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  1. #14
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    So, what’s the proper solution?

    Exactly what the tech suggested, replacement.

    CO poisonings from improperly adjusted furnaces were much more common as well, back in the day.
    Today’s modern furnaces make it very difficult for a furnace to cause CO related deaths.
    "The only true wisdom is in knowing you know nothing" Socrates

  2. #15
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    Quote Originally Posted by mgenius33 View Post
    So, what’s the proper solution?

    Exactly what the tech suggested, replacement.
    Or, an older tech that has done capping, and knows more than just to say, you need a new furnace. After 30 years, the only thing a combustion analyzer will show, is a false high O2(unless its an old barometric and each individual cell is checked like it was suppose to have been done). Along with an accurate low flue/stack temp. That could cause condensation in the flue, but not the cells.
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  3. #16
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    Quote Originally Posted by beenthere View Post
    Or, an older tech that has done capping, and knows more than just to say, you need a new furnace. After 30 years, the only thing a combustion analyzer will show, is a false high O2(unless its an old barometric and each individual cell is checked like it was suppose to have been done). Along with an accurate low flue/stack temp. That could cause condensation in the flue, but not the cells.
    With a low gp setting because it was over heating? So, you’re saying CO is not an issue with this configuration?

    In any case, there’s absolutely no reason a tech should place the company or client at risk. It’s absurd to condemn a tech for protecting the interests of his company and client.
    "The only true wisdom is in knowing you know nothing" Socrates

  4. #17
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    Hmmm... we seem to have a variation of a 'catch 22' here...

    *Guessing... the furnace was installed in a time when small furnaces were not readily available... so the installer modified the furnace (something that is seriously frowned on today... ).
    *A tech came along and tried to set the unit back to factory specs (what techs are trained to do)... resulting in problems due to the rigged installation.
    *Over-heating resulted...
    *The furnace is WAAAAY beyond its useful life... and may well be dangerous!

    Conclusion:
    There is not really a simple and easy fix here... because:
    *The original install was not done properly...
    *The unit is grossly oversized (remember: in heating and AC... bigger is NOT better, it is WORSE... even worse than too small).
    *And the unit is beyond its normal service life.

    The best solution... would be a new furnace...
    However...
    Be ABSOLUTELY SURE the contractor you choose... will size the furnace properly for your home...
    AND
    Install it correctly!

    Installation is more important than the brand name on the box.

    Here is an analogy:
    Does it matter what brand of filling a dentist puts in a cavity???
    And does it matter if the dentist does the filling properly???


    Oh, and we could carry this to glasses/contacts also...


    One last thought: While the highest price may not guarantee the best job...
    The cheapest price WILL usually guarantee the worst job!
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

    GA's basic rules of home heating and AC upgrades:
    *Installation is more important than the brand of equipment
    *The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
    *Cheap is not good, good is not cheap; however expensive is not a guarantee of quality!
    Choose your contractor wisely!

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  6. #18
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    Quote Originally Posted by mgenius33 View Post
    With a low gp setting because it was over heating? So, you’re saying CO is not an issue with this configuration?

    In any case, there’s absolutely no reason a tech should place the company or client at risk. It’s absurd to condemn a tech for protecting the interests of his company and client.
    The manifold pressure was at 3.2" which is what most manufacturers list as the min. And many furnaces do burn better at slightly less than 3.5".

    Those techs may have just been interested in getting a sales commission. None of know if they get commission or not.

    No reason to believe those techs were thinking of their company's liability about it, other than making a sell.

    I've met several techs that recommend replacement simply because a furnace is older than 15 years.
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  7. #19
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    Quote Originally Posted by beenthere View Post
    The manifold pressure was at 3.2" which is what most manufacturers list as the min. And many furnaces do burn better at slightly less than 3.5".

    Those techs may have just been interested in getting a sales commission. None of know if they get commission or not.

    No reason to believe those techs were thinking of their company's liability about it, other than making a sell.

