G2 Gas Technician Module 18 Revised with Verified Solutions

G2 Gas Technician Module 18 Revised with Verified Solutions What is a temperature control made of in a water heater? Which one is the sensing element? Rod and tube. Rod is steel and tube is copper. Copper is the sensing element. Temperature settings on a water heater? Hot - 160 F Normal - 130 F Warm - 120 F What does a unitrol have in it? Temperature and pressure relief valve, E.C.O., Main Gas valves, Pilot Gas Valve and a gas regulator What temp does a temperature and pressure relief valve fusible link melt at? Pressure relieve at? Melts at 210 F and relieves itself at 150 psi How does a dip tube function? Allows cold water to enter near the bottom of the tank as hot water exits the top What do anodes do in a water heater? When do you need to change them? Prevents the interior of the tank from corroding and should be changed when its diameter is 3/8" What are the components of an instantaneous water heater? Pump, pump control, flow switch, temperature and pressure relief valve, and a limit control What must be done with a Twinned Water heater system to ensure it runs properly? Inlet and outlet piping must have equal resistance on each tank. What clearance must a direct vent water heater have on the burner side? 3 feet What metals are not acceptable in potable water applications? Ferrous metals What is the maximum allowable length of supply and return piping in a combination water heating system? Max supply and return piping is 50 feet Can you use chemicals in a combination system? No How do you size the pumps in a combination system? To match the flow requirements of the heating system What is the minimum size and type of water heater that is recommended for a combination system? 40 gallon high-recovery or high efficiency gas-fired water heater What temperature difference do you want from inlet to outlet on a combination system? 20 F How do you size a circulating pump? 1 gpm for each 10000 btuh and friction loss is 1 foot for each 40 feet of pipe What controls the water temp and gas pressure on a direct fired storage heater? Unitrol What are the components of a direct fired storage heater(under fired storage heater) Dip tube, anode, temperature and pressure relief valve, and mixing valve What are the components of a hi-efficiency water heater? E.C.O., temperature and pressure relief valve, anode and dip tube What are the normal operating temps of a unitrol 130 F What does an E.C.O. do? Shuts off gas valve in a high temperature situation How is temp rise determined on an under fired storage heater? Inlet compared to outlet How can you tell a water heater has a build up of lime? Sounds like it is percolating. How do you delime a water heater? How do you prevent it from starting? Delime with a vinegar or a chemical solution(environmentally friendly) and prevent it with a water softener What type of solder do you use when soldering water lines? Lead free What is the purpose of a mixing valve and what is the temperature setting? Controls water temperature and sets it at 120 F How is legionnaires disease created? Temperatures lower then 105 F in ponding water. What acts as a heat exchanger in an underfired storage water heater? The flue(baffle) What improves heat transfer in a residential water heater? Having the baffle spiral What does an expansion tank do? To allow room for heated water to expand so it doesn't burst pipes Where are isolation valves installed on a combination system? At each unit and wherever necessary What are two reason check valves are used in a combination system? To stop return water from cooling the supply water and to prevent cold water from entering the rad Can you use chemicals in a combination system? No What is the purpose of a pressure reducing valve? To reduce pressure from street to system pressure (12 psi) What is the purpose of a circulating pump? To keep fluid circulating the pumping system