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Air Compressor setup electrical and pressure switches.

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Strouty

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I am working on setting up my air compressor, it came to me in pieces, so I was missing a few components and I have been sourcing others as I go. I am now at the point that I am starting to understand things enough to ask questions.

First, the pressure switch, the current ones say they are 80 PSI on and 100 PSI off, so I am assuming these are low pressure? What is a good unit to purchase? These are square D, but were wired for the old three phase motors. The tank has a working pressure that is rated at 200 PSI, the plan is to keep things in the 150 to 175 range, then regulate as needed.






I know now that I also have an undersized motor starter, so I am going to have to source a new starter as well. At this point I only have one motor and I am not sure what I will be using for the second motor. What would you guys recommend, I have seen cheap new ones on eBay, I have found some used ones as well. I have no real experience with the imported brands, but my guess is all the new ones are imported anyways.




Current setup is single phase 10 HP motor running quincy #350 pump on a horizontal 200 gallon tank.



 
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Strouty

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After doing a bit more research I did find that the pressure switches are adjustable up to 200 PSI shut off. I now have the motor turning off at 170 PSI. Just have to figure out what pressure is best to have the motor start the pump.

I did a few tests as well, the motor is drawing about 37 AMPs while running and draws 230 at startup. Then I messed with temperatures on the pump and outlet tube, so now I have to try and figure out what is normal on those as well.
 
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250

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As I look at that switch, and I'm no means an expert on the subject, shouldn't it be cutting in at 150 if its cutting out at 170? IIRC, only one value was adjustable, with a fixed gap of 40psi, so it cuts in at 95 or so and out at 135. I could have set it higher but I didn't really see any need at this time.
 
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Strouty

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250, these pressure switches are actually adjustable with two separate springs, so it has more flexibility in the stop and start range. I just played around with it a bit, but right now it was set with 120 being the start and about 170 being the stop. Once I get things really hooked up, I will be able to figure out the best place to have them set.

Motofool, that looks like a nice setup, I am still in research mode, but that may be my answer. The 18 month warranty is really a nice thing too.

Sberry, depends on what type of sandblasting unit is being used. This compressor will allow me to use more air as needed. I know my old 7.5 HP 24 CFM unit did not really like a 1" drive impact. It also ran constantly with the needle gun and my die grinder with a roloc disc, hopefully this one will work better. I am sure having a 200 gallon tank will be a huge difference as well.
 
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sberry

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As a side babble and this is all super generalization. About 4 cfm per hp from 2 stage. 5 hp is really a bench mark, well adequate for a man, 2 1/2 more for a second and a 10 will run 4 in a body shop no problem. Normal industrial averaging is 25 to 30% and some demand may be way lower depending on the nature of the work.
There isn't really too much for blasting. If that is a regular goal you are on the right track. Other than that the extra is simply resources parked.
I know several truck type shops, even the county garage lives on 10 hp air most of the time.
I have a 3 and a 5 with 200 in tank and use the 3, so much better on rural electric service. Some extra tank allows for operator synch, I never run out, am done before there is a lag, letting it run longer is fewer cycles and easier to resume work before shut off making for basically continuous run.
Some rural services are limited to 7.5, I can see a 5 run on mine on a recip pump. The 3 I don't notice.
A larger starter wont hurt.
 
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sberry

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The 200 tank will help a lot. Something is amiss, 5 hp will run a scaler and a roloc and will run a 1 inch gun fine if the pipe and hose are up to it. It should be sized to run constant with the sanders. 1 start on a motor half the size may be preferable to several from 1 2x.
This was part of my babble, I actually sized mine to the demand with the smallest motor. Instant water heaters have some of this drawback and I thought of something else and forgot it that reacts this way but as you said, 230A comes slamming on for every air need.
As we said, blasting is another matter, its rather cheap in many cases to up size a blast system to take advantage of air capacity. I watched a couple episodes of a resto show. Their prices were too low and one of the ways they were making some back was over quoting the blast time.
If its taking 4 hrs its too slow, about like welding. They could fund new equipment in super short order, it would take me all of 5 minutes as a production consultant to up size some demand air and bigger nozzle.
95 % of the rest of the air in a small shop comes out a drop at a time and thru a 3/8 hose.
 
