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  1. #1
    Join Date
    Jan 2008
    Location
    East berlin, PA
    Posts
    281

    Superior model DS-41TN- limit switch is open- where is it?

    This unit is in a restaurant. The unit won't fire till I bypass the 2 wires that go up the left side of the unit. Must be a limit switch somewhere that is open. I was hoping to look at a diagram of the unit so I knew how to get to it. Also, I can feel hot air on the left side beside the glass. Does this mean the glass gasket is shot?- No, I did not leave anything bypassed. Looked at the Lennox site, I can't find the model number I'm looking for because they seem to be called names instead of models. Might be tough getting any parts if this unit is obsolete. Any info would be helpful.


    Thanks

    Tony
    "Delay is preferable to error"- Thomas Jefferson

  2. #2
    Join Date
    Jun 2011
    Location
    Fresno, CA
    Posts
    196
    Not sure if its HHT or Lennox but was calling tech to ask some questions about superiors. Been running across alot of them and seen some familar components in them step down transformer,

    ignition robert shaw 745/845 modules, door switches, limit switches, direct spark etc... Asked my boss about replacing components in these old units and was told if I was to replace the ignition

    module then replace the ignition system as well. The limit I saw was top front screwed into the top of the unit very easily assessible, the others I run across are hidden behind the bottom burner

    tray/logs. Lennox didn't recommend to replace the module on the system I was working on because it was an existing 745 Robert shaw and the parts house only had a 845 which was compatible

    but not the exact part number etc.. and wanted me to suggest them buying a new unit?? It may be obsolete and its not like A/C units you can't just put a part that works it has to exact match or

    manufacuer recommended etc... The model number is somtimes hidden on the side panels and the diagram should be under the transformer plate/compartment or under the unit. let me know how i

    goes and good luck.

  3. #3
    Join Date
    Dec 2011
    Location
    PA
    Posts
    199
    Sounds like it could be a B-vent set up, and your spill switch is tripping or is bad. First check all connections, reconnect every spade connection you can find. Most no starts I find its just a bad connection in the switch loop. If all that checks out and the unit stilll wont fire, check for continuity on your switch.

    Now back to the spill switch if there is one, on B-vent units mfg. put a spill switch on, so if the exhaust is blocked the flue gases start coming out the front of the unit, tripping the spill switch and shutting the unit down for safety. The fact you feel hot air tells me there is a problem with the glass gasket or possibly the exhaust. Make sure the glass is seated and latched.

  4. #4
    Join Date
    Jan 2008
    Location
    East berlin, PA
    Posts
    281

    After further investigation- Problem solved!

    Sometimes with these kinds of problems I'm hesitant to just start tearing things apart for fear of something falling apart or whatever. And then not having any info on the unit,trying to figure how to get it back together.

    I went back to this unit and on the reverse side of the model plate was the wiring diagram and the problem was the door switch. I located the door switch and then noticed because of the heat I had felt coming out beside the glass when I had bypassed that switch temporarily the glass door was not on right. I removed the two spring loaded screws from both sides at the top and removed the glass/frame. There are pins at the bottom of the glass/frame that were not seated in the slots so there was a gap. Once I reinstalled the glass/frame starting at the bottom and then reinstalled the screws at the top, there was no more leakage and the door switch was closed and everything worked. As a side note there was an awful lot of turbulence while the glass/frame was not installed right and as soon as the gap was sealed everything calmed down, including the pilot. I suspect someone removed the glass to clean it and never reinstalled it correctly.
    "Delay is preferable to error"- Thomas Jefferson

  5. #5
    Join Date
    Dec 2011
    Location
    PA
    Posts
    199
    cool, glad everything worked out.

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