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  1. #1
    Join Date
    Jan 2011
    Posts
    7

    Possible bad cap situation on my outside fan unit? (35mfd was replaced with a 7.5)

    Our downstairs AC went out last August and our home warranty folks sent out a serviceman to fix it (dual zone heat pump setup). He said it was a bad capacitor & replaced it. Our AC worked again and we were happy.

    Now it's winter and I noticed the downstairs wasn't warming very well & the thermostat says "heat 2 pump". The fan unit outside is not running at all, and I don't notice any sounds coming from it when I flip the circuit breaker (the upstairs fan unit is running like I'd expect). I guess the "heat 2 pump" means that the air handler is heating the air with the electric heater strips instead of using the heat pump with the fan unit.

    So I opened up the service panel on the fan unit to see if anything looked burnt. I noticed that the repairman zip-tied the new (much smaller) capacitor to the old one and rerouted a couple connections to it, but left the old one mostly hooked up. Either that, or he replaced an old 3-terminal one with 2 dual-terminal ones in such a way as to work the same as the old one? I only suggest that since both capacitors look pretty shiny & new with no bulging. I didn't try to disconnect them to test them with a meter since I don't really know what I'm doing.

    The big cap in the back is 35mfd. The little one is 7.5mfd. I forgot to take a pic of how they are hooked together - I can get that if it would help.

    I'm going to attach a couple pics in the hope that someone could mention if it looks fishy. I plan on making a service call tomorrow but want to know if I should complain about the current capacitor situation. Or is this a normal way to use two dual-pole caps to replace a dead 3-pole cap?

    The last pic is of the unit's label: unit # & serial number if it helps. It's a Carrier brand.

    Thanks!
    Attached Images Attached Images    

  2. #2
    Join Date
    Nov 2010
    Location
    Central Florida
    Posts
    556
    I'm not an HVAC expert, and keep in mind the pics make it a bit difficult to see the connections, but if I'm seeing things correctly then it looks like you had a single tri-pole replaced by two bi-pole start capacitors. If that is the case then you should be fine, at least WRT to the configuration. Whether or not the caps are functioning or properly sized is another story.

  3. #3
    Join Date
    Sep 2008
    Location
    VA
    Posts
    1,844
    The old dual capacitor he removed, and put two in it's place. It's fine, actually probably better for heat dissipation. Even better he used 440v caps instead of 370v. Not needed for the fan though, can't quite see the 35f, but probably a 440v as well. 35f sounds right for a 2ton.
    I probably wouldn't have zip tied them together, but it's not hurting anything. I just prefer strapping them separately if there is room.

    Capacitors fail for a lot of reasons. It could be power surge, power dip, thunderstorms, failing compressor, bad capacitor itself (they're made cheap now-a-days), excessive heat...etc
    "The only true wisdom is in knowing you know nothing" Socrates

  4. #4
    Join Date
    Jan 2011
    Posts
    7
    Thanks for the replies - they give me some peace of mind. I'm going to call the same folks to have them take a look at what is wrong with it now. Maybe one of the caps went bad again, or maybe the motor or compressor is dead. The fan spins freely when I spin it, but I have no idea how to diagnose what is wrong. Plus it's going to be pretty cold in the foreseeable future with some snow, so I'd like to get the heating back up to par as quickly as possible. Too bad my home warranty has expired.

    I did turn the thermostat to 'cool' and set it to 65 and verified that the fan & compressor did not come on after a few minutes.

    - Anthony

  5. #5
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,051
    Try resetting the breaker labeled Heat or Air Handler.

  6. #6
    Join Date
    Jul 2009
    Location
    Plant City, Florida
    Posts
    2,198
    Quote Originally Posted by ap42 View Post
    Thanks for the replies - they give me some peace of mind. I'm going to call the same folks to have them take a look at what is wrong with it now. Maybe one of the caps went bad again, or maybe the motor or compressor is dead. The fan spins freely when I spin it, but I have no idea how to diagnose what is wrong. Plus it's going to be pretty cold in the foreseeable future with some snow, so I'd like to get the heating back up to par as quickly as possible. Too bad my home warranty has expired.

    I did turn the thermostat to 'cool' and set it to 65 and verified that the fan & compressor did not come on after a few minutes.

