roll-out tripping!
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  1. #1

    Confused roll-out tripping!

    Hi guys,

    new guy on here, working on a HEIL Model # H9MPD075F12A2 that is tripping the rollout swith after watching the thing run and start many times it has become evident that there is no flame rollout it is simply overheating and it is only the right switch which mounts a little higher on the box than the left side, I have switch the switches around and it trip on the same spot. the furnace does have a little higher than normal heat rise but nothing to alarming maybe 50-60 but it is already on med-hi speed. filter clean and all registers open. pressure on the collector box is 2.80" H2O unfortunatelly cant get a reliable reading @ the burner box as its cabinet not just the box. Both intake and exhaust returned my golf ball, so not sure if I want to condem the secondary HE or is something else going on. I wish there was some data on the design static of the draft @ the collector box oddly enought I think it is related to the high heat rise but how?

  2. #2
    Join Date
    Jun 2004
    Location
    Eugene, Oregon
    Posts
    1,018
    Could be over-fired. Did you check gas pressures?

  3. #3
    Join Date
    Nov 2012
    Location
    Tahlequah OK
    Posts
    131
    I used to install Heil equip. but it's been a few years since I sold any. Is this a 90+ or above furnace? Sounds like it is. Sounds like you have a leak in the burner box somewhere close the the roll out switch that's tripping. You must have a blockage of some sort in the air flow causing the high heat rise and tripping the ROS

  4. #4
    I thought about that but could not make any sense why it would start all of the sudden, but that will be next probably monday!

  5. #5
    Join Date
    Oct 2012
    Location
    Danville, KY
    Posts
    30
    I worked on my first goodman furnace for a friend a few months ago doing the same thing, it was a 90+. I never saw any flame rollout but it tripped when it was cold and had to run a lot overnight.

    I went down on the gas pressure to about 3" and it helped a lot but didn't fix. after cleaning the secondary and didn't get better results we changed out the heat exchanger and took care of the issue. I couldn't find a hair crack in it but I guess it had to be there though.

  6. #6
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,032
    Easy to diagnose with a combustion analyzer...

  7. #7
    sorry, forgot to mention that has been done the flue readings where about 89% efficiency 122F & 6.2 CO

  8. #8
    Join Date
    Jun 2012
    Location
    Northern NV
    Posts
    148
    CO rots steel! Any CO. If you have pulled a water heater burner covered with flakes of rust, you have seen CO at work. I concur with the flakes in the secondary. ALSO; you mentioned the Delta T being high. Perhaps a restricted duct? What is the External static on the system?

    Quote Originally Posted by frustraded tech View Post
    sorry, forgot to mention that has been done the flue readings where about 89% efficiency 122F & 6.2 CO

  9. #9
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,309
    Quote Originally Posted by Juan Madera View Post
    CO rots steel! Any CO. If you have pulled a water heater burner covered with flakes of rust, you have seen CO at work.
    The acidic condensate during cold opperation rusts the steel, not CO. Before the discovery of natural gas, CO from coal gasification was delivered through the same steel gas lines for lighting coal burners and it did not rot them out.

  10. #10
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,032
    Quote Originally Posted by chippert View Post
    I worked on my first goodman furnace for a friend a few months ago doing the same thing, it was a 90+. I never saw any flame rollout but it tripped when it was cold and had to run a lot overnight.

    I went down on the gas pressure to about 3" and it helped a lot but didn't fix. after cleaning the secondary and didn't get better results we changed out the heat exchanger and took care of the issue. I couldn't find a hair crack in it but I guess it had to be there though.
    I would bet if you took the plate off the hot side of the secondary, you would have found a lot of rust flakes plugging some of the tubes going through the secondary.

  11. #11
    Join Date
    Oct 2012
    Location
    Danville, KY
    Posts
    30
    Quote Originally Posted by chuckcrj View Post
    I would bet if you took the plate off the hot side of the secondary, you would have found a lot of rust flakes plugging some of the tubes going through the secondary.
    There was a little junk in them. I used a 45 caliber bore to clean them. looked like need when I got done though.

  12. #12
    I don't know what you mean by hot side of the secondary?? but I've inspected the collector box, I guess they are prown to cracking and while it was off all the pipes of the secondary looked pretty clean, some rust but nothing flaking off.

  13. #13
    this particular unit did not have any sludge what so ever!

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