• Resistance of door holder magnet.

    From Rick McAllister@21:1/5 to All on Tue May 24 06:35:41 2022
    I have been troubleshooting a school with 14 door magnets and cant seem to find the issue. They will be fine for days and then it shorts the 24vdc out and the fire panel has to be re-started to clear and then it is fine again. My question is, does
    anyone know the resistance reading of a typical door holder magnet? I have a newer style that is open when I measure it and several older ones that have a 420 ohm +/- reading.

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  • From legg@21:1/5 to rickmac1122@gmail.com on Tue May 24 11:38:17 2022
    On Tue, 24 May 2022 06:35:41 -0700 (PDT), Rick McAllister <rickmac1122@gmail.com> wrote:

    I have been troubleshooting a school with 14 door magnets and cant seem to find the issue. They will be fine for days and then it shorts the 24vdc out and the fire panel has to be re-started to clear and then it is fine again. My question is, does
    anyone know the resistance reading of a typical door holder magnet? I have a newer style that is open when I measure it and several older ones that have a 420 ohm +/- reading.


    You don't dick around with fire doors in a school.

    Get a professional in.

    RL

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  • From legg@21:1/5 to rickmac1122@gmail.com on Tue May 24 11:44:36 2022
    On Tue, 24 May 2022 06:35:41 -0700 (PDT), Rick McAllister <rickmac1122@gmail.com> wrote:

    I have been troubleshooting a school with 14 door magnets and cant seem to find the issue. They will be fine for days and then it shorts the 24vdc out and the fire panel has to be re-started to clear and then it is fine again. My question is, does
    anyone know the resistance reading of a typical door holder magnet? I have a newer style that is open when I measure it and several older ones that have a 420 ohm +/- reading.

    That being said:

    Use known-good circuit as reference. Replace anything substandard
    until uniformity is achieved.

    Hipot the branches for integrity.

    Look for exposed areas that are subject to damage or intentional
    interference - remember that this is a building full of active
    gremlins.

    RL

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  • From Rick McAllister@21:1/5 to legg on Tue May 24 09:13:27 2022
    On Tuesday, May 24, 2022 at 11:43:47 AM UTC-4, legg wrote:
    On Tue, 24 May 2022 06:35:41 -0700 (PDT), Rick McAllister <rickm...@gmail.com> wrote:
    I have been troubleshooting a school with 14 door magnets and cant seem to find the issue. They will be fine for days and then it shorts the 24vdc out and the fire panel has to be re-started to clear and then it is fine again. My question is, does
    anyone know the resistance reading of a typical door holder magnet? I have a newer style that is open when I measure it and several older ones that have a 420 ohm +/- reading.
    That being said:

    Use known-good circuit as reference. Replace anything substandard
    until uniformity is achieved.

    Hipot the branches for integrity.

    Look for exposed areas that are subject to damage or intentional interference - remember that this is a building full of active
    gremlins.

    I have been a NICET certified fire alarm technician for 30+ years now. I have worked on door holder circuits forever it seems. This one just has me baffled, since it shorts at different times when hooked up and unfortunately the Simplex panel shuts
    the PS down and you have to warm or cold start to get the 24volts back. I am separating it one holder at a time and waiting to see if it shorts. The school system knows they have to keep the door shut on the holder I am working on. I was just trying
    to see if anyone actually knows the correct impedance of one of the magnets. The cut sheets obviously tell you nothing. One of the issues is that they are all on the same circuit through the entire building.

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  • From John Robertson@21:1/5 to legg on Tue May 24 09:14:03 2022
    On 2022/05/24 8:44 a.m., legg wrote:
    On Tue, 24 May 2022 06:35:41 -0700 (PDT), Rick McAllister <rickmac1122@gmail.com> wrote:

    I have been troubleshooting a school with 14 door magnets and cant seem to find the issue. They will be fine for days and then it shorts the 24vdc out and the fire panel has to be re-started to clear and then it is fine again. My question is, does
    anyone know the resistance reading of a typical door holder magnet? I have a newer style that is open when I measure it and several older ones that have a 420 ohm +/- reading.

