ReplyProbably.
See how it runs with the new cap, you might be too late!
Regular Guest
I had looked at furnace with run cap for blower, unit was off on high limit. Did cap test and had 1.2 micro farads(cap rated for 5mfd) Cap wasnt bulged but my question is at 1.2 can I assume cap is at fault not blower? Even though it is not entirely open. Blower was hot. Didnt have cap in van at time so I will have to go back. Tested limit, when things cooled off and it was closed.
Professional Member*
Probably.
See how it runs with the new cap, you might be too late!
Professional Member*
yep.... change it all will be good..... well done lots of tecs would of changed a perfectly good motor... 1.2 is not close to 5 it should work.....
it was working.... played with it.... now its broke.... whats the going hourly rate for HVAC repair
Professional Member
next question....
why do you not have a blower cap on your truck????
Please, Please Please......keep the Factory Smoke in the Wires!!!!!
Is it Rum'Oclock yet???
Professional Member*
good point.....
it was working.... played with it.... now its broke.... whats the going hourly rate for HVAC repair
Regular Guest
Okay thanks, and agrred I do need to get some more van stock.
Professional Member*
Depending on the age/condition of the motor, it may not be a bad idea to replace both the cap and motor. Customers get pissy when you have to go back a few months later to replace the motor. .02
Professional Member*
1.2 mfd vs 5 mfd? This is off 76% of a 5 mfd cap. Most caps are (+/-) 5%-10% tolerance. Change is good!
CT
Professional Member*
I would check your amp draw on your motor after replacing capacitor to insure condition of the motor.
Professional Member*
Someone has been doing his homework, you are correct. I have seen numerous post here in my past years, that say "motors" have a 5%-10% tolerance. I have often wondered if the caps have a tolerance percentage, does this mean that the motor mfg. would say it ok for their motor designed for a 10 mfd. cap, to run at 9 mfd.? Maybe bypass a call to the distributor, straight to the mfg. would get you the correct answer, straight from the horse's mouth.Originally Posted by nsula_country
__________________________________________________ _______________________
“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
Professional Member*
I'm unsure about the motors, but can investigate. Most run caps are (+/-) 10% tolerance. So if a motor requires a 10 mfd cap, the cap should read 9 mfd-11 mfd (10%). The motor designers should have this variance factored into the motor design. I would say it would be better to oversize a cap than to undersize it, but not more than 1 size up and only until the proper replacement can be installed.Someone has been doing his homework, you are correct. I have seen numerous post here in my past years, that say "motors" have a 5%-10% tolerance. I have often wondered if the caps have a tolerance percentage, does this mean that the motor mfg. would say it ok for their motor designed for a 10 mfd. cap, to run at 9 mfd.? Maybe bypass a call to the distributor, straight to the mfg. would get you the correct answer, straight from the horse's mouth.
Reasons:
Efficiency - A capacitor attempts to correct a poor Power Factor by adding Capacitance Reactance. Since a compressor or fan motor is an inductive device with Inductive Reactance, a capacitor will largely zero the reactances, resulting in a compressor or fan motor that runs cooler and uses less electricity. Oversizing or Undersizing screws with the Power Factor on a RUN capacitor.
Rules for Capacitor Replacement:
-Voltage must be EQUAL TO or GREATER than the cap being changed (ie, 370V)
-Start Cap must be (+/-) 20% of mfd
-Run Cap must be (+/-) 10% of mfd
-If the Start Cap is UNDERSIZED, the motor might not start.
-If the Start Cap is OVERSIZED, the high start current might burn out the start winding (Hard Start Kit ???).
-If the Run Cap is incorrectly sized, the Power Factor will suffer, resulting in lower efficiency, higher operating costs, and possible motor damage.
A failing cap can:
--reduce the speed of the motor, which
--increases the motor’s temperature
--causes bearing wear and insulation breakdown
-- increases overall noise
Basically the capacitor values posted on nameplates are engineered to be optimum for peak performance. replace with like part!
Run capacitors are there to correct the single-phase power factor. Three-phase is nearly perfect at 1.00 power factor, but sometimes capacitor banks are used to balance power factor in imbalanced systems.
Good luck!
CT
Regular Guest
^This
Professional Member*
X3
Professional Member*
Yes checking amps is a good thing, but I never check just amperage until after I have check voltage.
__________________________________________________ _______________________
“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
Professional Member*
Low voltage will make the amps climb... Then we find loose connections, and burnt wires, and well you know the rest.Yes checking amps is a good thing, but I never check just amperage until after I have check voltage.
CT
Regular Guest
Changed cap ,motor hummed, gave blower spin to get going, noisy as hell, berrings are shot, going to replace motor. Thanks all for help.
Professional Member*
Motor runs hot on low mfd. cap. washes oil out of bearings, possible scenario.
__________________________________________________ _______________________
“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
Professional Member
I would be careful saying a run capacitor's main job is to correct power factor.
I'd rather say the capacitor shifts the phase of one of the windings so that the voltage across the winding is at 90° from the other winding. The effectivly makes it a two-phase motor (when loaded).
Now if the proper capacitor is used......then the currents through each of the windings, when fully loaded, should be equal....and under those conditions power factor will be close to 100%.
Professional Member*
I agree 100%. In a nutshell, this is what I was trying to explain, but it did not come out as cleanly as you described. I was thinking about the phase angles and the reactance the capacitor adds to shift the angle.
Thanks for the input. My wordiness probably confused some readers.
CT
Regular Guest
X2
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