Dewalt DXCM251 25-Gal Oiled Air Compressor

[user52165]

Originally Posted by samven
That is a nice unit, I wish mine would go to 200 psi. I have a very old Craftsman 4 hp unit that pulls 18A at 240v, rated at 12.8 cfm @40 and 8.3@90 but it only goes to 125 psi and when I run the air hammer or needle scaler the compressor runs almost constantly because I have to have the reg set at 125 to get 90 at the end of the hose so as soon as I pull the trigger the pressure starts to drop until I hit the switch and it cycles back up and shuts off. With a higher pressure I could maintain my 125 reg setting.



This is what you need as I mentioned earlier:

https://smile.amazon.com/Milton-S-2...cm_cr_arp_d_product_top?ie=UTF8&th=1

Really makes a difference. Your pressure drop should not happen.

Also, use a 3/8" straight hose, not a cheap 1/4" curly hose.

Use the pressure and cfm recommended for the tool.

Most air tools are about 90 - 100 psi, but you may need more volume - cfm.

Anything rated over 150 psi is advertising hype. dave 123 got it right.

Also, whenever 220-240 volts is available, use it. Many motors may be easily switched. You already have it, this is for general info.

 

[samven]

Originally Posted by dave123
Originally Posted by samven
That is a nice unit, I wish mine would go to 200 psi. I have a very old Craftsman 4 hp unit that pulls 18A at 240v, rated at 12.8 cfm @40 and 8.3@90 but it only goes to 125 psi and when I run the air hammer or needle scaler the compressor runs almost constantly because I have to have the reg set at 125 to get 90 at the end of the hose so as soon as I pull the trigger the pressure starts to drop until I hit the switch and it cycles back up and shuts off. With a higher pressure I could maintain my 125 reg setting.

Again the problem is CFM and the pump not PSI!! Something people just don't understand or get.


This is totally wrong, The cfm of my pump is greater than my tool draws but because the ON trip is set at 100 psi on 125 psi max compressors and I need the reg set at 125 to get 90 psi at the tool because of line and fitting loss, my tool operating pressure drops as the tank pressure drops till I hit the ON trigger and then the compressor pumps the tank back up to 125 and shuts off and it starts all over. If I had a compressor that had a higher rating and therefore a higher ON trip the regulated pressure would never drop below the set point.

 

[samven]

I am using High quality rubber 3/8 hose and High flow fittings with the quick disconnect at the tank, and inline air dryer at the whip on the tool end and another high flow quick disconnect at the tool. 75 ft of hose and when testing with a guage at the tool connection as soon as I pull the trigger on an impact wrench or scaler the tool pressure drops 30 psi from the tank guage reading. I guarantee you there is no way to not have a substantial loss across the hose and fittings when you pull 6 or 7 cuft through 50 or 75 ft of hose.

 

[user52165]

Exactly which model # old Craftsman do you have?

 

[dave123]

To start you should never have 30psi line drop at a tool setup correctly you need a diaphragm regulator much closer to the tool and what inline air dryer is this many can be really restrictive. Set up properly you should have very little drop off at the tool . I'm going to say it again it's CFM even if cut in is 100 it shoul take nothing to get to 125. You should at least have 100 at the tool setup properly.

 

[dlundblad]

Originally Posted by The Critic
Originally Posted by Donald
I do not think the price was steep as you got a 2 stage compressor. Are you sure your air tools want to run at 150 PSI? Seems high.

Did you consider getting cordless impact and a much smaller compressor for your other needs.

I have a small cordless inflator with auto shutoff at a given PSI that is very handy for filing tires.

I already have the Milwaukee M18 impacts and their M12 inflator. 150 is on the high side, but is about what most shops run.


Very interesting. I'd have to double check, but I think my Aircat 1150 wants 90 psi max.

Looks like you did good with your compressor choice.

 

[dlundblad]

Originally Posted by dave123
To start you should never have 30psi line drop at a tool setup correctly you need a diaphragm regulator much closer to the tool and what inline air dryer is this many can be really restrictive. Set up properly you should have very little drop off at the tool . I'm going to say it again it's CFM even if cut in is 100 it shoul take nothing to get to 125. You should at least have 100 at the tool setup properly.


I get what you're saying, but for my situation, it's not possible for me to have my regulator at my tool. I have 50' of 1/2" hose running to the center of my garage to a 3/8" hose reel that has enough hose to reach every square foot of the garage as well as out into the driveway. The end/ tool eventually gets choked down from a 1/4" fitting, but I'm using Milton high flow fittings too.

