurement is now often used for all energy types.

• Maximum Operating Pressure

  The maximum pressure existing in a piping system during normal operation.

• Megajoules

  The primary measurement of energy used in the Gas Appliance Industry. 1Kg of LPG will produce to 50MJ of energy.

• Operating Pressure

  The actual pressure at which a device operates under normal conditions. This pressure may be positive or negative with respect to atmospheric pressure.

• Outlet Pressure (Reduced Pressure)

  The pressure leaving the outlet opening of a valve (P2).

• Rate of Flow

  The volume of material passing a given point in a system per unit of time.

• Rated Working Pressure

  The maximum allowable pressure specified by the manufacturer.

• Temperature Rise

  Difference between existing and desired water temperature. Number of degrees (ºC) water must be raised, whether from inlet or preheated water.

• Thermal Efficiency

  The rate at which heat exchange surfaces transfer heat to the transfer medium (e.g., air to water or water or air). It is typically measured as the ratio of BTU output of hot water to BTU input of fuel. Types of heat movement that impact thermal efficiency: Conductive/Convective heating surfaces also referred to as secondary or indirect heating surfaces including all surfaces exposed only to hot combustion gases. or Radiant heating surfaces also called direct or primary heating surfaces and consist of heat exchanger surfaces directly exposed to radiant heat from the flame. Radiant heat transfer is tremendously more effective than conductive/convective heat transfer and, contrary to commonly accepted belief, is where most of the heat transfer occurs in a boiler, furnace or forced air system.

• Watts

  Measurement of power. One watt is equivalent to one joule per second of energy (or one unit of power = one volt x one ampere).

• Weight, Specific

  The weight per unit volume of a substance. The same as density.

Energy Systems

• Compressor

  The compressor is often referred to as the heart of the refrigeration or heat pump system. It serves two main purposes. The first is to circulate the refrigerant fluid through the circuit like a pump, the other is to compress and raise the pressure and temperature of the refrigerant vapor so that it can easily be condensed back into a liquid to resume the heat transfer process.

• Condenser

  In refrigeration systems the condenser is the heat exchanger where Hot, compressed refrigerant gas is condensed to a liquid and further cooled to recommence its journey around the circuit.

• Convection Heater

  Convection heaters provide quiet background warmth. The air adjacent to the heating element is warmed causing it to rise and creating natural warm air circulation in the room. Convection heaters are best suited to space heating.

• Cooker

  This is a cooking device which may be installed (see cook top) but can be a free standing device including pans and woks with a feed from an LPG cylinder. These can be used in camping situations but are often used in kitchens. In such situations, cylinders should not exceed 4.5kg and should not be in a sealed or enclosed environment if installed in a building.

• Countdown Timer

  A countdown timer turns the heater off after a preset amount of time and is a useful economy measure for commercial rooms with limited occupancy such as cafeterias, motels and classrooms.

• Heat Exchanger

  A device that transfers heat from one medium to another via a physical conductive material without a mixing of the mediums, such as air to water, water to water, water to air and air to air.

• Heat Settings

  Heat settings allow the thermostat to be adjusted to the desired level of comfort.

• Mobile/Portable Heater

  This is a mobile gas fired heater which is designed for mobility and in many cases will be on wheels. These are usually run on LPG but may be run on compressed natural gas from a cylinder inside of the heater. Some heaters may be capable of running from a bayonet style fitting from line gas. There should always be sufficient ventilation when using these heaters. It is recommended that, where possible, windows be kept open.

• Patio Heater

  A gas heater used to heat an outdoor or semi enclosed area. These are free standing devices and usually have a cutout switch for protection if knocked over. Typically these are run on LPG cylinders however they may be run from natural gas if properly fitted by a Craftsman Gasfitter subject to the manufacturers' instructions. These should not be used inside, or in a fully enclosed area without good ventilation.

• Radiant Heater

  Radiant heaters provide quiet directional heat. The heating element emits infrared heat that travels through the air to heat objects directly. Radiant heaters are best suited to spot heating objects in open or enclosed spaces.

• Radiation

  The combined processes of emission, transmission, and absorption of energy traveling as electromagnetic waves.

