This out building is used for recycling and is fed with a 3 phase 100 amp service. One of the rooms has 5 4oowatt lamps for lighting. We installed a motion sensor in that area and when we shut off the circuit the lights just went dim. I measured voltage on the hot and neutral in that area and when the circuit is off it has about 63 volts, and when it is on it is about 116 volts. My quess is a lose neutral. I'm having a tough time visualizing this problem. Would someone help me out with finding where the problem is and the theory behind it.
Troubleshooting branch circuits
- Thread starter JdoubleU
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hardworkingstiff
Senior Member
- Location
- Wilmington, NC
I agree you need to be looking for a neutral problem.
It could be at or close to the service equipment.
It could be at or close to the service equipment.
cadpoint
Senior Member
- Location
- Durham, NC
IF you took a reading of all that you could read from a meter or any appropriate device
Why do you qualify that is at point of orgin of the point of service?
Why do you qualify that is at point of orgin of the point of service?
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
081128-2033 EST
Jakewhis:
It is necessary to more clearly define what you are talking about.
First, some assumptions.
1. Assume the source is 3 phase Y and presumably with a neutral from the source to the load area (outbuilding). Also means there should be an EGC (Equipment Grounding Conductor) from the main panel to the destination. That line to line the voltage is 208 V and any line to neutral is 120 V at the source and should be at the destination.
2. The lights are 120 V and one side of the lamps is connected to neutral.
3. No idea where the dimmer is located or how it is wired.
4. No idea if the lamps are fed from a single pole breaker or one pole of a three pole breaker.
5. No idea what other loads are connected to the three phase system at the destination.
6. What does this statement mean? "I measured voltage on the hot and neutral in that area ----". Does this mean between hot and neutral or to some other reference like earth, or the EGC, or what?
You do not measure voltage on something without a reference. You measure voltage between points, and you measure current at a point.
We need to know what all the loads are that are connected to the four wires (A, B, C, and neutral) coming from the main panel? What kind of breaker or breakers are supplying the destination? How many wires to the destination? Is there an EGC?
Most likely from your description you were measuring the voltage across your destination lamps, and that there are other loads at the destination that connect to other legs of the three phase source, and that there is not one single three pole breaker at the main panel supplying the destination.
To troubleshoot this problem you need clarification of the actual circuit and loads.
.
Jakewhis:
It is necessary to more clearly define what you are talking about.
First, some assumptions.
1. Assume the source is 3 phase Y and presumably with a neutral from the source to the load area (outbuilding). Also means there should be an EGC (Equipment Grounding Conductor) from the main panel to the destination. That line to line the voltage is 208 V and any line to neutral is 120 V at the source and should be at the destination.
2. The lights are 120 V and one side of the lamps is connected to neutral.
3. No idea where the dimmer is located or how it is wired.
4. No idea if the lamps are fed from a single pole breaker or one pole of a three pole breaker.
5. No idea what other loads are connected to the three phase system at the destination.
6. What does this statement mean? "I measured voltage on the hot and neutral in that area ----". Does this mean between hot and neutral or to some other reference like earth, or the EGC, or what?
You do not measure voltage on something without a reference. You measure voltage between points, and you measure current at a point.
We need to know what all the loads are that are connected to the four wires (A, B, C, and neutral) coming from the main panel? What kind of breaker or breakers are supplying the destination? How many wires to the destination? Is there an EGC?
Most likely from your description you were measuring the voltage across your destination lamps, and that there are other loads at the destination that connect to other legs of the three phase source, and that there is not one single three pole breaker at the main panel supplying the destination.
To troubleshoot this problem you need clarification of the actual circuit and loads.
.
wallyworld
Senior Member
Did the lights before the motion sensor? If so look at the motion detector
donselectric
Senior Member
- Location
- nh
if the breaker is off and your reading voltage there has to be a backfeed somewhere and or your reading thru something.... be my thinking
agree.. off the top of my head I'd say someone has a 240 (208) volt piece of equipment tied to another breaker and yours. Turn off other breakers until the 63 v disappears and see what's connected.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Is this a two wire or is it a three wire motion sensor? When you say the lights go dim when the circuit is off, are you meaning when the breaker is turned off, or when the motion sensor turns them off? Also there is a motion sensor that is used with HID lights that does dim them when there is no motion, since it is not practical to turn them all of the way off. Are these incandesant, or HID?
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
I just reread the original post, being 400 watt lamps I would venture a guess that these are HID, probably metal halide. The motion sensor will be one that dims the lamps instead of turning them off if designed properly. You will get 63 volts when they are dimmed.
I was wondering about that!
Why on earth would someone put a motion sensor on 400 watt lights? But now this makes sense so long as it just dims them...
And a couple of questions...
This I assume would save half the electricity?
And do the lights come up full brightness when someone enters the room?
Or does it take awhile to get to full brightness (HID)?
Can this work with MH and HPS?
Why on earth would someone put a motion sensor on 400 watt lights? But now this makes sense so long as it just dims them...
And a couple of questions...
This I assume would save half the electricity?
And do the lights come up full brightness when someone enters the room?
Or does it take awhile to get to full brightness (HID)?
Can this work with MH and HPS?
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
I know that it is used on Metal Halides, and I think I have seen it on High Pressure Sodiums also. It instantly goes to full brightness when motion is detected. Used a lot for aisle lighting, when the forklift enters the aisle, lights come up to full. Since the arc is not interupted, cool down is not required for the lamp to come back to full brightness. The orange box used to use something simular, but without the motion sensing. A large dimming cabinet called a Peschel dimmer would slowly dim the lights in the store on sunny days. The problem was surges would take out the rectifers on the brushes that ran up and down the transformer face, causing the lights to flicker as they dimmed in the best case, and a fire in the worst case. They no longer use this system now, and are converting to T5 flouresents.
donselectric
Senior Member
- Location
- nh
didnt he say with breaker off...???.... :-?
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