3 phase motor reversing with no circuit changes.

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Ultrafault

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We had a situation at work where 2 of our three phase 208 volt motors started running in the wrong direction without any cause and needed to have the leads swapped to go in the forward direction. They ran in the correct direction the day before.

This is not the first time this has happened in this building, however, to different equipment; according to my co-workers. The two motors are directly across from eachother on the panel. The panel has 4 other similar pumps which continued to run in a forward direction without modification. The 4 other pumps would not have been on for some time as they supply chillers and condensors. These pumps supply hot water.

I have attached the nameplates of the pumps that have reversed without cause and apicture of the contactors. You can see that the left contactors have leads swapped to reverse the motors.

I would have said this was impossible if it had not happened. Could anyone help me understand what has happened or suggest things I should check to figure out?
Any help or ridicule would be appriciated.
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MAC702 said:
Check wires at the breakers, too. Maybe someone is screwing with you?

To verify, the motors that did not change direction are also 3-phase?
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good call. They are not modified. The panel looks good.
I should add measurments to help.
motor 1:
L1-L2 209
L1-L3 212
L2-L3 208
L1g 122
L2g 120
L3g 122
I L1 1.8A
I L2 1.5A
I L3 1.6A

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Ultrafault said:
I would have said this was impossible if it had not happened. Could anyone help me understand what has happened or suggest things I should check to figure out?
Any help or ridicule would be appriciated.
Click to expand...

actually, no.

to clarify this, you are saying two, and only two, 3 phase motors
had to have their direction reversed, and none of the other three
phase motors in the building needed reversing?

all on the same service? did you look inside the peckerhead, and
see if leads were changed somewhere else?
 
Ingenieur said:
how did you determine the rotation was incorrect?
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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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Fulthrotl said:
actually, no.

to clarify this, you are saying two, and only two, 3 phase motors
had to have their direction reversed, and none of the other three
phase motors in the building needed reversing?

all on the same service? did you look inside the peckerhead, and
see if leads were changed somewhere else?
Click to expand...
Only 2 of 6. The are actualy fed from the same distribution panel. Only the 2 that are reveresd were on within the last 3 weeks. I have not checked the connection box. someone tampering in this locked room is unlikely.

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Any two phases were changed. Otherwise, it is impossible to change rotation. Trace the wiring completely to locate where phase change has taken place.
 
how long has the installation been completed?

it is not uncommon for pumps to be wired backwards, and not noticed
they still flow water, but low flow and pressure
might take a cold day to notice it

unless miswired, no way for a pump to spontaneously change direction
 
Ingenieur said:
how long has the installation been completed?

it is not uncommon for pumps to be wired backwards, and not noticed
they still flow water, but low flow and pressure
might take a cold day to notice it

unless miswired, no way for a pump to spontaneously change direction
Click to expand...
In place for at least 10 years. This has been right next to the desk where at least 3 seperate HVAC techs have sat all day.

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Your conductors got contaminated with positrons. I have seen it before. Seriously though, every now and then we get some really strange ones and there are 2 explanations:

1. Some one misunderstood or got incorrect information.

2. Some one is screwing with somebody
 
It has been reported to me that the chillers in the same buildig jave had this same problem. I did not belive it untill today.

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Locked room, who was:
1) In that room last and why?
2) In that gear and why?
3) When was the last time pm/ new equipment feed from that gear was done?
4) Do you have one or two maintenance personnel that are "qualified" yet we all know they are not, who might fix the color sequences when in the gear to "help" since I'm in here anyway?
 
Possibility: a phase reversal happened on the POCO service to the building and either nobody noticed that some pumps were (and still are) running backwards or somebody "corrected" the phasing, but only on those pumps that were operating at the time.

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I have seen single phase motors spontaneously reverse direction when enough counter-torque was applied by the load.

I didn't think that was possible in a 3 phase motor because of the orientation of the windings. But if the 3 phase motors were single phasing, and the backpressure on the impeller was able to spin the pumps in reverse, I think the motor would take off in the opposite direction.

That said, you say you've got current readings on all three phases, so unless there was a measurement error, it would tend to rule that out.
 
Ultrafault said:
It has been reported to me that the chillers in the same buildig jave had this same problem. I did not belive it untill today.

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Click to expand...

it is not physically possible without:
someone intentionally doing it
the service was reversed

do you actually believe it reversed rotation all by itself with no change to the service or wiring?
 
After reading your posts and talking with the lead HVAC I think the most likely scenario is this: The pumps feed the same loop. The top pump apears signifigantly newer than the bottom. The lead said he wouls not be suprised if the tech responsible for that building put the new pump in going in reverse. It is most likley that the bottom pump ran in reverse since orignal install and the top pump has since it was changed. They probably did not notice this untill the demand reached the point both of the boilers in the loop were needed.

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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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