Air compressor limit switch problem

I have a small Grizzly G2889 air compressor that I run my finish nailer off of. It does fine for the first 4-6 shots and then it leaves the nail above the wood surface. After two to three shots like that the compressor comes on and I'm back in business but I don't like to have to go back to set the nails.
I cannot seem to find any way to reset the lower psi limit switch to come on sooner. Anybody out there had a similar problem and know of a solution?
RonT
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Do you have it turned up to maximum pressure?
Dave

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clearly he does , but the 'low pressure switch' is his problem - not sure on your particular compressor - but most of the 'better' compressors have adjustable switches - may be via changing a spring tension or a screw adjustment. Best bet is to take the cover of the switch box and watch it ) and perhaps have a multimeter with you to watch what switch does what and when.
If this is all above your skill level then take it to an authorized repairer and get them to adjust it for you
Boc
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I agree but... the best way to add this to your skill level if it isn't already there is to dig in, study the operation of the thing and figure it out. It ain't rocket science. Persevere. You can do it.
bob g.
Ozboc wrote:

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You did not state what the pressure drops to before the compressor starts up. I would have to pay atention to my compressors but I think they start up about 90 psi. Some switches have an adjustment. Take the cover of the switch and see. Unplug the electricity first of course.
snipped-for-privacy@webtv.net (Ron Truitt) wrote:

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Naw, don't unplug the compressor. Keep one hand in your pocket. Almost all compressor switches consist of a bunch of stuff inside a rounded corner, rectangular gray box. The power line usually goes directly to the thing and a cable from it goes directly to the motor. You can't miss finding it. One brass nut usually holds the cover on. Take the brass nut and cover off. Many such switches have two adjustments. One is the max pressure cut out. It's a conspicuous nut on a long bolt, usually with some colored paint on it the shows the factory setting. Change the factory setting and you crack the paint. Some have a second adjustment, the differential. If it has one, it's usually conspicuously identified with stamped lettering that you can't miss. This sets the range between the cut in and cut out. Not all switches have the differential adj. If yours has the differential adjustment, reset it to narrow the range a little. If you don't have the differential adj., adjust the max pressure so that both cut in and cut out are above where your nailer starts to act out.
bob g.
p.s. I've never seen one that didn't have at least one adjustment.
Jim Behning wrote:

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On Sat, 30 Oct 2004 22:49:32 -0500, snipped-for-privacy@webtv.net (Ron Truitt) wrote:

I don't know Grizzly, or that model.

Tank pressure is too low.

Buy a new switch. There's no usually much that can be done with them. There aren't usually "high and low switches", there's a single switch with some hysteresis. The better made these are the more chance there is of them being adjustable or fixable.
While you're about it, fit a tank gauge. Then use it to set your tank pressure - usually about 130psi, allowing for 90psi working output.
--
Smert' spamionam

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On the contrary, a lot of the compressors I've seen do have a cut-in/cut-out adjustment inside the switch cover. It's usually on the crude side, but there is some adjustment possible.
One of the things I've noticed with some of the cheaper compressors is that their cut-in is set quite low, often around 80-85 lbs. You can raise the cut-in/cut-out at the expense of going above the tank safety ratings and shortening the life of the compressor, not to mention likely voiding the warranty.
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Older/larger Emglos had a brass cut-in regulator near the tank inlet fitting adjacent to the tank pressure gauge. A small copper tubing runs up to the compressor head. Hi/Lo adjustment was made by turning two concentric brass nuts on the end. I recall this as a somewhat mystical process (never saw a manual), so you may wish to mark the current position on your Grizz, if it uses a similar setup.
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to set the pressure do the following.
remove the cover of the pressure switch after you verify that the power is turned off first. The reason is that some units power the motor directly through the switch...this is bad by the way. if the leads from the pressure switch go to a mag starter then you can put power to the unit. be aware that the leads on the pressure switch will be live when the switch closes.
look at the top of the switch there may be two nuts on screw shafts that are threaded. a large one and a thinner one. The large one ususally raises pressure when turned clockwise. The smaller one changes the pressure band the unit runs in. with the unit in power adjust the large nut clockwise to increase pressure ONE TURN ONLY. bleed air out of the unit until the unit starts. observe the gage for shutoff pressure. if pressure has increased to close to where you want it adjust in 1/4 turns in succession. If no pressure change is noted then turn one more turn. try again. If pressure does not respond your switch is bad. Graingers sells a 5B408 switch for most units. you need to bleed down the tank to replace the switch. Never isolate the switch with a valve. I work on compressors as a job and am an Atlas Copco factory trained tech. If you have any further questions email me at
snipped-for-privacy@sbcglobal.net
there may be only two screw heads visible on the switch. The large one increases pressure and the small one the band. Most compressors in the 5HP range run 145-175 psi and you should run a pressure reg on the outlet.
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cut-in/cut-out
that
You will be hard pressed to get your pump to exceed the tank rating. Tanks are rated something (1.5X?, 2X?) higher than what the pump will produce. The pump has its limitations and you wouldn't want to try to get 25% more out of your pump, but you generally can get 10-15% with no difficulty. Warranty - that's a whole 'nother issue.
--