I could get a gauge and hook it to the end of my hose reel and see where I'm at in relation to what the regulator is set to.

 

[dave123]

Originally Posted by dlundblad
Originally Posted by dave123
To start you should never have 30psi line drop at a tool setup correctly you need a diaphragm regulator much closer to the tool and what inline air dryer is this many can be really restrictive. Set up properly you should have very little drop off at the tool . I'm going to say it again it's CFM even if cut in is 100 it shoul take nothing to get to 125. You should at least have 100 at the tool setup properly.


I get what you're saying, but for my situation, it's not possible for me to have my regulator at my tool. I have 50' of 1/2" hose running to the center of my garage to a 3/8" hose reel that has enough hose to reach every square foot of the garage as well as out into the driveway. The end/ tool eventually gets choked down from a 1/4" fitting, but I'm using Milton high flow fittings too.

I could get a gauge and hook it to the end of my hose reel and see where I'm at in relation to what the regulator is set to.
what size fitting output is on the tank and curious why you can not have regulator at the hose real if the tank fittings not 1/2 inch plumbing to everything downstream that could be big issue everything getting choked off not enough CFM.

 

[dlundblad]

Originally Posted by dave123
Originally Posted by dlundblad
Originally Posted by dave123
To start you should never have 30psi line drop at a tool setup correctly you need a diaphragm regulator much closer to the tool and what inline air dryer is this many can be really restrictive. Set up properly you should have very little drop off at the tool . I'm going to say it again it's CFM even if cut in is 100 it shoul take nothing to get to 125. You should at least have 100 at the tool setup properly.


I get what you're saying, but for my situation, it's not possible for me to have my regulator at my tool. I have 50' of 1/2" hose running to the center of my garage to a 3/8" hose reel that has enough hose to reach every square foot of the garage as well as out into the driveway. The end/ tool eventually gets choked down from a 1/4" fitting, but I'm using Milton high flow fittings too.

I could get a gauge and hook it to the end of my hose reel and see where I'm at in relation to what the regulator is set to.
what size fitting output is on the tank and curious why you can not have regulator at the hose real if the tank fittings not 1/2 inch plumbing to everything downstream that could be big issue everything getting choked off not enough CFM.


It's 1/2" at the tank. 18 CFM at 90 psi.

The reel is hanging from the ceiling. I guess I could have it at the reel, but I'd need a ladder every time I wanted to get to it.

 

[dave123]

You have to look up charting and drop off at 1/2 inch pipe to cary that many feet 12 cfm is about max. Now add in a 3/8 hose reel and 1/4 inch fittings it's just starved. 3/4 inch pipe even at 25 feet is the min for 20 cfm for that many feet it's the reason for all this line drop.

 

[clinebarger]

Originally Posted by dlundblad

Very interesting. I'd have to double check, but I think my Aircat 1150 wants 90 psi max.


I've run all my air tools at 150-175 psi for 30+ years, My old IR 231 broke after 13 years of HARD abuse, We're talking 100's of hours. Your regulator could be a major restriction. Though I do agree that 50' of 1/2" hose coupled to a 3/8" hose reel isn't doing you any favors.

My distribution is 3/4", But I do most jobs off a 25' coiled 1/4" hose & it works great 'til i run into something I need to run my Impact or Air Hammer more than a few short burst, Then I need to break out a 25' 1/2" hose.

My compressor On is set at 125 psi & Off at 150 psi....No inline regulator or dryer. My pump (332TVX Kellogg American) is rated 18.1 CFM @ 150 PSI.

Saying PSI doesn't matter isn't completely accurate, I've worked in shops that regulate air @ 90 PSI & it flat sucks!!!! Though it's NOT a replacement for CFM!!

Storage capacity is also important with these smaller pumps, 60 gallons is about minimum & more the better! Dave123 states he has 400 CFM @ 125 PSI.......WOW, That's impressive & I don't know of any single phase compressors that could do that. I did rental fleet maintenance for a couple years & we had Airman 400 CFM compressors with 4 cylinder diesel engines.

 

[user52165]

No one said psi doesn't matter. What dave123 and I have said is it should not be the only or primary consideration when making a purchase. It is too often stressed in advertising above the importance of CFM, storage, and recovery time. High psi alone will not compensate for inferior specs of other parameters.

