Restaurant Maintenance Glossary

A Alternating Current (AC) – Electrical current that alternates the direction of its flow at regular intervals. In the US, electric companies transmit alternating current. Transformers increase and decrease the voltage of alternating current, so that, for instance, commercial buildings may receive a different voltage than residential buildings. Most US restaurant and food preparation equipment operates on Alternating Current.  If an appliance uses direct current (DC), it usually contains a battery that is charged by AC from a wall outlet and then runs off the battery. Ampere (AMP) –  Amps measure the flow of current through a wire. The faster the current moves, the higher the Amps.  Most electrical appliances are built to handle a certain number of amps. If more amps travel through the device, they can burn out circuits and destroy other components. Surge protectors, circuit breakers, and fuses are designed to protect against excessive currents. If the electrical current exceeds the amps a device can handle, they’re designed to shut down the appliance before the current can destroy vital components. Armature – An armature is copper coils wrapped around a steel shaft as part of an electric motor. If the armature moves, it is also called a rotor.  Armatures can short out, break, or jam.  They’re a common component in appliances which depend upon rotary motion like mixers and fans.   B Bimetal – A piece made of two different kinds of metal welded together. When a bimetal piece is heated or cooled, one metal expands faster than the other, causing it to bend.  The bimetallic strip can be used to control thermostats in ovens, refrigerators, and other temperature-sensitive devices. Certain electrical devices also use bimetallic strips to complete or break circuits. Bleed Gas – Bleed gas is diverted from the main gas line in order to control the pressure in a system. In devices like ovens, pizza ovens, and deep fryers, bleed gas valves control the flow of gas to ensure accurate, even temperatures. Boiler Horsepower – Boiler Horsepower measures the work done by steam boilers. It measures how fast the boiler can generate steam. One Boiler HP is equal to converting 34.5 pounds of water to steam in an hour at 212 degrees Fahrenheit. Devices such as steamers and various cleaning tools may be rated by Boiler Horsepower. Booster – A part used in commercial dishwashers to boost the temperature of the water beyond the temperature of water that comes directly from a hot water heater. Boosters can be gas or electric, and heat the water to 180 degrees Fahrenheit, or about 140 degrees above the level provided by a normal water heater. BTU – A British Thermal Unit. The amount of heat needed to raise the temperature of 1 pound of water by 1 degree Fahrenheit. Gas-powered cooking equipment like ovens, ranges, and grills measure their output in terms of BTUs.  The more BTUs a burner has, the faster in can heat water and food. Bypass – A passageway in a valve that allows gas or liquid to pass around a closed valve.  Valves in ovens, stoves, dishwashers, and other devices have bypasses built in.  A bypass can prevent leaks and relieve pressure. You should never replace a valve that has a bypass with one that does not have a bypass.   C Capacitor – A component used in electronics for storing electricity, smoothing output, and blocking direct current. Many electric motors use capacitors to store the energy needed to start the motor. Most devices which contain electronics have capacitors, including drink dispensers, refrigerators, and ovens. Capillary – A thin, hollow tube that allows liquids and gasses to flow in temperature control systems.  They’re often used in refrigeration systems to help maintain a constant temperature. Centigrade Scale – A measure of temperature used throughout the world. On the Centigrade scale, water freezes at zero degrees and boils at 100 degrees. Many European recipes and products display temperatures in Centigrade instead of Fahrenheit. To convert a Centigrade temperature to Fahrenheit, multiply it by 9, divide by 5, and then add 32.  So, for instance, 10 degrees centigrade is 50 degrees Fahrenheit. CFM – CFM means Cubic Feet per Minute. It describes how quickly a system can move gas. It’s important for judging dryers, blowers, and other systems designed to move gas from one place to another. Combination Gas Valve – A gas control valve that combines the functions of two or more other valves. Combination valves can include smanual valve, actuator valves, automatic safety shutoff valves, pressure regulator valves, and pilot adjustors.  