    That being said:

    Use known-good circuit as reference. Replace anything substandard
    until uniformity is achieved.

    Hipot the branches for integrity.

    Look for exposed areas that are subject to damage or intentional
    interference - remember that this is a building full of active
    gremlins.

    RL

    If this uses sealed glass Reed Switches then the resistance, when
    changed state (either N.O. or N.C.), should be virtually zero ohms. 470R
    sounds like a problem either in line resistance or the switch itself.

    John :-#(#

    --
    (Please post followups or tech inquiries to the USENET newsgroup)
    John's Jukes Ltd.
    MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
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    www.flippers.com
    "Old pinballers never die, they just flip out."

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  • From ABLE1@21:1/5 to Rick McAllister on Tue May 24 13:09:35 2022
    On 5/24/2022 12:13 PM, Rick McAllister wrote:
    On Tuesday, May 24, 2022 at 11:43:47 AM UTC-4, legg wrote:
    On Tue, 24 May 2022 06:35:41 -0700 (PDT), Rick McAllister
    <rickm...@gmail.com> wrote:
    I have been troubleshooting a school with 14 door magnets and cant seem to find the issue. They will be fine for days and then it shorts the 24vdc out and the fire panel has to be re-started to clear and then it is fine again. My question is, does
    anyone know the resistance reading of a typical door holder magnet? I have a newer style that is open when I measure it and several older ones that have a 420 ohm +/- reading.
    That being said:

    Use known-good circuit as reference. Replace anything substandard
    until uniformity is achieved.

    Hipot the branches for integrity.

    Look for exposed areas that are subject to damage or intentional
    interference - remember that this is a building full of active
    gremlins.

    I have been a NICET certified fire alarm technician for 30+ years now. I have worked on door holder circuits forever it seems. This one just has me baffled, since it shorts at different times when hooked up and unfortunately the Simplex panel
    shuts the PS down and you have to warm or cold start to get the 24volts back. I am separating it one holder at a time and waiting to see if it shorts. The school system knows they have to keep the door shut on the holder I am working on. I was just
    trying to see if anyone actually knows the correct impedance of one of the magnets. The cut sheets obviously tell you nothing. One of the issues is that they are all on the same circuit through the entire building.

    Hi Rick,

    I don't do Simplex panels much but it would seem to me that something on
    that NAC circuit being used for the door holders is intermittently
    failing. First I would suggest changing the NAC circuit to one that
    may not be in use or available. I am assuming that the Door Holder
    circuit is on a NAC output that is programmable to various options.
    This is true of a Silent Knight Panel. Simplex...... don't know.

    Since the Door Holders would be all in Parallel if one would fail
    the others would still hold. So I would not think is would be
    just one failing unless it was a dead short. If it would be
    dead short then I can't imagine it would be intermittent.

    The other thought would be when you check the voltage output
    at the panel are you reading exactly 24vdc or something higher??
    Like maybe 25vdc to 28vdc. That would indicate that the output may
    be part of the Battery Charge Circuit. If yes, then the Backup
    Batteries could be pulling the circuit down to a point where the
    Door Holder can't hold. This is just a guess of a maybe??

    Again it comes back to the DC Voltage supply that may be weak to
    some degree and there is a component on the board that is failing
    for some unknown reason. And moving the Door Holders to another
    circuit could be the fix but not the answer.

    That is about all I have at this point.

    Good Luck!!

    Les

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  • From ohger1s@gmail.com@21:1/5 to Rick McAllister on Tue May 24 09:19:59 2022
    On Tuesday, May 24, 2022 at 9:35:44 AM UTC-4, Rick McAllister wrote:
    I have been troubleshooting a school with 14 door magnets and cant seem to find the issue. They will be fine for days and then it shorts the 24vdc out and the fire panel has to be re-started to clear and then it is fine again. My question is, does
    anyone know the resistance reading of a typical door holder magnet? I have a newer style that is open when I measure it and several older ones that have a 420 ohm +/- reading.

