Hayward H250 (pictured with cover off). It works great, but only when the temperature is set to almost the max. If I turn it down at all, it kicks off. Pilot light
Found a Dangerous Hayward H-250 Millivolt Pool Heater with Multiple Switches Bypassed - YouTube
Amazon.com : Hayward FDXLHXA1250 Heat Exchanger Assembly Replacement for Hayward H250FD Universal H-Series Low Nox Pool Heater : Swimming Pool And Spa Parts And Accessories : Patio, Lawn & Garden
Hayward Universal H Series Heater H250FDP 250000 Btu 250k Low Nox
Hayward Pool Heater (W3H250FDP Universal H-Series 250,000 BTU Pool and Spa Heater) - YouTube