Replies to this message

Re: Modifying a shop air compressor
Re: Modifying a shop air compressor -- reynoldrodriguez	Post Reply	Top of thread	Forum

Posted by: randykimball ® 12/04/2005, 00:26:53 Author Profile eMail author Edit

So, ... rewording your statement you have said it, your problem is heat. Also, you apparently are concerned about the expense of solving the problem or you would have already "thrown money" at a fix. I'd try a realistic approach. I'm sure you are going to get some hi-tech thermo engineering answers, but here is a "down to earth", "rubber meets the road" type answer. My suggestion is this simple. ... I would be sure the compressor is in a location that allows air to circulate, not the little room that gets hot from the work the compressor is doing, unless it has plenty of louvers to allow the hot air to escape upwards. Then I'd use my shop skills to put a small squirl cage blower from a local shop supply vendor in such a way to have a good supply of forced air pointed right at the vent openings in the motor housing flowing the same direction the motor frame is already trying to move it, be creative. 'One of those little fans with a 4 or 5" diameter squirl cage, you want some CFMs but you need the velocity provided by a squirl cage to push the air through the motor frame. Then I would do the came across the fins of the compressor to add to its life cycle. These little squirl cage fans are inexpensive and easy to suspend with simple shop skills. Additionally, if the compressor is in a small room or shed I'd force exchange the air in that space with enough CFM to evacuate the BTU's created by the motor AND the heat of compression. These things should go a long ways to increase the duty cycle longevity of the compressor/motor team without spending a ransom. You can always backup to plan B and throw money at a more robust system or expensive motor, if you must, later. Plus, this way the air flow you have created continues to bull BTUs away from the compressor and the motor after the unit has stopped at presure shut-off. Set yourself up a switch that you flip with the lights or even wire the fans into the lights so when air is being used the unit gets forced air, these little fans don't draw much current. That is exactly what I did, ...... wink ... and it is still working, ... and working, ... and, ..... like the silly pink rabbit. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Sun, Dec 04, 2005, 00:59:23

Post Reply Tell a Friend (must be logged in) Alert Admin About Post

Where am I? Original Top of thread

| |

Re: Modifying a shop air compressor
Re: Re: Modifying a shop air compressor -- randykimball	Post Reply	Top of thread	Forum

Posted by: reynoldrodriguez ® 12/04/2005, 19:01:16 Author Profile eMail author Edit

Thanks for the reply, now more specifically on the motor replacement;(as mine is now fried and replacing is inevitable) minecame with a 5hp/3450rpm. Question is, Can I "upgrade" the motor to a stronger alternative, if so which would u recommend A 5hp/1725rpm a 7.5hp/3450 rpm In other words more HP or less RPM or both?

Post Reply Tell a Friend (must be logged in) Alert Admin About Post

Where am I? Original Top of thread

| |

Re: Modifying a shop air compressor
Re: Re: Modifying a shop air compressor -- reynoldrodriguez	Post Reply	Top of thread	Forum

Posted by: randykimball ® 12/05/2005, 00:50:00 Author Profile eMail author Edit

Yes, you can increase the HP so the motor works less hard to a point. But, you are still going to do the same amount of work and produce the same heat. If you increase the HP and increase the RPM you are right back where you started except with a quicker recovery time, plus you may over work the compressor. If you drop RPM you will have to run the compressor for longer periods. Try a 7.5 HP with the same PRM. If the 5HP is not being able to keep up to full RPM it will fry prematurely, IF this is the case, the 7.5 HP will run at the proper speed and not over draw on current and thus produce too much heat. Be sure you are furnishing enough current through the wire you provided to the motor. Check with a local electrican to meed code for your new motor size. Still, GET RID OF THAT HEAT to increase the duty cycle. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

Post Reply Tell a Friend (must be logged in) Alert Admin About Post

Where am I? Original Top of thread

Re: Modifying a shop air compressor
Re: Re: Modifying a shop air compressor -- reynoldrodriguez	Post Reply	Top of thread	Forum

Posted by: zekeman ® 12/04/2005, 23:57:12 Author Profile eMail author Edit

Never change the RPM spec. I would further check with the mfr on the advisibility of increasing the power, since the original design probably "matched" the compressor to the 5 HP motor drive.

Post Reply Tell a Friend (must be logged in) Alert Admin About Post

Where am I? Original Top of thread

| |

Re: Modifying a shop air compressor
Re: Re: Modifying a shop air compressor -- zekeman	Post Reply	Top of thread	Forum

Posted by: reynoldrodriguez ® 12/05/2005, 08:38:07 Author Profile eMail author Edit

Do these motors work at the same torque throughout their cycle or do they have starting phases? At some point an electrician checking the motor on its first failure, told me something about it not switching properly from starting phase to running phase. Im thinking this might account for the motor running so hot. IN any case, what kind of motor would be a good quality Heavy Duty Replacement. Ive heard... Farm Duty?

Post Reply Tell a Friend (must be logged in) Alert Admin About Post

Where am I? Original Top of thread

| |

Re: Modifying a shop air compressor
Re: Re: Modifying a shop air compressor -- reynoldrodriguez	Post Reply	Top of thread	Forum

Posted by: randykimball ® 12/05/2005, 20:14:54 Author Profile eMail author Edit

Ahhh.. My past comment about reaching running speed comes back to mind. Exactly what happens as your electrician explained. If the motor is not reaching full run speed the centrifical contacts used to power up the starting fields never open so the motor continues to run on them, resulting in an overheat. If you will notice, when a single phase motor (some others too) reaches near full operating speed you will hear a click and the sound will change. This is when the starting contacts have opened. So let us ammend the "same heat for same work" statement to allow the statement (as long as the motor reaches full operating RPM and the starting contacts open). Heavy duty or farm duty most likely speaks to better bearings, heaver frame, heaver mounts, better cooling... things of this mature. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Mon, Dec 05, 2005, 20:20:55

Post Reply Tell a Friend (must be logged in) Alert Admin About Post

Where am I? Original Top of thread

| |

Re: Re: Modifying a shop air compressor
Re: Re: Modifying a shop air compressor -- randykimball	Post Reply	Top of thread	Forum

Posted by: CompressorProfessor ® 10/02/2006, 23:50:44 Author Profile eMail author Edit

Another thing to consider when a motor is failing prematurely is the duty cycle. A compressor that has to cycle on and off frequently can cause the motor to fail prematurely as well as other problems like decreased bearing life and need of frequent compressor oil changes. During your work day, check to see how many times your compressor is cycling. If it is short cycling, you can increase the size of your air receiver or put in an additional receiver, which is common for areas where there is a sporadic or large air demand. Additionally per the post, you may want to go to a 7.5 HP compressor. With single phase power, this will be the largest HP that you will be easily able to find in stock. Modified by Administrator at Tue, Oct 03, 2006, 07:41:12

Post Reply Tell a Friend (must be logged in) Alert Admin About Post

Where am I? Original Top of thread