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HVAC capacitor questions

Discussion in 'Electronic Design' started by mook johnson, Aug 5, 2012.

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  1. mook johnson

    mook johnson Guest

    I have a 4 ton Carrier A/C that the original GE cap (Dual 60uF/5uF 440VAC)
    went out last summer in ~May. It was about 6 years old. The top was bulged
    badly so it was pretty clear the capacitor was bad.

    Went to granger and found a Dayton capacitor that had the same ratings but
    slightly smaller diameter (2.5 vs 2.75").

    For $25 I figured what the heck. Cap worked great through the drought and
    100+ Houston TX temperatures of 2011 and the temperatures of this summer,
    not as hot but it is south Texas.

    Well that cap died last night and of course on a Sunday granger is closed so
    a borrowed window unit is keeping life support for now.

    My question is:

    Dual caps have essentially two caps in one package. My understanding this
    is just for convenience of mounting and shortened assembly/repair times.

    Looking at single 60uF 440V caps they are almost the same size as the dual
    capacitor I have now. Do you think going with two separate capacitors would
    be more reliable than going back with a Dual cap since not tradeoffs need to
    be made to fit in a certain package size?

    I found that Granger now stocks the GE dual cap (Genteq)

    These are the two separate single caps. Costs more but if its more reliable
    I'll give it a try.

    What do you guys think?
  2. Joerg

    Joerg Guest

    Not sure which quality is better. But ... methinks ... this time you
    should buy _two_ sets so that when it goes kablouie on a hot Friday
    night the missus ain't gonna be unhappy. Then you could walk out there,
    fix it in minutes, and be the family hero :)

    Note to self: Got to buy spare float valve for evap cooler. Same reason.
  3. mook johnson

    mook johnson Guest

    That is the plan. Being the perpetual cheapo I fond something that will
    satisfy the cheapo in me and get the redundancy I need for next time.

    I going the easy route and getting the dual Genteq tomorrow for ~$35 then
    trying this guy as a backup

    I tool a look at QE Quality capacitors website and it look pretty decent.
    Assuming its all true.

    Not bad for a backup to allow me to get through a weekend before I get a new
  4. Tim Williams

    Tim Williams Guest

    Obvious answer.. don't be the cheapo, buy a real film cap that'll last ten
    years. It won't even cost ten times more!

  5. mook johnson

    mook johnson Guest

    Suggestions? What is a real film cap? Are you talking about the black
    plastic bricks with the cap potted inside

    I have wondered about the internal construction of metal packaged A/C caps
    vs the potted film run capacitors. The metal can ones are sometimes
    referred to as film as well.

    I wondered if it wise to use these with an outside A/C unit.

    My understanding is that the traditional metal can A/C caps are built that
    way so when they fail the tops bulge out and break the electrical
    connections inside thereby isolating the fault.

    Would those black plastic ones just catch on fire when hooked to a 40A
  6. Joerg

    Joerg Guest

    And write down where it was purchased and file that into a manila folder
    that says "A/C" or something on there. I neglected to do that on faucet
    rubbers because when moving to the US I could only by a 25-pack (only
    one faucet leaked when we bought the house). So I thought this is going
    to last a lifetime ... *wrong* ... used the last one a while ago. The
    water here is so chlorinated it literally eats rubber.

    Luckily we have the oldest hardware store west of the Mississippi right
    here. If they ain't got it then it doesn't exist :)
  7. Nico Coesel

    Nico Coesel Guest

    Can't you remodel it to use an inverter? When I had to replace our
    central ventilation unit I choose a model with an inverter. I replaced
    the capacitors on the previous one several times.
  8. Tim Williams

    Tim Williams Guest

    AFAIK, film caps (the film-in-oil, metal can type) last essentially forever.
    I don't know about 40A, but I'd be surprised if a film cap operated at 140F
    ambient didn't last more than 20 years.

    The small physical size suggests to me that, at least the start section, is
    a bipolar electrolytic, which is typically used for motor-start
    applications, and short lived (not only at the >40A surge, but even just
    being at 140F ambient for a few years).

    The 30uF 370V can I've got sitting in my junk box is about 1-1/4" thick,
    2-1/2" wide (oval shape) and 4" tall. Unless they've really changed the
    game with film thickness these days, I don't see 60uF 440V fitting in a much
    smaller package unless it's electrolytic. (The run part might still be film

    Obviously, you'd need the space to fit such a capacitor...

  9. miso

    miso Guest

    It was damn cold on Saturday even deep inland in the bay area. I was in
    Livermore freezing in the sub-70 deg F weather. Brrrr!

    When I see those tubby nudists in the fog on Baker Beach, I have to say WTF.
  10. miso

    miso Guest

    I never heard of an inverter in an air conditioner, but the wiki seems
    to make sense: I suspect the air conditioning itself is better since it is a continuous
    flow versus duty cycle modulation. [There are some high end
    refrigerators that run continuously with what I guess is a similar scheme.]

