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HVAC Equipment Questions and
Answers | New One | Grade A+
Absorption Chiller Ans: UTILIZE A THERMAL OR CHEMICAL PROCESS TO PRODUCE REFRIGERATION EFFECT NECESSARY TO PROVIDE CHILLED WATER NOT VCR- NO MECHANICAL COMPRESSION Air Filter Ans: CLEANS THE AIR OF UNDESIRABLE ELEMENTS sound attenuating filters-reduce level of sound moving through ductwork Air Handing Unit (AHU) Ans: PREASSEMBLED OR SITE BUILT EQUIPMENT DEVICE CONTAINING COILS AND FANS THAT IS USED TO CONDITION AND CIRCULATE AIR AS PART OF AN HVAC SYSTEM
made up of fan(s), cooling and heating coils, dampers, and filters delivers air to supply air ductwork that conveys conditioned air into zones (rooms) often integrated ventilation operation heating and cooling coils to condition air dampers control flow outside air return air mixed air supply (conditioned) air air filter(s) removes dust particles from air fans move air and deliver conditioned air to building Air-Cooled Condenser Ans: PASS OUTDOOR AIR OVER A DRY SURFACE COIL TO CONDENSE REFRIGERANT CONTAINED INSIDE THE COIL RESULTS IN HIGHER CONDENSING TEMP AND LOWER PERFORMANCE UNDER PEAK CONDITIONS COMPARED TO WATER COOLED CONDENSERS
Advantages: individual room control allows independent heating and cooling fair reliability - only single zone affected by malfunction low initial cost Disadvantages short life noise within space poor humidity control, air filtration, and ventilation All-Air HVAC System Ans: HEAT, COOL, VENTILATE BY PROVIDING AIR ONLY TO THE SPACE BEING CONDITIONED Cooled/heated air from central plant/AHU via ducting Includes chiller(s), boiler(s), AHUs, terminal boxes AHUs deliver heated/cooled air to space through ductwork Advantages heating/cooling delivered via air only allows good temperature and humidity control
good humidification and heat recovery allows for complex zoning can use outside air for economizer cycle Disadvantages special care for maintenance access greater volume of equipment space needed supplemental perimeter radiation may be needed Types Constant Air volume (CAV or CV) single zone terminal reheat multizone dual duct Variable Air Volume (VAV or VV) Variable Volume Variable Temperature (VV-VT) (Large building/large application)
Individual Supply system Perimeter-loop system Trunk duct - 2 way Trunk Duct - 1 way Full Exhaust- 100% Outside Air no return air because the return air may contain contaminants Mixed Air outside air is combined with return air All-Water (Hydronic) HVAC System Ans: HEAT AND COOL BY CIRCULATING HOT WATER FROM A BOILER OR CHILLED WATER FROM A CHILLER THROUGH A FINNED COIL IN A FAN-COIL UNIT OR UNIT VENTILATOR IN THE SPACE Basic types: steam hot water chilled water
Chiller plant (or chiller) plus boiler to produce conditioned (chilled and/or hot) water Includes chiller(s), boiler(s), and room terminal units Conditioned water is pumped to room terminal units (ie. convectors, convector-radiators, chilled beams, etc.) (large building/large application) system components piping/fitting equipment and distribution valves pumps terminal devices (heat/cool emitting) Piping arrangements one pipe two pipe* (two pipe changeover) three pipe* four pipe*
