ETC Sensor rack low volt error

[domiii]

Our Sensor 48 rack had a blip today.

Half the dimmers in the rack were working and the blue beacon was flashing.

The errors on the rack were:

Phase C Volts Low
Phase C Headroom
Phase C Off

The rack is powered from 240v split phase not three phase so there is not phase c.

We usually shut the rack down after use.

I reset the rack a few times and the problem seems OK, and Oh I did check the votage on the two legs and all is usual.

Any ideas?

Maybe a setting changed?

Thanks

 

[Jay Ashworth]

I'm not familiar with that pack, but off hand, I would say that if it's suddenly complaining about Phase C, and you're set up for 240 split phase, that a configuration knob got frobbed somewhere, and it suddenly *thinks* it's supposed to be in 3-phase.

 

[KGacho]

What kind of CEM do you have in the rack?

 

[DavidNorth]

I am assuming you are using a CEM+ or CEM3 and that it is in a rack that is installed as opposed to a touring rack. Is this correct? If so, your power feed should be tied to A and C with B not fed. Therefore, if there was an issue with C, you would still have half the dimmers working fed by A.

Either the C feed was faulty, the control module was not fully plugged in or there may have been an issue with the control module. Did you have any storms come through? Have you had this problem before? It would be good to know.

David

 

[domiii]

I am assuming you are using a CEM+ or CEM3 and that it is in a rack that is installed as opposed to a touring rack. Is this correct? If so, your power feed should be tied to A and C with B not fed. Therefore, if there was an issue with C, you would still have half the dimmers working fed by A.

Either the C feed was faulty, the control module was not fully plugged in or there may have been an issue with the control module. Did you have any storms come through? Have you had this problem before? It would be good to know.

David

David,

Sorry it took so long to get back, but this show was cursed. We had an actress quit the Tuesday before our Friday opening so I was very busy, oh it is a six character show so she was a major character. Then I had a short vacation after opening.

Yes it is a CEM+. Sensor 48 rack.

I plugged the CEM in and out a few times and it just started working.

Yes we have had some weather we are in NJ so we have had snow, sleet and rain but, I don't think that was an issue.

I did check both legs and the voltage was OK.

Yes we have had this problem twice before. We repalced two air conditioning units since then and I thought that might be the problem. AC units kicking in and dropping the voltage, but this time no AC only heat (oil not electric).

We are leaving the rack on until the run is over. We usually shut it down. All seems OK now.

Any ideas?

 

[DavidNorth]

Oh my. You've had quite the show.

I'm glad to hear that it is working again but since the problem has happened before, I am assuming that it will happen again. Let's see what we can do to nail this down.

Temporary power glitches by devices such as AC units should not create a lasting error such as what was posted. For some reason, the control module thinks there is no voltage feed on Phase C. Now, I do have concerns regarding what may have happened to require two AC units to be replaced. If a power hit caused them to fail, the same incident could have damaged the CEM+. Not likely, but possible.

- The CEM+ may have a fault that occasionally causes loss of Phase C sensing. We would have to see it here.
- The backplane connector and or power harness may be damaged and need to be replaced. This could be done by a technician.
- The nut for the door lock could be in the wrong position thereby pushing on the CEM+ and causing a loss of contact to the power connector. You can check this.

Ok, so those reading, and of course you, will want to know what I'm talking about. On a SR48+, take a quick look on the inside of the door where the door lock is mounted. There will be a hex nut securing the lock in place. The flats of the nut need to be vertical and if they are not [such as some early racks or upgraded racks], then tighten the nut slightly so that the hex nut points are up and down. Does that make sense?

Why does this matter? With the flats horizontal, it is possible that the point of the nut will push on the right side of the CEM+ and cause the left side to rock out of the rack slightly with a loss of power sensing.

Take a quick look. If that isn't the problem, then we likely will want to send someone in there to take a look at the power connections and harness.

Let me know,

David

 

[Jay Ashworth]

For the record, David, that's probably too tight a tolerance in design. :-}

 

[DavidNorth]

For the record, David, that's probably too tight a tolerance in design. :-}

I can't disagree with you. Things looked great in Solidworks, and then we put the door on. Oh well.

 

[zmb]

Oh Solidworks. Are you sure the drawing pulled in all the dimensions and that you added the needed driven dimensions? Better run another Interference Check and hope for the suceess chime.

I just finished a quarter long technical drawing and CAD class. Had a semi-relaxing evening trying to clean up a drawing for my final project.

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