• Refrigerant

  The heat transfer fluid contained in a heat pump refrigeration circuit. Normally this is a chemical contained in a hermetically sealed circuit that has a low temperature boiling point; refrigerants can be one of a number of man made Fluorocarbons or a Hydrocarbon compound (refined Propane or Isobutane).

• Smoke

  Visible gaseous product of incomplete combustion. Smoke varies with its source, but it usually comprises hot gas and suspended particles of carbon and tarry substances, or soot. Proper firing techniques and equipment can eliminate or greatly reduce the smoke produced by any fuel. Wood gives little smoke if burned when dry and if the fire is given a good supply of air.

• Test Gases

  This is a description used in Standards and Regulations to describe a gas mixture that is required to be tested before being deemed legal to sell in New Zealand. New Zealand test gases are different to those in other countries due to the nature of the gas presently delivered by gas retailers. Test Gases are described in Standards documents and can be mimicked by test laboratories within or outside of New Zealand. All gas appliances must be capable of burning New Zealand gases so this must be demonstrated. If a gas appliance burns Propane or Butane only, this must be made particularly clear to the buyer.

• Thermostat

  A thermostat maintains the room at an even temperature and conserves energy by operating the heater only when needed.

Fuel and Exhaust Terminology

• Butane

  Component of raw natural gas, contains . A gas best known for being contained in cigarette lighters and aerosols. Often this gas is sold in prepackaged containers as it is used in camping for lighting and cooking.

• Carbon Dioxide (CO₂)

  A colourless, odorless, tasteless gas that is about one and one half times as dense as air under ordinary conditions of temperature and pressure. It does not burn, and under normal conditions, is stable, inert and nontoxic. Although it is not a poison, it can cause death by suffocation if inhaled in large amounts. Carbon dioxide occurs in nature both free and in combination. Because it is a product of combustion of carbonaceous fuels (e.g., coal, coke, fuel oil, gasoline, and cooking gas), there is usually more of it in city air than in country air. Some sources indicate that the natural balance of carbon dioxide in the atmosphere is growing from its stable level of 0.13% to a predicted 0.14% by the year 2000. It is anticipated that this extra carbon dioxide will fuel the greenhouse effect, warm the atmosphere, and further disrupt the natural carbon dioxide cycle (see Global Warming).

• CNG

  Compressed Natural Gas used for transport fuel.

• CO

  This is more commonly known as Carbon Monoxide and is an unwanted gas. It is created when fossil fuels are burnt with insufficient oxygen for correct and complete combustion to occur. It is a potentially lethal gas in large quantities. Output of CO from gas appliances is strictly governed with appropriate warnings where potential dangers exist. CO is dangerous in confined and unventilated spaces and there are risks of excess CO leaking from old appliances which have either not been serviced or have been modified in such a way as to not allow the gas to burn correctly and completely.

• Coalgas

  Gas produced from Coal. Use of this gas has declined to virtually nil in favour of Natural Gas.

• Flare Up

  This occurs when there are excessive fats and oils building up on a burner resulting in their ignition and additional flames being created .

• Fuel Gas

  A commonly distributed gas used for fuel, such as natural gas, propane, landfill gas, etc.

• Gas

  That state of matter which expands to fill the entire container which holds it. Gas is one of the forms of matter (solid, liquid, and gas).

• Liquefied Petroleum Gas (LPG)

  Butane, propane, or a mixture of the two, obtained from oil or gas wells, or as a by product from the refining of gasoline. It is sold in metal bottles under pressure as a liquid: hence, sometimes called bottled gas. Liquefied Petroleum Gas is a mixed gas made up of Propane and Butane in New Zealand.

• Natural Gas

  Combustible mixture of methane and higher hydrocarbons used chiefly as a fuel or raw material. This is the main reticulated gas in New Zealand sourced from North Island gas fields such as Maui, Kupe and Kapuni.

• Propane

  An easily liquefiable hydrocarbon gas. Propane is one of the components of raw natural gas, and it is also derived from petroleum refining processes. Its chemical formula is C₃H₈.

Industry Terms

• AGA

  The American Gas Association or Australian Gas Association.

• Air Intake Terminal

  Fitting at inlet of air intake pipe allowing outside atmosphere into air intake pipe or burner venturi.