    Well, you don't measure magnet resistance... If you're talking about magnetic door contact switches, they should read 0.1 ohm give or take. Now, some door contacts have what's called "end of line" resistors installed. The idea is that the panel
    monitors a known resistance instead of a pure open or closed situation to make sure the contact isn't jumped out to fool the panel into thinking the switch is in circuit. The value of the resistor depends on what the panel manufacturer specs out.

    How do you know it's shorting out the 24V line? Is there an error code at the panel?

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  • From Akakios Peretz@21:1/5 to Rick McAllister on Tue May 24 20:46:46 2022
    Rick McAllister <rickmac1122@gmail.com> wrote:
    On Tuesday, May 24, 2022 at 11:43:47 AM UTC-4, legg wrote:
    On Tue, 24 May 2022 06:35:41 -0700 (PDT), Rick McAllister
    <rickm...@gmail.com> wrote:
    I have been troubleshooting a school with 14 door magnets and cant seem to find the issue. They will be fine for days and then it shorts the 24vdc out and the fire panel has to be re-started to clear and then it is fine again. My question is, does
    anyone know the resistance reading of a typical door holder magnet? I have a newer style that is open when I measure it and several older ones that have a 420 ohm +/- reading.
    That being said:

    Use known-good circuit as reference. Replace anything substandard
    until uniformity is achieved.

    Hipot the branches for integrity.

    Look for exposed areas that are subject to damage or intentional
    interference - remember that this is a building full of active
    gremlins.

    I have been a NICET certified fire alarm technician for 30+ years
    now. I have worked on door holder circuits forever it seems. This
    one just has me baffled, since it shorts at different times when
    hooked up and unfortunately the Simplex panel shuts the PS down and
    you have to warm or cold start to get the 24volts back. I am
    separating it one holder at a time and waiting to see if it shorts.
    The school system knows they have to keep the door shut on the
    holder I am working on. I was just trying to see if anyone actually
    knows the correct impedance of one of the magnets. The cut sheets
    obviously tell you nothing. One of the issues is that they are all
    on the same circuit through the entire building.

    Placing your reply on a line prefixed by >> results in it appearing as
    a quotation of what the grandparent-previous responder wrote. In the
    future, do not start your replies on lines beginning with any >
    characters.

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  • From legg@21:1/5 to rickmac1122@gmail.com on Tue May 24 18:39:30 2022
    On Tue, 24 May 2022 09:13:27 -0700 (PDT), Rick McAllister <rickmac1122@gmail.com> wrote:

    On Tuesday, May 24, 2022 at 11:43:47 AM UTC-4, legg wrote:
    On Tue, 24 May 2022 06:35:41 -0700 (PDT), Rick McAllister
    <rickm...@gmail.com> wrote:
    I have been troubleshooting a school with 14 door magnets and cant seem to find the issue. They will be fine for days and then it shorts the 24vdc out and the fire panel has to be re-started to clear and then it is fine again. My question is, does
    anyone know the resistance reading of a typical door holder magnet? I have a newer style that is open when I measure it and several older ones that have a 420 ohm +/- reading.
    That being said:

    Use known-good circuit as reference. Replace anything substandard
    until uniformity is achieved.

    Hipot the branches for integrity.

    Look for exposed areas that are subject to damage or intentional
    interference - remember that this is a building full of active
    gremlins.

    I have been a NICET certified fire alarm technician for 30+ years now. I have worked on door holder circuits forever it seems. This one just has me baffled, since it shorts at different times when hooked up and unfortunately the Simplex panel shuts
    the PS down and you have to warm or cold start to get the 24volts back. I am separating it one holder at a time and waiting to see if it shorts. The school system knows they have to keep the door shut on the holder I am working on. I was just trying
    to see if anyone actually knows the correct impedance of one of the magnets. The cut sheets obviously tell you nothing. One of the issues is that they are all on the same circuit through the entire building.

    The newer ones may be internally rectified, for use in AC or
    DC circuits. This would produce a High-Z reading for low test
    voltages. A diode test might show continuity.

