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Thread: Single / 2-Stage Compressor question (sorry to resurface this)

  1. #1

    Default Single / 2-Stage Compressor question (sorry to resurface this)

    Yes yes, I know, this topic has been raised a million times but I'm still confused.

    I presently own a good, expensive 10-yr-old 5HP Ingersoll Rand SINGLE STAGE air compressor spec'd at 18CFM @ 90PSI and 100% duty cycle. Max pressure is 135psi.

    However, I am considering upgrading to a 2-stage 5HP air compressor. I have contacted both Ingersoll and Quincy for a better understanding of the advantages of a 2-stage. Surprisingly, both attempts to get a response from Ingersoll have yielded ZERO email or phone call responses. Quincy, on the other hand, seems happy to engage.

    Here are my questions:
    (1) Looking at both IR and Quincy specs, it looks like their 5HP 2-stage units will yield approx 4CFM LESS flow than my existing 2-stage compressor. So then, I'm confused, why would I invest in a 2-stage if this is the case? My existing 18CFM compressor barely keeps up with air hogs such as DA sanders, straight line sanders and my sand blast cabinet.
    (2) Quincy tells me that one advantage of their 2-stage units is that the air is cooled before entering the tank, therefore there will be less water in the line. If this is true, this seems like a very wise feature to have, for auto body painting. Is it correct that this is a major advantage of a 2-stage?

    In short, my existing compressor is still working just fine. However, I'm about to plumb out my shop with rigid air line and I'd like to consider whether or not I should upgrade my compressor at the same time.

  2. #2
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    Quote Originally Posted by sharpegunguy View Post
    Yes yes, I know, this topic has been raised a million times but I'm still confused.

    I presently own a good, expensive 10-yr-old 5HP Ingersoll Rand SINGLE STAGE air compressor spec'd at 18CFM @ 90PSI and 100% duty cycle. Max pressure is 135psi.

    However, I am considering upgrading to a 2-stage 5HP air compressor. I have contacted both Ingersoll and Quincy for a better understanding of the advantages of a 2-stage. Surprisingly, both attempts to get a response from Ingersoll have yielded ZERO email or phone call responses. Quincy, on the other hand, seems happy to engage.

    Here are my questions:
    (1) Looking at both IR and Quincy specs, it looks like their 5HP 2-stage units will yield approx 4CFM LESS flow than my existing 2-stage compressor. So then, I'm confused, why would I invest in a 2-stage if this is the case? My existing 18CFM compressor barely keeps up with air hogs such as DA sanders, straight line sanders and my sand blast cabinet.
    (2) Quincy tells me that one advantage of their 2-stage units is that the air is cooled before entering the tank, therefore there will be less water in the line. If this is true, this seems like a very wise feature to have, for auto body painting. Is it correct that this is a major advantage of a 2-stage?

    In short, my existing compressor is still working just fine. However, I'm about to plumb out my shop with rigid air line and I'd like to consider whether or not I should upgrade my compressor at the same time.
    It sounds like the compressor you have will do the job, the only additional consideration would be tank size. I'm using a single stage compressor that I've had for 50 years and I think the reason it's served me well for that long is the 80 gallon tank size.

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    I agree with Len. For autobody/paint use an industrial/commercial single stage compressor works just fine. I never heard about Quincy's 2 stage units "cooling" the air before it goes into the tank. I think it's a manipulation of facts - Like Bill Clinton saying " I never had sex with that woman". I have had a 5 hp oil pressure lubed 2 stage 80 gallon Quincy compressor since 1984 when I bought it new for $1800. Replacement cost on my compressor new right now is $5,000. On my compressor the copper pipe going into the tank from the pump is NOT cool to the touch. It gets downright warm if the compressor has been cycling.

    "they" say that a two stage unit is more efficient than a single stage unit but for doing what we do I don't see where it would make a noticeable difference.

    One real life Advantage to a two stage unit is it tops out at 175 psi while a single stage unit tops out at 130/135 psi. So if you need higher air pressure than the 130 psi then a two stage is arguably a better choice. But realistically no air tool in a body shop/paint shop uses more than 100 psi. Most air tools are designed to run on 60 to 90 psi.

    A top of the line 2 stage Quincy 5 hp 80 gallon oil pressure lubed air compressor is going to cost you $5,000. If you have a good single stage Ingersoll Rand compressor that puts out 18 cfm then spending $5000 to replace that unit is not a choice I would make.

    I find one thing troubling in the message you posted about your single stage Ingerolls running a lot using an air file or a da. That does not sound right to me. Not doubting your word, just wondering if there is a problem with your compressor. I know that cheap air files like the cheap chinese ones use a LOT of air compared to my Viking or even old Ingersoll Rand Viking copy air files. You should be able to run a DA for a LONG time without the compressor cycling.

    Running a sandblaster with ANY air compressor in the 5 to 7 hp 80 gallon tank range running it a full pressure is going to give ANY compressor a workout. It's the same as opening the valve wide open on your air compressor with the air coming out full blast. So point being running ANY sandblaster/sand cabinet with full air pressure is going to make any 1 to 3 man body shop air compressor run a lot.

