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08-29-2011, 06:24 PM   #16
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a hard start kit is a start capacitor and relay.......... again, in order to test a start capacitor you must remove the bleed resistor... if it were good then you would need to resolder the resistor back on. Better off to just replace the start capacitor.... You do understand that a start capacitor is not a run capacitor?

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08-29-2011, 09:37 PM   #17

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Quote:
 Originally Posted by thehvacguy Ok. But can you explain the technical aspect of why that would be? I was taught that you check the microfarads coming off the capacitor and as long as it meets the requirements then its good. Am I missing something?
Normal check would be to read the uFs. However, no mete reads uFs under load. Check the voltage.

Full check/test. Check amp draw on start winding. Multiply by 2650, then divide that by the voltage(voltage across the cap). that will give you the uF of that cap.

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08-30-2011, 12:48 AM   #18
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Quote:
 Originally Posted by beenthere Normal check would be to read the uFs. However, no mete reads uFs under load. Check the voltage. Full check/test. Check amp draw on start winding. Multiply by 2650, then divide that by the voltage(voltage across the cap). that will give you the uF of that cap.
Whoa you're taking me back to school here where does the 2650 come from? Also why do you need to test the uFs under load? In school they made us pull all the wires off and test it like that... of course we had to neutralize the bleed resistor by tapping a piece of metal across the terminals...

 08-30-2011, 03:00 AM #19 Member     Join Date: Oct 2010 Location: Austin - Texas Posts: 1,402 Rewards Points: 500 Actual microfarads = [ amp (start winding) X 2650 (constant) ] / Voltage Finding capacitance from measured volts and amps When testing motor starting capacitors to check the rating when markings aren't readable, the formula often stated is that capacitance in microfarads equals 2650 times the measured amperes divided by the applied volts. Where does this 2650 figure come from? When an a-c voltage is applied across a capacitor, the resulting current equals that voltage divided by the reactance of the capacitor. That reactance is: 1/[(2)(pi)(frequency)(capacitance C in farads)] or, for 60 Hertz, 1/(377C). Converting farads to microfarads, then solving for capacitance: C =[(1,000,000)(amperes)]/[(377)(volts)] and the value of 1,000,000 divided by 377 is 2650. __________________ **Always kill the power ** Hot air rises, but heat will always move from higher to lower temperatures. ** Real man shoot in manual. ** If it ain't grounded, it ain't dead. Last edited by JJboy; 08-30-2011 at 03:09 AM.
 The Following User Says Thank You to JJboy For This Useful Post: Doc Holliday (08-31-2011)
 08-30-2011, 06:57 PM #20 An old Tradesmen   Join Date: Oct 2008 Location: Somewhere Posts: 34,402 Rewards Points: 7,794 Many things can test good under a no load condition. but when it has to perform under a load, it fails, or becomes weak.
 08-31-2011, 01:23 AM #21 Still Learning   Join Date: Oct 2009 Location: Los Angeles Posts: 338 Rewards Points: 250 So how do I test the relay to make sure it needs to be replaced? Cause that one is like \$50 where as the cap is only \$5. I don't wanna waste money...
 08-31-2011, 01:32 AM #22 I'm Your Huckleberry   Join Date: Mar 2011 Posts: 5,884 Rewards Points: 2,270 Normal checking of a regular capacitor would mean removing ALL wires from the cap so it is standing alone and not connected to anything and then and only then checking between herm and common for it's rating and fan and common for it's rating, being a dual run cap if so. Plus or minus the given percentage of either rating would be considered within range.
 08-31-2011, 01:38 AM #23 I'm Your Huckleberry   Join Date: Mar 2011 Posts: 5,884 Rewards Points: 2,270 In other words if you have a 45/5 dual run cap with a percentage range of 6% than being that the bigger number of any dual cap relates to the compressor and the (much) smaller number relates to the fan motor, 45 multiplied by 6 percent will give you a number. Add or subtract that number from 45 and within those numbers would be considered acceptable. The same on the fan side, the 5. 5 x's 6% will give you the number to add or subract from the original 5 mfd. That's your range, plus or minus.
 08-31-2011, 01:44 AM #24 I'm Your Huckleberry   Join Date: Mar 2011 Posts: 5,884 Rewards Points: 2,270 45 multiplied by 6 percent is 2.7. 45 plus 2.7 is 47.7. 45 minus 2.7 is 42.5. 45 plus or minus 6% acceptable range would be 42.5 to 47.7. I think that's right.
08-31-2011, 04:46 AM   #25

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Quote:
 Originally Posted by thehvacguy So how do I test the relay to make sure it needs to be replaced? Cause that one is like \$50 where as the cap is only \$5. I don't wanna waste money...
Ohm the contacts and coil. Then check if its opening under load before it should. Or staying closed.

08-31-2011, 03:20 PM   #26
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Quote:
 Originally Posted by JJboy and the value of 1,000,000 divided by 377 is 2650.
The formula looks correct. But you need to change the constant to 2652

 09-08-2011, 05:09 PM #27 Still Learning   Join Date: Oct 2009 Location: Los Angeles Posts: 338 Rewards Points: 250 Ok this is where we are at... I replaced the relay and the start cap like beenthere said. There is one problem, there is no run cap... the compressor schematic shows a run cap (I can post a pic when I get to my computer) I called traulson and they told me that they lost all their recrds of all of the units that were manufactured in california when the company moved to new york... how do I determine what run cap to put on this sucker???
 09-08-2011, 05:26 PM #28 AKA HVACTECHFW   Join Date: Nov 2010 Location: NE Indiana Posts: 2,426 Rewards Points: 1,208 Blog Entries: 1 post a picture of what you are working on as well..... What is the start leg of the compressor currently wired to? other than the start capacitor..... __________________ IT IS WHAT IT IS
 09-08-2011, 05:45 PM #29 An old Tradesmen   Join Date: Oct 2008 Location: Somewhere Posts: 34,402 Rewards Points: 7,794 The compressor manufacturer can tell you what size run cap to use.
09-08-2011, 05:56 PM   #30
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It's usually on the sticker o the actual compressor, not nessisarly the unit

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