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Thread: Pool Heater small expolsion during heat cycle

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    Pool Heater small expolsion during heat cycle

    Hi everyone,

    I am a new memeber. Hopefully I get everything correct. My pool is IG and has an accompanying spa. Pool is 35k gallon, cartridge style filter system, hayward LXi no-nox heater. Have a worrysome symptom going on with the heater. When the heater is activated, the pr-blower comes on, the gas valve opens and the unit ignites normal. Later when the unit goes into another heat cycle, I hear a bif wooosh (small expolsion). It seems like there is too much gas in the area when the heat element fires. Looking for some help.

    Pump/filter/heater all replaced 4 years ago. Ignititon control replaced on heater in May this year. Pool located in Southern CA.

    Thanks,

    TOM

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    Smykowski's Avatar
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    Re: Pool Heater small expolsion during heat cycle

    Welcome to the forum.

    Does it sound any different than when your central heat in your house fires up? If I stand next to my furnace, I hear a bit of that whoosh you're talking about every cycle.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
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    Re: Pool Heater small expolsion during heat cycle

    This is definitely different. This is a large combustion, almost sound like far away thunder when I am in the house. I am not seeing an error code on the unit and the unit continue running. As I indicated, the initial ignition is normal with the small woosh you mention. The larger combustion happens when the unit goes back into another heat cycle.

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    Re: Pool Heater small expolsion during heat cycle

    Is this a propane gas unit? You say this is a Hayward LXI ?
    Paul
    http://www.gastekservices.com A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you. If you would like to provide a review of the help I provided, please use the following link to leave a review. gastek - Google Search,

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    Mod Squad zea3's Avatar
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    Re: Pool Heater small expolsion during heat cycle

    I would have it checked out and make sure the gas regulator and the ignition system is functioning properly. Is this the first time using the heater since the ignition system was replaced?
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    Mod Squad Bama Rambler's Avatar
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    Re: Pool Heater small expolsion during heat cycle

    It sounds like the gas valve may be leaking a little gas by when it cycles off and it's igniting the next cycle. Once it's been off for a while it clears out.
    Dave J. TFP Moderator
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    Re: Pool Heater small expolsion during heat cycle

    Sorry for confusion. Heater is a natural gas unit; Jandy LXi Lo Nox.

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    Re: Pool Heater small expolsion during heat cycle

    OK a Jandy. On this model the fan is used to help expel exhaust heat as well as any possible gas build up. It is possible the the fan isn't rotating at the correct speed thus causing the gas not to leave the unit. Or, the fan might be missing some of its blades and not performing as it should. Usually when a unit belches like this, it's a propane unit because propane is heavier than air and will "pool" up on the bottom of the unit.

    My guess is the speed isn't running at full speed for some reason. It could be even a bad motor capacitor causing it not to run correctly.
    Paul
    http://www.gastekservices.com A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you. If you would like to provide a review of the help I provided, please use the following link to leave a review. gastek - Google Search,

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    Re: Pool Heater small expolsion during heat cycle

    Those heaters run the fan at different speeds during the starting/run cycle. Are you aware that, when the fan comes on, the heater isn't actually firing at that point? the fan may run for 15 seconds before you hear a speed change, then the whoosh when it does fire. Maybe you can post a video of the heater as it fires? Then we may be able to tell if it indeed has a problem, or if it is just firing normally.
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    Re: Pool Heater small expolsion during heat cycle

    Thanks, I'll attempt to film a clip of the initial start up which happens normal, then during the next heat cycle when the combustion is much larger.

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    Re: Pool Heater small expolsion during heat cycle

    Quote Originally Posted by tom.burns60
    Thanks, I'll attempt to film a clip of the initial start up which happens normal, then during the next heat cycle when the combustion is much larger.
    The "explosion" you're hearing is rollout. It's caused by accumulated gas in the combustion chamber. Once this is lit, you'll hear the "explosion" you're referring to.

    This is a problem, but not as big a problem as you might imagine. The fact that the heater is still turning on is telling. The in-line (within the safety circuit) fuseable link will melt when the temperature in the cabinet becomes too hot. This fuseable link prevents the heater's other equipment (PIB, PDB, Fenwal, etc.) from being damaged, and by design, it turns the heater off and keeps the heater from firing once it is damaged. In short, if there were rollout to the point you should be concerned, the fuseable link would melt and the heater wouldn't continue to fire.

