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Thread: Laars LT low nox pool heater - seviceman 'stumped'

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    Unhappy Laars LT low nox pool heater - seviceman 'stumped'

    Hello all,

    I have a Laars LT low nox pool heater (>2003 model) - heater won't work.

    Between myself and one pool serviceman troubleshooted the heater but still can't figure out what is wrong. Perhaps someone can help!? Here is the issue:

    We followed the following appropriate manual (see link) on page 16 and 17 --- http://www.victormfg.com/_build/docs...tingGuides.pdf

    (this is the laars LT low nox pool heater troubleshooting manual)

    steps 1, 2, and 3 are fine
    step 4 - fan is on, yes.
    says skip to step 5.
    step 5, yes, working (24 vac purple wire at both ignition and ignition control terminal are fine)

    step 6:
    hot surface ignitor glowing? No.
    turned power off - ohm test 60 ohms - confirms working
    which suggests ignition control is faulty.

    I purchased $200 exact model and replaced. However, still NO change.

    I turn on for heat - and fan turns on, I hear click, gas turns on... but again, burners do not turn on and it recycles these steps x 3 and then turns off.

    So... I then (just in case) replaced the HSI (hot surface ignitor) with brand new one.

    Again, NO change in above pattern.

    I nor the pool serviceman was able to find a 'short' anywhere.

    Any suggestions please??

    Thank you!!!!!!

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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    It's possible that the old ignitor shorted out the new control module before you replaced the ignitor. What is the part number of the module you used to replace it with?
    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: Laars LT low nox pool heater - seviceman 'stumped'

    I work on a lot of hot water makers ( large commercial water heaters for apartment buildings) Laars is on of the brands that deal with. You possible could have too much air. Ive had units where it blows enough air down the burner tubes and will not let the burners light. You might need to throttle back on the air. There should be an adjustable air damper on the blower.
    27,000 Gallon Inground Gunite Pool with 150 sq ft tanning ledge. Jandy ProFlo pump, Jandy 400K LXi NG heater, Aqualink PDA w/ iAqualink. Polaris 280 cleaner.

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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    There is no damper on the blower. Blowers on pool heaters suck air out, an exhaust. Plus he says the ignitor is NOT glowing.

    Poolhaven, have you tested to see if the module is in fact putting voltage to the ignitor?
    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: Laars LT low nox pool heater - seviceman 'stumped'

    I misread that part about the ignitor. I thought he said it was light but no combustion.

    If your service man can not figure it out, its time to find another service man.
    27,000 Gallon Inground Gunite Pool with 150 sq ft tanning ledge. Jandy ProFlo pump, Jandy 400K LXi NG heater, Aqualink PDA w/ iAqualink. Polaris 280 cleaner.

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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    My apologies --- I actually replaced the ignitor before installing the new control module as I thought that was the initial problem. Any difference in suggestion given that info? Thanks.

    - - - Updated - - -

    Poolhaven, have you tested to see if the module is in fact putting voltage to the ignitor?

    Not yet will try that it in am (dark here). Thanks for the suggestion.

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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    Finally got chance to reassess.

    So to update anyone that can lend a helpful suggestion - I have a laars lt low nox pool heater
    The ags light went on early spring

    Ultimately I repalced the ignition control , the hot surface ignitor and the hsi still did not light
    Finally found a burn on the control module and repalced it.

    Thankfully, now the hot surface ignotor lghts up and the burners then turn on but within few seconds the burners turn back off and the fan turns on

    It does this only one cycle and then the ags light goes on again

    Based on this algorithm - http://www.fwwebb.com/docs/JandyPool...tingGuides.pdf
    Page 16-17 is the heater version I have

    It seems its now stating I should replace the thermostat.

    But 1) anyone agree? If not - any other suggestion?
    2) where is the thermostat?

    Thank you!!!