They’re common in ovens, pizza ovens, and other gas-powered cooking devices. Contactor – A switch, controlled by electricity, used for switching circuits with high electrical currents. Most electric heating units contain contactors, including the units in dishwashers and ovens. Continuous Circuit – Also known as a ‘Complete Circuit.’ Electricity only flows through a continuous circuit. If the circuit is broken, electricity ceases to flow. When one component in an electric circuit breaks, the whole circuit is broken.  Then the appliance containing that circuit will no longer function. Current – The rate of flow of electricity. Amps measure current. If an appliance cannot draw enough current or draws too much current, it will malfunction. D Direct Current – Electricity that flows at a steady rate in a single direction. Batteries produce direct current. While most appliances run on alternating current, rechargeable appliances often run on direct current. Diastat – A subassembly of a bulb and capillary thermometer.  It has three parts. The bulb stores the liquid which expands when heated, the capillary is a thin tube that the heated liquid flows through, and the bellows are pieces which the liquid displaces. When they move, they change the position of the mechanical parts that measure temperature. So, in a bulb and capillary thermometer, the diastat is the part that actually reacts in response to increases and decreases in temperature.  Any device which has temperature controls, such as a steamer, refrigerator, or fryer, may have a diastat in its thermostat. Differential – In devices with a cycling thermostat, the differential is the difference in temperature between when the heating or cooling element is ‘on’, and when it is ‘off’. Devices such as dishwashers often have cycling thermostats. Direct Spark Ignition – A continuous spark created by high voltage electrodes. Direct spark ignition is often used for the main burners on stoves and ovens. Disposer – Also called garbage disposal, a disposer is a device that chops up food waste so it can be washed down a sink and into the sewage system. Disposers require regular maintenance, especially for the blades, washers, and gaskets. Double Pole Switch (DP) – A double pole switch controls two electric circuits at once.  It can either turn them both on, turn them both of, or switch between them. For instance, a switch that turned on both an overhead light and an exhaust fan might be a double pole switch. Double Pole Double Throw Switch (DPDT) – A switch with two inputs but 4 outputs, so that it’s a combination of two double pole switches.  Both switches can be on, both can be off, or one can be on and one can be off. DPDT switches are used in a wide variety of equipment, including broilers, ovens, and fryers.   E Energy Cut-Off Device (ECO) – An energy cut-off device shuts down a water heater if the temperature or pressure exceeds certain limits. The ECO kicks in to prevent damage to the unit, explosions, and injury. For most water heaters, the cut –off is 210 degrees Fahrenheit or  99 degrees Celsius. The goal is to keep the water in a hot water heater from reaching the boiling point. This is an international safety standard. F Fahrenheit – A system for measuring temperature where water freezes at 32 degrees and boils at 212 degrees. The United States and its territories, The Bahamas, Beliz, Palau, and the Cayman Islands use Fahrenheit to measure temperature. All other countries use Celsius. To convert Fahrenheit to Celsius, subtract 32, then multiply by 5 and divide by 9. Field Coil – A coil of wire that becomes an electromagnet when electrical current flows through it. It is used in electric motors. You can find field coils in fans, mixers, and grinders.   G Gas Orifice Capacity – The size of the opening in a gas valve affects the BTU of an appliance. Larger valves make larger BTUs possible.  This chart shows the relationship between the size of an opening and BTUs. Glow Coil – A coil of thin wire. When electricity passes through the wire, it grows warm and glows. It lights the pilot light of gas devices like water heaters, stoves, and ovens. Gallons per Hour (GPH) – A measure of the rate of flow for liquid. Gallons per hour is the number of gallons that can flow through an opening every hour. Gallons per Minute (GPM) – A measure of the rate of flow for liquid. Gallons per minute is the number of gallons that can flow through an opening every minute. To find Gallons per hour, multiply gallons per minute by 60.  