how do you back flush a Laars xe pool heater?
Answers:
You don't backflush a heater. You backwash a filter. Is the filter pressure high? How about circulation in the pool? If the heater is causing the problem then the filter pressure will be high- even after backwashing. Lots of things in the heater can cause this. But first, will the heater fire? Let me know and I'll talk you through some testing.
Other answers:
turn it off
unplug it
flood with water
plug in
turn on
keep it submerged
air=bad
turn it off
unplug it
flood with water
plug in
turn on
keep it submerged
air=bad
Heaters never get backwashed, just filters. If your heater is firing, then it's pressure switch is satisified. Means that there's sufficient water flowing through to allow the burners to light. This wouldn't happen if there was not enough flow. If it ISN'T firing and the pilot is lit, try cleaning out your baskets and cleaning out the filter and then check your filter pressure. If that fails, come back with some more information. I'm trying hard to figure out how you came to the conclusion you haven't enough flow through the heater. The above is all I can suggest with the info you've given.