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Discussion Starter #1
Doing research on air compressor for the shop. I have 240-V single phase power,
I can go as high 50 amps on the breaker, possibly even a little more.

Without looking closely at my demands for air pressure and volume, I always assumed
more is better. With the above electrical, I figured I could power a 10-hp motor.

I find now that 7.5-hp seems to be the common cutoff for single phase power
compressor availability. Maybe that's enough. I think the largest air demand I'd need
would be for sandblasting. What are your opinions about 7.5-hp being enough
compressor for a home setup doing bodywork ?

One brand name I saw was JENNY, they have one model that has two 5-hp
motors/compressors mounted on one air tank. Seems like a good idea, as long as
both motors were somehow staged to not start simultaneously, to minimize
the startup current draw. Anyone familiar with JENNY quality-wise ?

Also, how smart would it be to buy a 3-phase compressor and also buy a
phase converter of some sort ? Too much money for not much return ?

Thanks everyone for your advice on this. I've never had a real good air setup
before in my life, never had the electrical power. I'd like to make a good decision.

JB Rossit
 

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Doing research on air compressor for the shop. I have 240-V single phase power,
I can go as high 50 amps on the breaker, possibly even a little more.

Without looking closely at my demands for air pressure and volume, I always assumed
more is better. With the above electrical, I figured I could power a 10-hp motor.

I find now that 7.5-hp seems to be the common cutoff for single phase power
compressor availability. Maybe that's enough. I think the largest air demand I'd need
would be for sandblasting. What are your opinions about 7.5-hp being enough
compressor for a home setup doing bodywork ?

One brand name I saw was JENNY, they have one model that has two 5-hp
motors/compressors mounted on one air tank. Seems like a good idea, as long as
both motors were somehow staged to not start simultaneously, to minimize
the startup current draw. Anyone familiar with JENNY quality-wise ?

Also, how smart would it be to buy a 3-phase compressor and also buy a
phase converter of some sort ? Too much money for not much return ?

Thanks everyone for your advice on this. I've never had a real good air setup
before in my life, never had the electrical power. I'd like to make a good decision.

JB Rossit
If it is any help it relly depends on the amperage of your service. I have set up our compressor units at work and we run two 7.5 hp compressors non-stop all day. It would help to know your service amps.
 

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Discussion Starter #3
Shop has a 240-V, 100 amp subpanel. Not much on it except some 120-V
lights and outlets.
 

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You could probably get more compressor for your dollar if it was 3 phase but phase converters arent cheap unless you can build it yourself.

If its just for hobby use I would say 80 gallon 5-7.5hp would probably get er done but everybodies definition of hobby is a little different. Mostly depends on how much sand blasting you plan to do. Are you restoring a car or are you restoring many cars. If its just one you probably wont mind the innconvenience of letting an 80 gal catchup once in a while. If your doing it all the time it will be a huge inconvenience

Aaron
 

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Make sure you look at the motor nameplate to before purchasing, it will tell you the full load current rating of the motor.

Phase converters draw some current too, I have a 5 hp convertor and it draws about 36 amps. They take up some floor space too.

Aaron
 

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Beware of what type of panel you have. Some are not set up well for things like this. You're breaker size may need to be sized 2-2.5 times higher than your full load current for startup purposes. sometimes that puts you in a breaker size that doesn't physically fit. The invertor is just not practical for your purpose. a 7.5HP 230V motor will put you in the 35-40 amp FLC range and a 10 HP will be close to 50 amps.
Any panel build within the past 20 years will be fine, (so long as you have the room) just some of the older ones are junk.

if you catch what i'm saying you could end up with a 100 amp breaker just for your compressor. looks kinda funny in a 100 amp panel. you wouldnt want to go any higher than that as you wouldnt want the main tripping rather than the designated circuit breaker.
 

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Discussion Starter #7
Diggindeeper,

Panel is a Square-D of some sort, I think about 10 years old.
I have not checked on breaker availability yet.

I admit I'm kind of leaning toward a 7.5-hp unit at this point, but maybe....

Thanks,
JBR
 

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i just put in a new shop and bought a new C/H 80 Gal 5 HP comp from Lowes. it has no problems at all and handles every air tool i have used including DA. it has 16 [email protected] and has max 165 psi. great compressor! for $800 bucks you get a $1,200 compressor.
 

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Jenny compressors

I know quite a bit about air compressors and I know Jenny is a reputable brand. They bought out Emglo several years ago and are using Emglo compressors on most of their units. Ask any building contractor about the durability of Emglos and I doubt you will hear anything negative. They support their product well and you can actually get repair parts for them.

With sandblasters pay attention to the nozzle size and keep spares on hand. By doing that you can sandblast almost continuously.

Phase converters force you to derate the compressor by about 1/3. You could buy a 7.5 HP unit but only get 5 HP worth of air out of it. As a rule of thumb, you get 3 to 3-1/2 acfm of air per HP on an air cooled 2 stage recip depending on what pressure you measure it at. The discharge pressure doesn't effect volume much because these are positive displacement pumps. However, it greatly effects brake horsepower load on the drive motor. In industrial compressors the limiting factor is almost always the motor. I hear all the time about people speeding up their compressors and letting the smoke out of the motor.
 

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square D's are fine. QO series, likely what it will be, have a nice breaker layout. Just the neutral bar sucks IMO but that makes no difference to you in this case.
 
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