air-compressor idea!----1 tank, 2 comp.?

[3/4tonYJ]

I've been planning and collecting parts for my compressed air system.
Nothing big; copper tubing from tank, a couple water seperator/filters, one 50ft. reel and 5 outlets.

I have a nice 20 year old compressor (with a new 115vac motor) and a rusty tank that needed replaced years ago.
So i couldn't pass up the deal on this 27 gallon tank/compressor............plan was to replace this small 125psi. compressor/motor with my old belt drive compressor...
after getting these "blingin" wheels and new air filter......

I GOT TO THINKING........
neither of my compressor have a large CFM rating, maybe i could run the both and use just the one tank...............what you all think?
I imagine a little manifold system with acouple check valves. and maybe "special" switch/relay to run both electric motors at the same time when i need more volume.

 

[JCByrd24]

Should work fine, without even any extra equipment, if the pressure switches are set close enough to one another. You don't need a check valve because if you think about it, 1 compressor is always seeing pressure against it in the tank, its already checks and unloads when stopped. Pressure switch isn't required either really. Both will just kick on/off at different times rather than simultaneously. They'll both run below 110 and both will shut off by 140 or whatever, what happens in the middle doesn't really matter to you. Just make sure 1 isn't a significantly higher pressure than the other...could be dangerous. So yeah, just hook them together and go.

 

[krooser]

Huh???????

 

[bobbyd]

I think it would be pretty easy to set up. If supply of both compressors are tied together downstream from the existing check valves, I don't think any additional ones would be required.

Electrically is a bit more complicated. I think what JC is saying would be OK but I think you're wanting a bit more control over when the slave compressor runs. It doesn't necessarily need to come on all the time, just when the extra volume is required. I think I would add a current sensing relay in the pressure switch circuit of the master compressor and let it act as the pressure switch for the slave. A simple toggle switch in the relay circuit gives you the control on when it comes on.

Other idea is a lower limit pressure switch on the slave. Master kicks on when tank psi goes below say 100 psi and slave kicks in when tank pressure drops below 60. Kinda like a homemade two-stage compressor. Automatic. I kinda like this idea. Off to ebay to see if I can find a used compressor (sans tank).

 

[krooser]

I guess I'd sell the two small ones and buy one big one...

 

[Ryan Wilke]

I know this isn't what you have in mind, nor have the parts for at this time.....but, isn't what most home shop compressor systems need is more air CF STORAGE capacity, not more compressor CFM size?

If you were to keep your old, but good, relatively small compressor, and then install a 40-80 gallon air storage tank AT EACH END your air piping system, wouldn't that allow you to have more air volume & pressure be able to maintain it longer? Recovery would take longer, but the compressor wouldn't be on/off nearly as much, and the on/off cycling is what eats all the electricity.....

As long as you install tank moisture drains AND USE THEM periodically, the tanks will last a very long time & consume no energy. Mount the tanks out of the way - in the rafters or on the wall - and you'd have all the air you'd likely need.



RW

 

[krooser]

I believe 3/4 ton is trying to re-invent the wheel. And, coming from one who has TRIED to re-invent it several times, it usually doen't work.

 

[JCByrd24]

I know this isn't what you have in mind, nor have the parts for at this time.....but, isn't what most home shop compressor systems need is more air CF STORAGE capacity, not more compressor CFM size?

If you were to keep your old, but good, relatively small compressor, and then install a 40-80 gallon air storage tank AT EACH END your air piping system, wouldn't that allow you to have more air volume & pressure be able to maintain it longer? Recovery would take longer, but the compressor wouldn't be on/off nearly as much, and the on/off cycling is what eats all the electricity.....

QUOTE]

Ryan, this is true and not...depending on usage. If you only need your high usage tools for short bursts, then yes, you need more storage and less CFM capacity...however this is not usually the case. The problem with your proposed solution is that the low CFM compressor will take forever to fill 60-100 gallons of storage and still won't keep up if running your air tools for more than a minute or two. My new 10 CFM takes a while to fill its 60 gallon. Also, cycling on and off doesn't really use that much electricity compared to the run time unless you're talking about a lot of cycling. The difference between a minute on/minute off and 3 minutes on/3 minutes off won't be noticeable in terms of electricity. I've actually thought the opposite before....bigger compressor, less storage. You can run all of your tools and don't need a huge tank to lug around, sure it cycles more, but who cares, its still on the same percentage of time...unfortunately, bigger compressors are usually 220V and therefore left in one place and made with big takes...My ideal compressor would be a 220V compressor (3hp, 10CFM) on a 30 gallon tank with wheels that I can put in my truck orand plug in someones drier outlet if I want, or lug out in the yard to fill a tire...doesn't exist. Just my 2 cents.

3/4ton is just looking for a solution to already having 2 small compressors and needing their capacity combined...and it is doable.

