Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 02-20-2009, 05:13 PM   #16
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Share |
Default

Craftsman air compressor blowing breaker


Quote:
Originally Posted by Frankenberry View Post
Well, I did cut off the plug and wired it directly in the box. I left the 20 amp breaker in. I have a job tomorrow that I will use it with, so I'll see how it's working.
If this works then the contact impedance of the plug/socket was to blame?
Unlikely, but who knows. . .?

Yoyizit is offline   Reply With Quote
Old 02-20-2009, 08:29 PM   #17
Idiot Emeritus
 
Join Date: Mar 2008
Location: Fernley, Nevada (near Reno)
Posts: 1,559
Default

Craftsman air compressor blowing breaker


If the compressor is permanently wired (no cord-and-plug), and it's the only thing on the circuit, then it's code compliant to use a larger than 20 amp breaker with #12 wire. How much larger depends on the motor HP or FLA (full load amps).

If you need the code references, just ask, and I'll post them. It's pretty long though.

Rob
micromind is offline   Reply With Quote
Old 02-21-2009, 11:39 AM   #18
Newbie
 
Join Date: Feb 2009
Location: Lancaster,Pa
Posts: 6
Default

Craftsman air compressor blowing breaker


Well it ran fine today. At least a dozen on/off cycles. I left in the 20 amp breaker. I don't know if it was the new breaker, the new contact switch in the compressor, or the elimination of the plug, but I hope that's the end of the problem. Thanks for everyones input and advice.
Frankenberry is offline   Reply With Quote
Old 09-05-2009, 03:45 PM   #19
Newbie
 
Join Date: Sep 2009
Posts: 10
Default

Craftsman air compressor blowing breaker


Quote:
Originally Posted by Frankenberry View Post
Well it ran fine today. At least a dozen on/off cycles. I left in the 20 amp breaker. I don't know if it was the new breaker, the new contact switch in the compressor, or the elimination of the plug, but I hope that's the end of the problem. Thanks for everyones input and advice.
So I have a "5.5 HP" 30 Gallon Craftsman doing the same thing. Replaced the check valve with no luck and was curious if your problem was fixed or not.

Mine starts from empty with 0 problems. It's when under pressure that it gives me a hassle.

Take care,
ceyko is offline   Reply With Quote
Old 09-05-2009, 05:22 PM   #20
Electrical Contractor
 
kbsparky's Avatar
 
Join Date: Sep 2008
Location: Delmarva
Posts: 3,360
Default

Craftsman air compressor blowing breaker


Please post all the nameplate information from your compressor motor, and provide details on how it is wired:

HP
FLA (full load Amps)
LRA (Locked Rotor Amps)
Volts
SF
etc

Is it connected to a dedicated outlet, or direct wired? Wire size, and breaker size? Brand name and type of breaker panel? Distance from panel to compressor? etc
__________________
-KB

Life is uncertain -- eat dessert first!!
kbsparky is offline   Reply With Quote
Old 09-06-2009, 08:07 AM   #21
Newbie
 
Join Date: Sep 2009
Posts: 10
Default

Craftsman air compressor blowing breaker


Quote:
Originally Posted by kbsparky View Post
HP
FLA (full load Amps)
LRA (Locked Rotor Amps)
Volts
SF
etc

Is it connected to a dedicated outlet, or direct wired? Wire size, and breaker size? Brand name and type of breaker panel? Distance from panel to compressor? etc
Greetings,
I'd like nothing more to answer those questions, but I looked and am unable to find that information right now. I'll look again and maybe tearing her apart tomorrow.

However, I'll answer what I can...
The instruction manual says to install a 15A/110V circuit. I installed a 20A, 110V, GFCI (garage, my code says it has to be) circuit just for it. So, it is not hardwired, but it is a dedicated circuit. The romex/wire I bought was 12/3. The run is all of about 2' long since I put it right next to my breaker panel box where the compressor sits. The compressor cord is around 5' long. I was very careful during installion of the breaker/circuit to make sure connections were good...etc. Also, to note the breaker pops, not the GFCI. Dunno if that helps.

People are saying, "just throw in a breaker/GFCI plus and be done with it." I just don't think that is a smart move considering 20A should be overkill.
ceyko is offline   Reply With Quote
Old 09-06-2009, 09:06 AM   #22
Member
 
Join Date: Dec 2008
Location: Dayton Ohio Area
Posts: 670
Default

Craftsman air compressor blowing breaker


If your unit has a starting capacitor, I would replace it. It has likely gone bad and is not able to provide enough current for the LRA of the unit.

If the unit is able to run on 220, I would convert it to 220. It cuts your current (amp) draw in half.

Also, you said you ran 12/2 in conduit under ground. Did you get UF 12/2 or are you using regular romex? Romex is not rated for underground/wet conditions.

