compressor starting problem.... electrical???

[Ice cold]

I've got a problem when I start my air compressor for the first time each day. subsequent starts are not a problem and I'm wondering if the "warm" pump/motor are a bit easier to start?

All check valves, safety valves and unloaders are new and working properly.

When starting it seems to "hunt". Waa...Waa...Waa...Waa... until the CB pops (5-10 seconds). I do notice some sparks inside the motor housing while it is hunting. If I unload the pump for a split second (pump outlet safety valve prior to tank check valve) it takes right off. Waaaaaaaaaaaaa. And when warm it takes right off.

Not sure where to start.....
Motor not adjusted properly?
Motor starter not working properly? It is an ebay "special" Noark brand and I can't find a user manual anywhere. Trying to contact the seller now.

Any ideas Guys?

See this thread for some background info on my conversion of air compressor from 3ph to 1ph.

http://www.garagejournal.com/forum/showthread.php?t=265571

 

[redmondjp]

So wait a minute here - explain this a little more. Are you: 1) pulling on the overpressure release valve momentarily and releasing pressure in the discharge line prior to the motor starting, or 2) pulling and holding the release valve open as the motor starts?

 

[Steevo]

You are relieving pressure on the pump side of the tank check valve, right?
If there is pressure in that line, then the tank check valve is leaking back.
I suspect a very slow leak-back from the tank check valve, since the issue is on the "first start of the day", but subsequent starts are ok.

I am assuming you shut off the power to the compressor when you leave the shop.

So imagine the check valve slowly seeping air back into the high pressure line, where it just leaks out the pressure switch release valve.

When the power is on, this is no problem, because when the pressure drops enough the motor kicks on, and since the bled-back pressure was being relieved by the switch release valve, it fires up fine.

When the power is shut off, after several hours of the slow seeping back of tank air into the line, the pressure in the tank drops to where the pressure switch kicks over to "on" position, but the power is off, so all it accomplishes is to close the release valve that should de-pressurize the line. This would let the pressure build up in that line, pushing against the pump. When you turn the power back on, the motor is trying to turn the pump against that head pressure.

 

[C96]

I think Steevo hit the nail squarely on the head!

Also, it could be as simple as the OP shutting off the compressor prior to it completing a full cycle thus not letting the combination pressure switch/unloader valve do its job unloading the head.

It is strange that the circuit breaker trips before the overload protection device opens the circuit. He must not have the overload relay adjusted properly, or the circuit breaker not sized correctly.

 

[Ice cold]

I'll try to be more clear.

Redmond- number 2... the compressor is starting without any load because i'm holding the release valve open as the motor comes up to speed then I release it. Otherwise the pressure just builds too fast in the plumbing for a clean start.

I see what you are saying Steevo. But, I am manually releasing pressure before that first start. And there is no pressure there when I pull up on the release valve. So I know the check valve is fine.

Maybe a solution would be to plumb a little more volume into the pre-tank plumbing that would release with the unloader giving the motor a chance to get up to speed before it has to start pushing so hard. This is a "jimmyrig" but....

I still think its an electrical problem like I need to fine tune something.

What about just hooking the compressor to a regular switch or directly to the circuit breaker (bypass the starter) and see if it will start? Not a long term solution but it may identify if the starter is the problem.

Could there be a voltage discrepancy with the contactor solenoids in the starter and maybe creating a bit too much resistance during that first start? I'm not an electrician, maybe someone out there can help.

Ice

 

[Ice cold]

C96 I'm trying to figure out how to adjust the overload relay. Can't find any literature on the Noark. 30 Amp CB #6 wire about 15ft from the CB to the motor.

 

[redmondjp]

You turn the green dial to adjust the overload setting - based upon the numbers on it, I'm guessing that you set it to the normal Full Load Amps (FLA) of the motor. But you can also set it by doing the following (may take a few iterations):

Turn the dial counterclockwise a few amps from where it is now. The let it attempt to start the first time without releasing the pressure (so you know it will trip the breaker). Keep dialing the setting back until the motor starter trips before the circuit breaker does. Keep in mind that home circuit breakers are thermal-magnetic. So they need time to cool off after tripping, as they will be extra-sensitive (trip at lower currents) for a period of time after tripping.

Of course, you have to have the dial set high enough such that it allows the motor to start under normal circumstances.

You also may have a problem with your centrifugal switch inside the motor, and/or have a bad starting capacitor. The centrifugal switch connects the starting capacitor into the circuit until the motor gets up to speed. If either is not working or the capacitor is weak, the motor will draw extra current for an abnormally long time in order to get up to speed, causing the circuit breaker to trip. The starting current should drop off to normal running amps in about 1 - 1.5 seconds.

 

[Arbybe]

What about a "hard start"capacitor from A/C compressor?
If not, plz explain.
Thanks.
RBB

 

[Ice cold]

somebody mentioned a voltage drop on the contact relays causing a higher resistance? I don't understand or maybe mis understood the concept....anyone explain?
I'll check and see if relays are 220 or 110. I do know I wired the relays using the same circuit.

Meanwhile I'll do some exploring with redmonds suggestions. thanks

Ice