3 phase motor reversing with no circuit changes.

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check voltage and current - you may have lost a phase.

If there is back-flow in the media when motor is energized with a missing phase - it very well may continue to run in the wrong direction.

Seen this with fans. Back flow device in piping or phase monitor can help prevent this.
 
Ultrafault said:
Thanks for the replies. I was hoping I had missed some arcane knoledge that would lead me to an anwser that was not incompetence. However as you guys pointed out improbility os not impossibility.

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Haha, you have heard of F.M. right and do you know the secret handshake?
 
Might sound dumb, but are you sure everything is fine now? I've seen something like this (not rotation being questioned), where the system actually drained down due to a frozen/burst heating coil. There was minimal flow, pumps were reported as being loud, etc. HVAC techs couldn't believe what they were seeing.
 
I have a similar issue on a two speed FWD and REV cooling tower fan. One day the fan motor was spinning backwards after some maintenance work and the electricians were 10000% sure the motor was wired back correctly. Found out the pads in the motor starter fell off on one of the starters. Replaced the starter and everything worked fine.
 
Please explain, or clarify, this statement:
Ultrafault said:
They ran in the correct direction the day before.
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(I kinda doubt this, but . . . ) can you confirm that some person had "eyes on" these two pumps the day before, and will certify that they were running in the right direction, only to come back the next day, had "eyes on" them again, this time seeing them running in the wrong direction? Or is it more appropriate to say simply that nobody noticed a problem the day before?

 
USMC1302 said:
Might sound dumb, but are you sure everything is fine now? I've seen something like this (not rotation being questioned), where the system actually drained down due to a frozen/burst heating coil. There was minimal flow, pumps were reported as being loud, etc. HVAC techs couldn't believe what they were seeing.
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I checked myself. it is ok now.

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charlie b said:
Please explain, or clarify, this statement: (I kinda doubt this, but . . . ) can you confirm that some person had "eyes on" these two pumps the day before, and will certify that they were running in the right direction, only to come back the next day, had "eyes on" them again, this time seeing them running in the wrong direction? Or is it more appropriate to say simply that nobody noticed a problem the day before?
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There is where I think I had inacurate information. After talking to the lead I realized the other techs may be wrong about it working correctly.

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Ultrafault said:
There is where I think I had inacurate information. After talking to the lead I realized the other techs may be wrong about it working correctly.

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That is in fact the most likely scenario. I find that MOST mechanical technician types, trained to deal with one particular machine or another, are inadequately trained on the little ins and outs of details that we encounter every day. One big one is what was said earlier, that some types of pumps will pump in both directions, just not efficiently in the wrong direction, which quite often goes unnoticed to the inexperienced eye. I've had to prove it time and again to people by changing direction and looking at flow rates, but if there is no flow meter, it can be very very difficult to tell.
 
Ultrafault said:
Thanks for the replies. I was hoping I had missed some arcane knoledge that would lead me to an anwser that was not incompetence. However as you guys pointed out improbility os not impossibility.

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I'm inclined to agree with others. Wire swapping seems to be the only reasonable explanation.
I don't think the how or why can be resolved at distance.
 
I have had run ins with pumps that you can not tell rotation very well so I usually put a clamp-on Amp Meter on them and check the current against the name plate data. If the pump is spinning correctly and your current is up close to FLA there you have it. But if the rotation is reversed you will see just better then no-load current.
 
Shortcircuit79 said:
I have had run ins with pumps that you can not tell rotation very well so I usually put a clamp-on Amp Meter on them and check the current against the name plate data. If the pump is spinning correctly and your current is up close to FLA there you have it. But if the rotation is reversed you will see just better then no-load current.
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the pump will always have an arrow
but often you can't see the motor
upon starting it should 'jerk' opposite the rotation
 
Ultrafault said:
The heating system was not working. When the HVAC came to the mech room the pumps were creating alot of noise. Upon visual inspection they could see the shaft was going in the wrong direction.