As for dave123's 400 cfm @125 compressor - it would most likely be a rotary screw type. Would sure like to know what and see it!

 

[dlundblad]

I didn't mean to hijack OP's thread. I do know there's math involved with calculating pressure drop over distance, but I'm having a hard time believing my compressor is restricted at all. It's designed for a small machine shop or mechanic shop.. both of which my garage certainly isn't. The fittings after all are 1/4", which is pretty much an industrial standard.

I do know technically it needs to be a loop that runs back to the compressor rather than just a line so it gets flow/ pressure from both directions, but I haven't had any issues yet. I may do it someday just to see if there's a difference.

 

[dave123]

Originally Posted by user52165
No one said psi doesn't matter. What dave123 and I have said is it should not be the only or primary consideration when making a purchase. It is too often stressed in advertising above the importance of CFM, storage, and recovery time. High psi alone will not compensate for inferior specs of other parameters.

As for dave123's 400 cfm @125 compressor - it would most likely be a rotary screw type. Would sure like to know what and see it!

Multiple rotary screw type 100+HP with multiple receiver tanks and dryers we bring them online as we go and what demand. We can be running multiple 5hp air driven motors at given times actually looking to add another unit.. Quincy, Sullair and IR personally I like the Quincy.

 

[clinebarger]

Originally Posted by user52165
No one said psi doesn't matter. What dave123 and I have said is it should not be the only or primary consideration when making a purchase. It is too often stressed in advertising above the importance of CFM, storage, and recovery time. High psi alone will not compensate for inferior specs of other parameters.

As for dave123's 400 cfm @125 compressor - it would most likely be a rotary screw type. Would sure like to know what and see it!

I was under the impression dlundblad was having issues & 90 PSI is low in my opinion. I don't fully understand why tool manufacturers chose that PSI when failures during the warranty period is unlikely @ 150-175 PSI.

I kinda see the issue with Die Grinders overspeeding & blowing up cut off wheels if you just held it wide open with no load, That's where common sense should prevail.

Consumer grade compressors have been advertised with misleading "smoke & mirror" specifications for years. Going out & buying a commercial/industrial grade unit isn't always a wise choice......Like your old Craftsman having honest specs is long gone in this segment, 2hp should draw 22 amps @ 120vac. Critic's Dewalt probably has a 1.5hp....Maybe a little under?

 

[dlundblad]

Yeah my mistake.

I'm having zero issues at all. I was just curious because I saw air tools being ran higher than 90 psi.

 

[JTK]

Looks nice! I'm surprised it's quiet given the 3450 RPM.

I've got the cheapo 21 gal 2.5hp cast iron oil lubed HFT vertical in my garage. It's obnoxiously loud.

Not like the 30yr/old belt drive coleman powermate I gave my brother. That thing is whisper quiet in comparison because of the slow loping RPM.

 

[user52165]

FWIW - 3450 is a very common rpm for AC motors. But it does not have that much affect for noise. The pump rpm would depend on the pulley sizes but would be less than motor rpm. Design of pump, oil capacity, number of cylinders, mounting, insulation, etc are all a factor for noise.

Something like this helps, but is a crutch for a poor design:

https://smile.amazon.com/Pack-Anti-Vibration-Rubber-isolation/dp/B002IA0WPI/ref=sr_1_13

 

[JTK]

Ahh! Good point on the flywheel size on that compressor end slowing things down.

In the case of my direct drive HFT junker, the compressor is whipping along at the same shaft speed of the motor.

 

[clinebarger]

Originally Posted by user52165
FWIW - 3450 is a very common rpm for AC motors. But it does not have that much affect for noise. The pump rpm would depend on the pulley sizes but would be less than motor rpm. Design of pump, oil capacity, number of cylinders, mounting, insulation, etc are all a factor for noise.

Something like this helps, but is a crutch for a poor design:

https://smile.amazon.com/Pack-Anti-Vibration-Rubber-isolation/dp/B002IA0WPI/ref=sr_1_13


Every compressor I own has a 1750 rpm motor & are quiet compared to just about any 3450 rpm motor equipped compressor no matter the pulleys/configuration.

I have my Kellogg American on hockey pucks as it was walking across my smooth concrete floor, I didn't notice much sound reduction but it's not all that loud to begin with.
My ancient Mills is welded inplace up high in my small shop/garage, Granted it does have quite the reduction & lumbers along at @ 400 pump rpm.