Laars Lite II LD400N - Pressure Switch Issue ?

[No hobo]

Hi All. I have a LD400N natural gas fed heater on my 26k gallon pool. 12th season here in PA. Heater will not startup and stay lit. I suspected the pressure switch because I had to load the loop up with oil last year to get it started, which I did again this year but it did not result in normal operations. I bypassed the pressure switch and got the electronic ignited going followed by the "click" and one quick ignition of the burners which only lasted a second, nothing sustained.

First off, is there a proper way to add oil to the siphon loop? Can I use household 3 in 1 oil?
Second, with the pressure bypassed, shouldn't I get normal start up or is it obvious I have something else wrong? Not sure if the PS provided some other cut out signal to prevent operation.

I'm going to go home and make sure there is water flow through the loop to the PS. I had to deal with a filter grid problem at startup and there was loose DE in the system. I get a sucking sound when I disconnect the loop connector now, without the pool pump running.

Any ideas or insights would be greatly appreciated.

 

[ps0303]

If the issue was the pressure switch, once you bypassed it, the heater would fire and run.

I can't help you with the oil questions as here in FL we don't have to do that.

 

[No hobo]

I replaced the pressure switch and now get the heater to consistently try to light. I observe the HSI doing its thing, a click, and most times I get the burners going along the back for 2-3 seconds and then go out. Three attempts at that and then I cycle the on-off switch. I was going to go after cleaning the flame sensor, but with only the back flaming initially I dont see how the flame sensor is positioned closer to the front. Does the flame sensor need to respond that quick, within 2-3 seconds of ignition?

My next plan is to pull the tray out and clean it out and clean the flame sensor while I'm there.

Are there any other components that would be suspect based on my description?

 

[ps0303]

So the flames are only igniting along the very back/ends of the burners? Check and make sure the burners are free of any cob webs etc. Although usually cob webs would prevent it from lighting all together but check them anyway.

 

[Pool Clown]

You should have a nice even flame from front to back. If not, clean the burner tray, that's your problem.

 

[No hobo]

Problem solved! The flame sensor has a small bracket / support for the ceramic insulator sleeve protecting the rod from the bracket. The insulator support must have rusted away allowing the ceramic sleeve to slide down. My guess is that the rod was grounding out on the bracket that attaches the rod assembly to the first burner which caused an instant shutdown of the flame. The whole rod assembly was loose and kind of sloppy. I was able to detach the flame sensor assembly and wedge a small piece of metal in to keep the ceramic insulator in place and prevent the grounding. I haven't look yet but I doubt the part is sold separately. I also used steel wool to clean the sensor rod tip.

I slide the burner tray back in and secured it, reconnected the gas, tested for leaks, connected the electric, and fired it up. Used the spa for the first time this season! Now I know a lot more about this whole system from reading all of the helpful posts and trying some things on my own.

Thanks

 

[ps0303]

Congrats on getting is solved. Enjoy the spa!