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  1. #1

    Evolution 32-Low Pressure Switch Open events

    I have an Evolution system (355CAV042060, 186BNA018000, CNPVP2417ATA, and SYSTXBBUID01-C). While I've owned this system I've seen a small number of 32-Low Pressure Switch Open events. IIRC, they've always occurred during heating season. ATM I can't remember what my contractor said about these but my impression was that they are nothing to be concerned about.

    A little while ago I heard unusually high air flow coming out of a supply register. Higher than I've ever heard before. I suspect it was the type of airflow that would be produced by the system running on High. My home doesn't require high output and my system is actually set to Low+Medium. The setpoint for heating is 72, all the time, and the system rarely even needs Medium. It isn't that cold out tonight, a bit windy at times but nothing that would challenge my furnace running on Low, nothing had caused the house to drop significantly below 72 to begin with, so this period of high air flow seemed very much out of place.

    It took me maybe 2-3 minutes to get to the room where the return intake and Evolution control are. As I got there the blower had just finished ramping down to a level consistent with Low. It remained on Low for a short period than turned off. Curious, I went into Last 10 System Events and saw what appeared to be an entry from just a few minutes earlier:

    FN 12/21/2012 1:55A F
    32-Low Pressure Switch Open Events
    6 Events

    Which leads me to believe that event and the period of unusually high airflow may have been related. The system has been operating OK since then, on just Low. However, I'd like to know what happened there. Any thoughts on this? Thanks, happy holidays.

  2. #2
    Well, the same exact thing just happened again. It seems something is causing the system to start running on High and high airflow (confirmed via control, despite staging be set to Low+Medium), it runs that way for a very brief period, then falls back to Low. Again there was a 32-Low Pressure Switch Open Event at or about the same time. I'll be calling this in, but would still welcome any thoughts you have or suggestions for information gathering before hand.

  3. #3
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    1,934
    Nice thing about the evolution system and the control you have is it is already collecting all the information that the technician should need to know as far as how the system is and has been working. Only other thing they'll be possibly interested in is the observations you have made on how it's been acting/sounding etc.

    Let us know what they find.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  4. #4
    Join Date
    Aug 2012
    Location
    Burgaw.NC
    Posts
    2
    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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    Last edited by jpsmith1cm; 12-21-2012 at 07:05 PM. Reason: Non AOP Member

  5. #5
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    24,940
    O.G.



    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

    You can find the rules for posting and qualifications here.

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  6. #6
    Quote Originally Posted by firecontrol View Post
    <snip>Let us know what they find.
    FWIW, by early morning I ended up with:

    FN 12/21/2012 5:52A
    32-low pressure
    switch open
    11 events

    FN 12/21/2012 5:36A
    12 blower on after
    after power up
    1 events

    and no additional faults since. That day and weekend got hectic and the system had settled down, so we ended up NOT contacting the contractor and simply monitoring it closely. I since dug up a troubleshooting guide...

    32 LOW-HEAT PRESSURE SWITCH DID NOT CLOSE OR REOPENED Indicates the low-heat pressure switch input failed to close on a call for low-heat, or opened during low-heat. If opens during blower on-delay period , blower will come on for the selected blower off-delay. If opens during low heat within 5 minutes after ignition the next heating cycle will be restricted to high-heat. Check for:
    <other things>
    - Excessive Wind
    <other things>

    I find it interesting that wind can be factor, and also that there is a scenario where high-heat would be triggered. Both having occurred that morning. I don't know what to make of:

    12 BLOWER ON AFTER POWER UP (115 VAC or 24 VAC) Blower runs for 90 seconds, if unit is powered up during a call for heat (RW/W1 closed) or (R-W/W1 opens) during the blower on-delay period.

    Perhaps if I carefully read through manuals I'll find an answer to this, but ATM just based on something my contractor said, I have the impression that if there was/is a serious fault you wouldn't have to go looking for it. It would in some way be displayed on the home screen so to speak. ATM I'm thinking I should just continue to keep a close eye on it. It was just inspected in early December and otherwise seems to be OK. Seem reasonable or would you want a customer to inform you of such a scenario?

  7. #7
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    1,934
    Quote Originally Posted by WhatsThatSound View Post
    FWIW, by early morning I ended up with:

    32 LOW-HEAT PRESSURE SWITCH DID NOT CLOSE OR REOPENED – Indicates the low-heat pressure switch input failed to close on a call for low-heat, or opened during low-heat. If opens during blower on-delay period , blower will come on for the selected blower off-delay. If opens during low heat within 5 minutes after ignition the next heating cycle will be restricted to high-heat. Check for:
    <other things>
    - Excessive Wind
    <other things>

    I find it interesting that wind can be factor, and also that there is a scenario where high-heat would be triggered. Both having occurred that morning. I don't know what to make of:

    Perhaps if I carefully read through manuals I'll find an answer to this, but ATM just based on something my contractor said, I have the impression that if there was/is a serious fault you wouldn't have to go looking for it. It would in some way be displayed on the home screen so to speak. ATM I'm thinking I should just continue to keep a close eye on it. It was just inspected in early December and otherwise seems to be OK. Seem reasonable or would you want a customer to inform you of such a scenario?
    Thank you for getting back and it's good to see you've had no further issues.

    The description of the 32 code spells out what I think you were experiencing: If opens during blower on-delay period , blower will come on for the selected blower off-delay. I think the blower off-delay response is what you were experiencing and thought it was high fire. Meaning that more than likely the low pressure switch was opening during the low fire operation of the furnace. The blower off delay would run the fan for about 90 seconds on high speed and then the furnace would recycle to it's normal heating mode.

    The low pressure switch monitors very small pressure differences that are present (basically) between the intake and exhaust piping that goes from your furnace to the outside of your home. The monitoring of this pressure difference is how the controls determine if the conditions are correct for the furnace to be burning. Certain windy conditions could cause this pressure to be disturbed enough to momentarily cause the switch to open.

    Do I want my customers calling me with this kind of questions or problems? Yes, of course. Main reason being that I want you to feel confident that your equipment is working properly. I keep records of all calls because that information is useful when and if a service call is needed, but it's also useful when performing yearly maintenance.

    This kind of issue is a lot of times unique to only a very few installations (when all manufacturer's recommendations are followed) and can, if reported back through proper channels, lead to modifications to the installation manuals.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

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