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  1. #1
    Join Date
    Sep 2008
    Posts
    7

    need independent opinion on past diagnosis of blocked vent sensor issue

    Hi,
    please, understand that my goal is to figure out if my current service provider is capable/willing to fix my issue or if they are the wrong people and I should hire someone else. It is NOT my goal to fix everything myself. But I DO need more info on this:

    OK, last december my 58UHV HVAC stopped working. Important detail: after it stopped working I realized that I never (maybe for a year or more) cleaned the air filter and it WAS real clogged. So I cleaned it but surely enough that alone did not make the unit work again. My service company sent a technician and he found that blocked vent safeguard sensor went off. He took some measurements, found nothing weird with the unit and he heard from me that air filter was clogged when it sensor went off.

    So, he reset the blocked vent sensor and the unit ran. He observed it for 20 minutes - it was still running. So he considered the case resolved and he wrote in his report: reset sensor, problem was due to clogged air filter.

    However, I had the same sensor coming off once every few months after that - once in March and two times just few days ago. Of course, I cleaned the air filter regularly. So I suspect that last time they did not diagnose the problem correctly and instead they used clogged air filter as an excuse that they resolved it.

    The more I learn (or I think so) about the nature of this issue the more I doubt that they are not messing with me. I need an independent opinion: is it at all possible that a clogged air filter which is obviously located on the air intake side could cause a blocked vent safeguard sensor to come off ???
    Why is it then called "blocked vent sensor" in the first place???

    I just talked to another technician from the same service company who was about to come to my place (I canceled him) and he seems to make sense out of that previous report. He even asked me: "well, do you have a clean air filter this time?"

    At this time I doubt he is either sincere with me or qualified. I understand that even if air filter is clogged but if at the same time flue is drafted properly from above then flue should not ever make it into the opening for the sensor to trip it off.

    Please, tell me: am I wrong and he makes sense covering the diagnosis made previously by his associate or do they just cover each other up making wrong statements instead of doing a fair work?

    I can't afford them just doing another "inspection" of the whole unit for $155 (that's what they are suggesting) and leave claiming that dusting something off and installing a new sensor really fixed the issue this time.

    And the problem is: I can't really verify that unit is any better after they leave. Because it trips off, well, just once every few months.

    I am thinking that maybe I need to switch to some other company. But again, they have only dispatchers on the phone who dispatch random technicians. Who knows if I will be more lucky with other company. Would it make sense to look for an individual (vs. a company) that I could talk to first and make sure he makes sense talking about possible causes of this issue before he comes?

    But again, then I need to know more myself. Please, do not close this thread too soon.

  2. #2
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Theou phores?

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Well, first you should read teh rules.
    Then you would know, not to post prices either. Like the diagnostic price you posted.
    Since the blocked flue switch is a thermal switch. A dirty filter could have caused it. So the tech was reasonable with his opinion.

    You don't know the chimney is drafting properly, since you didn't check its draft with a manometer/draft guage.

    Look in the phone book, for companies with NCI certs. Or go to their website and see if list any certified companies in your area.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    Mar 2005
    Location
    Houston, Texas
    Posts
    11,859
    If you don't trust your present service provider, then you need to find another one. Simple question, simple answer.

  5. #5
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,541
    Is it windy when the thing kicks off? If it is, it could be the wind preventing the flue gases from escaping, we get that once a year or so. Especially where it is very windy. The answer is a high wind vent cap. Since you had a dirty filter, there is a good chance your coil looks just the same which would cause the same thing. Another possibility is if you have a newer stubby Carrier furnace, there are perforated lips on the top of the furnace that need to be bent up when it was installed. I went to a class on them when they first came out and was told it could cause the switch to trip periodically.

  6. #6
    Join Date
    Mar 2003
    Posts
    1,234
    Quote Originally Posted by bmathews View Post
    Is it windy when the thing kicks off? If it is, it could be the wind preventing the flue gases from escaping, we get that once a year or so. Especially where it is very windy. The answer is a high wind vent cap. Since you had a dirty filter, there is a good chance your coil looks just the same which would cause the same thing. Another possibility is if you have a newer stubby Carrier furnace, there are perforated lips on the top of the furnace that need to be bent up when it was installed. I went to a class on them when they first came out and was told it could cause the switch to trip periodically.
    Newer units have an auto reset safeguard switch for that very reason--to prevent unnecessary calls when it goes off under windy conditions. Raising the vent 18-24 inches usually takes care of that issue.

  7. #7
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    This is a dup post.

  8. #8
    Join Date
    Jun 2006
    Location
    Southeastern Connecticut
    Posts
    841
    Quote Originally Posted by beenthere View Post
    Well, first you should read teh rules.
    Then you would know, not to post prices either. Like the diagnostic price you posted.
    Since the blocked flue switch is a thermal switch. A dirty filter could have caused it. So the tech was reasonable with his opinion.

    You don't know the chimney is drafting properly, since you didn't check its draft with a manometer/draft guage.

    Look in the phone book, for companies with NCI certs. Or go to their website and see if list any certified companies in your area.
    Please explain how a dirty air filter could cause a blocked flue switch to trip

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Answer is PMed to you.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

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