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Shop lights flickering

R

Royse

Well-known Member
Trying to make a long story short.
Two years ago I replaced my air compressor.
Old one was 6.5HP, two cylinder, single stage, 60 gallon, 125PSI.
New one is 6.5HP, two stage, 80 gallon, 175PSI.

Ever since I put this new one in, my fluorescent lights flicker
when the compressor is running. More specifically, they flicker
as it gets closer to shutting off. If the air pressure is really low,
they do not flicker while it is running.

They never flickered with the old compressor.

Shop has standard 200 amp service wired to code.
Normal? Or is there something I should look at fixing?
Two years, no issues so far. Just annoying.
 
The new compressors motor is cheaper and gets its rating pulling more full load amps. If it keeps up with your use you
could put smaller drive pulley on the motor to make it easier to finish the fill. If it just barely keeps up it might not
be possible. My best guess. Jim
 
Thanks for the input Jim. I still have the old compressor.
It works fine, I upgraded for the extra capacity and pressure.
Maybe I can swap the motors if the mounting, etc is compatible.
 
I agree with Jim on the cheap motor, but would changing pulleys result in faster RPMs on the compressor, and most likely will make scrap metal out of it? I remember the big compressors we had on my old job had to have a certain rpm motor, and it was replaced once with the wrong motor, which turned faster, maybe 100 rpms and the compressor lasted all of 10 minutes before rods went flying.
 
Look for a loose connection somewhere, could be anywhere between the meter and the compressor. Especially if any of the wire is aluminum it can "cold flow" out of connections resulting in a loose connection.
 
Look at the amperage draw on the plate on each motor. Does the new one pull more amps. Some compressor companies use motors that list a theoretical horsepower rather than the practical usable horsepower. The amps on the tag will tell the truth. A 'real' 5HP 3450 RPM motor will pull 23 amps on 240 volts single phase. (I think?) The new compressor is pumping up more pressure with what I assume is the same size motor so the motor is working harder unless the pulley size is different to compensate for it. With 200 amp service the compressor should not make the lights flicker. Where's John T?
 
I just got to thinking, which is dangerous, is the service down the line from the shop able to support the 200 amp service in the shop. I had that problem last summer and had to update some overhead wiring to a larger size to support the larger breaker box in the shop.
 
New compressor works harder getting up to the higher pressure. Working harder requires the motor to use more amps. When the motor pulls more amps the lights have less amps available. Best bet would be to move to the compressor to a different or new circuit.
 
No aluminum Paul, all copper. Same wiring the old one used.
I will check it though. Last thing I want is a fire!
 
You might want to open the service panel and do some voltage tests.

If that is a true 6.5 HP motor, on single phase, it should pull around 30 amps. I doubt the motor is over amping, if it was, it should be tripping the overload or would have burned up by now.

It would be worth checking the amp draw, and comparing it to the FLA rating on the motor. You will probably need an analog amp meter to get a good reading with the load variation of the compressor.

But also check the voltage at the motor, and check the voltage at the panel. Look for voltage drop from the panel to the compressor, across the breaker, across the disconnect, and voltage drop across the motor starter or pressure switch, which ever way it is set up.

And check the voltage across the main breaker or the buss bars in the panel, and check each leg to neutral, they should be real close to the same voltage. Also check the amp balance, each leg should be near the same load. Do all tests with the compressor running and the lights flickering. Again an analog meter will catch fluctuating voltage and amperage better than a digital.

A 30 amp load on a 200 amp service should not be causing the lights to flicker. There could be a problem with the incoming power, the meter base connections, the main breaker... Look for heat discolored connections.
 
I'm not sure how I would do this Glen.
The compressor is on its own 220V breaker out of the panel.
Nothing else connected to it.
My stick welder is on its own breaker out of the same panel
and it doesn't bother the lights that I've noticed.
Of course, it may be hard to notice with a welding helmet on.
 
Maybe if you lowered the pressure it would help. What do you need 175 psi for? Most air tool are only rated for 90- 110, IR does not
recommend going over 120. Of course they will have more power, but may not last very long.
 
