NHIE-Nachi HVAC System | Questions and Answers High-efficiency condensing HVAC systems produce excessive _______________. Condensate Forced-air furnaces
... [Show More] function primarily by ________. Convection Radiation is the transfer of heat energy by _________________. electromagnetic wave motion Heat can move from one body to another by _________. Radiation Heat is transferred _____________. in direct rays Heat transferred within a gas or liquid happens via __________. Convection Heat transferred through a solid happens via __________. Conduction If the heating system is a high-efficiency, gas-fired furnace, then the heat-conveying medium is _____. Air Is what carries the heat from the source to the enclosure being heated. The heat-conveying medium A(n) _______ furnace is also referred to as a counter-flow furnace or a down-draft furnace. Downflow To ignite natural gas, you need a mixture of gas and ______. Air The _______________ is the temperature below which the water vapor contained in the flue gas will turn into condensation. dew point temperature The lack of dilution air may cause a condition of ___________ at the furnace. Backdraft __________ refers to the flow of gases through the heat generating equipment. Draft Round or square supply ducts that are connected to and branch off the extended duct are called _________. side takeoffs The first step in the operation of a warm-air heating system is ______________. circulating fan draws air into the furnace Changes in the direction of ducts are made by _____________. angle ducts If you are inspecting a _______ duct system, you should find a large rectangular duct that comes directly out of the heating system and runs in a straight line down the center of the basement, attic or ceiling. Plenum The warm air in a gravity warm-air heating system rises up through warm-air ducts or pipes that are also known as __________. Stacks The older gas furnaces have a(n) ______ pilot light that is always burning. Standing ________ air is air that mixes with the gas before going to the burners. Primary The energy efficiency of a natural gas furnace is measured by its ________ rating. AFUE Steady-state efficiency measures how efficiently a furnace ___________. converts fuel to heat The three types of forced warm-air furnaces related to air flow are upflow (highboy or lowboy), downflow and horizontal. The three different types of ignition systems are standing-pilot, intermittent-pilot or direct-spark and hot-surface ignition. A thermocouple is used in gas furnaces that have a(n) _____________. standing-pilot light A mid-efficiency gas furnace's pilot light ____________. is shut off when the furnace is not in operation One cubic foot of water at 68° F weighs about ____ pounds. 62 A conventional oil furnace with a cast-iron burner likely has an AFUE rating of ______________. 60%, which is categorized as low-efficiency At the burner nozzle of the gun assembly for an oil furnace, ____________. fuel is combined with air On a conventional oil furnace, there is a safety device in operation when the burner is shooting flames called a ___________. cadmium sulfide photo-cell, or cad cell As hot gases cool, they release a lot of heat energy as they change their state from ____________. a gas to a liquid Burning natural gas creates ____________________. water (vapor) and carbon dioxide Solid-fuel, forced warm-air furnaces can burn _____________. coal or wood A hot-water system that supplies hot water at temperatures higher than _________ is referred to as a high-temperature system. 250° F Every hot-water heating system circulates water either by a ______________. pump or by gravity The first step in the heating cycle for a conventional oil furnace is ____________. the thermostat calls for heat A stack relay senses _______ instead of _______. heat... light When a high-efficiency condensing furnace is operating, a _____________ of condensate water may drain out every 30 minutes. Quart The __________ is located inside the outdoor condenser unit and receives the low-pressure refrigerant vapor through the suction line, and compresses or squeezes it into a smaller volume at a higher pressure. compressor [Show Less]