    Ps - I had a second serviceman confirm that the control module was not functioning - so was glad that after buying this part $125 (plus the hsi and ignition control purchases) the hsi now at least is working. But now I'm out >$500 total. Ugh. Can't imagine asking another serviceman to come back and tell me what else needs to be fixed as I keep paying more $ for someone to tell me buy another part.

    Please help! Thanks again.
    2)

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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    AGS - Automatic Gas Shutdown simply means the Ignition Control did not sense flame rectification. Make certain all gas cocks are open, and there is sufficient gas pressure and volume (gas line sized properly). If the heater fires and then the flame goes out quickly, it indicates the rectification signal is not returning to the Ignition Control. Check for poor or missing ground wire..

    Could it truly be faulty ground wire? Instead of the thermostat. As this is exactly what's hsppening... Heater fires and then flame goes out quickly.

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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    Definitely.
    The ground is as important as a power wire. You need both. I hope that fixes it.
    John (DIYer). Concrete, approximately 13,000 gallon in-ground pool with adjoining concrete spa. Approximately 40 years old. Hayward Super II pump for pool and legacy Anthony Sta-Rite bronze pump CF6 for spa, VA-26 filter,(2 sets), Rheem propane heater for spa. HASA Liquidator for pool.

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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    Quote Originally Posted by hoosierrun View Post
    Definitely.
    The ground is as important as a power wire. You need both. I hope that fixes it.
    There seems to be a few ground wires within the system. Two of them are within the circuits inside the heater unit and another one is 'outside' of the unit (along the base of the heater side door and then grounds to another ground wire at the pool pump. Which wire would I need to change?

    Thanks

    - - - Updated - - -

    See below

    Quote Originally Posted by Poolhaven View Post
    AGS - Automatic Gas Shutdown simply means the Ignition Control did not sense flame rectification. Make certain all gas cocks are open, and there is sufficient gas pressure and volume (gas line sized properly). If the heater fires and then the flame goes out quickly, it indicates the rectification signal is not returning to the Ignition Control. Check for poor or missing ground wire..

    Response:
    All gas cocks are open and gas pressure/volume are appropriate.

    Can u suggest 'how to check' which ground wire might not be working?

    Thanks

    Could it truly be faulty ground wire? Instead of the thermostat. As this is exactly what's hsppening... Heater fires and then flame goes out quickly.

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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    Heater fires and then flame goes out quickly.
    That can happen when the gas nozzles are blocked (usually by spider webs).
    Mark
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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    As for the grounds, I'd slightly loosen any screws and twist the back an forth a little to clean the contact surfaces and then retighten them. If they're spade plugs, unplug and replug them a few times to clean the contact surfaces.
    Dave J. TFP Moderator
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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    There is also the possibility that the heat exchanger could be sooted up causing the flames to roll around inside. Can you see the flames? Maybe a lazy flame. I also believe your unit has a separate flame sensor. Have you tested it?
    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: Laars LT low nox pool heater - seviceman 'stumped'

    Quote Originally Posted by ps0303 View Post
    There is also the possibility that the heat exchanger could be sooted up causing the flames to roll around inside. Can you see the flames? Maybe a lazy flame. I also believe your unit has a separate flame sensor. Have you tested it?
    No haven't tested the flame sensor

    Will clean ground contacts and check flame sensor

    No spider webs seen

    Thanks!

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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    Quote Originally Posted by Poolhaven View Post
    No spider webs seen

    Thanks!
    It's very hard to see spider webs in the orifices. It's best to take a pipe cleaner and push it into each one just in case they are there. You can also run a bottle brush, that's what I use carefully, thru the burners. In order to do this you have to remove the gas manifold.
    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: Laars LT low nox pool heater - seviceman 'stumped'

    The webs are on the inside of the gas nozzle so you have to remove them to see them. Did you remove them?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
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    Re: Laars LT low nox pool heater - seviceman 'stumped'

    Quote Originally Posted by mas985 View Post
    The webs are on the inside of the gas nozzle so you have to remove them to see them. Did you remove them?
    Yes used mirror and was not able to see any webs. But in addition i had used a long pipe cleaner to each one just in case

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