Compressors - What size

Submitted: Monday, Jan 07, 2008 at 17:50
ThreadID: 53213 Views:7571 Replies:9 FollowUps:20
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Hi Trendsetters!

I am in the market for a compressor for the workshop. Belt driven and a single or double cylinder compressor unit, and a cage around the belts so I cant hurt myself.

Question is, what CFM or l/min should I be looking for? I will be running a rattle gun and possibly doing some spray painting and would like something that would fit the bill. I am NOT in the market for a Bunnings special, neither do I want a rolls royce one that would look the goods in a V8 Supercar workshop.

I am thinking something like a 50 lt tank and 2300 l/min free air delivery. Am I anywhere near the mark?
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Reply By: Member - barry F (NSW) - Monday, Jan 07, 2008 at 18:00

Monday, Jan 07, 2008 at 18:00
G day Bonz, if you contact a reputable compressor retailer/supplier & give them the specs of the tools you intend to run off it they will advise you what cfm is needed. Cheers
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Follow Up By: Bonz (Vic) - Monday, Jan 07, 2008 at 18:10

Monday, Jan 07, 2008 at 18:10
I will do that Barry but I want some sort of idea if he is pulling the wool over my eyes or not.

For example I have just been told (by one supplier) to get one with at least 12 CFM, preferably 15 CFM. Thats 336 to 420 l/min. Even the $1100 peerless with a 70l tank wouldn't supply that and this "expert" was pointing at "that one" as an example of what I needed.

Hmmm maybe I shall talk to the bank manager anyways.....

ROACHIE Where fore art thou?
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Reply By: Crackles - Monday, Jan 07, 2008 at 18:10

Monday, Jan 07, 2008 at 18:10
14 CFM Peerless should work well with those tools. Quality equipment & Aussie company too. (See link)
Peerless Compressor
Smaller units would mean having to wait for the air to build up while using impact drivers & spray guns & bigger units may need 15 amp power points to run off.
AnswerID: 280311

Follow Up By: Crackles - Monday, Jan 07, 2008 at 18:19

Monday, Jan 07, 2008 at 18:19
Check this air tool flow chart to check what they will run. As you will see the direct drive compressors are out of the runnung while the 12 cfm is only rated at intermitant use for many air tools.
Cheers Craig......
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Follow Up By: Member No 1- Monday, Jan 07, 2008 at 20:55

Monday, Jan 07, 2008 at 20:55
i was gunna say 10-12 also but then i am a laymen when it comes to spray painting...rattle guns etc are generally intermittent stuff
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Follow Up By: Crackles - Monday, Jan 07, 2008 at 21:23

Monday, Jan 07, 2008 at 21:23
I have a 14 cfm which struggles to keep up with my elchepo small capacity rattle gun by the 5th wheel nut. When spray painting it keeps up just nicely. A 12cfm would do the job if you didn't mind waiting occationally.
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Follow Up By: Member No 1- Tuesday, Jan 08, 2008 at 06:56

Tuesday, Jan 08, 2008 at 06:56
i wouldnt have thought a rattle gun used much
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Reply By: Richard Kovac - Monday, Jan 07, 2008 at 21:18

Monday, Jan 07, 2008 at 21:18
The biggest your money can buy... so when it starts up it scares the crap out of the neighbours .... LOL

30cfm will be plenty, I have one of the small super shet ones and can pump up a tyre OK but wont run a air tool..

Cheers

Me
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Follow Up By: Bonz (Vic) - Monday, Jan 07, 2008 at 21:20

Monday, Jan 07, 2008 at 21:20
30cfm? wow, O was thinking like 200 l/min not 2300 like some dope (me) wrote up there. 30cfm is a expensive compressor, hmmm, I shall have to keep saving.
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Follow Up By: Richard Kovac - Monday, Jan 07, 2008 at 21:57

Monday, Jan 07, 2008 at 21:57
Sorry,, Just went out to the shed (in 37 deg heat) and had a look, and I've only got a 15 like everyone else... dam I was filling good for a moment there... ;-((
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Follow Up By: Bonz (Vic) - Monday, Jan 07, 2008 at 21:58

Monday, Jan 07, 2008 at 21:58
Sorry to put you thru a harrowing 37 degrees, but thanx for the effort mate! Looks like 15's the go dammit.
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Reply By: Des Lexic - Monday, Jan 07, 2008 at 21:29