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    One last point. If you do opt for a new Quincy 80 gallon, 5 or 7 hp two stage oil pressure lubed air compressor it will in all probability be the last air compressor you will ever have to buy. Realistically it should last you the rest of your life. In this world of planned obsolescence with throw away products the air compressor I mention is NOT in that category. I have been using my Quincy air compressor just about every day in a commercial setting continuously for the last 35 years with never a down time needing repairs. It's never had a wrench touch it in those 35 years. (I did have to change out the electric motor about 15 years ago, cost me $40 to repair the original motor).

    Bottom line -- if you want a compressor that will last you the rest of your life then a Quincy with oil pressure lube is a good choice.

    $5,000 is a lot of money to anyone. But think how man times you would have to replace a cheaper unit that will fail ?

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    Quote Originally Posted by Phil V View Post
    One last point. If you do opt for a new Quincy 80 gallon, 5 or 7 hp two stage oil pressure lubed air compressor it will in all probability be the last air compressor you will ever have to buy. Realistically it should last you the rest of your life. In this world of planned obsolescence with throw away products the air compressor I mention is NOT in that category. I have been using my Quincy air compressor just about every day in a commercial setting continuously for the last 35 years with never a down time needing repairs. It's never had a wrench touch it in those 35 years. (I did have to change out the electric motor about 15 years ago, cost me $40 to repair the original motor).

    Bottom line -- if you want a compressor that will last you the rest of your life then a Quincy with oil pressure lube is a good choice.

    $5,000 is a lot of money to anyone. But think how man times you would have to replace a cheaper unit that will fail ?
    What is the difference in lifespan or usage between the "Pressure Lubed" one of the Quincy "Splash Lubed" compressor heads?

    The Quincy QT-7.5 hp Splash Lubricated Reciprocating Air Compressor 7.5 HP, 230 Volt, 1 Phase, 80-Gallon Vertical, Model# 271CS80VCB is about half the cost of the Quincy 5hp 80hp model mentioned.

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    Quote Originally Posted by OldFatBald View Post
    What is the difference in lifespan or usage between the "Pressure Lubed" one of the Quincy "Splash Lubed" compressor heads?

    The Quincy QT-7.5 hp Splash Lubricated Reciprocating Air Compressor — 7.5 HP, 230 Volt, 1 Phase, 80-Gallon Vertical, Model# 271CS80VCB is about half the cost of the Quincy 5hp 80hp model mentioned.
    Any splash lubed compressor is cheaper built and will not last as long as a pressure lubed compressor air pump.
    My Quincy has a built in oil pump and the crank has chamfered bearings, rod bearings lubed under oil pressure also. If my air compressor doesn't build at least 10 psi of oil pressure it won't pump air.

    Oil pressure lubed air pump will last a lot longer.

    I don't like the saying "you get what you pay for" because a lot of times that saying is just plain wrong. But with air compressors you DO get what you pay for. You can cut corners and buy a cheap air compressor but what will it end up costing you over many years when you have to replace those cheap air compressors several times when they self destructed.

  7. #7

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    Thanks for the feedback guys. I remain perplexed. Two different reps from Quincy stated that their 2-stage 5hp compressors cool the air between the pump and the tank. If true, this in and of itself seems like a reason to buy one, when the application is for spraying paint.

    What I DO NOT LIKE, is the fact that these more expensive 2-stage units yield lower CFM values, at the same psi rating, than my ten-yr-old single stage Ingersoll.

    Note I'm talking about 60gallon units. I do not have space for an 80 gallon unit.

    To be transparent, I don't have the budget for a $5000 machine. I'm looking at Ingersoll-rand and Quincy 5HP 2-stage machines which run in the $1500-$2000 price range. In comparison, my existing single stage Ingersoll cost me about $1600 ten years ago.

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    the one advantage of a two stage compressor i think no one has pointed out is they can run higher pressure than a single stage compressor so if you have something that needs a lot of pressure a two stage is needed,

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    Quote Originally Posted by easymoney View Post
    the one advantage of a two stage compressor i think no one has pointed out is they can run higher pressure than a single stage compressor so if you have something that needs a lot of pressure a two stage is needed,
    Yes, Phil pointed that out but I've been running the same single stage/80 gallon compressor almost daily for 50+ years and it runs up to 175psi before it shuts off and still runs great. Knock on wood.

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    Quote Originally Posted by Len View Post
    Yes, Phil pointed that out but I've been running the same single stage/80 gallon compressor almost daily for 50+ years and it runs up to 175psi before it shuts off and still runs great. Knock on wood.
    A single state compressor that cycles off at 175 psi ?? All the single stage units I've been around cycle off at 130/135 psi.

    You have never rebuilt the pump on your air compressor using it for 50 years ? That is VERY out of the ordinary especially in a busy commercial environment. What brand is your air compressor ?

    To the original poster - You are seriously hobbling yourself with 60 gallon tank air compressor. No wonder it cycles often. Seriously an 80 gallon verticle tank is not going to take up much more space than a 60 gallon tank.

