HVAC question

Discussion in 'General Technical Questions and Answers' started by N8YQM, Sep 13, 2021 at 1:54 PM.

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  1. KA9JLM

    KA9JLM Ham Member QRZ Page

    That is way cool.

    I have never replaced a sewer system with a air conditioning system.

    I bet the seat is very cool. :)
    VE3CGA, KP4SX and WA6SW like this.
  2. AI5DH

    AI5DH Ham Member QRZ Page

    An open circuit cannot pass current, thus cannot pass current to the load and burn anything up. What do you think a switch or fuse does?

    The caps are in parallel with the compressor motor.
  3. K0OKS

    K0OKS Premium Subscriber QRZ Page

    That is pretty nice. Like I said, going from a 25+ year old system to a modern 20 seer system we went from like $450 to $435. Very little savings. Maybe our old system was actually quite efficient. Maybe it was because the old system couldn't actually keep the house as cool, though I would swear the old system was running the compressor a lot more of the time.

    Who knows. Glad to hear it worked out for someone.
  4. VE3CGA

    VE3CGA XML Subscriber QRZ Page

    my air unit blew its starter cap this summer. I rarely use it but its over 15yrs old
    Started searching for a schematic and went back to the unit to get mdl & serial and was
    very suprised to see the schematic stuck on the inside of the electrical cover
    The guy at the parts counter told me they had a huge run on those caps in august.
    At $14.00 cdn I bought 2
    If you are still looking for a wiring drawing check the electrical cover on the unit
    Cant believe the drawing was in there since almost everything previously done with this house had to be done by
    evil knomes
  5. N8YQM

    N8YQM Ham Member QRZ Page

    The caps are in SERIES with the start winding of the motor, to shift the phase angle so the induction motor can get started on a single phase power supply. The run winding is connected directly to the line, so it still takes current, hence the reason my compressor was still quite hot after being powered but not able to run because the capacitor had failed.
    KA9JLM likes this.
  6. N8VIL

    N8VIL Ham Member QRZ Page

    I have replaced many where the compressor has been trying to start for a few days. Put the new capacitor in and should be fine. Many fail with age and low line voltage will cause them to fail. The PDF file is a typical single phase compressor schematic. Buy an extra one for that 10 pm on a a Sunday repair when the replacement capacitor fails.

    Attached Files:

    Last edited: Sep 15, 2021 at 3:38 AM
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'm not an HVAC guy, but the starting cap in my system failed in July 2020, of course on the hottest day of the year as usual.

    I knew something was wrong because I could hear the contactor slam in about every three minutes; the unit would "start" for about one second and then shut off...and do that repeatedly. Thankfully, I was home to "hear" that. (I could always hear the contactor slam in, as the unit sits on a cement pad just outside our master bathroom; normally you hear that loud "click" and then the motor starts up and you don't hear it again until next time, which might be 20-30 minutes later...or longer.)

    So, of course I just shut the system down and went outside on this incredibly hot day, pulled the big fuse block out to disconnect AC from the unit and opened the cover. Cap "looked" fine, but was the problem. Luckily this was a Saturday and everyplace was open. Appliance Parts in Van Nuys, a 10-mile drive away, had the exact cap in stock so I drove there, bought it, installed it, put the big fuse block back in, and whew! -- it worked fine.

    "Repair" took five minutes. Evidently, no damage to anything as it's been working fine since.
    VE3CGA likes this.
  8. VE3CGA

    VE3CGA XML Subscriber QRZ Page

    same here, heard the dreaded hum from the fan motor and it took longer to get rid of the dust bunnies than replacing the cap
    I dont use the air much except when we get that >90 degF heat with extreme humidity and no breeze
    We couldnt escape the heat even in the pool
  9. NG1H

    NG1H XML Subscriber QRZ Page

    I live in an area where the A/C is used 11+ months out of the year. Capacitors failing on residential units is a regular issue.

    It may not be helping the long term life but I've never seen a case where a bad cap (usually for the condenser fan motor) allowed damage to the compressor. But in the rare case this happens be very careful in considering options. In the past several years the quality of new units has gone almost completely down the sewer. A very high percentage have (non-motor related) failures within 3-5 years. Out of 12 new installs in the past 6 years I've seen 5 that required replacement. Most were failure of the coils, both expansion and condenser. The brand name didn't seem to make a difference.
  10. N8YQM

    N8YQM Ham Member QRZ Page

    Success! Was just the caps. Arrived today, and it's making things cool again. Also took the time to vacuum the leaves out of the bottom of it. Thanks for the tips!
    K0OKS, K8XG, KM4FVI and 1 other person like this.

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