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  1. #1
    Join Date
    Jul 2007
    Posts
    75
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    Lennox LGA180SH1J heat issues

    Hi, been having a problem with a Lennox rtu from a service call. Two heat sections that run at same time. First sections ventor motor runs but trips off on air switch, had spare switch so changed out with same result, will run on heat with switch jumped out. Checked heat exchanger( no cracks) cleaned flame sensor etc. Put digital manometer on venter motor initially starts out at 1.47 inches water and runs down to .6(in about 6-10 minutes). Not jumped out will then short cycle off on pressure switch. I also pulled burners out as well and brushed out quite of a bit of crap out of heat exchanger tubes with boiler brush. Ventor motor rated for . 6 amps Was running with .5 amps

    Second burner also had similar air switch issue but not as consistent. The problem with this section is a error code saying gas valve not energied after 2 min after call and error saying secondary limit open heat 2. I was able to change limit with another working one so side no longer locked out but limit error code still appears every five minutes or so. I opened up economizer to get some cooler air in to get limit to stay closed. Can’t say because I couldn’t access space if some diffusers are closed.

    Any thoughts on what I am possibly not seeing?

  2. #2
    Join Date
    Jul 2007
    Posts
    75
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    Thread Starter
    Just to follow up, I replaced ventor motor about a week ago and the rtu is still heating.

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