You need to run either UF or individual THWN runs for the underground portion.
__________________
-Andrew
DIY hobbiest
AndrewF is offline   Reply With Quote
Old 09-06-2009, 11:22 AM   #23
Member
 
Join Date: Jun 2007
Posts: 3,503
Default

Craftsman air compressor blowing breaker


A five Hp motor draws 28 amps @230 volt. NEC Table 430-152 allows a maximum of 250% to size your single phase motor with a inverse time breaker. This is a common breaker like you have in your panel. Here are the instructions.

5Hp Single Phase Motor

28 amps x 2.50 = 70 amps. This is the maximum size breaker allowed to be used on your motor. This is size breaker I would use. Now, the wire. The motor pulls 28 amps full load. 28 is very close to 30 and #10 wire is good for 30 amps. So I woulds use #10 wire. #12 may work but it's to small in my opinion.
Install #10 wire and install a 70 amp breaker. No more tripping and code compliant.
J. V. is offline   Reply With Quote
Old 09-06-2009, 12:00 PM   #24
Newbie
 
Join Date: Sep 2009
Posts: 10
Default

Craftsman air compressor blowing breaker


Quote:
Originally Posted by kbsparky View Post
Please post all the nameplate information from your compressor motor, and provide details on how it is wired:

HP
FLA (full load Amps)
LRA (Locked Rotor Amps)
Volts
SF
etc

Is it connected to a dedicated outlet, or direct wired? Wire size, and breaker size? Brand name and type of breaker panel? Distance from panel to compressor? etc
Actually, I found a lot of what you're looking for...but some of what you listed is not on there. I'll line it out as it is on the label...

Motor - GE Model 5KCR49TN2312CX
HP HZ60
V120 PH1
RPM 3450 CODE K
A15.0 SF1.0
SFA-- FR56Z
AMB40 C

That is about it on the motor.
ceyko is offline   Reply With Quote
Old 09-06-2009, 01:29 PM   #25
Idiot Emeritus
 
Join Date: Mar 2008
Location: Fernley, Nevada (near Reno)
Posts: 1,559
Default

Craftsman air compressor blowing breaker


There are two possibilities here, electrical or mechanical.

First, mechanical. Every air compressor has to have some type of unloader. The purpose of the unloader is to relieve pressure at the pump when it shuts off. Very few cheap factory compressors (yes, your is indeed a cheap factory compressor, more on that later) can start against pressure. If the unloader has failed, it'll start OK when there's no pressure in the tank, otherwise, no.

There are two types of unloaders commonly used on these compressors. One is an unloader valve. This is a combination check valve and unloader valve. One end is screwed in to the tank, and the other goes to the pump. This valve has a small hole in the side, when the pump shuts off, the air in the line is released through this hole.

The other type, more common, is a valve at the pressure switch. This has a small (1/4") tube attached, and when the pressure switch shuts off, it opens the valve, thus releasing the pressure in the line.

Usually, you can hear the air hiss at these valves when the compressor shuts off. If the unloader has failed, nothing electrical is going to fix the problem. It simply won't start if it's not unloaded.

Now, for electrical. This motor is actually about 1-1/2HP. I know, the label says 5.5HP, there's absolutely no possible way that this motor will EVER produce 5.5HP. That being said, a 15 amp motor will not operate on a 15 amp breaker. I know, the book says use a 15 amp circuit, obviously, the book was written by an idiot. A 15 amp motor MIGHT operate on a 20 amp circuit. If it does, it's pushing the breaker to its limits.

This motor draws around 100 amps during starting. That's above the magnetic trip setting for nearly all 15 amp breakers, and very close to it for a 20. Worse, it's 3450 RPM. A 3450 RPM motor has substantially less starting torque than a similar 1725 RPM one. This magnifies an already questionable situation.

A 3450 RPM motor is less costly to manufacture than a 1725 is, hence the cheapness factor. As a side note, any air compressor that has a 3450 RPM motor was built primarily for low cost.

If this were mine, I'd get rid of the GFI, chop the plug off of the cord, get a metal blank plate with a knockout in it, and using a suitable cordgrip, hardwire it. Then I'd replace the breaker with a 30 or even a 40. This would be a code compliant installation, even with #12 wire.

Also, provided the unloader works, it'll start every time.

Rob

P.S. A few years ago, there was a good-sized lawsuit against several compressor manufacturers concerning the HP ratings of their products. It seem that the manufacturers were pretty much picking HP ratings randomly, and marketing their products as superior to others. I don't know the outcome, but I see more labels like 5.5HP, then in fine print (1.5 running HP).
micromind is offline   Reply With Quote
Old 09-06-2009, 02:15 PM   #26
Newbie
 
Join Date: Sep 2009
Posts: 10
Default

Craftsman air compressor blowing breaker


Hey micromind,
I replaced the "check valve" and I THINK I can hear the 'hiss' when it is done. I'll be running outside to check that for sure after this post, but I'm nearly certain that sound is present.