    Normal coil Z between 280 and 600R, depending on model.
    (that's derived from current rating and voltage on the
    sales sheet).

    You should probably replace the battery ~6-8yrs, whether healthy
    or not.

    RL

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  • From ABLE1@21:1/5 to All on Tue May 24 22:04:40 2022
    On 5/24/2022 1:09 PM, ABLE1 wrote:
    On 5/24/2022 12:13 PM, Rick McAllister wrote:
    On Tuesday, May 24, 2022 at 11:43:47 AM UTC-4, legg wrote:
    On Tue, 24 May 2022 06:35:41 -0700 (PDT), Rick McAllister
    <rickm...@gmail.com> wrote:
    I have been troubleshooting a school with 14 door magnets and cant
    seem to find the issue. They will be fine for days and then it
    shorts the 24vdc out and the fire panel has to be re-started to
    clear and then it is fine again. My question is, does anyone know
    the resistance reading of a typical door holder magnet? I have a
    newer style that is open when I measure it and several older ones
    that have a 420 ohm +/- reading.
    That being said:

    Use known-good circuit as reference. Replace anything substandard
    until uniformity is achieved.

    Hipot the branches for integrity.

    Look for exposed areas that are subject to damage or intentional
    interference - remember that this is a building full of active
    gremlins.

      I have been a NICET certified fire alarm technician for 30+ years
    now.  I have worked on door holder circuits forever it seems.  This
    one just has me baffled, since it shorts at different times when
    hooked up and unfortunately the Simplex panel shuts the PS down and
    you have to warm or cold start to get the 24volts back.  I am
    separating it one holder at a time and waiting to see if it shorts.
    The school system knows they have to keep the door shut on the holder
    I am working on.  I was just trying to see if anyone actually knows
    the correct impedance of one of the magnets.  The cut sheets
    obviously tell you nothing.  One of the issues is that they are all
    on the same circuit through the entire building.

    Hi Rick,

    I don't do Simplex panels much but it would seem to me that something on
    that NAC circuit being used for the door holders is intermittently
    failing.  First I would suggest changing the NAC circuit to one that
    may not be in use or available.  I am assuming that the Door Holder
    circuit is on a NAC output that is programmable to various options.
    This is true of a Silent Knight Panel.  Simplex...... don't know.

    Since the Door Holders would be all in Parallel if one would fail
    the others would still hold.  So I would not think is would be
    just one failing unless it was a dead short.  If it would be
    dead short then I can't imagine it would be intermittent.

    The other thought would be when you check the voltage output
    at the panel are you reading exactly 24vdc or something higher??
    Like maybe 25vdc to 28vdc.  That would indicate that the output may
    be part of the Battery Charge Circuit.  If yes, then the Backup
    Batteries could be pulling the circuit down to a point where the
    Door Holder can't hold.  This is just a guess of a maybe??

    Again it comes back to the DC Voltage supply that may be weak to
    some degree and there is a component on the board that is failing
    for some unknown reason.  And moving the Door Holders to another
    circuit could be the fix but not the answer.

    That is about all I have at this point.

    Good Luck!!

    Les


    Rick,

    If I may suggest that you pose your question to the newsgroup alt.security.alarms

    There are a few old guys there that have been in the business
    for a long time. If nothing else it will cause them to think
    a little extra for the challenge.

    Again good luck!!

    Les

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  • From Tim R@21:1/5 to All on Thu May 26 09:02:00 2022
    On Tuesday, May 24, 2022 at 1:09:43 PM UTC-4, ABLE1 wrote:

    The other thought would be when you check the voltage output
    at the panel are you reading exactly 24vdc or something higher??
    Like maybe 25vdc to 28vdc. That would indicate that the output may
    be part of the Battery Charge Circuit. If yes, then the Backup
    Batteries could be pulling the circuit down to a point where the
    Door Holder can't hold. This is just a guess of a maybe??

    Les

    Good thought. Not a tech myself, but have been an engineer overseeing building maintenance and battery charging on fire systems has been a significant problem often overlooked.

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