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OK...question....with a nameplate motor speed of over 3400 RPM, how could someone possibly see rotation direction visually? Just curious.......In your case, I would have guessed the load was driving the motor backwards due to backflow when the motor was off.

Also a comment....(of course)....When "bumping for rotation" I have always changed rotation in the pecker head, not at the starter. Starter load side was always ABC CW (that's also the way our utility wired services and substations) left to right when testing with a phase rotation tester. I also wrote the color connections on the inside of the pecker head cover. That way, you can always keep the color codes for motor loads the same at the MCC. Eliminates possible confusion if you disconnect the motor leads at the starter and you (after a rough weekend) or the guy on the next shift aren't sure how they were connected. Troubleshooting motor controls usually involves disconnecting the motor leads to prevent starting the motor. Many pumps can suffer severe damage if they are run in reverse, even for a short time. Mechanical seals, ratchet anti-backflow, etc. I guess it was my Navy and nuclear training. I taught all of the guys "under me" to do it that way as well. OK...another sermon over with! Happy New Year:dunce:
 
meternerd said:
OK...question....with a nameplate motor speed of over 3400 RPM, how could someone possibly see rotation direction visually? Just curious.......In your case, I would have guessed the load was driving the motor backwards due to backflow when the motor was off.

Also a comment....(of course)....When "bumping for rotation" I have always changed rotation in the pecker head, not at the starter. Starter load side was always ABC CW (that's also the way our utility wired services and substations) left to right when testing with a phase rotation tester. I also wrote the color connections on the inside of the pecker head cover. That way, you can always keep the color codes for motor loads the same at the MCC. Eliminates possible confusion if you disconnect the motor leads at the starter and you (after a rough weekend) or the guy on the next shift aren't sure how they were connected. Troubleshooting motor controls usually involves disconnecting the motor leads to prevent starting the motor. Many pumps can suffer severe damage if they are run in reverse, even for a short time. Mechanical seals, ratchet anti-backflow, etc. I guess it was my Navy and nuclear training. I taught all of the guys "under me" to do it that way as well. OK...another sermon over with! Happy New Year:dunce:
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Easy to check visualy, stick your finger in the coupler and see which way the blood splatters. seriously though I just bumped it while someone else observed. Your comment is dualy noted. I don't know another way to check rotation without a rotation meter however.

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A few years ago I had a small conveyor motor randomly go a different direction each time it was started, it smoked a couple days later. Other than wires getting swapped, I have nothing else to add.:)
 
Ultrafault said:
Easy to check visualy, stick your finger in the coupler and see which way the blood splatters. seriously though I just bumped it while someone else observed. Your comment is dualy noted. I don't know another way to check rotation without a rotation meter however.

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You can bump the motor and as it winds down you can usually tell which way either the shaft or motor fan is turning. Or if you have access to the fan, a small zip tie works
 
Ultrafault said:
Easy to check visualy, stick your finger in the coupler and see which way the blood splatters. seriously though I just bumped it while someone else observed. Your comment is dualy noted. I don't know another way to check rotation without a rotation meter however.

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You're right...a rotation (technically a "phase sequence meter") meter only tells you phase sequence of the voltage. They do make actual rotation testers for testing direction by rotating the shaft and watching the indicator, but I haven't used one since the nuclear plant days. Bumping the motor is the only sure way, but when a motor is already coupled or has an anti-reverse ratchet, it can get a bit tricky. Just be consistent with the starter connections and wire for rotation at the motor. Worked for me....
 
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meternerd said:
You're right...a rotation (technically a "phase sequence meter") meter only tells you phase sequence of the voltage. They do make actual rotation testers for testing direction by rotating the shaft and watching the indicator, but I haven't used one since the nuclear plant days. Bumping the motor is the only sure way, but when a motor is already coupled or has an anti-reverse ratchet, it can get a bit tricky. Just be consistent with the starter connections and wire for rotation at the motor. Worked for me....
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The same meter can do both. It will indicate rotation of supply voltages or you can spin the motor by hand to get rotation.
 
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