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Intermittent AC locked rotor condition-- resolved

DJohanson
DJohanson Member Posts: 4
edited August 2022 in A-C, Heat Pumps & Refrigeration
We're experiencing an intermittent failure on new (1 year old) GSXC 4Ton 2 stage Goodman condenser. The system has been running perfectly since installed but in the past couple weeks it has stopped 3 times on "locked rotor" code. The capacitor was suspect and replaced but it tested OK. A technician (not the original installer) tested all pressures, charge, SC, SH etc. and found everything in spec. When the 24V control voltage is reset, the unit comes back on line. Technician told us that next time he will call Goodman tech support. Any suggestions?

Comments

  • JUGHNE
    JUGHNE Member Posts: 11,266
    Have you had any power "blinks"?

    Do you have a time delay for restart?
    This is often a feature in t-stats.

    It provides up to a 5 minute delay to restart AC.
    Gives time for pressures to equalize.
  • ChrisJ
    ChrisJ Member Posts: 16,260
    That unit should have a 5 minute delay built into the PCB.  

    @DJohanson I assume the unit was tested in low stage?

    Is it wired as a legacy setup or as communicating?  
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,364
    If the voltage is up to spec (not low) and the wire is the correct size and the connections clean and tight then you may need a hard start kit (relay and start capacitor
  • HVACNUT
    HVACNUT Member Posts: 6,282
    Do you have a meter to capture (min/max) starting amps to verify the code?
  • DJohanson
    DJohanson Member Posts: 4
    Thanks for your fast response to our AC issue. To your questions, we have experienced some power blinks (Duke Energy) but the lockout issues haven't occurred at those times. (We had installed a whole-house surge protector, BTW.) The Honeywell thermostat does have a 5 minute start delay and is wired "legacy". The tech tested operation during low stage including line voltage and the L1-L2 terminal connections (original installer didn't connect the high stage and we've found that we don't need it.) I'll speak with the tech regarding measuring start current and a hard start kit. Again, I appreciate your suggestions and questions!
  • JUGHNE
    JUGHNE Member Posts: 11,266
    IDK about your AC in particular, but some multi stage equipment is designed to start in high stage and then step down to lower stages.

    Maybe the high stage start is needed.
  • ChrisJ
    ChrisJ Member Posts: 16,260
    JUGHNE said:

    IDK about your AC in particular, but some multi stage equipment is designed to start in high stage and then step down to lower stages.

    Maybe the high stage start is needed.

    The OP's equipment always starts in low stage by design.
    It's a Copeland Ultratech.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • mattmia2
    mattmia2 Member Posts: 10,819
    HVACNUT said:

    Do you have a meter to capture (min/max) starting amps to verify the code?

    You will need more than the average DMM/clamp meter to measure this, a DMM only samples a few times a second so it doesn't do a great job of capturing peak transients.
  • ChrisJ
    ChrisJ Member Posts: 16,260
    mattmia2 said:

    HVACNUT said:

    Do you have a meter to capture (min/max) starting amps to verify the code?

    You will need more than the average DMM/clamp meter to measure this, a DMM only samples a few times a second so it doesn't do a great job of capturing peak transients.
    You feel the HVAC equipment is alarming out on a spike that's shorter than a typical DMM can detect?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • mattmia2
    mattmia2 Member Posts: 10,819
    It certainly could be. An analog circuit driving an io pin set to interrupt could detect a very short transient.

    I guess we need to know what exactly triggers that code.
  • ChrisJ
    ChrisJ Member Posts: 16,260
    mattmia2 said:

    It certainly could be. An analog circuit driving an io pin set to interrupt could detect a very short transient.

    I guess we need to know what exactly triggers that code.





    That's the best I've got from them.
    They don't tell you anything useful.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • pecmsg
    pecmsg Member Posts: 5,271
    A list of operating information would help. Superheat, discharge temperature, sub cooling. Minimum on, minimum off. 
  • HVACNUT
    HVACNUT Member Posts: 6,282
    mattmia2 said:
    Do you have a meter to capture (min/max) starting amps to verify the code?
    You will need more than the average DMM/clamp meter to measure this, a DMM only samples a few times a second so it doesn't do a great job of capturing peak transients.
    My pos Fluke 17B which is not true RMS can capture min/max amps. I use it on every maintenance and it hasn't failed me yet. 
    If I really need it, I break out the 179.
  • ChrisJ
    ChrisJ Member Posts: 16,260
    edited July 2022
    HVACNUT said:


    mattmia2 said:

    HVACNUT said:

    Do you have a meter to capture (min/max) starting amps to verify the code?

    You will need more than the average DMM/clamp meter to measure this, a DMM only samples a few times a second so it doesn't do a great job of capturing peak transients.


    My pos Fluke 17B which is not true RMS can capture min/max amps. I use it on every maintenance and it hasn't failed me yet. 
    If I really need it, I break out the 179.
    I've had a 179 since 2002, but I don't have an amp clamp for it.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • ChrisJ
    ChrisJ Member Posts: 16,260
    pecmsg said:

    A list of operating information would help. Superheat, discharge temperature, sub cooling. Minimum on, minimum off. 

