I have noticed many people stating problems starting their Hydrotherm
heaters. They turn it on according to instructions and it rarely or never
lights. Well, the instructions are not detailed enough and left one thing
out. If you take the front panel off and look carefully near the gas
solenoid you will notice a small pushbuttom with an "S" on it. Turn on the
gas, push the button a few times and turn it on. Starts right up!  Drove me
crazy until I found the button.

Alan