    Those AC caps fail a lot. I know quiet a few Ca to Nv transplants, and
    they are routinely replacing the AC cap. Since an air conditioner really
    only lasts about 15 years, it would be wise to go inverter for the
    replacement. I assume heat pumps have similar schemes.
  11. mook johnson

    mook johnson Guest

    Something like these? Price isn't too bad.
  12. Tim Williams

    Tim Williams Guest

    Yes, and many others; I believe mine are old (not PCBs-old) GE parts (which
    I guess are Genteq or something now).

  13. mook johnson

    mook johnson Guest

    Just realized I got snookered by Grainger. They labeled the cap Genteq when
    actually they are Proline. Both made by the same manufacturer that makes GE
    but the lifetime spec on the Genteq is 60K hours while the lifetime spec on
    the Proline is 10K hours. :(

    Let see, 8700 hours in a year... Houston tx,..figure 5000 hours a year run
    time... 2 years before I can expect this guy to pop IF it meets its
    specifications. Genteqs sell for the same price ~$35 on other places
    besides Grainger.

    Oh well. I have my $11 china cheapo (Qe Quality) will be arriving Friday as
    a backup. Next purchase will be something like the CDE caps. At least a
    known name in the capacitor business.
  14. NM5K

    NM5K Guest

    Nope.. That's a run cap. A start cap would be the type used
    with a hard start kit.
    The caps they make these days are cheap and don't last.
    Even the better brands are pretty much junk these days.
    One thing I would do is use 440v rated caps vs 370v.
    I think they tend to last a bit longer before going kaput.
  15. NM5K

    NM5K Guest

    Nope... The 60 mf is the run cap for the compressor. The 5 mf
    is the run cap for the fan motor.
  16. NM5K

    NM5K Guest

    Not that I recall.. I said it though. Why? Because one
    said the cap was a start cap, which it is not, and then
    you claimed that the 5 mf was the run cap, and the 60 mf
    was a start cap. Neither statement was correct.
    And we don't want no incorrectness on this here interweb,
    now do we. :)
  17. NM5K

    NM5K Guest

    That is not what he has. Why would I care about obtuse examples
    that have nothing to do with what he has?
  18. NM5K

    NM5K Guest

    I know *exactly* what he has. He told us in the first post.
    I Quote..

    "I have a 4 ton Carrier A/C that the original GE cap (Dual 60uF/5uF 440VAC)"

    And for the usual residential type condensing unit, yes, a
    compressor motor with two run caps would be quite obtuse.
    Like a pretty much zero chance of seeing one.

    Almost all modern compressor motors use a single run cap,
    and if starting is an issue, they add a start kit, which is a
    start cap with a potential relay. Or they can slap a single
    piece start kit with a start cap and a S/S relay built on top.
    Not two run caps!

    None of the usual fan motors in a modern condensing unit use two run
    caps. Zero. None. Nada.

    I don't know where you get your information, and I really don't care.
    I've been working on air conditioners since 1977.
    Only for a couple of years in the late 80's, when I owned a different
    business, did I take a break from working on air conditioners, from the
    overall time period 1977 until 2012.

    I currently work on air conditioners, and I change out so many caps
    that's it's almost become a new sideline due to the pathetic quality of
    caps in the last few years. I make a lot of money due to these cheap
    ass caps. :) Easy money my man, very easy money... :)

    I've been in business long enough to remember when you rarely saw
    bad caps.
    I change some poor bastards, or bastardette, if they don't have
    hairy legs, blown out A/C cap almost every single freakin day!!!
    Some days, more than one case.
    I change so many that I have to keep a complete stock of every common
    value on the truck to avoid making store runs, and to make sure I have
    one when it's 8:39 in the PM and after store hours.
    How many A/C caps do you change out a week?

    Why do you insist on humping my legs over silly ass A/C caps?
    Sometimes when I'm in some bastards backyard changing an A/C cap, dogs
    try to do that... :/ I think from now on, I'll ask them..
    Hey doggy! are you happy to see me, or is your name Michael A. Terrell?
  19. NM5K

    NM5K Guest

    No, a typical response to a person that repeatedly tries to hump
    my legs.
    All I said to the other poster was that it was not a start cap,
    but actually a run cap, and that caps in general are cheap and of
    poor quality. And you seem to have some problem, and keep asking me
    idiotic questions about parts that don't exist for the persons unit.

    You don't know me for jack, and you have no idea what the quality
    of my work is.
    Almost everyone I do work for calls me back, and I get many
    referrals. I have enough work just from existing customers that
    know us, I don't have to advertise. And my prices to change a cap
    are probably among the lowest in this city. I know some companies
    that charge ridiculous prices. We don't. It's still good money
    being it takes about 3 minutes to do.
    All of the new equipment I install is permitted and inspected by the
    city, and trust me, if something is not kosher, they will let you know
    about it.

    You are the one with the bad attitude. You obviously got bent over
    by some unscrupulous moron HVAC tech, and you think everyone operates
    that way. I'm sure you could also say the same thing about certain
    TV techs too..
    Fake screen name? Chortle.. You kill me, you really do. :|
  20. mook johnson

    mook johnson Guest

    Do that hard start caps replace the 60uF compressor run cap or go in
    parallel with it until the compressor starts then drops out?

    I've heard some negative pres about kickstart caps causing more problems
    than they fix. Do you have experience with these lasting long term?
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