    I suggest contacting your installer and having him come out to inspect. Make sure he brings a manometer with him so he can measure supply and manifold side gas pressure. It's extremely unlikely the gas valve is the issue - they simply don't fail. If there were an issue here, it would be the Ignition Control. This would be because the pre-purge someone else mentioned will turn the fan on for 15 seconds to assist the heater in ridding any excess gas in the manifold or burner tray.

    In my experience, if the heater is newly installed and you're having this issue, manifold-side pressure is too high. If this heater isn't new, the heater is simply dirty and needs to be cleaned.

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    Re: Pool Heater small expolsion during heat cycle

    I agree with poolguy15. Also if you can see the burners while burning they should look like a near invisible blue flame. If it is yellow like a bic lighter then you probably have carbon built up and the burners need to be cleaned and or a flow problem.

    Quote Originally Posted by poolguy15
    Quote Originally Posted by tom.burns60
    Thanks, I'll attempt to film a clip of the initial start up which happens normal, then during the next heat cycle when the combustion is much larger.
    The "explosion" you're hearing is rollout. It's caused by accumulated gas in the combustion chamber. Once this is lit, you'll hear the "explosion" you're referring to.

    This is a problem, but not as big a problem as you might imagine. The fact that the heater is still turning on is telling. The in-line (within the safety circuit) fuseable link will melt when the temperature in the cabinet becomes too hot. This fuseable link prevents the heater's other equipment (PIB, PDB, Fenwal, etc.) from being damaged, and by design, it turns the heater off and keeps the heater from firing once it is damaged. In short, if there were rollout to the point you should be concerned, the fuseable link would melt and the heater wouldn't continue to fire.

    I suggest contacting your installer and having him come out to inspect. Make sure he brings a manometer with him so he can measure supply and manifold side gas pressure. It's extremely unlikely the gas valve is the issue - they simply don't fail. If there were an issue here, it would be the Ignition Control. This would be because the pre-purge someone else mentioned will turn the fan on for 15 seconds to assist the heater in ridding any excess gas in the manifold or burner tray.

    In my experience, if the heater is newly installed and you're having this issue, manifold-side pressure is too high. If this heater isn't new, the heater is simply dirty and needs to be cleaned.
    -Kevin
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    Re: Pool Heater small expolsion during heat cycle

    I'm assuming that since Hayward does not make an LXi, that you meant to say Jandy. That heater has a sealed combustion chamber, and has no roll out sensor. When you post the video of the heater operating, i think we will get a better idea of what is happening.

    Note: Gas valves can and do fail. Agreed they don't do it often. Just last week i had to replace a bad valve on a (brand new) Hi-E2. That was the second one I've had to replace this year alone.
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    Re: Pool Heater small expolsion during heat cycle

    Quote Originally Posted by Pool Clown
    I'm assuming that since Hayward does not make an LXi, that you meant to say Jandy. That heater has a sealed combustion chamber, and has no roll out sensor. When you post the video of the heater operating, i think we will get a better idea of what is happening.

    Note: Gas valves can and do fail. Agreed they don't do it often. Just last week i had to replace a bad valve on a (brand new) Hi-E2. That was the second one I've had to replace this year alone.
    Of course gas valves fail. That shouldn't have been taken so literally.

    Note: While the LXi has a sealed combustion chamber, it still has a fuseable link in the safety circuit. I have a picture and wiring diagram that will show this but they're too large of fill files to upload here.

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    Re: Pool Heater small expolsion during heat cycle

    Yes, you are correct about the roll out sensor (shows how often i work on those). But you must admit that a roll out condition is not the issue here because we are dealing with a possible pre-ignition problem here, roll out would be a symptom of a post -ignition problem, agreed? Also, if this were roll out, and this would have to be a significant roll out given it's a sealed chamber, that you would have to had an absolute fan failure. Also, a roll out would have tripped/melted the sensor by now, and heater would not run at all.

    I don't think i can comment anymore on this till we see a video. Otherwise we could speculate on the problem forever.
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    Re: Pool Heater small expolsion during heat cycle

    Thanks for all the dialogue. I had to replace the Fenwal back in May. My main breaker had tripped. Upon investigation my ignitor had broken, replaced it. (BTW- why did the designer place the ignitor in the worse possible location for aftermarket replacement). Still no ignition. Thru troubleshooting, boiled it down to the Fenwal. Removed and saw it was damaged on the panel. Installed the new one and it has been working good since May until just recently. I will get the video posted asap.

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