I just installed a new Raypak pool heater (106 cfh) for my spa yesterday. I'm avoiding calling the warranty hotline, in the event that it's a simple problem. I tried simply plugging it in with the 110V power cord, to no avail. Since I had 220V readily available from the existing pool heater, I wired it to 220V, in exact accordance with the owners instructions. Still refuses to fire. Does anyone on this forum know if this heater relies on flow or pressure differential to operate ?? The filters are clean, and there's enough flow to operate a Jandy pool cleaner (although I'm not overjoyed with its performance). If the heater relies on a pressure type switch to activate the gas valve, I can slow down the flow on the discharge side of the heater, and raise the pressure as needed. There may be a pressure switch that can be adjusted, as well. As the owners instructions seem to cover more than 1 heater (both digital and analog controls), it's a little confusing. Thanks in advance for any suggestions......