20 Most Recent Bosch 1600H-NG Natural Gas AquaStar AquaStar Natural Gas Tankless Water Heater... - Page 8 Questions & Answers

gas valve sticking

Replace the flame sensor.

Just unplug any electrical supply for at least 30 seconds.

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I believe this is a hydro-sparker pilot ignition then burner on when T-Couple/Flame Sensor acknowledges pilot lit. W/O the signal feedback the Gas Valve will not open and light burner. This is a Technician Service Job as you have insufficient knowledge to DIY this potentially dangerous LP/NG Control Valve/Sparker Assembly I assume that lack of knowledge by your lack of a Manual for the Unit You cannot force ignition on a hydro-sparker manually.

Depends how far away the tankless is located. Tankless are not instant hot water heaters Also check for cross connection http://waterheatertimer.org/Crossover.html http://waterheatertimer.org/Water-heater-recirculation-system.html http://waterheatertimer.org/How-to-install-under-counter-water-heater.html Gene If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

check the thermostat