I don't want to pretend to understand compressors, so I'll ask a straight forward question - will a 30A circuit, hardwired directly to the compressor be sufficient - assuming it is an electrical issue? I have no problems doing this and keeping my GFCI circuit for other things.

I'm just hesitant to do more then 30A.

Thanks for the big rundown too. I was under no illusions that this compressor was high end, I was just looking for a big tank (to me, compared to 6 gallon tanks I have), some okay CFM and reliability. I got 2 of 3, which reliability is the big one for me. :D If it seems 30A is enough, I'll try it and post up if it works. One thing I noticed on all these threads on the internet...no resolution.
ceyko is offline   Reply With Quote
Old 09-06-2009, 02:39 PM   #27
Electrical Contractor
 
kbsparky's Avatar
 
Join Date: Sep 2008
Location: Delmarva
Posts: 3,360
Default

Craftsman air compressor blowing breaker


Quote:
Originally Posted by ceyko View Post
Actually, I found a lot of what you're looking for...but some of what you listed is not on there. I'll line it out as it is on the label...

Motor - GE Model 5KCR49TN2312CX
HP HZ60
V120 PH1
RPM 3450 CODE K
A15.0 SF1.0
SFA-- FR56Z
AMB40 C

That is about it on the motor.
Notice that the HP rating is left blank. That is because it is not a 5 HP motor. According to the chart in section 430.248 of the NEC, it is more likely a one horsepower motor. Actually, the one HP motor is stipulated to require 16 Amps. So you might have a bit less than one HP available. But for the purpose of this discussion, let's assume that this motor is an energy-efficient type and only requires 15 Amps.

That is full-load current. Starting current is approx. 6 times the running current. This means you need 90 Amps to start the dang thing. Table 430.251(A) of the Code bears this out, and shows maximum 96 Amps locked rotor current for a 1HP motor. Locked Rotor Amps and starting current are similar values.

Now for the wiring. IF you install this motor on an individual circuit, you can upsize the breaker to 250% of the full load amps of the motor. This translates to 15x2=37 Amps. Since there is no such thing as a 37 Amp breaker, you are allowed to use the next standard size breaker. This means a 40 Amp breaker would be acceptable.

Section 430.22 of the Code mandates that the wire size for this motor be capable of carrying 125% of the full load current. 15x1.25=18.75 Amps. Table 310.16 shows a #14 wire being capable of handling 20 Amps. The limitations of section 240.4(D) showing 15 Amps max. for a #14 wire do not apply here, as we are dealing with section 240.4(G).

While the Code allows a #14 wire protected by a 40 Amp breaker in this instance, I personally would install a #12 wire, as that #14 is really max'd out.
__________________
-KB

Life is uncertain -- eat dessert first!!
kbsparky is offline   Reply With Quote
Old 09-06-2009, 03:23 PM   #28
Newbie
 
Join Date: Sep 2009
Posts: 10
Default

Craftsman air compressor blowing breaker


Lol, wow. 40A for a 15A motor. I'm glad I posted here and received yalls help. Initially I was going to do a 30A, but glad I did not waste the time ordering the GFCI circuit. I supposed it would not need to be any sort of GFCI for a direct connect to the compressor, so 40A - non-GFCI hardwired it is I guess. Wow, I had no idea.
ceyko is offline   Reply With Quote
Old 09-06-2009, 05:21 PM   #29
Idiot Emeritus
 
Join Date: Mar 2008
Location: Fernley, Nevada (near Reno)
Posts: 1,559
Default

Craftsman air compressor blowing breaker


kb is right on the dot.

If the compressor doesn't have a small pressure line at the pressure switch, then it most likely has an unloader valve. This can be confirmed by the hiss when it shuts off.

If you can turn the pump by hand, it should turn easily when unloaded. If its still pressurized, it'll turn easily, then hard.

Rob
micromind is offline   Reply With Quote
Old 09-06-2009, 06:46 PM   #30
Electrical Contractor
 
kbsparky's Avatar
 
Join Date: Sep 2008
Location: Delmarva
Posts: 3,360
Default

Craftsman air compressor blowing breaker


If you chose to use a cord-and-plug connection on this, I suppose that since it's in a garage, you would be required to have GFCI protection. Either a GFCI breaker or a GFCI receptacle. As you previously noted, it was the breaker and not the GFCI that was tripping out.

Direct-wired would not require this, however.

Since it is adjacent to the panel, no further disconnect would be required, either.

__________________
-KB

Life is uncertain -- eat dessert first!!
kbsparky is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wire size and Breaker size for remodel ?? Skydmark1 Electrical 12 12-15-2007 05:00 PM
Circuit breaker panel - Advice needed justtired Electrical 15 12-13-2007 05:55 AM
20 Amp Breaker tripping with GFCI panhandlion Electrical 7 12-12-2007 08:59 PM
Outdoor breaker panel questions lhoney2 Electrical 12 07-19-2007 05:44 PM
Breaker Buzz SkipI Electrical 2 07-13-2007 07:48 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.