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Thread: Condenser motor running in reverse

  1. #41
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    It makes sense & it's only logical that it's the compressor in the capacitor circuit causing the fan to run backwards & not the uf rating of the cap wired in series. A 35/5 cap wired in series would turn it into 4.38 uf & I don't see how that would cause the fan to run backwards.
    Gary
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  2. #42
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    I disagree w/ something. The cap does not change or alter the voltage.

  3. #43
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    Quote Originally Posted by TechmanTerry View Post
    I disagree w/ something. The cap does not change or alter the voltage.
    You may not see it on a PSC motor. If you run across an old unit with a "start" capacitor in the 130- 260 mfd range you will see higher voltage to the start winding if you look fast before the start relay drops out. " garyed" brain seems to be functioning better than mine, maybe he can help us out PLEASE. I recall something like the terminal from the start winding would pull start cap out of circuit and let motor run on "run capacitor".

  4. #44
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    Replace the cap. Ive seen many that were bad that caused to reverse rotation.

  5. #45
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    Quote Originally Posted by TechmanTerry View Post
    I disagree w/ something. The cap does not change or alter the voltage.
    The first thing that my father taught me ( while repairing CRT television sets)was that capacitors store enough energy to kill you even when the TV is unplugged.

  6. #46
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    That is sound advice for switched capacitors. But run capacitors are always connected and so discharge themselves automatically.

    PHM
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    Quote Originally Posted by stumpdigger View Post
    The first thing that my father taught me ( while repairing CRT television sets)was that capacitors store enough energy to kill you even when the TV is unplugged.
    PHM
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    The conventional view serves to protect us from the painful job of Thinking

  7. #47
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    Live from the window A/C test center: I rewired the cap as in original thread/ post. Fan motor operated forward every time. Put the stat in a glass of hot water to run compressor, held fan blade with stick while waiting for compressor to start, sure as dirt the fan took off in reverse as soon as compressor started. Cycled unit while fan was free spinning in reverse with no compressor and it took off in forward. It's all about phase shift.

  8. #48
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    Quote Originally Posted by TechmanTerry View Post
    I disagree w/ something. The cap does not change or alter the voltage.
    I'm definitely no expert on capacitors but my understanding is that the start & run windings of the motor create the higher voltage. The capacitor in the circuit releases a charge & creates a phase shift where the voltage raises to it's maximum & the current lowers. A properly sized cap in the circuit should have the highest voltage across it & cause the lowest amp draw on the motor. Capacitors have always been a mystery to me so I always just say they give a motor the boost it needs.
    Gary
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  9. #49
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    On any running 1 phase comp you can measure and see a "higher than line voltage volt reading". That higher than line volt reading is a result of the EMF & Back EMF produced by the diff magnetic fields from the start & run windings.Flapping Jaws here, line volt is 230,Back EMF is 130v so "total volts is 360v" which means a 370v run cap is good enough for that comp motor. The motor produces the EMF & Back EMF and the run cap gets picked to match that "produced voltage" .

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  11. #50
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    Quote Originally Posted by stumpdigger View Post
    Live from the window A/C test center: I rewired the cap as in original thread/ post. Fan motor operated forward every time. Put the stat in a glass of hot water to run compressor, held fan blade with stick while waiting for compressor to start, sure as dirt the fan took off in reverse as soon as compressor started. Cycled unit while fan was free spinning in reverse with no compressor and it took off in forward. It's all about phase shift.
    Phase shift and MFD is another part of capacitors. Voltage is a diff part.

  12. #51
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    Quote Originally Posted by stumpdigger View Post
    You may not see it on a PSC motor. If you run across an old unit with a "start" capacitor in the 130- 260 mfd range you will see higher voltage to the start winding if you look fast before the start relay drops out. " garyed" brain seems to be functioning better than mine, maybe he can help us out PLEASE. I recall something like the terminal from the start winding would pull start cap out of circuit and let motor run on "run capacitor".
    Measure the volts on a running comp,c-s, c-r, s-r. Measure the pot relay coil volt,or better called the "continuous coil voltage" w/ comp running.That voltage is there as long as the comp is energized.

    Lets say Cope has 33 diff comps available. By measuring the continuous coil volt on each comp, you will get 33 diff readings. That means that Cope also has 33 diff pot relays for sale,because the coils are rated at diff volts.( KindaSorta like a regular relay, coil volt is 24,120,240) That also means I have to carry a box of 33 diff pot relays so that I can better service my customers. That also means that the start winding length&thickness is different 33 times, 1 time for each diff comp.

  13. #52
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    some mini splits run in reverse for deice

  14. #53
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    Check out,
    RSES SAM #620-46A ,titled "Motor Capacitors" by Robert L.Thomas,Jr.,,8pgs

    RSES SAM # 630-111, "REMOVAL AND DISPOSAL OF CAPACITORS CONTAINING PCB's" by Richard D. Beard,,,2 pgs.