-Mike-
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(Ron Truitt)

An old trick for tack welded pressure switches - take a washer or two and cut or grind a small part of one side of them off so that you end up with more of a C than an O. Unplug the compressor and pry down the spring in the pressure switch. Insert the washers on top of the spring and release the spring. You've just increased the cut in/cut out pressure of the switch. You really should have a pressure gauge on your tank so you can make sure you don't exceed the manufacturer's max pressure rating, though all tanks are rated way beyond what the pump can produce. Still, it's a good thing to know where you've taken the pressure to.
--

-Mike-
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Buy a small air line regulator, (less than $10 usually) and use that to set your line pressure. Set the compressor to it's maximum setting.
--

Larry Wasserman Baltimore, Maryland
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Thanks for all of the ideas fellas. I have used compressors quite a bit but just now have my own to mess with. You have embolded me to tinker.
It is going down to around 70 psi before turning on to recharge the tank and is recharging to around 100-105 psi which I believe is the upper operating range for the Grizzly finish nailer I'm running.
I'll take a run at this thing and see what happens!
RonT
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Ron Truitt wrote:

Problem is, within the first stroke the pump is making tank pressure, even with an unloader. Is the motor strong enough to start at anything above 70 psi? If it does start how much life are you taking out of it by making starting harder?
Compressors, gotta love them, get one way bigger than you know you'll ever need just means it will take longer to see how small it truly is.
--
Mark

N.E. Ohio
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wrote:

Does this rule of thumb work in the USA ?
Here in the UK we all buy much the same model (except for the tiny nailer-only cheapies). Something about 12-14cfm displacement, single cylinder belt driven. The limit here is powering it from a 13A plug on a standard 240V socket. We don't hard-wire our machines, we don't use other voltages - 3HP is about the limit for an induction motor.
These compressors are big enough for most purposes. Random orbital sanders and gritblasters are about the hungriest tools, and the only ones that really rely on the reservoir capacity.
So what do you do in the USA ? Do you go for smaller machines so that you can plug them, or is it just accepted that any sensible sort of compressor is going to need cabling putting in for it ?
--
Smert' spamionam

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Actually Andy, just about any compressor that's going to be considered by folks in this group can be wired with a pig tail and plugged in. A lot of us hardwire them so that when it starts to walk across the floor the hardwire lead will stop it before it bumps into the tablesaw...
--

-Mike-
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"Andy Dingley" writes:

Compressed air is a lot like clamps, you can never have to much, IMHO.
A 5HP, capacitor start, capacitor run, 240VAC, motor belt driving a two (2) stage compressor and mounted on a vertical 80 gal reservoir is about the max for single phase equipment.
I can spray non stop, all day long with it
After that, it is 3 phase equipment.
Since you are basically starting the compressor at a low pressure, the cap start motor is acceptable.
A cap start motor is definitely starting torque limited.
BTW, you need to hard wire that unit to a 2P-40A c'bkr with #8 AWG wire.
At least that's what I did.
YMMV
HTH
Lew
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