Air compressor: Decrease cut-off pressure? Continuous use vs intermittent?

[BrBa]

First off, I'm a new member and I joined to ask this question. This seems to be a great site as it comes up first for a lot of my tool related google searches. I recently came across a used 60 gallon Husky Air compressor. Specs are: 135 max psi, 7hp(more like 3hp), 10.3cfm @90psi, single stage. The actual tank certification label says the max pressure is 150psi at 450 F.

The compressor cuts in at 90 psi and cuts off at 150psi. This is my first concern since the advertisement label states 135psi and it seems worrisome that it is filling up right to the max psi cert on the tank every time. The pressure switch, made by Condor, has 2 sping-loaded nuts that I assume adjust the pressures. The nuts have green paint on them and don't appear to have ever been tampered with. However, I do not know the history of the compressor so who knows if this is the original pressure switch, although I see no signs of it being replaced. I started using it for sand blasting and notice that it takes about the same amount of time to pump up from 140psi-150psi as it does to go from 90psi-140psi. Is there any reason not to decrease the cut in pressure to 80psi and the cut off pressure to 140psi or even a little lower?

It seems that that last 10psi takes a very long time and is putting unnecessary strain on the pump, but that's just my theory. If I were to lower it, would the pump then be subjected to more stops and starts than it should be?



Another question I have is about the way I am using the compressor. I started using it for sand blasting and it is able to keep up barely. However, I find that if I continue sandblasting while the pump is running, it takes a very long time to reach its cut-off point and I feel that I am putting unnecessary wear on the compressor. This may all be in my head but I have since started to take a break whenever the compressor kicks on to allow it to fill back up faster. I resume blasting after it cuts off.

My question here is what is worse? A long run time but less starts and stops, or an shorter run time but more stops and starts? Should I just keep blasting straight through or take a break when the compressor kicks on?

 

[happymachinist]

Someone has changed the switch or adjusted the original. They wouldn't advertise 135psi when it actually pumps up to 150. People like big numbers ya know?

Also single stage air compressors aren't made to pump up to 150psi. Back it down to 135 shut off. I'd leave the cut in at 90ish.

I especially don't like the idea of 150psi in a tank rated for 150psi.

You are correct that the screws in your pressure switch will adjust the pressure at which the compressor turns on and shuts off. Without anymore info or pics I can't be of any more help.

As far as continuously running see how it goes with the max pressure backed down. Part of the reason it takes so long to get from 140-150 is like I said above its not made to build that much pressure.

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[BrBa]

Someone has changed the switch or adjusted the original. They wouldn't advertise 135psi when it actually pumps up to 150. People like big numbers ya know?

Also single stage air compressors aren't made to pump up to 150psi. Back it down to 135 shut off. I'd leave the cut in at 90ish.

I especially don't like the idea of 150psi in a tank rated for 150psi.

You are correct that the screws in your pressure switch will adjust the pressure at which the compressor turns on and shuts off. Without anymore info or pics I can't be of any more help.

As far as continuously running see how it goes with the max pressure backed down. Part of the reason it takes so long to get from 140-150 is like I said above its not made to build that much pressure.

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Thank you for your advice. This was my train of thought as well.
Here are pics of the pressure switch. I cannot seem to find a definitive answer on which nut does what. Also most of the condor switches I find have a smaller 3rd spring loaded nut that this one does not have. What's odd to me is green paint shows no sign of tampering.

I posted pics, but they aren't showing. Is there a minimum post count for pictures? Here is link for the pics if you don't see them showing up either: http://imgur.com/a/YCEwN

 

[happymachinist]

Yeah it is strange your switch doesn't have the third smaller nut. It's purpose is to set at what pressure the compressor turns on, so it looks like that is fixed and not adjustable on your particular switch.

It does seem like you should be able to screw the two nuts you have counter clockwise to reduce the max pressure. Do them equally, how much is hard to say. Keep an eye on your gauge and shut her down if it goes beyond 150psi. Maybe also verify with another gauge to make sure yours is accurate.

I'm also surprised that your pressure relief valve never popped open, I would think it would be a 150 psi model since that's what the tank is rated for.

I agree it is strange that the nuts still have the green paint on them, by chance can you turn the keeper washers and also get the nuts to turn maybe this is what the pervious owner did idk.

Here's a video I found showing the three nutted version of your switch.

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[happymachinist]

I forgot to mention a cut in at 90 and an out at 150 is a 60psi range....waaaay more than it should be

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[BearsFan315]

Maybe They replaced the switch with one they picked up and it is pre set to 150 PSI ?!? when i rebuilt my compressor i got from craigslist i called Condor Air Compressor Switches and ordered a replacement switch to match what the original settings were. Most common are MDR11
Condor Number 11VC2FALE 110-135 PSI, Switch, Adjustable Range, 4x 1/4" Port, Unloader Valve

here is a picture of mine:

Motor wires in the bottom row

[/QUOTE]
power in the top row

top view w/ cover

bottom view

 

[BearsFan315]

Here is a pict of the original:

view of the Condor information on the switch

 

[BearsFan315]

Here are some pictures of the New One (Same as my First Post) BEFORE it was installed wired & plumbed up:

The Phillips Screw at the Top adjust the cut off pressure range, right increases, left decreases

Black Part is the unloader valve. connects to the compressor to Unload any pressure on compressor when it shuts off.

