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  1. #1
    Join Date
    Jun 2008
    Posts
    37

    Problem with airflow on Infinity System

    Quote Originally Posted by sastexan View Post
    I have a Carrier Infinity system and was using Honeywell MERV 12 filters without much of an issue, lasting about 6 months. I switched to Filtrete 1550 (16x25x4) and got a "dirty filter" notice on the controller after about 2 weeks. Seemed odd so reset the filter and the notice came back two weeks later. I replaced the filter (only because pulling it out destroyed the filter as it didn't have any tabs to help pull it out of the slot) and it looked somewhat dirty, but I know you can't tell just by looking.

    After replacing, I looked at the static pressure:
    Low speed - 525 cfm - 504 rpm - Static press 0.16
    Med speed - 792 cfm - 681 rpm - static press 0.28
    High speed - 1194 cfm - 1022 rpm - static press 0.63

    We run the fan on low continuously, but did before with the Honeywell filters. The pressure seems really high. My HVAC guy gave the generic "just replace the filter" response but was not knowledgeable about the actual pressures and didn't even realize that the Infinity system uses pressure to detect when to replace the filter, rather than time.
    Should I switch filters again (maybe I can ebay the Filtrete filters)?
    Thanks
    =======================
    Greetings,
    I don't think the problem with getting the notice to replace your filter is with the filter. I also have an Infinity system. I have been getting erratic filter usage readings from the T-stat for several years since it was installed. For example, with the 4" Merv 12 filter ( 20x25x4) being less than 2 months old, I got the notice the filter usage was 100% and to replace the filter. I ignored it. The next day it dropped to 10%. Days later, it was back to 100%. I ignored it and it dropped back to 10% for weeks. Occasionally, it later varied between 30% and 10%. This made no sense to me.

    The original T-stat had been replaced within a few months after the unit was installed but it did not help. A few days ago, they replaced that T-stat with the new SYSTXCCUID01-V-25. It started out at 0%, but by the 3rd day it had jumped to 10%. I think something other than the filter is causing the T-stat to not read the static pressure correctly (and therefor filter use). It seems that the % of filter use would progress from 0% to 100% at a reasonable steady rate, not jump around.

    My HVAC company is coming out next week to take a look at the duct work to see if something else can be done to solve this problem. Also, I was watching my neighbor's house while they were on vacation last week. They have an Infinity T-stat. They had just put in a new filter. It first showed 10% filter usage. A couple days later, it jumped to 30 or 40%. Couple days later, it went back to 10%. So I just think these Infinity T-stats are just giving out incorrect filter usage information. Exactly why, I don't know yet.

    After putting in a new 4" filter last week, here are my CFM, Static Pressure and RPM readings:
    CFM S.P. RPM
    Hi 1957 .67 1118
    Med 1307 .31 775
    Low 875 .18 541
    Gary

  2. #2
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    Quote Originally Posted by goddi View Post
    =======================
    Greetings,
    I don't think the problem with getting the notice to replace your filter is with the filter. I also have an Infinity system. I have been getting erratic filter usage readings from the T-stat for several years since it was installed. For example, with the 4" Merv 12 filter ( 20x25x4) being less than 2 months old, I got the notice the filter usage was 100% and to replace the filter. I ignored it. The next day it dropped to 10%. Days later, it was back to 100%. I ignored it and it dropped back to 10% for weeks. Occasionally, it later varied between 30% and 10%. This made no sense to me.

    The original T-stat had been replaced within a few months after the unit was installed but it did not help. A few days ago, they replaced that T-stat with the new SYSTXCCUID01-V-25. It started out at 0%, but by the 3rd day it had jumped to 10%. I think something other than the filter is causing the T-stat to not read the static pressure correctly (and therefor filter use). It seems that the % of filter use would progress from 0% to 100% at a reasonable steady rate, not jump around.

    My HVAC company is coming out next week to take a look at the duct work to see if something else can be done to solve this problem. Also, I was watching my neighbor's house while they were on vacation last week. They have an Infinity T-stat. They had just put in a new filter. It first showed 10% filter usage. A couple days later, it jumped to 30 or 40%. Couple days later, it went back to 10%. So I just think these Infinity T-stats are just giving out incorrect filter usage information. Exactly why, I don't know yet.

    After putting in a new 4" filter last week, here are my CFM, Static Pressure and RPM readings:
    CFM S.P. RPM
    Hi 1957 .67 1118
    Med 1307 .31 775
    Low 875 .18 541
    Gary
    This a common problem with units installed on duct systems that are too restrictive.

  3. #3
    Join Date
    Jun 2008
    Posts
    37
    Quote Originally Posted by second opinion View Post
    This a common problem with units installed on duct systems that are too restrictive.
    ======================
    Greetings,
    Could you give more details? Is it restrictive on the return side or the outflow side? If it is on the return side, would an additional return in my unfinished basement help resolve this?
    Thanks... Gary

  4. #4
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    Quote Originally Posted by goddi View Post
    ======================
    Greetings,
    Could you give more details? Is it restrictive on the return side or the outflow side? If it is on the return side, would an additional return in my unfinished basement help resolve this?
    Thanks... Gary
    It can be either supply, return or both. You first must find a company or individual that is knowledgeably about air distribution and have the supply and return checked to determine which one is causing the problem.

    I would first start with another company or individual rather than the one you have been using. Post your geographical location and see if anyone here is in your area, and check the dealer locator in the index.

  5. #5
    Join Date
    Jun 2008
    Posts
    37
    Quote Originally Posted by second opinion View Post
    It can be either supply, return or both. You first must find a company or individual that is knowledgeably about air distribution and have the supply and return checked to determine which one is causing the problem.

    I would first start with another company or individual rather than the one you have been using. Post your geographical location and see if anyone here is in your area, and check the dealer locator in the index.
    ============================
    Greetings,
    As I had mentioned in my previous post, my HVAC company is sending out someone to take a look at the system next week. So I will wait to see what they might say. Their initial reaction was to add a return duct in the basement but now they want to send out someone to re-examine the situation. I am in the DC metro area and am using CroppMetcalfe (who installed the Infinity hybrid system).

    To me it seems that the Carrier Infinity T-stat has a problem in how it is calculating the static pressure. Whether the duct work is restricted or not, the 'static pressure measurement' should not be jumping from 10% to 100% in one day and give false indicators to change your filter. I am sure Carrier knows this but seems to want to ignore this(?). It is not actually measuring the static pressure with a manometer, but calculating it based on some other measurements (cfms, rpms, amps or something...?).
    Gary

  6. #6
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,928

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