# Navien NPE\-240A2 Technician Training Training and skills assessment for the Navien NPE\-240A2 condensing tankless water heater with its cover removed By James Levin Topic: Engineering [Open the interactive Jig](https://ask.jig.com/j/YzgFrVnkGZhY) ## Guide ### 1. Navien NPE\-240A2 Technician Training This is the NPE\-240A2 on its wall, with the front cover off so you can see every part inside\. You will learn its parts, watch it fire, practise two service jobs, then take a 10\-question check\. Drag the scene to turn it\. Casing: 17\.3 x 27\.4 x 13\.2 in, 77 lb\. Interior layout is simplified: verify in manufacturer's installation manual\. ### 2. Tank heater versus condensing tankless A tank heater keeps a big tank hot all day and loses heat while it waits\. This unit heats water only while it flows\. A second heat exchanger pulls extra heat out of the exhaust, so the exhaust cools until water condenses out of it\. Rated UEF 0\.95\. Heat input 13,300 to 199,900 BTU/h on natural gas or propane\. ### 3. What the A2 adds The A2 has a small buffer tank and a recirculation pump built in\. The buffer tank smooths the outlet temperature during short draws\. The pump keeps hot water ready: ComfortFlow uses a return line, and NaviCirc uses a valve under the farthest fixture with no return line\. Buffer tank volume is often quoted as 0\.5 gal; an installation manual summary gives about 0\.4 gal\. Verify in manufacturer's installation manual\. ### 4. Combustion side The fan pulls air in through the intake collar, and the gas valve meters gas into it\. The burner on top fires down into the primary heat exchanger\. The hot gases then pass the secondary heat exchanger and leave through the exhaust collar\. Both heat exchangers are stainless steel\. ### 5. Water side Cold water enters through the inlet filter and the flow sensor\. It warms in the secondary heat exchanger first, then the primary\. The buffer tank, mixing valve and recirculation pump sit in the lower bay\. Tap any labelled part to highlight it\. ### 6. Condensate, controls and connections The condensate trap collects the water from the exhaust and keeps flue gas out of the drain\. The main PCB runs the whole sequence, and the front control panel is how you set and read it\. Gas, cold, hot and recirculation connect underneath\. Connections: 3/4 in gas, 3/4 in cold in, 3/4 in hot out\. Water pressure 15 to 150 psi\. 120 VAC, 60 Hz\. ### 7. Sequence 1: Hot water demand Someone opens a hot tap\. Cold water starts moving into the unit through the inlet filter\. Nothing is burning yet\. ### 8. Sequence 2: Flow sensor detects flow The flow sensor measures the water moving past it\. When flow passes the activation point, it signals the PCB to start a heating cycle\. Minimum flow 0\.5 GPM; under 0\.01 GPM with ComfortFlow \(product page\)\. ### 9. Sequence 3: Fan pre\-purge Before any gas flows, the fan runs to push air through the burner and heat exchangers\. This clears out any leftover gas so ignition is safe\. Fan speeds and purge times: verify in manufacturer's installation manual\. ### 10. Sequence 4: Ignition The gas valve opens and a spark lights the burner\. The flame rod then proves a flame is present\. With no flame proven, the gas valve closes again\. ### 11. Sequence 5: Flame modulation The PCB adjusts the fan and gas valve together to match the heat to the water flow\. Drag the slider to see the flame turn down and up\. Modulation range 13,300 to 199,900 BTU/h\. ### 12. Sequence 6: Water path through both heat exchangers Watch the flow\. Cold water warms first in the secondary heat exchanger, then reaches full temperature in the primary\. The mixing valve blends a little cold water in to hold the set temperature\. Exact internal routing: verify in manufacturer's installation manual\. ### 13. Sequence 7: Condensate forms and drains Cooler water in the secondary heat exchanger chills the exhaust, and water vapour condenses on it\. The drops run to the trap and out of the drain line\. Condensate is mildly acidic\. Route it to a drain or neutralizer per local code\. ### 14. Sequence 8: Recirculation in ComfortFlow mode With no tap