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Rafter One of a series of inclined structural roof members spanning from an exterior wall to a center ridge beam or ridge board. Rail The horizontal piece in a door, window sash or panel. Rake The inclined edge of a sloped roof over a wall. Rake Edge The edge of a gable roof system which runs parallel to the roof slope, from the eave to the ridge. Random-Tab Shingles Shingles on which tabs vary in size and exposure. Range The pressure or temperature settings of a control change within limits. Rat Refrigerant approach temperature Readily Openable Access Panel A panel provided for homeowner inspection and maintenance which has removable or operable fasteners or latch devices in order to be lifted off, swung open or otherwise removed and its edges and fasteners are not painted in place. Receiver Tank on the liquid side of a system that holds excess refrigerant in the system that needs to be there for proper operation. Receiver Heating Element Electrical resistance mounted in or around liquid receiver, used to maintain head pressures when ambient temperature is at freezing or below freezing. Receptacle Device in an electric wiring system to which a lamp, appliance or extension cord is connected b means of a plug on the end or a cord. Reciprocating An action in which the motion is back and forth in a straight line. Reciprocating Compressor A type of compressor used in air conditioners that compress refrigerant by using a type of "piston" action. Recirculated Air Extracted air, which is re-supplied to a space. Recirculated air is normally blended with outside air and is reconditioned. It can then be used for ventilation, heating, cooling, humidification, or dehumidification. Reclaiming Returning used refrigerant to the manufacturer for disposal or reuse. Recording Ammeter An electrical instrument which used a pen to record amount of current flow on a moving paper chart. Recycling Removing, cleaning and reusing refrigerant. Reflectance The ratio of reflected radiant energy to incident radiant energy. Reflective Glass Window glass coated to reflect radiation striking the surface of the glass. Refraction The deflection of a light ray from a straight path when it passes at an oblique angle from one medium (such as air) to another (such as glass). Refractory A material, usually nonmetallic, used to withstand high temperatures, as in the combustion chamber of an oil-fired heating system. Refrigerant Substance used in a refrigerator or air conditioner that absorbs and releases heat. The mechanism used by the chiller, which performs heat transfer by converting from liquid to gas and gas to liquid at various pressures and temperatures. Common refrigerants used in commercial HVAC are R-11, R-12, R-22, R-113, R-114, R-123, R-134a, R-500. A chemical that cools air as it evaporates. Air conditioning systems use refrigerant in the evaporator coil to cool air as it passes by. Refrigerant Analysis Laboratory analysis of a refrigerant sample to determine contamination, typically oil or moisture. Refrigerant Lines Two copper lines that connect the Condenser (Outdoor) Coil to the Evaporator (Indoor) Coil. Copper tubing through which refrigerant flows between condenser and evaporator coils. These lines are typically insulated when installed. Refrigeration (`Ton' Of) One ton of refrigeration is the term used to refer to 12,000 BTU's/hour (British Thermal Units/Hour) of cooling effect. (See BTU). Refrigeration Effect The amount of heat absorbed by the refrigerant in the evaporator. Register Grill at end of a supply or return duct in a forced warm-air heating system or refrigerated air conditioning system through which air enters or leaves a room. Reinforced Concrete Concrete that is strengthened by embedding iron or steel bars, rods or mesh in it. Relative Humidity A ratio between the actual moisture content of the air compared with the moisture content of the air required for saturation at the same temperature, i.e., at 100% relative humidity (also known as saturation point). The percentage of moisture in the air in relationship to the amount of moisture the air could hold at that given temperature. At 100 percent relative humidity, moisture condenses and falls as rain. Relative Humidity (Comfort) Indoor relative humidity in the range of 30 to 70% Relative Ventilation Efficiency A quantity describing how the ventilation ability of a system varies between different parts of a room. Relay An electromechanical switch. A device in which changes in the current flow in one circuit are used to open or close electrical contacts in a second circuit. Reliability The characteristic of an item expressed by the probability that it will perform a required function under stated conditions for a stated period of time cf. Availability and maintainability. Repairs Current expenditures for general upkeep to preserve a property's condition and efficiency. Representative Number For multiple identical components such as windows and electrical outlets - one such component per room. For multiple identical exterior components one- such component on each side of the building. RESFEN A computer program used to calculate energy use based on window selection in residential buildings. Residential Building A building whose main purpose is to provide living space for the occupants. Activities within them are limited to those of a domestic nature. Such buildings include single-family multi-family, communal, institutional and intermittent use building classifications. Response Time The time interval, with regard to a step input signal, between the input and the first coincidence of the output signal with the final steady-state value of the output signal. Restricted Flow Restricted flow is caused by an obstruction (blockage) in system piping, chiller barrel or tower system. Retrofit Adding or replacing items on existing buildings. For example, replacing a furnace, air conditioner, windows, or doors, with a newer more efficient model a new style compressor replacing an older, less efficient style or to use a different refrigerant to comply with new standards. The results can affect energy efficiency. Return Air Air removed from a space and then recirculated or exhausted (see recirculated air). Reverse Polarity Electrical outlets which have hot and neutral wire attached to the wrong terminals |