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Shop Talk - Tool and Shop Discussion! Tool and Shop Discussion! |
11-03-2017, 07:43 AM
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#21
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Name: zstroken
Title: For $$$ your name here
Status: Not Here
Join Date: Sep 2006
Location: Western Michigan(by the lake)
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Posts: 23,151
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Quote:
Originally Posted by 4x4dually
If both legs of a single phase motor aren't pulling the same amount of amps...then there is something wrong. It "is" possible. For instance, if a winding starts shorting or some oddball crap, so it is advised to run both thermal overloads. We were merely stating that he could jumper it if he wanted to so he could get it running. On a three phase, you could protect two out of the three if you wanted....but no one in their right mind would do it that way. You wouldn't believe the amount of Nigerian rigged schidt that shows up while doing service calls. It always amazed me what people thought was ok.
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Protecting 2 of 3 legs was a common practice for years, overloads are for overloading conditions, fuses/MCP are protection for shorts. Also on a single phase motor if one of the coils starts shorting windings (short out to themselves) then the single overload will still protect, as the impedance of the motor is decreased and the current goes up in the whole circuit. I do agree, that running the 2nd overload won't hurt anything, but I don't see a real scenario, that the circuit isn't adequately protected.
__________________
2008 4x4 Megacab, 68RFE
97 Dodge gone....
24V P-Pump Mafia member #1(retired)
Thanks to Mumau Diesel, Goerend Transmission, Northeast Diesel Service!
Last edited by zstroken; 11-03-2017 at 07:48 AM.
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11-03-2017, 07:57 AM
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#22
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Name: 4x4dually
Title: Moderator
Status: Not Here
Join Date: Jan 2007
Location: Stillwater, OK
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Posts: 31,812
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The winding can open up and the side from the jumper can be the one shorting to the case and it not be protected. There is ALWAYS a case for fukkery.
Just put the correct heaters in all positions and don't question it. That's my policy.
Speaking of fukkery.....I started the little chinesium band saw on some tubing the other night. Then I turned and started working on a gate facing the other direction. The wife stepped out and said "um...honey...." The blade was locked and the motor was just a boiling out black smoke. Melted the motor to the ground. 20amp breaker never bobbled. Square D Homeline too, not that FPE red handled crap. It was an amazing show. Now see, if I had a starter and heaters on it...that wouldn't have happened.
Last edited by 4x4dually; 11-03-2017 at 08:00 AM.
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11-03-2017, 08:07 AM
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#23
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Name: zstroken
Title: For $$$ your name here
Status: Not Here
Join Date: Sep 2006
Location: Western Michigan(by the lake)
Member`s Gallery
Posts: 23,151
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Quote:
Originally Posted by 4x4dually
The winding can open up and the side from the jumper can be the one shorting to the case and it not be protected. There is ALWAYS a case for fukkery.
Just put the correct heaters in all positions and don't question it. That's my policy.
Speaking of fukkery.....I started the little chinesium band saw on some tubing the other night. Then I turned and started working on a gate facing the other direction. The wife stepped out and said "um...honey...." The blade was locked and the motor was just a boiling out black smoke. Melted the motor to the ground. 20amp breaker never bobbled. Square D Homeline too, not that FPE red handled crap. It was an amazing show. Now see, if I had a starter and heaters on it...that wouldn't have happened.
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If the winding is shorted to the case, then it will pop the breaker. I am guessing your motor wasn't shorted to the case, . So yes a properly sized overload would have protected it.
Overcurrent protection is to protect the downstream devices, if the motor has bad insulation, it is already bad . Just keep the place from burning down when it shorts to the case! HAHA
__________________
2008 4x4 Megacab, 68RFE
97 Dodge gone....
24V P-Pump Mafia member #1(retired)
Thanks to Mumau Diesel, Goerend Transmission, Northeast Diesel Service!
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11-03-2017, 08:09 AM
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#24
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Name: 4x4dually
Title: Moderator
Status: Not Here
Join Date: Jan 2007
Location: Stillwater, OK
Member`s Gallery
Posts: 31,812
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Quote:
Originally Posted by zstroken
If the winding is shorted to the case, then it will pop the breaker. I am guessing your motor wasn't shorted to the case, . So yes a properly sized overload would have protected it.
Overcurrent protection is to protect the downstream devices, if the motor has bad insulation, it is already bad . Just keep the place from burning down when it shorts to the case! HAHA
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You realize you are preaching to the choir, correct?
HEY OP! Did you get that air pump working yet or not?
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11-03-2017, 04:53 PM
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#25
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Name: Red Sleeper
Title: Too Much Time
Status: Not Here
Join Date: Aug 2009
Location: Lone Star State
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Posts: 4,595
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Compressor Starter Box Wiring
Not yet Jory. One more week of travel and hotel living for me. Then I'll be home and have time to tinker.
I greatly appreciate the info! Will put this to use.
For the record, it's a 220v 5hp motor.
Nick
__________________
Nick J
'14 Silverado LTZ 5.3 4wd
'05 Cummins QCSB 4wd 48re
'91 Cummins w350 5spd
Last edited by Red Sleeper; 11-03-2017 at 05:00 PM.
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12-04-2017, 08:53 AM
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#26
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Name: Red Sleeper
Title: Too Much Time
Status: Not Here
Join Date: Aug 2009
Location: Lone Star State
Member`s Gallery
Posts: 4,595
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Update.
Compressor works without starter box. I had a "doh!" moment when looking at my cousins IR compressor that is identical to mine.
He pointed out that his has start and run capacitors with a pressure switch rated to take the 15amp kick at first start up.
I get home, see that mine too has start and run capacitors. Cleaned the dirt off the pressure switch label, and read that it's also rated for 15amps. Wired that sucker direct to the switch and it fired off! I don't even care at this point how long it took to figure all this out. Just glad to finally have compressed air.
Jory, I printed out your schematic and placed it in the starter box. Might just need it one day. Thanks for the insight.
__________________
Nick J
'14 Silverado LTZ 5.3 4wd
'05 Cummins QCSB 4wd 48re
'91 Cummins w350 5spd
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12-04-2017, 08:57 AM
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#27
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Name: 4x4dually
Title: Moderator
Status: Not Here
Join Date: Jan 2007
Location: Stillwater, OK
Member`s Gallery
Posts: 31,812
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Glad you got it going.
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