open, the built\-in pump moves water around the loop so hot water is waiting at the fixtures\. When the loop cools, the unit fires briefly to reheat it\. Recirculation uses extra energy\. Scheduling options: verify in manufacturer's installation manual\. ### 15. Filter clean 1: Disconnect power Unplug the unit or switch off its circuit before any service work\. The display goes dark\. ### 16. Filter clean 2: Close the cold water isolation valve Turn the blue cold water handle a quarter turn so it sits across the pipe\. Water can no longer enter the unit\. ### 17. Filter clean 3: Close the hot water isolation valve Turn the red hot water handle across the pipe\. The unit is now isolated from the house plumbing\. ### 18. Filter clean 4: Relieve the pressure Open the hot service port with a bucket under it to release the trapped pressure\. Expect a little water\. ### 19. Filter clean 5: Remove the inlet filter Unscrew the filter cap at the cold water inlet and pull the filter straight out\. ### 20. Filter clean 6: Rinse the mesh Rinse the mesh screen under running water and brush off any debris\. Check it for tears before you refit it\. ### 21. Filter clean 7: Refit and restore Push the filter back in and tighten the cap by hand\. Close the service port, open both isolation valves, check for leaks, then restore power\. ### 22. Descale 1: Disconnect power Scale is mineral build\-up inside the heat exchanger that cuts heat transfer\. Start, as always, by unplugging the unit\. ### 23. Descale 2: Close both isolation valves Turn the hot and cold handles across their pipes so the house is cut off from the unit\. ### 24. Descale 3: Connect the hoses Connect one hose from the pump to the cold service port\. Connect a second hose from the hot service port back into the bucket\. ### 25. Descale 4: Open the service ports Open both service port valves so the hoses connect to the water path inside the unit\. ### 26. Descale 5: Circulate the descaler Start the pump\. The descaling solution runs in through the cold port, through both heat exchangers, and back to the bucket\. Solution type, volume and circulation time: verify in manufacturer's installation manual\. ### 27. Descale 6: Flush with fresh water Stop the pump and drain the solution\. Replace it with clean water and run it through until the line runs clear\. ### 28. Descale 7: Close the ports and open the valves Close both service ports and remove the hoses\. Open the hot and cold isolation valves, check for leaks, then restore power\. ### 29. Skills assessment Ten questions, one at a time\. Some ask you to tap a part on the model, some ask for the right order, and some are multiple choice\. Your first answer counts\. You need 8 of 10 to pass\. ### 30. Question 1 of 10 Tap the secondary \(condensing\) heat exchanger on the model\. ### 31. Question 2 of 10 Tap the flow sensor on the model\. ### 32. Question 3 of 10 A tap is open but the fan never starts and nothing lights\. Which part should you check first? ### 33. Question 4 of 10 Put the start\-up sequence in order\. The four cards next to the unit are lettered A to D\. ### 34. Question 5 of 10 Before you open the cold water inlet filter, what must you do first? ### 35. Question 6 of 10 Tap the condensate trap on the model\. ### 36. Question 7 of 10 While the unit fires, water drips steadily from the condensate drain line\. What is the most likely cause? ### 37. Question 8 of 10 Put the descaling job in order\. The four cards next to the unit are lettered A to D\. ### 38. Question 9 of 10 Which option lets the A2 recirculate hot water in a home with no dedicated return line? ### 39. Question 10 of 10 Tap the part that holds a small reserve of hot water to smooth the outlet temperature\. ### 40. Your result Your score is on the board beside the unit\. You need 80 percent to pass\. If it says Not yet competent, review the sections listed and take the check again\. ### 41. Sign\-off When you pass, the board shows a sign\-off checklist\. Fill in the technician name, date and score, and have your assessor sign it\. Always follow the manufacturer's installation manual and local codes on the job\.