• ALPGA

  Australian Liquefied Petroleum Gas Association, Ltd.

• ANSI

  American National Standards Institute.

• Appliance (Equipment)

  Any device that uses gas as a fuel or raw material to produce light, heat, power, refrigeration, or air conditioning.

• Capacity, Flow

  The amount of a specified fluid that will flow through a valve, specific length and configuration of tubing. a manifold, fitting, or other component at a specified pressure drop in a fixed period of time. (SCFH, gpm, NmJIh, Lpm, bph).

• Capacity, Rated

  The rate of flow through the regulator specified by the manufacturer for a given inlet pressure, outlet pressure, offset, and size.

• CGA

  Canadian Gas Association.

• Clean Air

  A Governemnt requirement for fuel to be completely gasified and burned, producing a minimum of polluting by products such as smoke, creosote or ash.

• Cold Spot

  An area on a grill plate that is not reaching the desired temperature to ensure safe and consistent cooking conditions, a grill plate should achieve a consistent temperature.

• Combustion Efficiency

  This is a measurement (in percent) of how well solid and gas heating equipment converts fuel into useable heat energy. Complete combustion efficiency (100%) would extract all the energy available in the fuel, though this is not realistically achievable due to flue loss and boiler/heater shell losses. Combustion efficiency calculations assume complete fuel combustion and the following three factors:

  1. The chemistry of the fuel (the proportions of hydrogen, carbon, oxygen and other compounds this is the fuels calorific value CV) and how much energy is chemically bound in the fuel.

  2. The net temperature of the flue gases or how much heat is not being used.

  3. The percentage of oxygen (O₂) or carbon dioxide (CO₂) by volume after the combustion process or how much O₂ did the fuel completely burn (affected by the ventilation available for the heater to burn fuel correctly).

• Conduction

  Heat transfer through a material from more energetic particles to less energetic particles.

• Convection

  Heat transfer occurring between a fluid in motion and a bounding surface when the two are at different temperatures.

• CSA

  Canadian Standards Association.

• DVGW

  Deutscher Verein des Gas und Wasserfaches e.v. (German approval agency).

• Dynamic Unbalance

  The force exerted on a valve plug when fluid is flowing through the valve.

• EER (Energy Efficiency Ratio)

  This is the ratio of the energy in and the chilled air out when a heat pump is in cooling mode. The rated capacity is divided by the rated total power input. In practice this is expressed as a single figure or sometimes as a percentage. For example, a system that is rated in cooling at 7kW, with a rated power consumption of 1.9kW will have an EER of 3.68 or 368% (7/1.9 = 3.68). In this instance for every 1kW of electricity purchased the heat pump is producing 3.68 times the amount of chilled air.

• Electrode

  Conductor that transfers electric charges into or out of another conducting medium, or that influences the flow of current in another conducting medium.

• Flow Rate

  The amount (mass, weight, or volume) of fluid flowing through a valve body per unit of time.

• Fluid

  Materials in a liquid, gas, or vapor state, as opposed to a solid.

• Forced Air

  A system that uses fans and blowers to move heated air through ducts to heat the home.

• Fossil Fuel

  A hydrocarbon deposit, such as petroleum, coal, or natural gas, derived from living matter of a previous geologic time and used for fuel. All fossil fuels produce carbon dioxide when burned and are a main cause of air pollution. (See greenhouse effect.)

• NACE

  National Association of Corrosion Engineers.

• NES

  The National Emission Standards set by Ministry for the Environment.

• Non Clean Air

  This term refers to wood fires that do not meet the minimum air quality standards for particulate emissions (grams of carbon per kg of wood burnt). Non-clean air fires can still be used in properties located on land greater than 2ha.

• Radiant

  Radiant heat provides quiet directional heat.

• Range

  The region between the limits within which a quantity is measured, received, or transmitted, expressed by stating the lower and upper range values (Example: 3 to 15 psi; 40° to 212°F (40° to 1000 e»).

• Reseat Point

  In a relief backpressure valve which is opened by an increase in inlet pressure, the point where the valve closes.

• Rural Wood Fire

  A non-clean air approved wood fire on a section of 2 hectares or more.

• Safety Shut Off Valve

  Valve automatically closed by safety control system or by emergency device. May be automatic or manual type.