run capacitor sizing ? cannot determine original size and no manufacturer info is available

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pressure tank was made. the UL and CSA file on it is LR13758 label reads: 5HP 1 Phase 1740 Rpm m184t frame Mtr ref: r75334af881 thinking this is like a model number... 60Hetz, 230 volts, 23.0 amps, SF amps 24.5, SF 1.15 insulation class BR type TX KVA code G and then a final long number in the bottom right that is not labeled is 20(B or 8)046370200 ....it says everything but does not tell me the capacitor sizes. would appreciate a call if someone can educate me on this.. wife is pissed the compressor is still preventing me from finishing cleaning the garage... I am at the point where I want to simply measure current draw and try to dial in a size iteratively.
available... more importantly another website says a 5hp run cap is never over 40uF so I am begging for help.. will venmo or quickpay BEER MONEY! already replaced bearing and cleaned and painted this compressor up..
smallest current but I am just guessing at this point ... what I am thinking is the motor actually spun over in the winter with the blown capacitor so as long as I do not exceed the capacitance I believe I won't damage the motor, I really would appreciate learning a good method of getting to a value as this is not the first time in my life this would have been useful and I'm pretty sure it won't be the last..... I am in a dangerous state, I don't know what I don't know.
Do you have a clamp amp meter? Try some close to your computation and shoot for the lowest current under a load. (like tank about half full). The current will be a bell curve over the pressure.
Reply to
gfretwell
BEll curve...That's is a useful insight thank you... wanted to get some data logging current meters and rpm meters to work together so I can plot and get a better idea of iterative capacity values and performance / operational chacteristics.. was going to do the pump as a load without building pressure until I get closer to what I am hoping the correct value will be... thinking back emf voltage on the capacitor would also be relavent but do not know what to expect... maybe I will collect data on another working compressor with a 3 hp motor i have access too and know the original capacitor values of and then start working on the 5 hp..... any advice is appreciated... need to get a student copy of labview and get my daughter to install it... it's been years.. wonder if I will remember how to do the DAta acquisition... and I my old NI USB-6008 can still be used or if it's to old for current support....
Reply to
Pasieka
I was playing with my 3HP compressor in a similar situation. The run cap burnt beyond recognition. I had a box of capacitors and used the trial and error method to pick a size based on current draw at about half the rated pressure., That seems to be when it actually draws the most. As the pressure starts reaching max the current actually drops because you are moving less air and doing less work. That is similar to why a vacuum cleaner actually speeds up when you block the air flow. I started around 40 MFD as I recall and ended up at 50.
Reply to
gfretwell
Στις 1/8/2022 11:18 μ.μ., ο/η snipped-for-privacy@aol.com έγραψε:
google is your friend.
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Reply to
Dimitris Tzortzakakis
I just looked and add 100 to the numbers I posted. I am running a 150 (not 50) and when I went to 162 (the next higher I could make with the caps I had) current actually increased. I used the calc and I get to 190 MFD. The FLA marked on the motor is higher than actual readings so that may explain it. My guess is this motor was over sized for the application and never actually gets close to FLA. The bottom line is you want the one that makes the motor most efficient over the range it runs in.
Reply to
gfretwell
your link is broken... but more importantly. GOOGLE IS NOT MY FRIEND.. and you know that as well I hope... tried online calcs... they are say 80 plus microfarads... something is not right...
Reply to
mark.pasieka@gmail.com
full load amps continuous would most probably damage a motor.... I think you have a capacitive start motor. I am dealing with a capacitive run capacitive start... slightly bigger single-phase motor...
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Reply to
mark.pasieka@gmail.com
Re: run capacitor sizing ? cannot determine original size and no manufacturer info is available full size image
Think my clamp meter was not completely closed for the zero and 10.2 microfarad L Blue current measurements...
this is a YouTube video of me collecting data for the almost 40 uF test:
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your feedback is appreciated. THANK YOU!
Reply to
mark.pasieka@gmail.com

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