Design Help With Tripping ETC Dimmer Breakers

[Don Lomonaco CFCRC]

I'm posting this here because I was told that many ETC folks are around. I also chose Design Issues and Solutions because, in my research, I believe this lighting system was not designed with the 80% load rule in mind.

Hi all! We have an ETC Unison DRD 12-24-120 with 10 D20 modules and a CMeD control module. The entire Unison cabinet is wired to a dedicated 150 Amp breaker. We're using 19 circuits on those modules in the following way:

10 circuits each with 1 ETC Source Four 750 watt fixtures and a 575 watt lamp.

9 circuits each with 4 ETC Source Four PAR EA 750 watt fixtures with 575 watt lamps.

When we turn the all 19 circuits up all the way using our ETC SmartFade console we have a tendency to trip some of the dimmer module breakers that are wired to groups of 4 par cans. Doing the math it seems that four 575 watt lamps at 100% would require 2.3k watts on a 2.4k watt dimmer circuit. Am I correct in thinking that this plan is just too close to the maximum power available and that's why these circuits continue to trip?

Ok. With some further testing I have these results. I think we're close to getting to the bottom of this.

Circuit 1-4 lamps running will trip in 1:26.
Circuit 4-4 lamps running will trip in 0:33.
Circuit 3-4 lamps running will occasionally trip (time cannot be determined).
Circuit 9-4 lamps running will trip in 0:42.

Circuit 10-3 lamps running because 1 is burned out will not trip.
Circuit 2-3 lamps running because 1 is burned out will not trip.
Circuit 11-2 lamps running because 2 are burned out will not trip.
Circuit 12-3 lamps running because 1 is burned out will not trip.
Circuit 5-3 lamps running because 1 is burned out will not trip.

I've swapped out some modules from the circuits used to control the spots and the same banks of par cans trip regardless of the module.

All lugs are secure. None were loose. After a general dust blasting all dimmers are back in place with the same results. I've attached a pic of the inside of the unit.

I'm checking wall outlets in the building while I arrange a lift in place and obtain a twofer to take measurements at the light source and to verify that each lamp is a 575 watt. Verdict so far: each outlet is reading 124.7 or 124.8 volts ac.

Ok. Maximum fader values for each troublesome circuit are:

Circuit 1-8
Circuit 4-7
Circuit 3-10 (continues to be intermittent)
Circuit 9-8

I scrolled through the menu on the command module and verified that each circuit is set to the correct module (the D20), it's set to incandescent, it's DMX channel corresponds to it's circuit number, and that dimmer doubling is off.

I've exchanged emails with ETC. Very helpful in their responses and even cc'd a local service company. The software can be reprogrammed. They also recommended lamping down.

Our current wiring is 12AWG/600volt/20AMP.

Final thoughts:

1. If we want to move to a 5k dimmer we would have to buy a 230volt DRD unit, upgrade the building wiring to 6AWG/600 volt/55AMP and purchase new dimmers.

2. Best solution may be to swap out 1 lamp out of the groups of 4 with a 375 watt and determine if this voltage reduction is enough to eliminate trips when the fader is raised to it's full value.

 

[wolfman005]

I usually limit myself to 3 fixtures per 2.4kw circuit regardless of the lamp wattage. Rather have a stage that is a bit dimmer than a stage that randomly blacks out.

 

[Don Lomonaco CFCRC]

Does anyone even make a 375 watt 120 volt lamp? Or am I going to have to use a 375 watt 115 volt lamp?

 

[JohnD]

Has any thing changed with this system? How old is it, has it always been set up with 4 x 575W lamps, has it just recently started tripping breakers?

 

[Don Lomonaco CFCRC]

The system is appx 5 years old. No changes to it. It was installed with 575 watt lamps. The tripping has been going on for some time now.

 

[STEVETERRY]

I'm posting this here because I was told that many ETC folks are around. I also chose Design Issues and Solutions because, in my research, I believe this lighting system was not designed with the 80% load rule in mind.

Hi all! We have an ETC Unison DRD 12-24-120 with 10 D20 modules and a CMeD control module. The entire Unison cabinet is wired to a dedicated 150 Amp breaker. We're using 19 circuits on those modules in the following way:

10 circuits each with 1 ETC Source Four 750 watt fixtures and a 575 watt lamp.

