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  1. #1
    Join Date
    Sep 2008
    Location
    Portland
    Posts
    43

    Carrier 59MN7 with multiple faults

    Hey all, I'm returning for your advice on how best to resolve some issues with my furnace (and maybe my contractor).

    About a year ago, I had this furnace installed after doing quite a bit of research on what I wanted and needed.

    Overall, the furnace works great, but... it semi-regularly will throw fault codes. The biggest offender is the low pressure switch open code, which has happened 55 times(!) over the course of the year.

    The only noticable impact of all this is the furnace will kick into high fire unnecessarily - this is apparently the failsafe behavior after the low pressure switch fault. It's annoying because in my small house, 60k BTU is a lot of heat and will make you break a sweat when it's running full-tilt on a mild day.

    The total accounting of the errors:
    32- low pressure switch open 55 times
    42- inducer fault 2 times
    34- ignition fault 18 times
    33- limit fault 3 times

    Now I've had the contractor out 3 times, twice in the spring and again recently. They have gone through all the standard troubleshooting steps several times, including checking the intake/exhaust plumbing. In the spring they replaced the low pressure switch and increased the inducer speed, but summer came before I really had a chance to find out if they fixed anything. Now that cold weather has returned it's clear that nothing has been resolved.

    I had them come out again and they checked it out again, but didn't come up with anything better than "lets keep an eye on it". Of course the Low pressure fault has happened a couple times since then.

    I'm getting tired of their lack of results, so I'm hoping that you can tell me whether the manufacturer offers any troubleshooting assistance for the contractor on troublesome issues.

    Any and all advice is appreciated!

    Thanks.

    BTW my previous thread on this subject is here:
    http://hvac-talk.com/vbb/showthread....mal&p=12565271

  2. #2
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,956
    Where are you located?

    I would have a trained carbon monoxide/combustion efficiency expert perform an analysis on the system. They can not only make you comfortable but, can save you money on fuel bills.

    Post your location.

  3. #3
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,029
    Quote Originally Posted by gravity View Post
    Where are you located?

    I would have a trained carbon monoxide/combustion efficiency expert perform an analysis on the system. They can not only make you comfortable but, can save you money on fuel bills.

    Post your location.
    ^^^ that's something you should consider. To answer your question, yes all manufactures have technical support for their dealers. A lot of times it's easier for the tech to figure something out than call tech support but a lot of times tech support may know a quick fix to a the problem from past experiences with the same problem. If nothing else tech support will walk them through what to check and what readings they should be getting.

  4. #4
    Join Date
    Sep 2008
    Location
    Portland
    Posts
    43
    Thanks for the replies.

    I'm in Portland, OR.

    Can you elaborate on exactly what a CO/Combustion Efficiency expert would do? And how I would find one?

    As for saving $, I'm not sure they could make a significant difference - the highest bill over the winter was 52 therms for a whopping $66... I still haven't used up my $300 promotional credit from the installation a year ago!

    I've suggested/asked the tech about calling the manufacturer but he didn't seem too keen on it. My thinking was along the same lines as yours - the tech support might know something that's not covered in the standard troubleshooting flowchart. This guy is talking about redoing the plumbing or replacing the motherboard as a next step, but that sounds like he's grasping at straws.

    Anyway I appreciate your input!

  5. #5
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,956
    They would tune your furnace to the maximum efficiency. They also add safety to the furnace that it currently lacks from the manufacturer. You can find one by going to stopcarbonmonoxide.com

  6. #6
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,728
    Replace the circuit breaker dedicated to your furnace in your fuse box with a brand new one. You should also clear the history codes in the stat as well. Replace circuit breaker with same vendor of fuse box and exactly same amperage.

    Let the system run for a few weeks and report back. Should solve most all of your error codes. If not, then you know there are bigger issues to to deal with.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  7. #7
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,956
    I am trying to understand why replacing the breaker would correct any issues with the furnace.

  8. #8
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,728
    Its a noise issue. Computers are very susceptible to noise. Ever wiggle a speaker wire? Does it effect fidelity?

    Could probably plug in a UPS as a test. That should provide clean power. If that doesn't cure it, probably not the problem.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  9. #9
    Join Date
    Sep 2008
    Location
    Portland
    Posts
    43
    Quote Originally Posted by tedkidd View Post
    Replace the circuit breaker dedicated to your furnace in your fuse box with a brand new one. You should also clear the history codes in the stat as well. Replace circuit breaker with same vendor of fuse box and exactly same amperage.

    Let the system run for a few weeks and report back. Should solve most all of your error codes. If not, then you know there are bigger issues to to deal with.
    Thanks Ted, this is an intriguing theory. I believe that the CB was new when the furnace was installed because we moved the furnace from the location of the previous one, and because the previous furnace wasn't on a dedicated circuit, so we had to add a new circuit to comply with code.

    However - it wasn't a new "home run" circuit from the furnace to the panel... in order to avoid tearing up the finished basement ceiling, we got creative and adopted the disused wires from the old AC unit (which happened to run past the old furnace location) and then extended that circuit to the new furnace location.

    So, to hopefully make things more clear... the circuit runs on the old AC feed (formerly 240v, so the wires are oversized) to the site of the old furnace, into a junction box, and then new wires for the run to the new furnace.

    Since it was switched from 240 to 120, I'm pretty sure he had to change the breaker. And clearly the connections/splices are new, so unless he screwed something up it doesn't seem likely that this would introduce noise... but I guess the condition of the old AC wires behind the drywall is unknown.

    Also FWIW the whole panel was replaced just about 2 years prior to the furnace install.

    I guess running off a UPS would be an option to see if the issues are resolved, but how would we be able to connect it to a UPS in a code-compliant way? Doesn't the furnace need to be hardwired?

    Thanks again for your thoughts.

  10. #10
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    What does the outside vents look like? Any chance it's throwing this fault on windy days? I could see the unit being much more suspeptible to draft issues in low stage than high stage.

  11. #11
    Join Date
    Sep 2008
    Location
    Portland
    Posts
    43
    Quote Originally Posted by motoguy128 View Post
    What does the outside vents look like? Any chance it's throwing this fault on windy days? I could see the unit being much more suspeptible to draft issues in low stage than high stage.
    I've considered the wind possibility but there doesn't seem to be any correlation between windy days and faults.

    The vent kit looks like this:
    http://www.ncweb.com/users/jsbuilder...170K00000S.jpg

    Anybody know anything about issues with these vent kits?

  12. #12
    Join Date
    Feb 2011
    Location
    Cloverdale,Ca
    Posts
    316
    Is there any chance the low pressure safety switch is doing its job and warning you of a low incoming gas situation? I have fixed a few Bryant furnaces by adjusting the lp pressure starting at the regulator coming out of the lp tank, and then resetting the gas pressures and temperature rise by strictly adhering to the instillation instructions. Find out what the incoming gas pressure is and go from there. Good luck.
    Living the dream !!

  13. #13
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,956
    Good call tedkidd.

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