    RSES Journal Oct,2011, titled "Understanding and Selecting CAPACITORS"by Anthony Colone III.

    SUPCO, "The Benefits of AC Hard Starts",,5 pgs.

    Copeland, form # 78-35(5-78) "MISWIRING IS MURDER",,6 pgs

    Tecumseh, "A Review of Single Phase Hermetic Compressor Motors and their Electrical Components" 8pgs.

    MARS,"CAPACITOR BASICS",15pgs.

    ALL a Good Read.

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  16. #54
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    Electric Motor Start / Run Capacitor Operation

    https://inspectapedia.com/electric/S..._Operation.php

    Some starting capacitors such as those designed by and used in Copeland HVACR compressor motors, include a bleed-through resistor wired between the capacitor's two terminals. Typically a 15K-18Kohm two-watt resistor is used for this purpose

    Copeland describes the bleed-through resistor as follows:

    The use of capacitors without these resistors will result in sticking relay contacts and/or erratic relay operation especially where short cycling is likely to occur. This is due to the start capacitor discharging through the relay contacts as they close, following a very short running cycle.

    The resistor permits the capacitor charge to bleed down at a much faster rate, preventing arcing and over-heating of the relay contacts.

    ... If sticking contacts are encountered on any start relay, the first item to check is the start capacitor resistor. If damaged, or not provided, install a new resistor, and clean the relay contacts or replace the relay.

    Suitable resistors can be obtained from any electronic parts wholesaler or retailer. - Copeland Electrical Handbook p.A5- A6.

    A pack of five 15K ohm [15K Ω 2W], 2 Watt Resistors from Electron Components, an online vendor in July 2018, sells for as little as less than $1.00 USD.

    In addition
    SUPCO offers this explanation of why a potential relay hard start kit would be used:

    Most single phase air conditioners and heat pumps use non-bleed thermostatic expansion valves (TXVs or TEV's) to control refrigerant.

    A problem with TXVs occurs when a reciprocating compressor shuts off, refrigerant pressures dont fully equalize. Pressures do equalize in scroll compressors; which, typically do not need hard start kits for this condition.

    When a TXV is used, a potential relay hard start kit is employed. This will increase starting torque by a minimum of 300 % over using just a run capacitor.

    ... Systems with capillary tubes or fixed restrictors usually dont need a full hard start kit, unless the compressor bearings are tight. In such cases, the compressor is probably near the end of its useful life anyway. - SUPCO Hard Starts booklet cited below.

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  18. #55
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    Quote Originally Posted by TechmanTerry View Post
    Check out,
    RSES SAM #620-46A ,titled "Motor Capacitors" by Robert L.Thomas,Jr.,,8pgs

    RSES SAM # 630-111, "REMOVAL AND DISPOSAL OF CAPACITORS CONTAINING PCB's" by Richard D. Beard,,,2 pgs.

    RSES Journal Oct,2011, titled "Understanding and Selecting CAPACITORS"by Anthony Colone III.

    SUPCO, "The Benefits of AC Hard Starts",,5 pgs.

    Copeland, form # 78-35(5-78) "MISWIRING IS MURDER",,6 pgs

    Tecumseh, "A Review of Single Phase Hermetic Compressor Motors and their Electrical Components" 8pgs.

    MARS,"CAPACITOR BASICS",15pgs.

    ALL a Good Read.
    X2 GREAT SUGGESTIONS

  19. #56
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    Thank You, Back EMF explains the higher voltage reading on cap when running. I have not really dealt with back EMF since people switched from belt drive blowers and started melting humidifiers.

  20. #57
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    Quote Originally Posted by gustavhorna View Post
    some mini splits run in reverse for deice
    Run in reverse? As in reverse rotation? Or as in reverse cycle as in a heat pump?

  21. #58
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    Quote Originally Posted by TechmanTerry View Post
    Run in reverse? As in reverse rotation? Or as in reverse cycle as in a heat pump?
    fan runs in reverse. not sure why this would be better than the forward gear

  22. #59
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    I just had to change another dual cap today & i had some time so i did an experiment. Things worked out exactly as I expected.
    First I put the power lead(L1) on "Herm" & did not hook up the compressor so nothing was hooked up to the "C" terminal . The fan cap lead was hooked to the "Fan" terminal.
    The fan turned on & ran in the correct direction seemingly at full speed.
    Then I added the compressor start lead to the "C" terminal & that's when the fan turned on in the opposite direction but still seemingly running at full speed.
    So there is some kind of phase shifting going on with the compressor in the circuit that causes the fan to run backwards when "C" & "Herm" are wired in reverse.
    I'm sure there's a very interesting explanation but it's above my pay grade<g>
    Gary
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    The best things in life are free but not everyone is willing to pay the price.

  23. #60
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    Thread Starter
    I have now run into 3 this month guess it's the downside to people buying caps ironically noone admits to putting in the brand new miswired cap

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