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Old 07-31-2007, 09:33 AM
hartkem
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Default Quincy compressor & electrical requirements

Hello, I just recently purchased a Quincy 80 Gallon 5hp single phase compressor. I recently moved to california and I am having problems with the amount of electricity required to start this thing. When I first bought this thing about 2 months ago I tried it out back in Illinois at my parents house. It performed just fine. I then moved it to California and it did run good at first. The thing is when I first tested it the tank was completely empty. When I went to actually use it is when I started having my problems. I started sand blasting and the compressor ran continuously for about 10 minutes. It then cycled off for about 10 minutes and kicked back on or should I say tried to. The thing threw the breaker. Well I got to looking and I saw that the sub panel that was put in the garage only had a 20 amp breaker on the 220. I called quincy and they said this thing required a 40 amp breaker. So I installed a 40 amp breaker and retested. Now it doesn't throw the 40 amp breaker but throws the pressure switch/starter overload protection, or I think that is what it is. Anyway the little switch goes from auto to off when it does this or I have to cycle the switch to get it to kick back on. Long story short if I bleed the tank down below 110psi it will start and run perfect. But if I start it up with 150 psi in it it kicks out. Now when this thing kicks on the lights dim pretty bad. The house had new wiring installed recently. I have 10/3 wire going from the compressor to the wall outlet. I am not sure what size wire is going from the sub panel to the outlet. I do know that them main panel on the house has a 50 amp breaker that is feeding the entire garage. The house has 100 amp service where as my parents house has 200 amp service. Does this thing need 200 amp service or do I have wire to small somewhere. What could I do to test or fix my situations. Help and suggestions needed. thanks everybody. Mike
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Old 07-31-2007, 10:44 AM
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Scotts Scotts is offline
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Mike, First off welcome in. When you used your compressor before, did you do the same thing with it?

I would quit using it until you find out what size wire you have going to all the circuits you have. I would go with #8 wire for a 40 amp breaker. If it only had a 20 amp breaker it may only have 12 ga wire going to it. Get that nailed down first.

If you have other things running in the house with the compressor and a 100 amp service you will see the lights dim when it goes to start up. If the A/C or the oven electric water heater and such were to come on, be on at the same time it would do it.

Next issue is the hard starting. There should be a valve in the line going from the pump to the tank. It looks like a fitting going into the top of the tank, The ones I have dealt with have a little disk in them that takes the tank pressure and seperates it from the pump to let it get started until the pump builds up more pressure than the tank.

HTH

Scott
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Old 07-31-2007, 11:18 AM
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Yep, welcome aboard, Mike.

Quote:
Originally Posted by Scotts View Post

Next issue is the hard starting. There should be a valve in the line going from the pump to the tank. It looks like a fitting going into the top of the tank, The ones I have dealt with have a little disk in them that takes the tank pressure and seperates it from the pump to let it get started until the pump builds up more pressure than the tank.

HTH

Scott
Scott, that sounds to me like you're describing the check valve but what I'm wondering about is the unloader.

Mike, when the compressor shuts off do you hear a hissing sound of a small burst of air being released? That would be the unloader relieving the head pressure so that the pump can turn freely next time the motor starts. That allows the motor to reach full speed/power before the load builds up.

But if the check valve is leaking back & allowing pressure from the tank to build back up in the compressor head, then that would defeat the unloader too.

You may have more than one issue here - mechanical (unloader) and electrical.
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Old 07-31-2007, 11:42 AM
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GWIZ GWIZ is offline
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Yes you have too get the wiring right first.
How long is the run to the compressor ?

The unloader valve,
You may see a small line going up to the pressure switch, that should be the unloader valve

The valve Scott is talking about prevents air from feeding back from the tank through the unloader valve when it opens.
Its a one way valve.
If the one way valve has a problem you will hear air leaking from the unloader valve all the time when the pump is off.
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Old 07-31-2007, 11:43 AM
hartkem
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Thanks to all the replies so far. I do hear a loud hissing noise after the compressor cycles off, it seems as if its coming from the pressure switch area. I looked into the manual and it says that my particular quincy pump (Qt-5) does not have head unloaders, Im not sure if these are for continuous run or for the loadless start. This compressor is the Air master series so It is an entry level compressor for quincy. It doesn't have a mag starter just a pressure switch/load switch combination. I had a quincy repair man come out after work to look at it and he said that he didn't see anything wrong, but he was off company time and only ran it once and the tank was down to 50psi when it kicked on so he didn't see it kick out. If I have two small of wire going from the sub panel box to the outlet will this cause this problems. The outlet is only about 2 feet from the sub panel. Thanks mike
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Old 07-31-2007, 11:46 AM
hartkem
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I do not here a constant hissing noise coming from the compressor, it is quit once cycled off. The only valves that I see on this thing are pressure relief valves. one on the head, one where the pressure inlet goes into the tank and one by the pressure switch. thanks mike Should my 100amp service be big enough to run this compressor, I have almost everything off in the house but the frig.
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Old 07-31-2007, 01:31 PM
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Yes Mike, your 100 amp service is adequate but the way it is distributed may not be. You need to figure out what gauge wire you have running to the subpanel and to the outlet. Chances are whoever wired it was not planning for a 5 hp load.

Now, something that's bothering me, kinda rattling around like a pea in my head is you have twice said something abou the pressure being down to 50psi when you turned the switch on. Is it leaking down that much over night, or what? It you're losing 100psi over night, where is it leaking? This could be a clue that the check valve is leaking back through the compressor head and re-loading it, thus causing a hard start condition for the motor.

Here's a simple thing to try & see if it offers any clues:
Pump the compressor up to shut off. Unplug it from the electrical supply, turn all valves off to try to minimize any pressure loss. Wait an hour or two, then check your gauge to see how much pressure has leaked back. It may take longer than an hour, but get a sense of how fast you're losing air down to maybe 120 psi or to a point below wherever you have your pressure switch set to kick back in.

Then with the cord still unplugged, try turning the compressor wheel by hand - in the correct direction. Is it hard to turn? It should turn pretty easily. If it is hard to turn, then I would suspect the check valve is leaking enough to keep the head pressurized.
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Old 07-31-2007, 01:40 PM
hartkem
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Cutter, thanks for all the help. To clearify the 50psi thing, I have been bleading it down to 50psi because thats were the motor starts real easy. The unit will hold full pressure over night without any problems. I just have been bleading it down to get it started. What size wire should I have running from the Main house panel into the sub panel. And then what size wire do I need to go from the sub panel into the outlet.
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Old 07-31-2007, 01:43 PM
hartkem
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I thing I forgot, would setting the pressure down to cycle on and off at a lower pressure be helpful. I don't need the 175 psi. Also what about a 1 size smaller pulley on the motor. I would really like to find the actuall problem though. I just thought maybe one size smaller pulley or lowering the psi would help the compressor last longer. I don't have a huge air demand. Just sand blasting here and there.
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Old 07-31-2007, 03:06 PM
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Well according the ol' slide rule, a 5 HP single phase, 230V motor needs a minimum of 10 gauge wire, and with you only being 2 feet from the panel, not a problem. How is your cord, what gauge is it? The slide rule also says you need a 60 A breaker, or a 40 A fuse. Not sure about the 60 A, seems a bit high, and you aren't tripping it right now, so you may be okay there. Sberry or someone else may chime in on this.

Whats your amp draw on the motor under load? It should be 28A, or whatever your name plate says.
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