Monday, Jan 07, 2008 at 21:29
G'day Mr Bonzarelli, HNYTYA
It will depend on the demand from your largest air tool that your going to use. I think most air tools are around 8cfm. Spray gun to hide the rust on the Nissan shouln't need that much supply LOL
Keep an eye out on any clearing sales around the area. You might pick up an oldie for cheap.
AnswerID: 280365

Reply By: Member - Roachie (SA) - Monday, Jan 07, 2008 at 21:29

Monday, Jan 07, 2008 at 21:29
Quote: " and a cage around the belts so I cant hurt myself."

hahahahaha, Lucky will be along any minute now to suggest that the cage needs to be around the WHOLE WORKSHOP if it's going to have any chance of preventing you from hurting yourself!!!! hahahaa

Bonz, I think you need one of those BIG suckers (at least 15 CFM) that has it's own shed outside the workshop and with permanent plumbing throughout your workshop/garage etc.....

Cheers

Roachie
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Follow Up By: Bonz (Vic) - Monday, Jan 07, 2008 at 21:32

Monday, Jan 07, 2008 at 21:32
I got my little one plumbed thru the workshop Bill with three outlets and a retracting air hose like the big boys at the servo.

I think you have misunderstood the question I am looking for a compressor, not a vacuum pump, so I am looking for a BLOWER not a SUCKER.

15 CFM - everyones saying that
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Follow Up By: Richard Kovac - Monday, Jan 07, 2008 at 21:39

Monday, Jan 07, 2008 at 21:39
I'm not
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Follow Up By: Bonz (Vic) - Monday, Jan 07, 2008 at 21:41

Monday, Jan 07, 2008 at 21:41
No Riccardo, you said 30 hehehehehe, I love the way we spend others money :0)
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Follow Up By: Richard Kovac - Monday, Jan 07, 2008 at 21:59

Monday, Jan 07, 2008 at 21:59
Whoops read above... LOL
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Reply By: Louie the fly - Monday, Jan 07, 2008 at 22:09

Monday, Jan 07, 2008 at 22:09
Bonz, I was in the industrial compressor business for some years and have sized units for all types of applications (28000 cfm). Large or small, Rolls Royce or Lightburn Zeta, consider the following;

1. Duty cycle required - how long per day will it be required to run?
2. Air requirement - based on the tools you will use. I.e. will you ever use a 1/2" ratchet gun and a spray gun together at the same time?
3. 240V or 415V
4. Noise level - is noise an issue?
5. Cost of ownership (purchase price and maintenance over a given period) - yep, they need to be maintained.

Don't forget air treatment. A good 5 - 10 micron filter is a minimum as cheapo machines, and even some good ones, pass lots of oil that ends up in your pipework and tools and even in your paint- not good. Also worth knowing is that cheaper recip's are commonly rated in swept volume whereas "industrial" compressors are rated in Free Air Delivery (FAD). Swept vol. is around 0.7 - 0.8 of FAD depending on the efficiency of the unit. So if they say 12 cfm it may only be 8.5 - 9.5 CFM FAD. Thats the actual volume of air (expanded back to atmospheric conditions) that it will deliver due to all the internal losses. It all sounds confusing and so it can be. BTW, for a 12 - 15 CFM unit 50L receiver is OK for up to about 40% duty. As an indication, I sold dozens of 40CFM machines with 147L receivers for general workshop use. These machines were rated at 100% duty.

Try someone like CAPS, Air Technology Group or Southern Cross Compressors in Melbourne as a starter. If they don't have what you need they will steer you in the right direction. This may all seem over the top but you make your living from using this stuff (I'm assuming). Hope I haven't confused the issue for you.
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Follow Up By: Bonz (Vic) - Monday, Jan 07, 2008 at 22:21

Monday, Jan 07, 2008 at 22:21
Thanx Louie, the duty cycle will be lucky to be 5%, but on days when I am at home from work, weekends it may be like more. This compressors just for my home workshop not a business thing, but I like the 147l tank idea, got any laying about?

I am really looking for something to drive the rattle gun, give me gollops of air for the blow gun and like and maybe one day use it for painting, probably high pressure. Also I will get a framing gun to go with the bradder and stapler I have, and I alsi have a air hammer/air chisel and may get an air sander etc.

I have been fairly careful to compare FAD on the units I have looked at. I am looking at spending a little more than the run of the mill 40l self driven Bunnings special but not over the top. Looks like something 13-15 CFM is the go, but I have a conversion rate of 1cfm=28.328 l/min although the Peerless 14 (cfm) = 275l/min at 100PSI gives a conversion rate of 19.6 so thats confused me more.