    - Anthony
    it probably had a 35/7.5 dual capacitor and he replaced it with 2 individual capacitors, could have done a little nicer job on the install but it works.

    Probably lost a capacitor, not a big deal, its frustrating but it happens, it seems like we have either been getting bad capacitors lately or spikes are taking them out, sucks for the customer to have to pay for another repair.

    I only buy cpacitors rated at 440v,the capacitor he used is made in china so the quality control is pretty much non existant, unfortunately more and more stuff is being made in china, I don't think my supplier has any capacitors that aren't made in china.

  7. #7
    Join Date
    Aug 2010
    Location
    Memphis
    Posts
    343
    Pretty common practice to do it that way as most parts houses don't carry dual caps.

  8. #8
    Join Date
    Jan 2011
    Posts
    7
    I turned off the circuit breakers for the downstairs AC & heating unit (which I'm pretty sure is for the compressor/fan outside & the air handler under the house). Counted to 10, turned them back on, and everything is the same. The air vents are blowing slightly warm air, the thermostat flashes "heat 2 pump", and the unit outside isn't doing anything.


    I have a question on testing the caps: if I turn off the breaker, do I have to disconnect the caps before I can discharge them with a screwdriver to test them? I would think so to avoid hurting anything it is connected to?

    I only ask because it turns out one of my multimeters has a capacitance setting, and I thought I could try hooking it up to see if they are within spec.

  9. #9
    Join Date
    Jul 2009
    Location
    Plant City, Florida
    Posts
    2,198
    Quote Originally Posted by ap42 View Post
    I turned off the circuit breakers for the downstairs AC & heating unit (which I'm pretty sure is for the compressor/fan outside & the air handler under the house). Counted to 10, turned them back on, and everything is the same. The air vents are blowing slightly warm air, the thermostat flashes "heat 2 pump", and the unit outside isn't doing anything.


    I have a question on testing the caps: if I turn off the breaker, do I have to disconnect the caps before I can discharge them with a screwdriver to test them? I would think so to avoid hurting anything it is connected to?

    I only ask because it turns out one of my multimeters has a capacitance setting, and I thought I could try hooking it up to see if they are within spec.


    This isn't a DIY site and we aren't supposed to tell you how to do it yourself and i probably already said too much inmy previous post.

  10. #10
    Join Date
    Jan 2011
    Posts
    7
    Quote Originally Posted by bwalley View Post
    This isn't a DIY site and we aren't supposed to tell you how to do it yourself and i probably already said too much inmy previous post.
    Understood. Thanks for the response - hopefully it will be a cap & be an easy same-day fix for the repairman.

  11. #11
    Join Date
    Jul 2009
    Location
    Plant City, Florida
    Posts
    2,198
    Quote Originally Posted by ap42 View Post
    Understood. Thanks for the response - hopefully it will be a cap & be an easy same-day fix for the repairman.
    it looks like the repair was done about 6 months ago, if it was my company that did the repair, I would warranty it, but since a home warranty company paid for the repair and the a/c contractor probably got paid peanuts for the repair, you will proably have to pay for it.

    since the compressor and the fan aren't coming on, it may not be the capacitor's, it is probably something else very minor.

  12. #12
    Join Date
    Jan 2010
    Location
    over here
    Posts
    463
    Quote Originally Posted by bwalley View Post
    it looks like the repair was done about 6 months ago, if it was my company that did the repair, I would warranty it, but since a home warranty company paid for the repair and the a/c contractor probably got paid peanuts for the repair, you will proably have to pay for it.

    since the compressor and the fan aren't coming on, it may not be the capacitor's, it is probably something else very minor.
    Ooh ooh me,me, i know, pick me, me,

  13. #13
    Join Date
    Jan 2011
    Posts
    7
    It turns out there was a coolant leak at the outside unit. There's a thin coolant line going from the compressor that had some power wires rubbing against it. One of the wires wore through to the copper, and it looks like there was some arcing that burned a hole int he copper line. When pressure is applied to the system it leaks like crazy.

    The tech will be back later (he ran out of juice for his torch) to try to solder it up. With any luck that will fix us up while we decide whether to replace the outside system or if we want to replace the entire HVAC to a more efficient one.

    He said to brace ourselves for a big electric bill this month.

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