Compressor 5HP direct drive. No Start with full tank of air

by Anthony
(Orleans Vermont)

Compressor 5HP direct drive

Compressor 5HP direct drive

Compressor 5HP direct drive
5HP direct drive capacitors

Doug. The only wiring diagram i have is for the caps. That shows 2 start 1 run cap. I have 2 start in series and 2 run caps parallel. This compressor came with 4 caps. Also the compressor has the run (start switch) and a constant switch. If i use the constant when 150 psi is reached the air is discharged out to the room. When the compressor drops to 110 psi it will act the same way and not start BUT NOT ALWAYS maybe 50% of the time. When the comp turns of you will hear a shhhhhhh from the unloader line on the left up to the air filter. My old ao smith released air with a phhhhh loud and quick. The automan was always quite and slow and released air for about 5-7 sec

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Aug 01, 2017
No Start with full tank of air
by: Anthony

Well, put new run caps in with no change. Will continue to work on it a little at a time.

Jul 21, 2017
No Start with full tank of air
by: Anthony

Hi. Well I tested the caps while running. With the compressor running I tested the run caps for vac. The meter showed 325-330 this looks good. The Run caps showed at the stationary switch on the back of the motor at 330. The runs are rated at 440. This seems low but does not give me a + or - %.

I then tested just at the caps and had the same reading.

I tried to test the starts at the switch but my meter is not fast enough to read, by the time it is the runs are already engaged. All this happens in a second.

Jul 20, 2017
No Start with full tank of air
by: Anthony

Hi Doug. Yes i did test the caps. The starts are new but i tested them anyway and they showed good. Original starts were 710 mfd 165 VAC. New starts are 710-830 mfd 165 VAC. They tested 719 mfd. The run caps are the original ones are rated at 15 uf 440 vac. I tested them and they came in at 17 uf. (maybe i should have replaced them any way beings they are 40 years old)

I did separate motor from the pump and it will start 50 times fast. Compressor start at 0 psi runs to 150 psi turns off the electric motor is barely warm.

The cylinders on the pump will get hot to the touch (the cast iron fan throws a tremendous amount of air back over the pump. Has been this way since day one. RPM Is 1750.

How would i test to make sure the run caps are putting out 440 vac. When running. At the cap terminals ??

Jul 20, 2017
series - parallel caps
by: Doug in s.d.ca.

Well, the two start caps in series, if they are the same value, give twice the voltage rating and half the capacitance of a single unit.

Two run caps in parallel, gives the sum of the capacitance ratings, and a voltage rating of the lower voltage one.

You already tested them, right?

Jul 19, 2017
No Start with full tank of air
by: Anthony

Thanks Bill

Jul 19, 2017
Won't start 5HP direct drive
by: Bill

I have to OK this first, then I will merge the two threads.

When you get notification, please wait 30 minutes or so for the whole process to complete.

Cheers,

Bill

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5HP direct drive, no start with full tank of air

by Anthony Evans
(Orleans Vermont)

compressor control box

compressor control box

compressor control box
compressor unloader break down

Compressor 5HP direct drive. No Start with full tank of air. Will start with finger covering air filter.

Was running the compressor start at 120 psi off at 150 psi.

When the compressor called for air it would try to start but was acting like the switch was being turned on an off. It sounded like it was going from start to run and back to start back to run.

The centrifugal switch and the main switch were arching on and off. I shut it down. If i bleed the tank down to 30-50 psi it will start but a little slower. On an empty tank it starts perfect.

I do hear air being released when the compressor stops running from the unloader back up to the air filter.

NOW if i put my thumb over the air intake when the compressor calls for air at 120 psi it will start every time. The unloader is on the side of the compressor (see photo).

When the compressor stops at 150 psi i can turn it by hand very easy with no Resistance.

I believe this problem is what caused the start caps to go bad. (replaced them) Any thoughts?

Does anyone know what the green switch does to the far right. It slides in a shaft and small air line goes to it.

Also the pressure control switch does not have an unloader. It does thread on a manifold with other small air air lines going to it.

