Some time back at an auction I picked up an older air compressor. Below the compressor on the tank mount is a tag with Brunner Mdl. HO25 209. The actual compressor tag shows Quincy Mdl.212 28, Size 2 1/2 x 2 1/2. The motor is a A.O. Smith Century AC Motor, 22 amp, 5 HP at 3450 rpm, 220 V single phase.
The old guy selling, (that's a relative term since he was likely only a very few years older than me) had it hooked to a generator to show it ran and made air.
Today I ran power to it and with the discharge valve open it started and started making air. I shut it down at 100 psi and checked for leaks. Bled some air off and it wouldn't restart. Tripped a 30 amp breaker. So I bled the tank to zero, same thing. One last effort, turned the power on and helped the motor by turning the big pulley, it then picked up speed and ran fine till I shut it down.
Confession, power is supplied by 10' of 12 ga romex from the breaker box. I know 12 ga. is too small, however it's the same circuit I've had my old Sears 5 hp. compressor on for the past 35 years, no issues.
I've got a couple SPP6 ac capacitors. No specs on the capacitors but the packaging shows good up to 10 hp motors on ac units. r Any possibility one or both capacitors might help start the motor? Anyone have thoughs on what all might be going on. I really think the gentleman at the auction may have been running the compressor without letting it pump up much air, just demonstrating that it ran.
RonR
added in edit; little Bro just offered some 10 ga or 8 ga wire. Free, so there's one more thing to try.
Likely the original capacitors on the motor are bad, since you were able to help it start. You might consider taking the motor to a shop to have them check it out. Or you could just wire in the new capacitors you have and see if that works.
I don't think the larger wire is going to help. 10 Ga is recommended for a 5 HP motor, but 12 Ga will work, it'll just get a bit warmer.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
I had one way older than that, but it did have a belt guard. I sold it as an antique. The relief valve had a patent date of over 100 years ago. I drug it all the way up here from California, then discovered it wasn't powerful enough to keep up with my paint gun.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Quincey Compressors are of high quality. I think your motor may be newer than the compressor/tank. Replacing the start capacitor would be a good next step on a project like yours.
Quincey Compressors are of high quality. I think your motor may be newer than the compressor/tank. Replacing the start capacitor would be a good next step on a project like yours.
Paul, I agree with your suggestion. The motor is newer for sure. It looks like it has 3 capacitors (or is one of the small 3 top motor housings not for a capacitor), is the best way to identify the start capacitor to look at all 3, with the highest microfarads being the start capacitor?
Once again, I'm out of my comfort zone.
edit; once again more searches yield more info. Seems the middle housing on top isn't a capacitor. To answer my own question, I removed the covers and the start capacitor is pretty easy to identify, it's the one that's about 50% bigger.
A 3450 RPM motor won't have much starting torque, even with a good capacitor. Aren't those usually used for things like table saws, etc, where there's pretty much of a no-load start? I'd suggest going to a smaller diameter pulley at the motor to give it a little more mechanical advantage on startup. Jerry
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Yes it definitely needs a belt guard. Some shops take them off when the compressor is placed in an outdoor enclosure.
It may have a start capacitor and a run capacitor. The can (top center) is a thermal protect and maybe a run switch. The capacitor with the highest capacitance will be the start capacitor...a wild guess maybe 750 microfarads (750 μF). The run capacitor will be a smaller value....again a wild guess maybe 30 microfarads. The start capacitor is the one having to work the hardest (phase shifting) and usually fails first. A replacement capacitor needs to be the same microfarad value. Also the capacitor voltage needs to be the same or higher voltage.
Totally agree on the guard. If just me, I'd be ok without. But we have 4 grandkids from 16 months to 11 years and they spend time in the shop/barn/hay shed area. Luckily everything to build a guard is in the precious metal inventory.
I ordered a new start capacitor this morning. The one being replaced has a 2009 manufacture date so it's due. In searching Ebay and Amazon I didn't find a single 216-260 MFD 250 VAC capacitor, but they had many 216-259, 250 VAC units. That's what I ordered. We'll see.
Make sure you are not over speeding the compressor, the last (3) single stage Quincey compressor's I've had all had 1750 rpm motors. The compressor pump should be running at about 900 rpm max. making about 120 psi max.
Also, be careful with OLD tanks, they rust on the inside and will violently explode when they fail. That tank look really old...what the date on it?
