Phase Monitor Question

[jsharvey]

I have a question about a phase monitor we have on one of our A/C units here. The local utility is coming tomorrow to change out a voltage regulator on their lines. The A/C in question has a phase monitor and has been tripping a 60 3 pole breaker that is part of the control box, and this unit provides cooling for a building that has a genset and ATS. My questions are, if the voltage on one phase was dropping to a point where the increased amperage would be high enough to trip the 60A breaker, shouldn't the phase monitor drop out and open the control circuits to the contactor that provides power to the unit? And secondly, wouldn't the sensors in the ATS detect the drop of power on the one phase and start up the genset? Sorry I don't have any better specs on the equipment as I was notified of this via email after I was home from work.
And for our utility guys, Where would a voltage regulator be on the utility lines? I don't work on the utility stuff and I've never heard of on used primaries.
TIA

 

[ptonsparky]

Depending on how the monitor is set and if it is working will determine why it shuts down the control. Sounds like you have an overload or faultnof some sort if it trips a breaker first.

I believe the regulators are on the primary.

 

[Jraef]

"Phase monitor" can mean just about anything, people throw that term around without knowing what it is actually looking for. It may be just a phase LOSS monitor and the condition for detecting a "loss" may be a very low threshold. No way to know without specs.

It also could be that you had a CURRENT increase in one leg without it being caused by low voltage. If the PM was looking only at voltage and not current, it may have been perfectly happy.

Also, some el-cheapo PMs look only at voltage levels and not voltage balance, so they can get fooled by the motor regenerating on a lost leg, like a rotary phase converter. Better one's have better monitoring, but my experience with the HVAC industry is that they rarely use the "better ones" of anything.

 

[Cow]

Depending on how the monitor is set and if it is working will determine why it shuts down the control. Sounds like you have an overload or faultnof some sort if it trips a breaker first.

I agree. If you're breaker is tripping I'd be looking for a fault/overload, not at the phase monitor....

 

[qcroanoke]

I have a question about a phase monitor we have on one of our A/C units here. The local utility is coming tomorrow to change out a voltage regulator on their lines. The A/C in question has a phase monitor and has been tripping a 60 3 pole breaker that is part of the control box, and this unit provides cooling for a building that has a genset and ATS. My questions are, if the voltage on one phase was dropping to a point where the increased amperage would be high enough to trip the 60A breaker, shouldn't the phase monitor drop out and open the control circuits to the contactor that provides power to the unit? And secondly, wouldn't the sensors in the ATS detect the drop of power on the one phase and start up the genset? Sorry I don't have any better specs on the equipment as I was notified of this via email after I was home from work.
And for our utility guys, Where would a voltage regulator be on the utility lines? I don't work on the utility stuff and I've never heard of on used primaries.
TIA

If it is a Bard wall mount unit the phase monitor only looks at phase rotation being correct as far as I know. It will not let the compressor run if phase rotation is not ABC. It will let the fan run though. It is mostly to protect the compressor from damage because if it is a scroll compressor they do not like to run backwards.

 

[jsharvey]

More Info

More Info

OK, now that I'm at work, what I have is a ICM Controls ICM 450 programable 3 phase voltage monitor that has a memory for 25 fault events. It has a set of NO/NC dry contacts on it that are wired into the 115V control voltage line, that are programed to open if there is a fault condition. Over and undervolt are programed to 10% and a %5 phase inbalance, 5 second delay on a fault. With that being said, assuming it was intalled and programmed correctly and is still operational, it seems to me that the contact would open long before there was enough of an amperage increase on the faulted leg to trip the breaker? And if that was the case the gensets monitors would detect it also and start the generator?

 

[Jraef]

...assuming it was intalled and programmed correctly and is still operational, it seems to me that the contact would open long before there was enough of an amperage increase on the faulted leg to trip the breaker? And if that was the case the gensets monitors would detect it also and start the generator?

That unit is not looking at amperage, only voltage issues. It also is supposed to just drop out the control circuit, but the breaker will not trip based on what this unit does (unless there is a Shunt trip connected to the 115V circuit).

So to answer your question, I agree; any voltage anomaly serious enough to cause the breaker to trip should have long-ago been detected and acted on by this device. So that leave non-voltage related current problems as the likely source of your issues here; i.e.
1) You have a short somewhere, or
2) You have a serious overload, or
3) It maybe a short-cycling problem. Check the "Delay on Break" programming for that issue. If it's set to "0" and you have a LV trip because the regulator was bad, it will auto-reset immediately if the LV problem corrects when the load drops out, meaning it will rapidly cycle on and off repeatedly, which could definitely make the CB trip.

Check your log of the last 25 events. If they are all LV and follow each other very closely (can't tell if it time stamps them though), I'd guess it is #3.