Thank you

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Jul 24, 2017
No Start with full tank of air
by: Anthony

Hi Doug. Can you check if I have the run caps hooked up properly for parallel. Also today I started the compressor at 20 psi and it was good. Then I tried at 30 psi and while looking at the switch on back of motor when it started and the runs disengaged the motor was slow getting to full run. So I tried at 35 psi and this is interesting the motor started and spun fast enough to disengage the start caps but took awhile to get to full speed (about 3 sec). At 40 psi no start . The run caps are rated at 440 volt but the best reading I get is between 360-270 volt. Would that make the difference. Seems low to me.

Jul 18, 2017
Anthony
by: Doug in s.d.ca.

OK then.

You can send more pix by starting a new thread with this same name, and Bill can merge them into this. You're right, you can't edit, but Bill can.

Please do send the wiring diagram, if you have it.

Thanks, and you're welcome.

Jul 17, 2017
Wont start
by: Anthony

Doug I have had this compressor for 38 years. It is single phase. It use to operate my large glass bead cabinet in my machine shop rebuilding cylinder heads and auto repair (not any more)

Yes it is a complicated compressor but has work perfect for 37 of the 38 years.

I wish I could and a photo of the unloader but have not figured out how to edit.

This issue started slow about a year ago every 10-15 restarts it would happen then more often finely taken out the start caps. If the main switch left in photo had pitted or burned contacts would they have a tendency connect and then disconnect. Thank you for your help.

Jul 17, 2017
Crud. Still won't start.
by: Doug in s.d.ca.

I realize I haven't asked some questions that I'd like to ask, since this isn't making a lot of sense.

Is this machine new to you?

Has it worked for you in the past?

Have you looked at the motor itself? Because this is starting to sound like a three-phase motor, even though it may be somehow wired for single phase. I understand it's not likely, but I'd like to know for sure.

I'm going to be trying to find a decent wiring diagram (or is there one in your manual?) as it looks unduly complicated in your pic.

Thanks.

Jul 17, 2017
Compressor still won't start
by: Anthony

Hi. I took the intake off and tried to start the compressor and it would not start.

Covered one intake port and it started right up.

As the compressor was running no cylinder was blowing air out, if it was it was very very little.

Put my hand within an inch of the ports and it like to suck my arm in.

Shut down compressor and tried to restart no go.

Cover either port and started fast.

Does not matter if compressor has been running hot or cold 30 psi or more no start thumb over air filter fast start thumb not over air intake engages disengaged's engages disengaged's.

Could the main switch contacts be pitted enough? Motor not running continuity at switch on back of motor start caps in circuit . Motor starts no continuity run caps in circuit.

In photo what does the blue green switch do. I pulled it off the shaft started compressor touched inside with a screw driver and it was magnetized. There are 3 air lines going to it. One to the pressure switch. one bleed off and one to the unloader valve. Thank you

Jul 16, 2017
AE7
by: Doug in s.d.ca.

I think maybe the problem is one of the intake valves is broken.

Try taking the intake manifold off and see which one pumps air *out* the intake.

Air pressure from the atmosphere plus pressure leaking from one cylinder is probably putting too much air in other one, which, plus the pressure from the tank, is stalling the motor.

Or something. It's all I can see that would make putting a finger on the intake let it start.

Anyway, see what happens.

Jul 15, 2017
Auroman AE7 no start with full tank of air
by: Anthony

Thank you. Compressor is an Automan AE7 5 HP 220 volt single phase 40 year's old sold by snap on.

Yes the start caps are engaged.

Shined a light in side and with a mirror the contacts are closed.

Today I started the compressor with 80 psi showing and no start just sounded like it was switching between start and run.

Shut it down and put my thumb over intake hole of air filter and it started right up. You can hear the difference when when the start caps are engaged and the run caps take over. Its quick about a second but you can hear it. From 0 to 30 psi it starts right up.

Also I can hear air bleeding back to the air filter from the unloader for 5-10 seconds.

I took the fan cover off and with no pressure in tank it spins easy. With a full tank of air 150 psi it turns over just as easy.

I did replace both start caps (it would not start at all) and i believe this issue took out the start caps.

The run caps (2) tested good. I can still use the compressor just cannot leave it on.

Jul 14, 2017
not starting
by: Doug in s.d.ca.

Couple of things:

Got a model number for this?

Are you running it on 220V?

Have you verified that the start cap is actually "in circuit" when the motor is stopped?

Thanks.

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