Gallons per hour and gallons per minute can be used to measure the capacity of water heaters, water coolers, and dishwashers.  A device with a higher gallons per hour rate operates more quickly than a device with a lower rate of flow.   H Hertz (HZ) – A measure of frequency used for alternating current.  It measures the number of cycles in a second. AC current in the US is 60 HZ, abroad it is 50HZ. This is one reason why devices manufactured for use in one country may need an adaptor to function in other countries. Hot Surface Ignition – In a hot surface ignition switch, electricity heats up a metallic element which then lights the pilot light. These switches are found in water heaters, stoves, and boilers. On average, they last from 3-5 years. If the switch fails, the pilot won’t light. However, replacing these switches is often a fairly inexpensive and easy repair. Horsepower – A measure of work used to describe engines and motors. For instance, a typical commercial stand mixer has a .5HP to 1HP motor.   I Inch Water Column (Inch WC) – A measure of pressure used for air or natural gas at low pressures. There are 27.7 Inches of Water Column in one PSI. Infrared Burner – A new cooking technology which allows food to cook very quickly without an open flame, with very high efficiency.  Infrared burners are powered by natural gas, but safer, faster, and easier to clean than traditional gas burners. Intermittent Pilot Ignition – A pilot light that only ignites when an appliance is ready to run, as opposed to one that remains lit all the time. Intermittent pilot ignition is more efficient than a traditional pilot light, because the appliance only burns gas when it is in use. Ovens, water heaters, and other appliances powered by natural gas may use intermittent pilot ignition. Internal Diameter (ID) – The diameter of the opening of a pipe, excluding the pipe’s walls. This measurement is important when you’re considering the rate of flow for appliances such as ovens, dishwashers and steamers. IPS – Iron pipe size. An older pipe-sizing system. IPS is still used by the manufactures of PVC pipes. Older equipment may express pipe size in terms of IPS. J Jet Burner – A burner in which the gas and the air combine above the burner before combustion. Jet burners are superior for heating large pots, pans, skillets, and woks, because they heat the whole bottom evenly. K KPA – Kilopascal. A measure of pressure used in the metric system. One KPA is equivalent to .145 PSI. kW – Kilowatt. 1,000 watts. KWH – Kilowatt hour. A measure of energy production. Electric companies measure use in KWHs. A more energy-efficient appliance uses fewer KWHs for the same amount of work. Line Voltage – The voltage provided by the main power supply to a building. Commericial, Industrial, and Residential buildings all receive different line voltages. Older buildings often have a lower line voltage than newer ones. If your power use regularly exceeds your line voltage, you may trip circuit breakers or cause lights to dim. When shopping for appliances, keep your current electricity supplies and use in mind. Load – Components of an electrical circuit that consume electric power. Anything that produces heat, light, or movement has load. LPG – Liquid petroleum gas, more commonly known as propane. Many appliances can run on propane instead of natural gas. Because propane is delivered to a tank on-site by a distribution company, it makes it possible to use gas stoves, boilers, etc. in areas where there is no municipal gas supply. M Manometer – A device that measures the pressure of gas. It can be useful for troubleshooting gas appliances. Milliamp – one one-thousandth of an amp. Millivolt – one one-thousandth of a volt. Minipilot – A device that combines a thermocouple and a pilot. Minipilots are used in many brands of ranges. N Natural Gas – A naturally occurring form of Methane than can be pumped from the ground and transported by pipeline. Natural gas is a clean-burning efficient energy source. In many areas, it is available as a public utility and is used to run appliances that need heat- for instance, pizza ovens, steamers, ovens and water heaters. Since only certain parts of the country have access to natural gas, many appliances come in both an electric and gas variant. N.C. Switch – A switch that it normally closed. It opens when power is applied. For instance, on many ranges and ovens, the ‘normal’ position for the gas is ‘closed.’ The appliance only opens the valve and releases gas when turned on. N.O. Switch – A switch that is normally open. For instance, many drains on appliances such as dishwashers are normally open. They only close during certain points in the wash cycle, and power must be applied to close them. NPT – The National Pipe Thread Taper. This national standard ensures that the threading on pipes is constant, so that replacement pipes fit with existing pipes and valves.  If a pipe complies with the NPT, it should work with existing appliances and pipes. O OD – Outside diameter. The total diameter of a pipe from edge to edge. Ohm – A unit that measures electrical resistance. If a material has a resistance of 1 Ohm, 1 amp of current will result from 1 volt of electricity. Ohm’s Law – The equation that expresses how resistance relates to current and voltage.  It is most commonly expressed as Ohms= (volts)/(amps). Ohm’s law does not apply to diodes and batteries. Open Circuit – A circuit with a switch open or a break. Since the circuit is not complete, electricity cannot flow through it.   P Parallel Circuit – A circuit with 2 or more paths for electricity to flow through. If one path is incomplete, electricity can still flow through the other paths. Many appliance use parallel circuits so that if a minor component like a light bulb breaks, the device can still function. Pilot Safety Valve – A pilot safety valve is a feature on ranges, ovens, steamers and boilers to prevent gas from leaking when the pilot light goes out. If an appliance has a pilot safety valve, when the pilot light is out the gas line closes and gas cannot escape into the surrounding area. Pipe sizes – In the United States, pipes come in standard sizes. However, the name a pipe is called by does not accurately reflect its diameter. The following chart gives the sizes for standard pipes.

Nominal Pipe Size	Inside Diameter	Outside Diameter
1/8"	.269	.405
1/4"	.364	.540
3/8"	.493	.675
1/2"	.622	.840
3/4"	.824	1.050
1"	1.049	1.315
1-1/4"	1.380	1.660
1-1/2"	1.610	1.900
2"	2.067	2.375
2-1/2"	2.469	2.875

  Pressure Drop – As gas passes through pipes, it loses some of its pressure. The pressure drop is the amount of pressure the gas loses. When running pipe, you need to make sure that the pressure drop is not so large that appliances at the far end of the pipe will be unable to function. Primary Side of Transformer – The side of a step-down transformer that has the higher voltage. The “input” side for the transformer. Pressure Reducing Valve – A valve that can be set to reduce water, steam, air, or gas pressure to a certain amount. PSI – Pounds per square inch. A measure of pressure. PSIG – Pounds per square inch gage. A measurement of pressure on a surface excluding atmospheric pressure. Q R Relay – The part of a control circuit that provides power to switches, valves, or motors. If the relay is damaged, the switch, valve, or motor will not receive power and will not operate. Most appliances contain one or more relays. Resistor – A device that limits the current flowing through a circuit. If a resistor blows, too much current may throw through the circuit and some delicate devices could be damaged. Rheostat – An adjustable resistor. In a circuit containing a rheostat, the amount of resistance can be adjusted depending on the need. S Safety Pilot Valve – An alternate name for Pilot Safety Valve Secondary Transformer Winding – The output side of a step-down transformer. It has the lower voltage. Series Circuit – An electrical circuit with only one path for the flow of current. If there is a break or a broken component anywhere in the circuit, electricity cannot flow and none of the components can work. An example of a series circuit is a string of Christmas lights where all the lights go out if one bulb breaks. Solenoid – An electro-magnet composed of copper wire wrapped around a metal core. Solenoid Valve – A valve that opens, shuts, or changes direction using an electromagnet. When the magnet is energized, the valve is in one position, and when it’s not energized it’s in another position. Many ovens, dishwashers and other devices use solenoid valves. Solid State Relay – Also known as an SSR, a solid state relay has no moving parts and uses a low voltage to switch between ‘on’ and ‘off.’ Because it has no moving parts, it can switch more quickly than an typical electromagnetic switch. Many ovens use solid state relays Single Pole Double Throw Switch – Also known as a toggle switch, a SPDT switch controls two circuits at once. When one circuit is closed, the other is open. The switch changes between the two. SPDT switches are used to switch between ‘modes’ on an appliance. For instance a switch that changes an ice machine from ‘crushed ice’ to ‘cubed ice’ might be a SPDT switch. Single Pole Single Throw Switch – The most basic type of switch. A single pole switch can either make a circuit (when it’s on) or break a circuit (when it’s off). Power switches on appliances and light switches are common single pole switches. Standing Pilot – A pilot light that always remains lit. Standing pilots use a small amount of gas even when an appliance like an oven or boiler is not in use. Many older models of appliances have standing pilot lights. Steam Temperature/Pressure – The pressure reading on a gauge can help you determine the temperature of the steam in your steamer.  Use the following table to relate steam pressure to Steam Temperature:

Steam Pressure Reading (PSIG)	Steam Temperature (Degrees Fahrenheit)
0	212
2	218.5
4	224.4
6	229.8
8	234.6
10	239
15	249.7
25	266.8
30	274
40	286.7
50	297.7

T Therm – A measure of heat equal to 100,000 BTUS. One hundred cubic feet of natural gas produce one therm of energy. Thermal Overload Protector – A device which prevents motors, components, and wires from becoming overheated due to excessive current or excessive movement during use. Many appliances such as mixers and slices heat up as you use them. At certain temperatures, insulation and components can melt, causing damage to the appliance. A thermal overload protector will forcibly power down the appliance when a certain temperature is reached in order to prevent irreversible damage. Thermocouple – A device to measure temperature. It consists of two different metals bonded together at 2 or more points. When one of the bonds is hotter than the other, it produces an electric current proportional to the temperature difference.  Many thermostats use thermocouples to measure heat. They’re also used as ‘flame sensors.’ They can detect whether the pilot light is lit in a boiler, oven, or stove, and trigger an alert if the pilot light goes out. Thermopile – A group of thermocouples. Thermopiles are used in some water heaters, ovens, ranges, and steamers. Thermostat – A device which ensures that something stays at a preset temperature. It usually contains a thermometer. When the temperature falls below or rises above the set point, the thermostat can send an electrical signal that turns heating or cooling devices on and off. Boilers, ovens, dishwashers, steamers, refrigerators and freezers all use thermostats. If the thermostat fails, a device will not be able to maintain a constant temperature. Transformer – A transformer changes electricity from a high voltage to a low voltage or from a low voltage to a high voltage. A transformer that goes from high to low is a step-down transformer, one that goes from low to high is a step-up transformer.  Tubing size – The name for a tubing size does not always reflect its actual size. For instance, 3/8” copper water tubing is actually ½” across. When replacing tubing, use this chart to figure out the actual and nominal size of the replacement tube.

Nominal Tubing Size (inches)	Actual Outside Diameter of the Tube (inches)
1/4	3/8
3/8	1/2
1/2	5/8
3/4	7/8
1	1 1/8
1 1/4	1 3/8
1 1/2	1 5/8
2	2 1/8

  Two Stage Pilot System – A pilot light that consists of two lights: a small standing pilot light which remains lit at all times, and a larger pilot light which only burns when the appliance is in use. The standing pilot light lights the larger flame. U V Vacuum – An area where the air pressure is lower than the surrounding pressure. Air moves towards the Vacuum. You can create a vacuum using fans or a motor to create a low pressure area. VAC – Volts of alternating current. Wall outlets deliver VAC. Because voltage changes constantly for alternating current, VAC refers to the Root Mean Square (RMS) voltage of the current. VDC – Volts of direct current. Batteries deliver VDC. Venturi tube – A section of pipe that changes the velocity of a liquid or gas by forcing it through a narrow opening to speed it up, then flaring out. It’s used on gas lines to increase flow in appliances like ovens and boilers. Volt – A measure of electric force. Voltage is the amount of energy released when current flows. W Watt – A measure of power. Watts measure how much work electricity does in 1 second. Watts = Amps x Volts. X Y Z