9 circuits each with 4 ETC Source Four PAR EA 750 watt fixtures with 575 watt lamps.

When we turn the all 19 circuits up all the way using our ETC SmartFade console we have a tendency to trip some of the dimmer module breakers that are wired to groups of 4 par cans. Doing the math it seems that four 575 watt lamps at 100% would require 2.3k watts on a 2.4k watt dimmer circuit. Am I correct in thinking that this plan is just too close to the maximum power available and that's why these circuits continue to trip?

Ok. With some further testing I have these results. I think we're close to getting to the bottom of this.

Circuit 1-4 lamps running will trip in 1:26.
Circuit 4-4 lamps running will trip in 0:33.
Circuit 3-4 lamps running will occasionally trip (time cannot be determined).
Circuit 9-4 lamps running will trip in 0:42.

Circuit 10-3 lamps running because 1 is burned out will not trip.
Circuit 2-3 lamps running because 1 is burned out will not trip.
Circuit 11-2 lamps running because 2 are burned out will not trip.
Circuit 12-3 lamps running because 1 is burned out will not trip.
Circuit 5-3 lamps running because 1 is burned out will not trip.

I've swapped out some modules from the circuits used to control the spots and the same banks of par cans trip regardless of the module.

All lugs are secure. None were loose. After a general dust blasting all dimmers are back in place with the same results. I've attached a pic of the inside of the unit.

I'm checking wall outlets in the building while I arrange a lift in place and obtain a twofer to take measurements at the light source and to verify that each lamp is a 575 watt. Verdict so far: each outlet is reading 124.7 or 124.8 volts ac.

Ok. Maximum fader values for each troublesome circuit are:

Circuit 1-8
Circuit 4-7
Circuit 3-10 (continues to be intermittent)
Circuit 9-8

I scrolled through the menu on the command module and verified that each circuit is set to the correct module (the D20), it's set to incandescent, it's DMX channel corresponds to it's circuit number, and that dimmer doubling is off.

I've exchanged emails with ETC. Very helpful in their responses and even cc'd a local service company. The software can be reprogrammed. They also recommended lamping down.

Our current wiring is 12AWG/600volt/20AMP.

Final thoughts:

1. If we want to move to a 5k dimmer we would have to buy a 230volt DRD unit, upgrade the building wiring to 6AWG/600 volt/55AMP and purchase new dimmers.

2. Best solution may be to swap out 1 lamp out of the groups of 4 with a 375 watt and determine if this voltage reduction is enough to eliminate trips when the fader is raised to it's full value.

What voltage are the 575W lamps--115V or 120V?
What is the voltage at the circuit outlet with the dimmer at full and the load connected (measured using a true-RMS-responding meter)?

We may be able to help if we know the answers to those questions.

Steve Terry
VP R&D
ETC

 

[Don Lomonaco CFCRC]

120volt lamps. GE HPL575X-C. I'm arranging a lift and a twofer to get to the outlets to verify voltage and physically verify that all lamps are that model.

 

[John Palmer]

Hi Don,
I think there are a few issues that are compounding your problem.
Please excuse me if I ask simple questions to better understand the situation, I do not mean anything personal by it.

This is a Unison system. Do you have the problem with breakers tripping when you use any Unison presets?
Are you able to read the Unison configuration to know what level those dimmers with 4 PARs are being driven at by Unison? (unison menu [Diagnostics]-[Dimmers])
Has the problem only been noticeable since you started using the SmartFade console?

Now, some observations.
Ohm's law is arbiter of Amperage not W=VA. 120V lamps on a system of 124.7V are drawing around 4.98A.
(Math - to find current draw of 120V lamp at 120V W=VA __ 575=120/A A=575/120 A=4.79 amps
to find the resistance of the filament I=V/R__4.79=120/R R=120/4.79 R=25.05 ohms
to find the current draw of this lamp at 124.7V I=V/R__ I=124.7/25.05 I=4.98 amps So, 4 lamps create a load of 19.92 amps.)

If the wire pulls are long, the use of 12awg wire for a 20A load is possilbly not code compliant and probably inadequate. In the lobby of my space, the 20A dimmers are wired with 10awg wire. The stage circuits are 8awg for the 20A circuits. I don't know my NEC code well enough to be sure without pulling out my book, but I think that resistance due to wire size/# per conduit/load is also increasing the current draw on the breaker of your dimmer. Dimmers are often not thought to be continuous use devices, but if a 20A load is placed on the circuit for 3-4 hours as for a lobby circuit during a performance, it really should be designed with a maximum of 80% rated capacity.