    I've met several techs that recommend replacement simply because a furnace is older than 15 years.
    Well, all that aside, and answering one of the OP's questions, did the gp adjustment from 3.2" to 3.5" cause overheating and a burning smell? I highly doubt it. Having worked on many older ribbon style, cast iron heat exchanger and atmospheric draft furnaces, I would suspect there's more to this furnace than what is being described.
    This furnace doesn't even sound like it's all that old. From the description of work it appears to be a 3 wire pilot, 5 wire gas valve type.
    "The only true wisdom is in knowing you know nothing" Socrates

  8. #20
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    Quote Originally Posted by mgenius33 View Post
    I would suspect there's more to this furnace than what is being described.
    Could be the blower motor is over heating if its 30 years old, or the transformer. Which would have nothing to do with the gas pressure.
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  9. #21
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    The original installer probably adjusted the burner input to better match the furnace with the house 36 years ago. Which used to be a somewhat common practice. Any chance the original manual is there somewhere near the furnace? I always leave them on furnace installs and it may well detail the capacity reduction procedure. The gas pressure reduction was probably a part of the capacity-to-space adjustment of the furnace as well.

    Ignition delay / poor flame propagation often results from corrosion, and/or accumulated dust/dirt - something which any truly thorough inspection and cleaning would have remedied.

    If the original install ran well for 36 years - was then changed and the furnace subsequently exibited adverse symptoms - it seems reasonable to project that the changes were the genesis of the adverse situation.

    What was the gas pressure turned up TO?

    What is the gas pressure supposed to be? And how do we know that?

    Ws the heat exchanger examined with a camera or otherwise?

    Was any combustion analysis done?

    Was the temperature rise checked and found to be within the furnace's rated range?

    PHM
    ----------



    Quote Originally Posted by Warmest View Post
    Recently had my 36 year old Carrier furnace checked and cleaned by the same tech that came last year. He said that he adjusted the gas flow up even though the 3.2 rate wasn't causing an issue. He also readjusted the angle of the ignighter because there was a delay between the lighting of the pilot and the burners. During this visit he was pressing me to buy a new furnace. After he left I noticed a hot plastic smell coming from the ceiling vents. Within 30 hours the fan was running continuously and the burners were not turning on.
    I called and another tech came and told me that the furnace overheated and the safety shut off was tripped. He also said the fan board wasn't working unless he kicked it and needed to be replaced. Without asking, he replaced the the ignighter because he did not like the delay between the pilot and the burner lighting. During this visit I was again pressured to buy a new furnace. I again refused. After several days of waiting for a fan board, and stalling by the tech, I called a supervisor and explained my concerns. He refused to entertain that turning up the gas flow caused it to overheat and damage the fan control board. He agreed to send a tech and to turn the gas flow back to where it was and to replace the fan control board but all at my expense. He replaced the fan board but refused to turn down the gas flow.
    The home is 816 sq ft. The furnace has 4 burners with one capped so only three ignite. The vents are in the attic and are buried under wooly insulation.
    What is your take on my situation? The hot plastic odor still comes from the vents when the heat is on..
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  10. #22
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    In what way exactly?

    Quote Originally Posted by pecmsg View Post
    One burner is capped? That's dangerous!
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  11. #23
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    Whew!
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  12. #24
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    Thread Starter
    Thank you for understanding my situation. I am concerned with safety and want to know if turning up the gas pressure is causing the furnace to overheat.

  13. #25
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    I agree with PHM on this one.

    You didn't have a problem until someone messed with it, at least not performance wise. Sure, you could replace it, but I doubt it's necessary to get it working like it was.

    I don't think that having a capped burner and then turning the gas pressure down makes a lot of sense, if you have a pipe with a certain amount of flow, you then cap one, then you adjust it to be 3.3" or whatever it is on furnaces, but it's adjusted that way AFTER the pipe was capped.

    If you took the burner and capped it without adjusting gas pressure after, you would have excessive gas, but that obviously wasn't the case here since it worked fine for ages and then someone messed with it.

    In theory, excessive gas CAN cause an overheat if there is EXCESSIVE gas, as in the tech turned it above the manufacturers recommendation, but otherwise it shouldn't. Considering that you didn't have a problem until it was turned up, I would just turn it back down to where it was or actually find out why it's overheating if the gas pressure is at the right setting.

  14. #26
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    Quote Originally Posted by Warmest View Post
    Thank you for understanding my situation. I am concerned with safety and want to know if turning up the gas pressure is causing the furnace to overheat.
    In short it seems like it is.

    That furnace setup is not unusual at all for the time it was installed. If the airflow is low as suspected, temp rise was probably used to set the manifold pressure after the burner was plugged. As long as the heat exchanger is intact, it is safe to operate if setup properly again.

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