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  1. #1
    Join Date
    Feb 2006
    Location
    michigan
    Posts
    175

    Tripping vent switch on Nordyne furnace issue

    I recently ran into a issue with a tripping vent stack switch on a Nordyne 90% 1 pipe upflow furnace. I found the blower wheel dirty along with a dirty secondary heat exchange and evap coil. I have blown out all listed componenets with CO2 as best as I can.. I also have checked the exhaust vent going outside. Everything appears to be clear. But i am still tripping out on a vent limit. Is there a better way to clean out the secondary heat exchanger. It still feel like the top of the furnace is getting real hot. I am going back to do a temp rise and combustion analysis. I ran out of time when I looked at it the other day. Any suggestions would be helpful. If needed, I can provide the model and serial.

  2. #2
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,699
    Just a few quick suggestions.
    Check draft while you're at it. And get the specs on the pressure switch to make sure it has not been changed improperly.
    And verify the installer used the right size PVC pipe. I found a 120k furnace vented with 2" PVC because that was the size of the fittings on the furnace. Of course it should have been 3" PVC.
    Never take anything for granted.
    Nordyne furnace - is this on LP? Check the gas pressure and manifold pressure. An undersized gas line will cause the secondary heat exchanger to become plugged.
    Just a few quick suggestions.

  3. #3
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,356
    Remove the inducer and check to see if the restrictor orifice is in the inlet. I bet it has rotted away. Get a new one and you'll be good to go. With the orifice missing, the gasses get pulled through so fast they dont have time to give up their heat

  4. #4
    Join Date
    Feb 2006
    Location
    michigan
    Posts
    175
    the furnace is only 80,000 BT U's . It is vented with 2 inch PVC and only goes about 8 feet. I check the outlet of the flue and it is clear. I will pull of the inducer today and take a look at the plate

  5. #5
    Join Date
    Feb 2006
    Location
    michigan
    Posts
    175
    It is on natural gas. I did have to go through and clean the blower wheel. I also tried to blow.out the secondary heat exchanger and evap coil with co2. It seems that the upper back side.of.the cabinet is getting hot. I will check gas pressure. Not that i can adjust it because there doesnt appear to be a adjustment screw on the valve.

  6. #6
    Join Date
    Dec 2011
    Location
    Twin Cities Minnesota
    Posts
    223
    Have you verified the "hi limit' is good. I've been using my digital temp probe.,remove limit.insert into cabinet,works well!

  7. #7
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    3,255
    did you check hx? had one last week tripping limit. hole in hx was reducing flow into hx, flame off burner was heating top of furnace and hitting rollout sw.
    Col 3:23


    questions asked, answers received, ignorance abated

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