Chosing Correct Capacitor


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Old 05-27-11, 10:19 AM
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Chosing Correct Capacitor

I have an old York central A/C model # CHE 42-10A. I want to change the compressor capacitor and have the schematic but it looks like the capacitor wiring has been altered. There is a dual capacitor (herm, com, fan) in the system and the diagram indicates this is correct. The wiring dia indicates that L2 is connected to the line in side of the contactor to engage the run winding. The capacitor herm side is connected to the T2 contactor and the com side of the capacitor is connected to the start winding - so far so good. What puzzles me is that the fan side of the capicator is connected to L2 and there is a bleed resistor from fan to com on the capacitor. This looks like power is provided through the capacitor to the start winding all the time. My assumption is that this is done to provide some heat in the compressor like an external heater would provide (please correct me if I am wrong). The real questions are, the capacitor is marked as a 20/15 uf, so, to replace the cap, what size resistor should be placed on the cap, and are the 2 sides of the cap really running in parallel so that the compressor really needs a 35 uf cap if the heater side is not used? The fan has a separate capacitor. I remain confussed. All help will be greatly appreciated.
Randy H.
 
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Old 05-27-11, 05:18 PM
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bleed resistor is just so it doesnt hold a charge once the unit is powered off. usually they will just keep one leg hot if they need to warm the crankcase. usually yellows go to the common and your brown is for your fan, possibly blue for herm (compressor) herm just means its a hermetic compressor (fully enclosed-no serviceability) there are two capacitors inside the one unit, they are only connected by the common leg. are you sure its 20/15. seems a bit high for the fan and slightly low for the compressor.
 
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Old 05-27-11, 08:37 PM
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Thanks for the reply. Both sides of the dual capacitor are wired to the start winding of the compressor. One side (side labled fan) is connected to L2 all the time. The common terminal of the capacitor is wired to the start winding of the compressor. The terminal labled hermetic is connected to the T2 terminal of the contactor. When the contactor shuts, current flows from the Hermatic side of the capacitor as well as the fan side of the capacitor. This capacitor is not connected to the condenser fan at all. The condenser fan has it's own 7.5uf capacitor. So my assumption is that when the contactor closes, I affectively have both sides of the run capacitor in parallel and connected to the start winding terminal giving me a total compressor run capacitance of 35uf. Does this sound like I'm on the right track? Please see the diagram http://dl.dropbox.com/u/14153604/201...2015.36.07.jpg
 
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Old 05-28-11, 09:49 PM
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looks like its a cscr compressor. meaning that you will have a start cap as well as a run cap. how many capacitors are in the unit. looking back in the posts it looks like you have two caps inside the unit. they are probably using the 1 dual cap as a start and run. why are you changing the cap??
 
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Old 05-29-11, 11:26 AM
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Dual Capacitor

It is a dual capacitor. Both sides are in parallel with the start winding but one side is hot all the time. Hermatic side is connected through the contactor, fan side (which is not used for the fan but for part of the run cap) is direct wired and hot all the time so i have a total run capacitor of 35uf (20 uf + 15 uf = 35 uf). I think I'm on the right track. Agree?
 
 

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