 

[Kruse]

As I see it too, it should work out just fine...
With a regulator after the tank or at the tool-stations:
Adjust the start pressure differently on the two compressor's.
Shut-off pressure could be the same.
Let's say you have a system pressure of 125 psi, with min pressure at 80 psi...
Depending on your normal air use (primary to big or small);
have no1 to start set at 100 psi,
have no2 to start set at 90 psi.
- When no1 can not keep up the pressure, no2 will set in to assist.
You could set these numbers to your liking, the principle being that you would normally run just one compressor, with the other one kicking in to support. You do not need any extra valves or electronic.
Show us some pics, when you have decided on a solution.

 

[3/4tonYJ]

thanks for all the replys/thoughts:
i do understand that i could just go buy a compressor that suites my needs, but i'm pretty "cheap" and i do also like "re-inventing" the wheel, many times it doesn't work out, but is enjoyable.

i do have a designated location in my garage for the this new compressor, and plan to permanently mounting the "old compressor" and a shelf just above the it. Using a hose to connect the portable compressor to the copper tubing system, making it easy to unplug/transport.

i guess this could be much simpler than i first thought.
i should be able to just lower the automatic "turn on" PSI of the 2nd compressor, which would only allow it run when the primary compressor can't maintain enough supply.

 

[bahamasair]

thanks for all the replys/thoughts:
i do understand that i could just go buy a compressor that suites my needs, but i'm pretty "cheap" and i do also like "re-inventing" the wheel, many times it doesn't work out, but is enjoyable.

i do have a designated location in my garage for the this new compressor, and plan to permanently mounting the "old compressor" and a shelf just above the it. Using a hose to connect the portable compressor to the copper tubing system, making it easy to unplug/transport.

i guess this could be much simpler than i first thought.
i should be able to just lower the automatic "turn on" PSI of the 2nd compressor, which would only allow it run when the primary compressor can't maintain enough supply.

I did it with mine. I have a crappy 20gal oil less comp and had a nice old belt drive with an iron pump. The tank went bad on the belt drive one so I put a t fitting on my 20gal tank and added a contactor to turn on the 2nd motor with the pressure switch that runs the 20gal motor. I made the belt drive connect with a quick connect fitting and the contactor has plugs on it so I can disconnect everything and still wheel the oil less comp round. I only really hook up the 2nd one when I want to sand blast or something like that.

 

[Ryan Wilke]

JCByrd24,

You said:
"If you only need your high usage tools for short bursts, then yes, you need more storage and less CFM capacity...however this is not usually the case."

--- I was thinking that the air useage by most folks was just that - mostly for short bursts - like air rachets, nut crackers, grinders, etc. However, I can see in the case of someone painting or sandblasting they'd require a more constant CFM air supply, thus requiring a high CFM capacity or dual compressor system.


"....cycling on and off doesn't really use that much electricity compared to the run time unless you're talking about a lot of cycling. The difference between a minute on/minute off and 3 minutes on/3 minutes off won't be noticeable in terms of electricity."

--- I guess I was wrong then. I always figured there was a spike of electricity necessary to start any electric motor, then once running, it would draw a lesser amount of electricity. A water pump, a grinder, will "dim the lights" only with the activation of the on trigger, then it'll run without the lights being dim.......as a result there would be less wear & tear on the motor and less total power used over 15 minutes if it ran for 5 mins then off for 10 minutes; rather than run for 1 minute and off for 2 minutes, back on for 1 minute, off for 2 minutes, etc.


"3/4ton is just looking for a solution to already having 2 small compressors and needing their capacity combined...and it is doable."

--- I did get off track from 3/4Ton's question. I just figured that he was bring out an idea & I simply thought I'd throw out another idea that may result in some additional related discussion.... In hindsight, I suppose I should of just posted it on the board as a separate topic. Sorry.

RW

 

[Kruse]

If your system is tight, and you use a good amount of air at a regular basis, extra tank capacity is always a good idea.
If you run in to another tank, you can always attach it to the system.
The pressure will even out through the system.

Watching out for maximum "weakest link" pressure, you can basically attach an air system as you like.
Only need to watch out for restrictions (heat build-up) and water-traps.
Do not put things too close together, and remember to isolate (flex-tubes) for vibrations.

 

[JCByrd24]

Ryan, you're definitely right that with more storage you will get the larger bursts you need and then allow the compressor to catch up. That is very true. You're also right about the wear and tear on stuff starting and stopping and the electrical spikes will be there, my feeling was the duration wasn't enough to be sucking electricity. Probably the only real problem with adding on a much larger tank would that during the initial fill the little compressor would have to run for a long time to fill it up, possibly exceeding the duty cycle. Overall you are right though, more storage would help, as long as some one doesn't think that means they have a bigger compressor.

 

[Ryan Wilke]

.... more storage would help, as long as some one doesn't think that means they have a bigger compressor.

I hear ya there!

RW