    The only single stage IR compressor with a 60 gallon tank I found that put out 18cfm was $1100 and it's rating was 18 cfm @ 90 psi and 15 cfm @ 130 ps. iMy Quincy puts out 22 cfm @ 120 psi and 19 cfm @ 175 psi I could boost the CFM of my air compressor by changing the pulley diameter ratio's but I like how it turns slow.

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    one of the things i look at is the compressor head rpm. the lower rpm your pump runs while still getting the cfm you're after usually translates to longer life. of course there's always exceptions to the rule, but generally that's the situation.
    i have also known folks to add a second compressor when higher capacity is required only occasionally. i've seen shelves built over the top of the original so they're stacked for reducing floor space required. then if you're running a high draw,(two sanders, blast cabinet,ect...)you switch on the second compressor to help with the demand. not saying it's the answer for everyone, but it's a solution for some.
    b marler

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    Quote Originally Posted by bmarler View Post
    one of the things i look at is the compressor head rpm. the lower rpm your pump runs while still getting the cfm you're after usually translates to longer life. of course there's always exceptions to the rule, but generally that's the situation.
    i have also known folks to add a second compressor when higher capacity is required only occasionally. i've seen shelves built over the top of the original so they're stacked for reducing floor space required. then if you're running a high draw,(two sanders, blast cabinet,ect...)you switch on the second compressor to help with the demand. not saying it's the answer for everyone, but it's a solution for some.
    All the major air compressor companies make what's called a Duplex air compressor. It is two motor and two air pumps mounted on the same air tank. You can run one or run both air compressors at the same time.

    https://www.northerntool.com/shop/to...5002_200375002

    https://www.ingersollrandproducts.co...en-duplex.html

    Another advantage of a slow turning air pump is less heat generated which means less moisture produced. I big problem for the smaller air compressors is they use faster electric motors with faster turning air pumps to produce more air. Those compressor heads get VERY hot which as previously mentioned by bmarler it shortens the life of the compressor to run that hot and they produce a lot more moisture.

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    Quote Originally Posted by Phil V View Post
    All the major air compressor companies make what's called a Duplex air compressor. It is two motor and two air pumps mounted on the same air tank. You can run one or run both air compressors at the same time.

    https://www.northerntool.com/shop/to...5002_200375002

    https://www.ingersollrandproducts.co...en-duplex.html

    Another advantage of a slow turning air pump is less heat generated which means less moisture produced. I big problem for the smaller air compressors is they use faster electric motors with faster turning air pumps to produce more air. Those compressor heads get VERY hot which as previously mentioned by bmarler it shortens the life of the compressor to run that hot and they produce a lot more moisture.
    absolutely correct. that duplex system is a really neat option for those that only need high capacity intermittently. i only mentioned adding a second unit as it might be a cost effective solution for someone that already has an existing system but needs more cfm now and then. obviously if you were starting from scratch (or had the extra scratch to spend) your options would be many, and maybe a duplex would be the answer.
    b marler

  14. #14

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    Just remember this.
    The CFM ratings at 90 PSI are how much air the compressor can put out
    when pumping against a 90 psi tank. As the tank pressure increases the
    CFM output goes down, usually way down.

    So if you keep a tank at 175 PSI your compressor output is way lower than
    the 90 PSI rating that everyone compares against. It takes a lot longer
    to recapture than a lower pressure tank would.
    That's why some reset the pressure limit to around 125 PSI on a 175 PSI unit.
    It runs less and no one needs higher than 90 PSI anyway, for tools.

    But a 175 PSI tank has a whole lot more reserve air than a 125 PSI tank.
    On the other hand, the higher the pressure the more heat generated.
    Everything is a trade off.

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    Quote Originally Posted by JCCLARK View Post
    Just remember this.
    The CFM ratings at 90 PSI are how much air the compressor can put out
    when pumping against a 90 psi tank. As the tank pressure increases the
    CFM output goes down, usually way down.

    So if you keep a tank at 175 PSI your compressor output is way lower than
    the 90 PSI rating that everyone compares against. It takes a lot longer
    to recapture than a lower pressure tank would.
    That's why some reset the pressure limit to around 125 PSI on a 175 PSI unit.
    It runs less and no one needs higher than 90 PSI anyway, for tools.

    But a 175 PSI tank has a whole lot more reserve air than a 125 PSI tank.
    On the other hand, the higher the pressure the more heat generated.
    Everything is a trade off.
    When I bought my air compressor new back in 1984 the guys at the compressor shop who sold me the compressor suggested I drop the shut off pressure from 175 psi down to 155 psi . They said that last 20 psi from 155 to 175 made the compressor work the hardest. It kicks on at around 130 and off at 155 psi and it's worked great ever since. I also plummed the compressor air intake up into the attic of my shop using white PVC pipe with the air cleaner up in the attic. The compressor is quiet enough that I can have a conversation standing next to the compressor while it's running. The air cleaner also stays clean a lot longer because there is very little dust and no paint overspray in the attic area. I do have ventilation up in the attic for those hot summer days.

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