|
Occupancy Time The times during which people are in a building (generally expressed in hours per day). Occupant Behavior The pattern of activity of occupants in a building, including the number of occupants, their distribution, activities and time spent within the building, and how they interact with the buildings facilities, such as ventilation systems, window opening etc. Generally used in calculations for commercial building HVAC system calculations. Occupied Zone The region within an occupied space between 75 and 1800 mm above the floor and more than 600mm from the walls or fixed air-conditioning equipment. Off Cycle That part of a refrigeration cycle when the system is not operating. Offset A sustained deviation between the control point and the set point of a proportional control system under stable operating conditions. Ohm (R) A unit of measurement of electrical resistance. One ohm exists when one volt causes a flow of one ampere. Ohmmeter An instrument for measuring resistance in ohms. Ohms Law The mathematical relationships between voltage, current and resistance in an electric circuit, discovered by George Simon Ohm. It is stated as follows voltage (E=Amperes (I) x Ohms (R) or E = I x R. Oil Used as the lubricant in the compressor system to lubricate and protect bearings, shaft, etc. Oil Analysis Tests used to determine impurities and the ability of the oil to lubricate. Oil Change Interval The length of time between oil changes, determined by hours of operation, oil analysis, etc. Oil Tank A tank used to supply oil burning appliance such as a furnace, boiler or water heater. Oil tanks are frequently buried underground. On Center ( Abbreviated By O.C.) The measurement of spacing for framing members, fasteners, etc., which designate the distance from the center of one member or component to the center of the next. Also called center to center spacing. On Off Control A special case of two-step control in which one of the output signal values is zero. Open Beam Construction Frame construction in which the ceiling and ceiling joists are eliminated, leaving the beams and deck of the roof exposed and treating them as an element of the interior finish of the room. In this type of construction the structural members or the roof are usually heavier and may be on wider centers. Open Valley Method of valley construction in which shingles on both sides of the valley are trimmed along a chalk line snapped on each side of the valley. Shingles do not extend across the valley. Valley flashing is exposed. Operable Window Window that can be opened for ventilation. Operating Conditions The values of temperature, flow rate, and pressure of the heat transfer fluids as they enter and leave the heat exchanger. Used to determine the heat transfer rate for the heat exchanger. Operating Cost The day to day cost of running your home comfort equipment, based on energy use. Operator Crank-operated device for opening and closing casement or jalousie windows. Optimum Start/Stop Controller This controller alters the time that the HVAC equipment starts/stops depending on the weather conditions. It works by using an external sensor and, occasionally, an internal sensor, to bring in the heating/cooling plant at the latest possible time to get the building/zone(s) to the required temperature by the start of occupancy. Organic Felt An asphalt roofing base material manufactured from cellulose fibers. Oriel Window A window that projects from the outer face of a wall, especially from an upper story, and is supported by brackets or a cantilever, as distinguished from a bay window, which is at first-floor level and usually supported by a foundation. Outdoor Air Air taken from the external surroundings and therefore not previously circulated through the system. Outdoor Coil/Condensing Unit The portion of a heat pump or central air conditioning system that is located outside the home and functions as a heat transfer point for collecting heat from or dispelling heat to the outside air. Outward Directed toward the outside, usually at a 90 degree angle (perpendicular to) the exterior surface. Overhang That portion of the roof structure that extends beyond the exterior walls of a building. Overpressure An induced pressure above ambient atmospheric pressure or other given reference pressure. Oversized Fuse A fuse which does not provide adequate protection for an electrical circuit. Fuse are design to be a fail-safe for electrical systems by failing before the electrical charge is too high for the electrical system. Packaged Or Self-Contained Refrigeration system where everything including the air moving hardware is kept in one box, such as a window air conditioner or a roof-top unit. Pane One of the compartments of a door or window consisting of a single sheet of glass in a frame also, a sheet of glass. Panel A major component of a sliding glass door, consisting of a light of glass in a frame installed within the main (or outer) frame of the door. A panel may be sliding or fixed. Panel Or Panel Board A panel to which are attached electrical meters and control equipment for electrical service distribution. Panel Building Or Panel-Type Building A building composed of pre-fabricated concrete facade and other building elements. Usually the panels have a low level of thermal insulation, and often the panels are poorly jointed which leads to relatively high levels of infiltration. Consequently many panel buildings suffer from high levels of energy consumption, and often poor comfort conditions inside. Panel Heating A radiant heating system one in which pipes or coils are embedded in walls or ceilings to serve as heating panels. Panning In replacement window work, the outside aluminum trim that can extend around the perimeter of the window opening used to cover up the old window material. Panning can be installed in the opening before the window, or can be attached directly to the window before installation. Parapet A low wall or railing along the edge of a roof, balcony, bridge or terrace constructed for protection, to control water, resulting from rain or artificial flooding or to insulate against sun's rays. Parapet Wall That part of a wall which extends above the roof line Part Load Load conditions below full load design. Most chillers operate at part load ~99% of the time. Partial Pressures Condition where two or more gases occupy a space and each one creates part of the total pressure. Particle Dispersed Glazing Glazing in which the orientation of small particles between two sheets of glass is controlled electrically, thus changing its optical properties. |