Ancient Westinghouse
M: SP018CAW
Style: 3958A46G01
Serial:MF63004
Big capacitor from pub era.
Thanks.
M: SP018CAW
Style: 3958A46G01
Serial:MF63004
Big capacitor from pub era.
Thanks.
Rundhaug- need capacitor size
knave
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That doesn't help me. No way to test a bad one. Old with no numbers on cap
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Unfortunately, if the motor isn't running then you have one equation with two or possibly three unknowns. The unknowns being Voltage at the capacitor terminals, and the Mfd of the cap.. The third unknown is the FLA of the motor if the nameplates can't be read.![Image]()
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With no info make an educated guess. 35uf probably a good start. Then if compressor starts take amp on common and run together then on herm alone. If they agree within .5 amps your good. If not try a different size.
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Never tried this, but I might play with my own system.
If we are talking about the condensor fan motor, what about trying a 5 mfd. If it starts the motor, then read volts, and amps. on the capacitor.
If the voltage is over the capacitor's rating then try a 7.5 mfd. Again, if the motor starts then read volts and amps..
Find the capacitor that has voltage within its rating and amperage...
Oh, never mind... we still wouldn't have any idea if amperage was in line or not unless maybe the motor over heating and seized. Then we would know we got it wrong.
If we are talking about the condensor fan motor, what about trying a 5 mfd. If it starts the motor, then read volts, and amps. on the capacitor.
If the voltage is over the capacitor's rating then try a 7.5 mfd. Again, if the motor starts then read volts and amps..
Find the capacitor that has voltage within its rating and amperage...
Oh, never mind... we still wouldn't have any idea if amperage was in line or not unless maybe the motor over heating and seized. Then we would know we got it wrong.
That's incorrect. That only gives you the operating capacitance of the capacitor when the motor is running. The amperage used is the start winding and the voltage used is the voltage between the start and run windings.
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http://www.electricneutron.com/electric-motor/single-phase-capacitor-sizing/
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Slow day for me. So, I was just thinking out loud.
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No, wait; don't give up so soon.
Let's use what we Do know:
018 in the M# almost certainly indicates an 18,000 BTU or 1 1/2 ton unit.
At comfort cooling conditions it takes about one horsepower per ton of cooling.
My general ROT is 12 amps per HP at 120V
So we can probably go with the idea that this system runs on 240V - so: 6 amps per HP. Or: a 9.0 FLA for the compressor.
PHM
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Let's use what we Do know:
018 in the M# almost certainly indicates an 18,000 BTU or 1 1/2 ton unit.
At comfort cooling conditions it takes about one horsepower per ton of cooling.
My general ROT is 12 amps per HP at 120V
So we can probably go with the idea that this system runs on 240V - so: 6 amps per HP. Or: a 9.0 FLA for the compressor.
PHM
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Let's see how that works:
Let's say I have a standard 3 ton 10 SEER condensing unit. So the compressor FLA is about 18 amps.
18 times 2650 = 47,700
47,700 divided by 240 volts = 198.75 uf (???)
I must be doing something wrong - that doesn't seem like it can possibly be right - you work it out now. <g>
PHM
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Let's say I have a standard 3 ton 10 SEER condensing unit. So the compressor FLA is about 18 amps.
18 times 2650 = 47,700
47,700 divided by 240 volts = 198.75 uf (???)
I must be doing something wrong - that doesn't seem like it can possibly be right - you work it out now. <g>
PHM
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Doing it this way would give you an insane capacitance. The ampsx2650/volts equation is meant to measure actual capacitance on a running unit. It wont work to figure out what size is needed.
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The voltage used in the divisor would be something in the range of 370V or something less than the capacitor's rating.
Check link I posted. Ridiculous amount of math to it but had a few rule of thumb charts. Posted wrong picture while I was trying to explain to a guy that if you have 115v from T1 to ground & 115v from T2 to ground does not mean you have 208/230 from T1 to T2. Some of these "techs" scare me to death. Had 1 leg of power back feeding through compressor
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I looked at the post, but when it came to the equations, I couldn't read the operators. So, I couldn't tell if they were addition, subtraction or multiplication.
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Sorry I'm late to the party.
I do not have a parts list for this unit, but if you can read the model number off the compressor, I might be able to find something.
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