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Boucher
08-22-2009, 01:15 PM
I have a single stage 5 hp Ingersol Rand air compressor. I would like to reduce the pressure setting. I have been adjusting Square D and Furnas pressure switches in the water pump controls for years. I suspect this switch is probably made by or for Ingersol Rand. Does anyone know how to turn one down?

ligito
08-22-2009, 01:45 PM
Use a regulator, unless you have a specific reason to reduce the tank pressure.
Some of these compressors come with instructions that say not to adjust their pressure switches.

MTNGUN
08-22-2009, 01:50 PM
You say you are familiar with water pressure switches -- the air compressor switch should be about the same thing, two screws to adjust.

Jim Shaper
08-22-2009, 03:01 PM
Could just be a nut you loosen or tighten to adjust the preload. That's how my square D's work.

radkins
08-22-2009, 03:40 PM
Do you have the IR compressor with a 5 HP Emerson motor and CFM rating of 18.4 CFM (I may be off a tad on the CFM but it should be rated slightly over 18)? If so these things are running on the ragged edge of the motor's amp rating at cut-off pressure and setting the max pressure down about 10% is a darn good idea.

Boucher
08-22-2009, 04:06 PM
This thing goes to 130 psi and is struggleing. The motor overload has popped a couple of times in this hot weather. I keep the regulator into my shop set down about 60 psi. The bead blast cabinet is in another building. Airing the RV tires is the only thing that I do that needs high pressure and I generally use a small portable for that anyway. I have a partial cover over the compressor which is located on a small slab outside the old barn with a lean to type roof. This restricts the visual access but I have never seen a pressure switch like this one. I have been looking at some switches in The Surplus Center catalog. I am going to order one if I don,t get this figured out. Does anyone know how the head pressure blead down works on these little switches? On the big 600cfm compressors that I am familiar with there was a pilot valve and a regulator to furnish pressure to an unloader that was built into the Suction valve head. It just held the valve open.

Jim Shaper
08-22-2009, 04:53 PM
The unloader on the switch I have on my compressor is just a plunger valve that works just like a tire valve. When the switch is turned off, the mechanism rotates down to depress the plunger and release the air contained in the line going to the tank check valve (that's where mine is plumbed in).

It's about as simple a system as it gets.

radkins
08-22-2009, 06:29 PM
You will need the switch with the unloader built in but Surplus Center has them, in fact I think most of their compressor switches have them. 18.4 CFM@90 PSI is way too much for 5 HP and when I first saw these things I figured that Ingersol had just started doing like most of the companies and were just inflating their figures. After a buddy of mine bought one we timed it from dead empty and sure enough it actually did make 18 CFM, well almost anyway, but the motor was really struggling at shut-off. After about 6 months in his shop the motor smoked which came as no surprise and when we brought it up on a couple of different sites it seems this is a common problem for these compressors-again no surprise because of the way the motor was laboring. 14 CFM@90 PSI is more like it for a 5 HP motor and 18 is just unrealistic so that is why, IMO, de-tuning these things a little is a good idea. Changing the pulley on the motor and leaving the peak pressure the same is another easier option, just go slightly smaller with the pulley and it will take the load off the motor from start-up to shut-down and as long as you only go about 10% smaller you won't lose much CFM.

Jim Shaper
08-22-2009, 06:45 PM
18cfm @90psi isn't at all out of the realm of 5hp with proper displacement and pulley size. Mines rated close to that at 175psi (but I don't run it that high). It's an old two stage IR from the mid 80's. I've got a Leeson high efficiency 5hp motor on it and it's not working that hard to spin it.

http://www.bigbluhammer.com/products/air_compressors.htm

Of course, we're talking about real motors and pump heads - not the hobbyist crap they sell at the box stores.

koda2
08-22-2009, 08:37 PM
Byron,
I am certainly not an expert but here's my two cents. I have seen only two kinds of regulators on my smaller air compressor systems.
Underneath the regulator cover (is it unplugged?) on some:
A)There is the line in and motor out electrical connections and a means of depressing the contactors(the on/off switch).
There will be some spring loaded screws or nuts which are the cut-in and cut-out adjustments. By varying the spring tension you vary the resistance to overcoming pressure in the regulator and thereby the turn on/shutoff pressure.
B) There may be a cam-like lever which is the on-off switch and which controls the contactors. As the pressure increases the contactors rise until they "overcam" and shut off/cut out. In this case there is only one spring(?) and it maybe hidden by a plug of some kind. I think the only control is the cut-out pressure.

One of mine was this way and I lowered the pressure because the compressor pump was laboring way too hard just before cut out and I was afraid it would blow a gasket (and maybe something else). It decreases the capability of the machine a little because of the lower pressure.

Most of these regulators have some sort of paint, glue, wax or something to keep the springs/nuts/screws from vibrating to a different setting (for good reason).

Have you checked to see if the overpressure valve is still working?

Screwing around with the regulator (pun definitely intended)<G> probably voids any warranty,is not something you should do if you are not capable of it,(legal disclaimer) and done at your own risk. Otherwise, I say, get help.
Cheers,
koda2

radkins
08-22-2009, 09:50 PM
18cfm @90psi isn't at all out of the realm of 5hp with proper displacement and pulley size. Mines rated close to that at 175psi (but I don't run it that high). It's an old two stage IR from the mid 80's. I've got a Leeson high efficiency 5hp motor on it and it's not working that hard to spin it.

http://www.bigbluhammer.com/products/air_compressors.htm

Of course, we're talking about real motors and pump heads - not the hobbyist crap they sell at the box stores.


Jim you have a two stage pump there (congrats on that! :D ) and it is more efficient than a single stage like the subject here so you are of course right and I should have said 18 CFM@90 PSI is unrealistic for a SINGLE stage compressor with only 5 HP.

radkins
08-22-2009, 10:04 PM
Byron,Screwing around with the regulator (pun definitely intended)<G> probably voids any warranty,is not something you should do if you are not capable of it,(legal disclaimer) and done at your own risk. Otherwise, I say, get help.
Cheers,
koda2


In the 14 or so years I spent working on these things I saw quite a few messed up regulators where the owner had tried to "adjust" them and had things out of whack but in every one of those cases it was done in a futile attempt to increase the compressor's performance (it won't!). In the case of the compressor in question here adjusting the regulator down will help, at least in the sense it will make the thing last longer. Actually I am willing to bet that lowering the peak pressure slightly or better yet decreasing the motor pulley slightly could possibly even result in a small increase in performance, or at least no loss of performance. The reason for this, I am thinking anyway, is that the motor is so labored at the pressure just before cut-off speed it seems to lose RPM and thus efficiency. It of course would require testing to confirm this but I would almost bet that any performance loss from a small pulley decrease would be negligible.

Boucher
08-22-2009, 10:39 PM
Koda2 I think that you hit on it. There is a blue glob that is probably covering the adjustment screw. I would like to lower the setting from the 90 to 130 to about 60 to 100. I like Radkins thought about changing the Motor puller to a smaller size. I have been working on pressure switches and seen enough that were screwed up by people that didn't know what they were doing. I built a test bench where I could cycle them very quickly and with an accurate test gauge. I will probably buy a better quality pressure switch. Being curious I will then disassemble this thing to see how it really works. There really is some pretty good engineering that is the basis for the Square D design. All those little shuttles and linkages with the diaphram force and small springs balanced very precisely. And a wholesale price less than $20.