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  1. #1
    Join Date
    Nov 2019
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    Lennox XP16 Elite Series

    New to the site. Thanks for having me.

    Installed a Lennox heat pump system with matching air handler system 9 years ago to provide upstairs A/C, and heat. Started nickel, and diming me about 2 years ago. So far I've replaced the heat pump defrost board, air handler fan motor, and recently the evaporator coil with txv.

    So now with it being cold outside the heat pump will not perform it's function. All heat for the upstairs is supplied from the aux heat strips, or emergency heat. Some heat is actually coming from the downstairs supplied system.

    I've carefully watched the diagnostic board lights, and timed it's cycle. Here are the results:

    1. Heat is being demanded on the thermostat with set point at 75 degs. Actual temp is 69 degs.
    2. System normally starts up: air handler, and heat pump. (Simultaneous Slow Flash of the Green/Red Diagnostic Lights indicating normal operations).
    3. After 2.5 - 3 mins of run time, the heat pump shuts off. Air handler continuous to run. (Alternate Slow Flash of the Green/Red Lights indicating anti-short cycle).
    4. After 30 secs. the heat pump is still off, but lights change. (Slow flashing Green Light with Red light completely OFF indicating high pressure switch fault.
    5. After another 3 mins. the system returns to normal operations with the heat pump running (Simultaneous Slow Flash of the Green/Red Lights).
    6. This cycle will continue for an additional 4 more cycles before it completely locks out the heat pump. (Solid Green Light with Red Light completely OFF indicating high pressure lockout.

    Can anyone help me diagnosis this issue? What else can I look for? I have limited tools for HVAC, and my gauges are for 134A only. Any suggestions will help please.

    Thank You,
    82 Airborne

  2. #2
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
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    DIY info cannot be given on this site, but you could verify nothing is limiting the indoor airflow, like a dirty airfilter or evap coil. After that you would need to see what's going on inside the refrigeration circuit. This requires gauges, temp probes and more knowledge than a youtube video will get you. It could be that the system was overcharged when the coil was replaced or something is not metering the refrigerant correctly. I'd call back the company that changed the coil, if its overcharged that's on them. Thanks for your service!

  3. #3
    Join Date
    Nov 2019
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    Thread Starter
    Thank you Makeitcold, for the response. Yes sir, I fully understand no DIY info can be given on this site. Makes sense to me. I see it as protecting me, or some other unqualified person from injuring ourselves. And yes I did verify the common simple stuff like air flow blockage is clear, filter is clean, outside condenser coil is clean, and as mentioned in the original post, the evaporator coil is new. If I had the manifold gauges I would be able to perform other diagnostics. I've not watched any YouTube videos, but now I will. I guess I wasn't to clear on what I was asking. What diagnostics should I be looking for from the tech that I hire to troubleshoot this issue? I don't want to get involve in "Easter Egg" hunting as what was occurring with the tech that replaced the evap. coil. PS: I have a fluke multimeter with contact temperature probe (LOL). Seriously though, I do have some background in HVAC R, and industrial from the job I retired from as a supervisor in a nuclear power station. I don't want to stand overtop of the tech while he's investigating (as I did in my previous job), just what should I look for?

    Thank you,
    82airborne

  4. #4
    Join Date
    Mar 2018
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    Chico, Ca #StateofJefferson
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    I'd start by checking the fan performance first(psc or ecm?), the inside of the evap coil, blower wheel, all registers are open and then I'd measure the ducting static pressure and compare that to the blower performance curve for your system. Once I knew that, gauges with temp sensors on each line measured while running in a/c, if its above usually 55 outside and 75 inside. This should give an idea using sh and sc if its overcharged, if that looks good put into heat and see if its shutting off at the correct pressure and find out why if its is. If it works fine in a/c it's not the compressor, seems to be the go to answer for the tech that doesnt know how to troubleshoot. Finding a good contractor with knowledgeable techs is the hardest part, so ask friends, family, employers who they trust, online reviews are for suckas

  5. #5
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
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    What kind of air filter are you using?
    Most high performance filters are very restrictive to air flow and will cause the problem you are having in heat mode. Try using a cheap fiberglass filter. If that helps, call a contractor to measure the air flow, and adjust it if necessary.

    Good luck.
    Remember, Air Conditioning begins with AIR.

  6. #6
    Join Date
    Nov 2019
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    Thread Starter

    Fixed

    Thanks guys, all is better now. I did do the simple stuff like filters, air flow unrestricted, new coil, and blower functioning fine. I did get another tech from a reputable service. After carefully listening to me telling him all the symptoms, he started at the air handler systematically working his way to the heat pump. He used his digital manifold to discover I had too much Freon in the system. All this was checked using the SC method. So overcharge was the problem. Lesson learned: make sure tech uses some method when adding/removing Freon other than (I think that's enough). Again, thanks for all the education, and help. 82airborne

  7. #7
    Join Date
    Mar 2018
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    Chico, Ca #StateofJefferson
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    Was the charge checked in cooling? If not I'd recommend having that company recheck in the spring. Charging a heatpump during heating mode will get you in the ballpark but you want to do a final check/charge once a/c season starts again

  8. #8
    Join Date
    Nov 2019
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    Thread Starter

    Lennox XP16 Elite

    Yes sir Makeitcold, I will do that. Was planning on it if I don't get my own Manifold/Gauge set. Now the tech explained why he used the sub cooling method to check the Freon at the current outside temperatures. Made sense to me having a lot of experience with SH/SC from my previous job in the nuclear industry. Again thank you all for the help, and knowledge. 82airborne ie: Any recommendations on a good homeowner "Manifold/Gauge" set?

  9. #9
    Join Date
    Mar 2018
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    Chico, Ca #StateofJefferson
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    You just started a Chevy/Ford/Dodge battle with that last question. Pressures mean nothing without pipe temps on R410a, so I'd try to find the Fieldpiece SMAN 360 on Craigslist or something. Has pressures and temps all on one screen with about 50 different refrigerants programmed in.

  10. #10
    Join Date
    Aug 2002
    Location
    Southold, NY
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    The absolute last thing you want to do is gauge up. With little to no experience even worse.

    At the very least are you licensed?

  11. #11
    Join Date
    Nov 2019
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    Thread Starter

    Just asking

    I guess now that you guys have gone digital, the analog gauge sets should be a lot cheaper. The digital units are way out of my price range. Those are for the pros. I can always use my contact pyrometer to measure line temps, and do the math to get the SH/SC based on manufactures information. No pecmsg I'm not licensed, but I do have experience calculating SH/SC. I promise not to deplete the ozone layers when installing the gauges, but even the pros release a little Freon went hooking up their equipment. I appreciate looking out for my safety.

  12. #12
    Join Date
    Aug 2002
    Location
    Southold, NY
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    You are aware it’s illegal then! Not that there are refrigerant police.

    Honestly the last thing you want to do is gauge up.

  13. #13
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
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    Agree with above. Even with low loss fittings a little escaped, so it eventually adds up. You'll also probably introduce contaminants into the system. I never gauge up, unless I suspect an issue with the refrigerant circuit, let sleeping dogs lie

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