G2 Gas Technician Module 20 Revised Questions 100% Pass

G2 Gas Technician Module 20 Revised Questions 100% Pass What prevents the water in a hydronic heating system from boiling into steam when the system is operating above the atmospheric temperature? Pressurization of the system List the four subsystems of a hydronic space heating system? Heat Source, Circulation system, Heat Emitters, Control system What must be done to protect the potable water supply to a hot water boiler? Approved backflow preventer installed in the water supply Above what input is a low water cut-off a required component of a hot water boiler? 400,000 BTU Why are cast-iron sectional boilers used only in closed loop hydronic system? Purge itself of Air and reduces corrosion Why does a copper fin-tube boiler require less surface area to transfer heat than a steel fire tube boiler? Copper Tube has a higher thermal conductivity than steel tube What happens to the water vapour in the combustion products if the flue gases are cooled below the dew point? The water vapour condenses into liquid state How is an automatic vent damper interlocked to ensure it is in the open position before the burner can fire? The damper actuator has a proving switch that is interlocked with the thermostat controlling the burner Which is the simplest hydronic distribution system? Single Series Circuit What two purposes are served when a combination system is used? Space Heating and Domestic Water May chemical additives be introduced into a combustion system? No What device within a closed hydronic system is required to provide provision for the volumetric expansion of the system fluid under normal operating condition? Expansion Tank List four common air elimination devices used on hydronic heating system. Manual Air Vent, Automatic Air vent, Air purgers, and Microbubblers Which device within a hydronic heating system is required to release water during an unsafe condition caused by excessive pressures? ASME Pressure Relief Valve Which type of valve is best suited for throttling flow? Globe Valve or Gate Valve What two types of drive heads can be used on a thermostatic radiator valve? Mechanical and electrical On three and four-way mixing valves, where does the mixing take place? Within the valve body Where should an outdoor temperature sensor be placed? Away from direct sunlight, away from other heat sources and away from a shielding structure What are the three general methods used to control temperature zones in a building? Circulating pumps, zone valves, and thermostatic radiator valves What is the purpose of a balancing valve? Modulate and balance the flow through each branch Where is the circulating pump in a hydronic system located? Typically on the supply side The pressure difference produced by a pump between it's inlet and outlet ports is a partial definition of what? Pump Head If two identical pumps are installed in series, what happens to the system pressure? Pressure Increases What happens if the same pumps are installed in parallel? GPM Increases If a check valve chatters, what must be done? Must be replaced How is an immersion-type low water cut-off tested? By draining the system, same as Float Type What is the primary cause of sooting on heat source surfaces? Flame impingment Air in the system or low flue gas temperature can cause what? Corrosion Incomplete combustion and very high stack temperature may indicate what? Over Firing What can be done to correct overfiring? Manifold Pressure should be checked and adjusted or check burner orifice size In a hydronic heating system, air can cause what three problems? Corrosion, Insufficient heat output and noise in the system Can the installation of air vents help prevent pump cavitation? Yes What forces of nature have effects on pool heating? Direct sunlight, wind, shade from trees and structures Which pool component is most likely to corrode? and why? Heat exchanger and burner because of chemicals, ph, salt and condensation. Where must chlorine be injected into the pool circulating system? Down stream of the heater How should galvanized pipe and copper be joined together? Dielectric Insulation Fittings If the filter pump is not running, will the pressure switch allow the heater to fire? No What is the only recommended procedure for cleaning heat exchanger tubes that does not require removal of the heat exchanger? Wire Brush Is it acceptable to leave water in the heater when the system is winterized? and why? No because of Freezing, Expansion, Splitting Pipes, Damaging Equipment What reduces the pressure of incoming water coming into the boiler through a domestic water distribution pipe? Pressure reducing valve and boiler feed water valve Insufficient heat output is generally a result of? Insufficient or no flow in the system and incorrect temperature settings The limit is set below system design temperature what happens? Boiler fires but cycles on/off limit control and insufficient heat throughout building What causes no heat in upper floor of a building? Air in the system. Circulator making loud rattling noise. Pump cavitation, broken pump coupler Gurgling sound in pipes, cause? and how to fix? Air Bubbles, you should shut down the pump and bleed all radiators Operated by thermostat. Opens water flow and activates burner and pump with it's end switch. Zone control valve