 

[gungatim]

they sell 2 different switches at the farm and box stores. someone probably put the wrong one on, the 150 is for the 2-stage compressors. spend $20 and swap it out is what I would do...

 

[sberry]

Sandblasting with a small comp is a matter of timing, same for sanding. This is a place synth comp oin doesn't hurt. If you cant turn it down I wouldn't lose sleep but when blasting regulate the air and its nice to be able to see a gage so you resume blasting just prior to shut off so the comp isn't all the way down, thing isn't at 90 when it comes on but can make it run continuous. If you take a break start blasting when its 140.

 

[happymachinist]

Sandblasting with a small comp is a matter of timing, same for sanding. This is a place synth comp oin doesn't hurt. If you cant turn it down I wouldn't lose sleep but when blasting regulate the air and its nice to be able to see a gage so you resume blasting just prior to shut off so the comp isn't all the way down, thing isn't at 90 when it comes on but can make it run continuous. If you take a break start blasting when its 140.

This doesn't fix the problem, a single stage piston pump Husky air compressor is not made to pump up to 150 psi. That puts extra strain on the motor and pump.

Yeah he can start blasting again at 140 which is close to the design of the compressor, but what is he to do when it's done run over and shut it off as soon as the blasting is done?

The switch needs to be adjusted if possible or replaced with one closer to the OE pressure switch.

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[sberry]

Yes, it is probably a little hi and it takes some extra work to get there. We still havnt seen a pic of the OM unit, should have some kind of cut out adjustment. I see the pics now, that is likely an OM unit. I agree with making sure the gage is right.

 

[BearsFan315]

Can you get the Condor number off the unit ??
that would help you figure out EXACTLY WHAT the cut off & cut in pressure is on the unit.

should be located same place as mine is above, per my conversation with Condor they are generally all in the same location.

also how many Ports ??
i see ONE for the Tank, One for the Gauge, One for the Relive Valve, is there another one that is Plugged ?? my new one was a 4 port.

 

[BearsFan315]

Never mind, see the plugged port in the second pict now... so it is a 4 port

 

[BrBa]

Can you get the Condor number off the unit ??
that would help you figure out EXACTLY WHAT the cut off & cut in pressure is on the unit.

should be located same place as mine is above, per my conversation with Condor they are generally all in the same location.

also how many Ports ??
i see ONE for the Tank, One for the Gauge, One for the Relive Valve, is there another one that is Plugged ?? my new one was a 4 port.

I couldn't get a picture due to the wiring being in the way but here is the info inside the Condor unit:

ABEDCX100135G
CW209300AV
100-135PSI
002312

Considering it says 100-135PSI, I am pretty sure this is the factory pressure switch and the gauge may be faulty. I'll have to pick up an extra gauge to try it out.

Thank you and everyone else for the help so far.

 

[matt_i]

It always seems to me like sandblasting is going to grenade the compressor. But you have to think the manufacturers hopefully have had their compressor running nonstop against a variety of tank pressures for months on end to validate their unit.

I think Quincy advertises something like 50k hours, I would think 5k-10k would definitely be possible with a lower price point model.

In the end, the electric cost will like supercede the initial cost of the compressor, consider a 3hp (2.2kW) unit running for 5000 hours, at $0.15/ kW-hr. Its unlikely it would be drawing 100% of the FLA 100% of the time, but the upper limit is around $1650. I'd WAG 75% of this is about right.

 

[BearsFan315]

I couldn't get a picture due to the wiring being in the way but here is the info inside the Condor unit:

ABEDCX100135G
CW209300AV
100-135PSI
002312

Considering it says 100-135PSI, I am pretty sure this is the factory pressure switch and the gauge may be faulty. I'll have to pick up an extra gauge to try it out.

Thank you and everyone else for the help so far.

Part Number "CW209300AV" references a Condor Pressure Switch for Campbell Hausfeld Compressor

Genuine OEM Air Compressor Pressure Switch CW209300AV
Part # CW209300AV
4-Port Universal Use
Cuts in at 100psi - Cuts out at 135psi
1/4" quick disconnect fitting for check valve line

I would borrow a guage and validate the pressure, just because the Pressure switch could also be bad, they do not last forever (dirt, debris, etc). That is the older style model, the new replacement looks much like the one i have. and for around $35 all day from most anywhere.
$28.99 via Amazon Prime
and can order them Direct from Condor, where I got mine, they were inexpensive, and shipped fast !!

may be wise just to replace it and move on, one less thing to fret about later going bad.