Three pipe systems have a hot-water loop and a cold-water loop so that hot or cold water can be introduced to any terminal unit at any time a single "common" return is used provide both supply heating and chilled water to units hot water, chilled water, common return three way modulating valve at inlet of unit allows hot or cold water depending on load water leaving unit is carried in a common return pipe to either chiller or boiler- inefficient Four Pipe System uses supply and return heating piping and Annual Fuel Utilization Efficiency (AFUE) Ans: efficiency rating AFUE ACCOUNTS FOR THE EFFECT OF PART-LOAD EFFICIENCY AND CYCLIC LOSSES A SINGLE AFUE NUMBER REPRESENTS PERFORMANCE UNDER A SPECIFIC SET OF CONDITIONS
serves well to compare two boilers under the same conditions residential only 78% AFUE - minimum AFUE natural gas furnaces 80 - 82% AFUE - medium-efficiency furnaces employing efficient heat exchangers, better intake air control, and/or blowers to exhaust combustion products
90% AFUE - high-efficiency (condensing) furnaces Axial-Flow Fan Ans: PROPELLER TYPE FANS THAT USE A PROPELLER TO DRAW AIR INTO THE FAN AND DISCHARGE IT IN THE SAME AXIAL DIRECTION Typical indoor residential fans used to circulate air Boiler Ans: piece of equipment that produces hot water or steam
solid fuel coal wood biomass automatic fuel feeding, ash extraction and soot blowing (Pressure and temperature) (steam) low pressure (<15 psig) medium pressure (15-160 psig) high pressure (> 160 psig) (Hot Water) low temperature (<250F and <160 psi) medium temperature (250 to 350F) high temperature (>350F) (Heat Exchanger Type) (Water Tube) straight tube bent tube
(Fire Tube) single pass multiple pass (modular/Sectional) (Materials) (Non-Condensing) Carbon Steel Copper Cast Iron (Condensing) Stainless Steel Aluminum Cast Iron (Draft Type) Atmospheric (natural draft) Forced draft Induced draft
Includes only stack losses Thermal/Overall Efficiency Includes stack losses and jacket losses Com Boiler Horsepower (BHP) Ans: DEFINED AS THE EVAPORATION OF 34.5 POUNDS OF WATER INTO STEAM AT 212*F AT STANDARD ATMOSPHERIC PRESSURE type of gross output rating ONE BHP = 33475 Btu/hr = 9.81 kW Building Energy Management System (BEMS) Ans: (building automation systems - BAS) CONTROLS ENERGY-CONSUMING EQUIPMENT IN A BUILDING TO MAKE IT OPERATE MORE EFFICIENTLY WHILE MAINTAINING A COMFORTABLE ENVIRONMENT Central Air Conditioner
Ans: A DX REFRIGERATION COOLING SYSTEM. 4 BASIC PARTS CONDENSING UNIT(COMPRESSOR, CONDESNSER, EXPANSION VALVE) COOLING COIL (EVAPORAROR IN AHU OR DUCTWORK NEAR FURNACE) DUCTOWRK (DISTRIBUTION) CONTROL MECHANISM (THERMOSTAT) Central Chilled Water System Ans: USED IN LARGE BUILDINGS CONSIST OF CENTRAL CHILLER TO COOL WATER Centrifugal Fan (squirrel cage fan) Ans: A FAN IN WHICH THE AIR IS TURNED FROM PARALLEL TO THE AXIS OF ROTATION ON ENTRY TO A DIRECTION TANGENTIAL TO THE ARC DESCRIBED BY THE TIPS OF THE ROTATING BLADE OR VANES air turns 90 degrees as it travels from inlet to outlet most common supply fan
(components) chiller condenser (ie. cooling tower, air-cooled condenser) air handling unit (AHU) chilled water pumps condenser water pumps potential equipment being served by system: fan-coil units unit ventilators chilled beams chilled sails air handling units Chiller Ans: PRODUCES CHILLED WATER cooling machines that make chilled water mechanical (VCR) chillers
(use vapor-compression refrigeration process to chill water) centrifugal chillers (large capacities) screw chillers (medium capacities) scroll chillers (smaller capacities) reciprocating chillers (smaller capacities; older) Absorption (thermal) chillers direct-fired absorption chillers indirect-fired absorption chillers absorption chillers chilled water machines use thermal energy to chill water consume energy from excess steam excess process (hot) water natural gas, oil, or kerosene solar energy
