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Help -- Pool Heater Won't Ignite Lt400N-L

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mdwheaton    0

I have a Laars/Jandy LT400n-l. Installed in 2003.

Up until the last week, it seemed to work fine.

About 5 days ago, I noticed a large amount of soot on the fence that the heater in installed near.

I started paying more attention, and I notice the exhaust gas is really HOT. I'm not sure how hot it is supposed to be, but if you hold a piece of paper in the exhaust stream, it will turn brown nearing ignition.

I planned on heating the pool for Christmas, so I let the heater run overnight, and all seemed to be OK, until last night.

The pool reached the set temperature and turned off like I expected, except now it won't re-light.

Before, when it would go through its lighting cycle, I would see the orange glow from the HSI in the little sight window.

Now, there is no orange glow, and no ignition.

I'm having trouble figuring out where the HSI is mounted so I can inspect it. Is it a major dismantling operation to check this part?

What should I expect for exhaust temperatures? Does the sooting sound like a problem? There is a lot of rust down around the burner openings.

How long should I expect this heater to last?

I'm fairly handy, but I don't want to get in over my head.

Any help greatly appreciated!



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PoolGuyNJ    0

Sooting is a significant problem. I usually indicates a problem with the gas to air ratio being too low, resulting in an inefficient burn of the gas. The soot this generated coats the heat exchanger. This reduces it's ability to absorb the heat for the flame and transfer it to the water. It also, if left unchecked, clogs the exhaust, preventing it from escaping/ This creates additional heat in the combustion chamber, further reduces air flow, creating more soot....

The HSI (Hot Surface Igniter) is located under the burner tray in the back. There are two wires that come out the front that go to the ignition controller. Disconnect the the two wires and check the resistance. The check the ignition control and make sure it's putting out the save voltage as is coming into the heater. If the heater is wired for 120, 120 should be present. The same if its wired for 240.

To get at the HSI, the burner tray needs to be pulled. Check for rusted out burners too. This frequently requires some dis assembly of the gas feed unless the split union is in the cabinet. Make sure the gas valve is OFF. Any threaded pipe ends need to be cleaned and a fresh smearing of pipe sealant applied. If you aren't comfortable with working with gas pipe, bring in a qualified heater tech.

Cleaning the soot of the exchanger is imperative too. Usually a hosing down (cover any open gas connections!) with the burner tray removed and the the top removed is sufficient.


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Pool Clown    0

Your heater is not getting enough gas to the burner. that can be pipe size, problem with gas valve, something imparing jet, or burner opening.

Regarding the restart problem. The HSI is kind light, compared to some of the other types, and my have been damaged by the over temp, Exhaust limit temp switch, or the fuse-able link opened. I'm thinking the HSI or the temp switch because if it were the link, it would have had to have opened right at the point when the pool temp reached set point, possible though. Link is easy to check. it should have continuity all the time, like the temp switch. checking the HSI as Scott directed should tell you if HSI is good or open.

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