Will take a look at the places you mention as I will be in Melb Thu/Fri. Thanx, this is exactly the advice I needed.
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Follow Up By: Louie the fly - Monday, Jan 07, 2008 at 22:55

Monday, Jan 07, 2008 at 22:55
Sorry, no air receivers. I bought a Clisby 14 CFM piston compressor some years ago for home. Cost me about $650 (1998 or so). Has never let me down other than the unloader poppet valve bleep itself. Got a newie for a few bucks and good as gold.

A bigger air receiver is sometimes a benefit - I have an axillary tank made from a 80L steel LPG autogas tank plumbed up on the opposite side of the shed as a buffer tank. In my Dodge I've even used a piece of heavy wall 180 dia pipe, volume about 17L with a 1/2" pressure relief valve for my tank for the rear air bags.

Try your local Agricultural Field Days - the vendors at them generally have good stuff at good prices.
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Follow Up By: Louie the fly - Monday, Jan 07, 2008 at 23:19

Monday, Jan 07, 2008 at 23:19
Also, CFM / 2.12 = L/second. Multiply this by 60 gives you L/min.

Here's a good conversion site
Conversion calculator

My 14cfm with the extra storage volume runs my spray gun nicely at around 40psi. It also runs my small sandblaster with 1/4" nozzle OK at 90 - 100 PSI.
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Reply By: Member - Jiarna (NT) - Monday, Jan 07, 2008 at 22:35

Monday, Jan 07, 2008 at 22:35
Hi Bonz
My brother picked up a nice compressor at a clearing sale a while ago. It is an ex District Council roadworks compressor which can run 2 jackhammers continuously, and is driven by a Holden grey motor. Maybe you need something like that? Make all your mates jealous anyway LOL
Cheers
John
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Follow Up By: Bonz (Vic) - Monday, Jan 07, 2008 at 22:38

Monday, Jan 07, 2008 at 22:38
I like the way you think John, if it was run by a Ford motor I would be into it.
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Reply By: Member - JohnR (Vic)&Kath - Monday, Jan 07, 2008 at 22:45

Monday, Jan 07, 2008 at 22:45
Bonz, look for a rotary screw compressor if you want the best. Perhaps 7.5hp. Continuous duty. Three phase power shouldn't be a problem to get hooked. I know someone in your area, I that knows someone. ;-))) Hook it up with 25mm diametre pipe and curlie one for the tools. Keep the nurse close to hand.
AnswerID: 280391

Follow Up By: Bonz (Vic) - Monday, Jan 07, 2008 at 22:49

Monday, Jan 07, 2008 at 22:49
7.5hp and I only have two phases here John. Nah 15a plug is the biggest I can go.
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Follow Up By: Member - JohnR (Vic)&Kath - Monday, Jan 07, 2008 at 22:57

Monday, Jan 07, 2008 at 22:57
Bonz, I have a good replacement motor or three for you. On a pallet, two phase, 480v. Even a couple of 15hp 480v going spare....... 15 amps eh. I better get some 8 gauge fuse wire, or a penny.
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Follow Up By: Bonz (Vic) - Monday, Jan 07, 2008 at 23:37

Monday, Jan 07, 2008 at 23:37
No such thing mate, its single phase 480v, and I have two phase 415v here, the 480v has a 180 degree phase displacement, whereas the 415v has 120 degree, they wont work sadly.
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Follow Up By: Member - JohnR (Vic)&Kath - Tuesday, Jan 08, 2008 at 15:20

Tuesday, Jan 08, 2008 at 15:20
Two phase 480 was the way the sparkies used to talk about the 180 degree 240->240 legs. Haven't had the electrical problems since we went three phase :-))) SWR systems were (are) troublesome in comparison.

Took a bit of convincing for some neighbours and all ones on the road have benefitted even though they didn't participate in the scheme. Not much benefit in dwellings in town though.
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Reply By: rumpig - Friday, Jan 11, 2008 at 23:47

Friday, Jan 11, 2008 at 23:47
being a carpenter i use a compressor every day just about. i've only ever owned the one compressor in about 13 years of work, most of it knocking up stick frames of new houses, so i'm talking lots of framing gun work, lots of coil gun nailing, and lots of rattle gun work doing up all the tie down. the compressor i have is a PUMA V11, i would have gone bigger but found the current draw was to much on the 13 CFM when i was on some sites running more then one compressor, we kept tripping out the power all the time with a mates 13 CFM so i was advised to get a 11 and have been more then happy with it.
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