"I just got to thinking, which is dangerous,"

That, sir, sounds like me! LOL
I believe the downstream service is adequate since the air
compressor is the only thing that bothers them. Stick welder,
MIG welder, band saw etc doesn't seem to bother the lights.
 
"It would be worth checking the amp draw, and comparing it to the FLA rating on the motor."

That's the plan for tomorrow. Clamp on ammeter should do it.
Thanks for the suggestions. It just doesn't seem right.
 
i would get that new compressor set at a lower cutoff. that is nuts. why do you need 175 lbs psi.??? no wonder the lights are flickering. you are pulling more amps to get this 175 psi. actually never heard of anything needing that high of pressure. safety first.
 
The psi ratings have nothing to do with the
lights. 175 psi is a industry standard
setting for a 2 stage compressor. Royse I
would be leaning toward the loose connection
or the motor with parts from the land of
almost right. We have had a couple motors on
the farm give us some issues with less than
stellar parts out of the box.
 
175 psi is the standard rating for larger air compressors.
The sand blaster really likes that extra pressure.
As does the one inch impact wrench that requires a 3/4 inch
diameter hose at a minimum of 120 psi to get the rated torque.
 
The higher pressure provides more reserve before the compressor kicks in if the air tools are on a regulator set at a lower pressure.
 
Sounds like maybe a bad connection or
undersized wire somewhere. Another thing to
try is to move the breaker for the lights to
the other phase and see if there is any
difference.
 
My compressor started doing that, found a bad place in the aluminum underground that was restricting the current on one of the phases. I would put a meter on the incoming, phase to phase and phase to neutral under a high load condition. My compressor also kicks out at 175 and kicks in at 150, gives me a lot more reserve capacity.
 
rustred:

80 gal. @ 175 psi is just a drop in the bucket. When I worked in the Mines we had two huge, water cooled Ingersol Screw Compressors that EACH put out over 300 psig . They were supplying air pressure to operate Air-Track Drills and dozens of Jackleg Rock Drills thru 2.5 inch diameter Bull Hoses; 1200 ft. underground and 5 miles from where the Compressors & Storage Tanks were located (on the Surface) . - We had over 12 miles of Tunnels in that Mine.

Doc :>)
 
Air compressor needs a bigger "flywheel".

Likely, if you could monitor instantaneous Amps the greatest draw (and dimming of lights) would occur as a piston comes up on TDC.

Even notice how big/heavy the cast iron pulley/flywheel was on older compressors?

I'll bet there isn't much to yours, and it is aluminum.
 
Wonder if the check valve between the compressor and the tank is leaking back at higher pressures. A friend 40 years ago tried to put together a compressor from random parts. The check valve was missing from the tank he picked up and he didn't realize he needed one. The first problem he noticed was the motor slowed with each stroke once the pressure reached around 80 lb's and actually stalled the motor at a little over a hundred. It could not restart at cut on pressure. Granted this is an extreme case with no check valve but a leaky one could cause your problem I wound think. Not sure where the check valve is located on yours but if it is easy to get to unhook it at hi pressure unit shut off and do a soap bubble test on the valve.
 
Break out your voltmeter. Sounds like you've got a voltage drop issue, possibly in the service coming into your circuit breaker panel.
 
I'll let you know if/when I find the answer Tom.

I should have also made it clear that by flickering I mean the
fluorescent lights pulse in brightness. Flickering.
They never go dark or off, just more or less brightness while on.
 
Didn't take much more than a good visual inspection once I took
it apart. The original air compressor wiring used these spade
terminals to connect the motor to the pressure switch.
They're not burnt, but the push on part was not very tight.
I replaced them with crimp on terminals and then soldered them.
If there is any flicker left at all, it is barely discernible. Thanks!

45562.jpg
 
6.5HP peak, I assume, since that's the advertised rating.
The data plate did not differentiate the two.
Data plate says 20A current draw, it is running on a 220V
20A circuit breaker and it has never tripped that breaker.
Neither did the old one. I shut both the air lines and the
breaker off at night so it doesn't run when not needed.
Quick disconnect fittings tend to leak a bit even when new.
 
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