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Strouty

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Right now I am the 10 HP doesn't even seem to phase the lights, my welder will actually dim them a bit. The old (actually pretty new) IR 7.5 HP compressor would dim the lights like a kid playing with a dimmer switch. I know that is not scientific, but I would think that having a 200 amp service with a motor that has an inrush of 230 amps would do more than dim the lights, I wish I had the meter to measure things with the old compressor. If I do a 15 HP, it will have a soft start feature for sure, looks like some of the VFDs will allow me to run a 15 HP 3 phase motor without any derating.

I am also looking to set this up with a dual control with a pilot valve, this will allow me to run the compressor continuos while doing my sandblasting. From what I have read if your compressor starts and stops more than 6 times an hour, you should be running in a continuos mode anyways.
 
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Strouty

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sberry said:
The 200 tank will help a lot. Something is amiss, 5 hp will run a scaler and a roloc and will run a 1 inch gun fine if the pipe and hose are up to it. It should be sized to run constant with the sanders. 1 start on a motor half the size may be preferable to several from 1 2x.
Click to expand...

Sorry, I need to qualify my previous statement. I did not mean that the compressor would not actually make them work, what I meant was the compressor was constantly playing catch up with them. This was an 80 gallon vertical tank. Plumbing was up to the task, I made sure of that.
 
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sberry

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I mentioned this to the truck driver on here. He does his own work. He needs a 2 stage comp and while his need is above a hobby level or a Jack Olsen he has to pump up some truck tires. A too large a comp is costly, a truck service center would need it but he is pumping them 1 at a time. He would only save an hour if he was doing 48 in a row with a unit much above 5 hp and a lot of that would have to do with the discipline of the operator.
 
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sberry

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I know you have 3/4 pipe, I don't remember what the tank to manifold connector is but I found an error in my own where I used a 1/2 hyd line and it was pitiful, I used one going in to the regulator too. and even when I had it all hosed it was just hitting a ceiling with a 3/4 gun and even turning it up didn't help much. I have it all full ported with minimum of 1/2 steel pipe all the way and its much zippier. But,,,, used it 2 times last year and it worked, fixed it since.
Now,,, the interest here is what I call utilities and I can feel guilty cause I didn't over size everything a couple levels but when one gets a grip on real demand factors the ability to spread some asset helps it go a lot further.
It took me a long time to get the estimation accurate or valid or useful. I know how Strouty may feel about 7.5 hp but I am a grade above a hobby and do these same tasks on 5 or less and down a 1/2 pipe, when a guy (not him) this is a generalization says I am goi9ng to put 10 wire on all the outlets and add double circuits to every box I know he has missed the assessment of his demand, no amount of good estimation is worth a dam.
He may even look at a calculator and figure 20A for 50 ft and while that is correct it isn't the real load.
A guy is wanting to increase air so his compressor shuts off is different than meeting adequate demand. The 3 hp on a 60 or 80 gallon used to be popular, it has been passed up for 5 hp today as electric service has been improved but it was for "mechanic shops" It had a run current of under 20 and 175 psi. They were a little small for body work but you could blow up a truck tire, a lot of them come with a gate valve and a 1/2 port.
They were horizontal with a drop tube for water removal and had starters. Champ made a lot of them for Wards etc.
 
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sberry

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what I meant was the compressor was constantly playing catch up with them. This was an 80 gallon vertical tank.
Click to expand...
To some extent its sposed to. If its oversize it runs short cycles. Similar to water heaters, instant may take 100A to wash hands, electric stored may not come on and when it does at 1/3 the rate. Its kind of a poor comparison due to the fact that there isn't hi load starting.
When plumbing and wiring and supplying any utility itds often worh a demand calc of sorts, I know that there may be an occasion I want to run a big air gun so I make a simple provision for it, doesn't mean I need it every where every place I want to put a hose reel for tire air or sufficient for the real work with a 1/2.
As a whole we tend to size trunk and branch for multiple users which is not the case here when home runs are only slightly less efficient when used one at a time and better for multiple users.
We all want to run 3/4 mains so 2 at a time can work but systems work as good or better when each one has their own smaller pipe, when there IS some restriction not causing user losses such as a sink supply tube or cord whip.
That is a super nice unit, once its working should never need service from use hours. A guy couldn't live long enough to wear it out. .
 
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