Raypak P-R266A backfiring

[Michael F]

I have a Raypak gas pool heater that is around 15-16 years old and I noticed recently that it has been backfiring when in use. This heater is only used to heat the hot tub. The backfire is quite loud and I've noticed black soot at the top of the heater so until I can figure out the fix I have discontinued using it. Any ideas as to why this is happening and if it's a simple fix or do I need to find someone to repair this? TIA

 

[1poolman1]

I have a Raypak gas pool heater that is around 15-16 years old and I noticed recently that it has been backfiring when in use. This heater is only used to heat the hot tub. The backfire is quite loud and I've noticed black soot at the top of the heater so until I can figure out the fix I have discontinued using it. Any ideas as to why this is happening and if it's a simple fix or do I need to find someone to repair this? TIA

Very likely the burner orifice for the far right burner (and possibly some others near) is clogged with spider nests. The gas that is sent when the main valve opens goes to the ones farther left, builds up, hits the pilot, and then "boom." That's called explosive ignition. Happens regularly to heaters that aren't used a lot, especially. Firing the heater at least once a month (weekly is better) for about 5 minutes usually eliminates that issue.
For now, the burner tray will have to be removed to clear the orifices with a small copper wire or very tiny brush.
At that age, it could be that the burner tray has damage, but you'll find that out when it is removed. Fifteen to sixteen years is a long life for a heater.