Mike B
Mike Boteler
1956 Chevy 3100 Resto Rod 1952 Willys M38 Army Jeep 1983 Jeep CJ7 Laredo 1984 Jeep CJ7 +++++ Silver Spring, MD
Moparguy, I would not use the air conditioning Hard Start capacitors in that application. The motor has it's own internal switch to disconnect the start capacitor when it reaches a specified RPM. The Hard Start caps are designed to connect in parallel with a run capacitor in an air conditioning system and they have a relay built in under the black plastic cap, that relay drops the capacitor out of the circuit based on current or voltage difference and may not be the best for that motor. I would first research the correct RPM for that compressor as Mike B has noted, then replace both capacitors if you are going to use the motor, the run cap is as important or more than the start cap.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
Today, a hard worked capacitor lasting 10-15 years is typical. Time for a new one.
The end of the black capacitor looks nasty. Hard to tell if that is just dirt or the capacitor leaking. Leaking and swelling are the telltale signs of a bad capacitor. The connectors look like they are oxidized a little so I would do a little cleaning.
Fingers crossed.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
First things First, THANKS ALL! Your comments, questions and guidance have been a huge help. My new start capacitor showed up yesterday as promised. Yes, I was surprised.
Before I plugged it in, I was wondering "how does the capacitor get energized that first time to start the motor since the motor is trying to start before the capacitor has had a chance to energize. Since I didn't find any online info with a quick search, my assumption was that it likely happens (literally) at the speed of light when the breaker is flipped.
I plugged the cap in, flipped the breaker, no start. Go out, position the compressor at the beginning of the easy spin point, flip breaker.....no start. I walk away.
My plan today was to pull the end of the motor and check the start circuit contact points. But First I measured the pulleys in order to determine the pump rpm with the 3450 rpm motor. The pump pulleys overall od is 14", deduct the .6 flange height x 2 (1.2") and it's a 12.8 od pulley (?). With the 4" drive pulley and same .6 flange height, it's a 2.8" pulley (?). If my logic is sound on how to determine pulley diameter, the drive ratio is 4.57 to 1. 3450/4.571=754 pump rpm. Now if I'm just goofy and you use the overall pulley diameters to calculate ratios, the pump rpm is 986 rpm. I'm constantly amazed at the things I don't know!
I think pump rpm is OK. I haven't found a spec for this exact Quincey pump though.
But the big news is......When I walked into the shop after measuring the pulleys I tripped the breaker just to see.....motor spun up instantly!!! Let pressure build to 50 psig, did the start test 3 more times. Started perfectly every time!
So, did the start cap charge due to stray voltage from the breaker box? Is this why it worked today and not yesterday immediately after installation?
Don’t get em wet and don’t feed them after midnight!
Martin '62 Chevy C-10 Stepside Shortbed (Restomod in progress) '47 Chevy 3100 5 Window (long term project) ‘65 Chevy Biscayne (Emily) ‘39 Dodge Business Coupe (Clarence) “I fought the law and the law won" now I are a retired one! Support those brave men/women who stand the "Thin Blue Line"! Hug a cop! USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)
Good Advise Martin. Gremlins I guess we gotta have em, but it applies to a lot of things! I don't understand exactly what happened, but I'm taking it as Win.
A stationary single phase motor is like a car trying to take off in 4th gear from a stop light. AC voltage has in-phase current and voltage cycles at 60 per second. With a capacitor added to the circuit, the current is phase shifted 90 degrees ahead of the voltage (it leads the voltage by 90 degrees). A motor is an inductor so a quick current surge creates torque (think automobile starter motors, they are especially wound for current to develop torque). So the compressor motor gets a very quick torque "kick-in-the-rump" to get it spinning. The voltage follows 90 degrees later.
If the start capacitor is too small (not enough capacitance) or defective, or if the load is too great, such as a bad bearing, compressor stuck, starting under pressure (unloader not working), the motor can't spin. But for now let's say all that is good.
If you turn the breaker on and the compressor main switch (on/off switch) is on and the tank has no pressure and the compressor doesn't run, it may not have voltage applied to the motor. Bad pressure switch, bad start relay, bad on/off switch or loose wiring in the power plug or power connection.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
(Before I plugged it in, I was wondering "how does the capacitor get energized that first time to start the motor since the motor is trying to start before the capacitor has had a chance to energize. Since I didn't find any online info with a quick search, my assumption was that it likely happens (literally) at the speed of light when the breaker is flipped.)
there is a centrifugal switch that opens when a certain RPM is reached disconnecting the cap. Closes again as the motor spins down. If you start it with no load and then shut it off so it can freewheel you will hear a click before it's stops spinning. That's the switch closing again.