    The manufacturer most likely wants around 6-8 degrees of subcooling and 7-9 for superheat in low stage, going from memory.

    What the OP actually has, along with the type of metering device and lineset length and evaporator location, would be nice to know.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • mattmia2
    mattmia2 Member Posts: 10,819
    ChrisJ said:

    mattmia2 said:

    It certainly could be. An analog circuit driving an io pin set to interrupt could detect a very short transient.

    I guess we need to know what exactly triggers that code.





    That's the best I've got from them.
    They don't tell you anything useful.
    If it is somehow detecting the compressor failed to start within a minute then that is a long enough period for min/max on a dmm to capture.

    The next step would be to look at the schematic and maybe the control itself and see what it has connections to that it uses to decide the compressor didn't start. Does it have a way to measure line voltage? Does it have a way to measure current? Is it only connected to pressure switches and some thermistors and is inferring that the compressor didn't start by what it is reading from those senseors?
  • ChrisJ
    ChrisJ Member Posts: 16,260
    mattmia2 said:

    ChrisJ said:

    mattmia2 said:

    It certainly could be. An analog circuit driving an io pin set to interrupt could detect a very short transient.

    I guess we need to know what exactly triggers that code.





    That's the best I've got from them.
    They don't tell you anything useful.
    If it is somehow detecting the compressor failed to start within a minute then that is a long enough period for min/max on a dmm to capture.

    The next step would be to look at the schematic and maybe the control itself and see what it has connections to that it uses to decide the compressor didn't start. Does it have a way to measure line voltage? Does it have a way to measure current? Is it only connected to pressure switches and some thermistors and is inferring that the compressor didn't start by what it is reading from those senseors?
    I've never been able to find one.
    The PCB used is made by Emerson / Copeland, not by Goodman / Amana and the diagram shown can't be trusted. At least it couldn't back in 2017 when I metered out the board to wire in a condenser fan control on mine. And even that was only a crude diagram showing where the fan, compressor etc wire into the board.

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • HVACNUT
    HVACNUT Member Posts: 6,282
    ChrisJ said:
    mattmia2 said:
    Do you have a meter to capture (min/max) starting amps to verify the code?
    You will need more than the average DMM/clamp meter to measure this, a DMM only samples a few times a second so it doesn't do a great job of capturing peak transients.
    My pos Fluke 17B which is not true RMS can capture min/max amps. I use it on every maintenance and it hasn't failed me yet. 
    If I really need it, I break out the 179.
    I've had a 179 since 2002, but I don't have an amp clamp for it.
    I have an Amprobe A400 attachment that's great for me but the wires are shredded so I need to open it and try to rebuild. In the meantime I'm using a Fluke i410 but the clamp is too large for what I need.
  • DJohanson
    DJohanson Member Posts: 4
    ChrisJ..... lineset is 20' long, evap coil is ~3' higher than condenser. Txv metering. Downflow furnace installed with ample supply and return ducting. At 93F outside temp on low stage, 325psi and 142psi, SH at 8 and SC at 2. Typical run times that day were at least 1 hour. I did notice a current loop on the control board which likely measures the compressor current, if that helps any.
  • ChrisJ
    ChrisJ Member Posts: 16,260
    DJohanson said:

    ChrisJ..... lineset is 20' long, evap coil is ~3' higher than condenser. Txv metering. Downflow furnace installed with ample supply and return ducting. At 93F outside temp on low stage, 325psi and 142psi, SH at 8 and SC at 2. Typical run times that day were at least 1 hour. I did notice a current loop on the control board which likely measures the compressor current, if that helps any.

    Separate subject but SC should be 6-8 from what I recall, so the system is a tad undercharged.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • heatandair
    heatandair Member Posts: 5
    Talk to your electrician about the surge protector, sometime changes in amp draw when it changes stages will cause problems
    SuperTech
  • pecmsg
    pecmsg Member Posts: 5,271
    heatandair said:
    Talk to your electrician about the surge protector, sometime changes in amp draw when it changes stages will cause problems
    Care to explain?
    mattmia2
  • DJohanson
    DJohanson Member Posts: 4
    Locked rotor condition again; called the technician to investigate. While testing the compressor windings, found a loose spade connector on circuit board powering the condenser fan. Not sure why this wouldn't trigger a high pressure lockout instead of "locked rotor" but it's now trouble free for past 2 weeks. Thanks everyone for your comments!
    mattmia2ratioPC7060
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,364
    Thanks for letting us know
    ratio
  • nlt999
    nlt999 Member Posts: 1
    Hi! I have the same problem on an Amana 2-stage. Has yours stayed trouble-free from this problem??
    Thanks for your help! Nick
  • ChrisJ
    ChrisJ Member Posts: 16,260
    https://forum.heatinghelp.com/discussion/comment/1799580#Comment_1799580

    Did you ever figure out the problem on your unit?

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • mattmia2
    mattmia2 Member Posts: 10,819
    https://forum.heatinghelp.com/discussion/comment/1707997#Comment_1707997

    Maybe the pressure switch isn't interlocked with a time delay correctly and when the pressure falls because the compressor shut off it resets and tries to restart the compressor before it has equalized so the compressor then fails to start.

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