When you fix the burnouts, the breakers on those dimmers will most likely trip as well.

One 575W/115V lamp in this mix will certainly put you over the max current.

A loose hot or neutral on different circuits which causes arcing and therefore an increase in heat will increase the resistance in the cable. I know that you checked the lugs, but all terminal strips and connectors and two-fers could be suspect.

You have to be careful how you balance your load across the whole rack. This rack is being fed by single phase power and is not balanced. One leg is feeding dimmers 1-8, and the other leg feeds 9-19(or 24 if the rack was fully loaded). Nominally, you have 115A on the first leg and 100A on the second. With the feed being 150A, you are near the maximum that you would want it to be if you derate the main breaker to 80% for continuous use.)

More than an entertainment lighting company, I think you need a licensed electrician and/or electrical engineer.

Good luck,
John

 

[Scenemaster60]

Do you know what your incoming line voltage is? That can have an effect on this issue as well.

 

[Don Lomonaco CFCRC]

Hi Don,
I think there are a few issues that are compounding your problem.
Please excuse me if I ask simple questions to better understand the situation, I do not mean anything personal by it.

This is a Unison system. Do you have the problem with breakers tripping when you use any Unison presets?
Are you able to read the Unison configuration to know what level those dimmers with 4 PARs are being driven at by Unison? (unison menu [Diagnostics]-[Dimmers])
Has the problem only been noticeable since you started using the SmartFade console?

Now, some observations.
Ohm's law is arbiter of Amperage not W=VA. 120V lamps on a system of 124.7V are drawing around 4.98A.
(Math - to find current draw of 120V lamp at 120V W=VA __ 575=120/A A=575/120 A=4.79 amps
to find the resistance of the filament I=V/R__4.79=120/R R=120/4.79 R=25.05 ohms
to find the current draw of this lamp at 124.7V I=V/R__ I=124.7/25.05 I=4.98 amps So, 4 lamps create a load of 19.92 amps.)

If the wire pulls are long, the use of 12awg wire for a 20A load is possilbly not code compliant and probably inadequate. In the lobby of my space, the 20A dimmers are wired with 10awg wire. The stage circuits are 8awg for the 20A circuits. I don't know my NEC code well enough to be sure without pulling out my book, but I think that resistance due to wire size/# per conduit/load is also increasing the current draw on the breaker of your dimmer. Dimmers are often not thought to be continuous use devices, but if a 20A load is placed on the circuit for 3-4 hours as for a lobby circuit during a performance, it really should be designed with a maximum of 80% rated capacity.

When you fix the burnouts, the breakers on those dimmers will most likely trip as well.

One 575W/115V lamp in this mix will certainly put you over the max current.

A loose hot or neutral on different circuits which causes arcing and therefore an increase in heat will increase the resistance in the cable. I know that you checked the lugs, but all terminal strips and connectors and two-fers could be suspect.

You have to be careful how you balance your load across the whole rack. This rack is being fed by single phase power and is not balanced. One leg is feeding dimmers 1-8, and the other leg feeds 9-19(or 24 if the rack was fully loaded). Nominally, you have 115A on the first leg and 100A on the second. With the feed being 150A, you are near the maximum that you would want it to be if you derate the main breaker to 80% for continuous use.)

More than an entertainment lighting company, I think you need a licensed electrician and/or electrical engineer.

Good luck,
John

Thanks John! I will test the system using the Unison control panel and report the results. In addition I will check the menu settings you suggested. I'll also research the install and verify the NEC code in my area. All great observations. Thanks!

 

[Don Lomonaco CFCRC]

Do you know what your incoming line voltage is? That can have an effect on this issue as well.

I'll test the incoming line voltage and report back.

 

[JD]

Circuit breakers are not perfect devices, they have some tolerances. Sounds like a combo of high line voltage, fully loaded circuits, and breakers that may be tripping a bit too early. Yes, you might be able to have the breakers changed and that -may- fix the problem, but there is just no headroom in the setup. You may also find that the new breakers trip as well. Lamps have a bit of tolerance in design as well. ETC is rated for 100% duty cycle, but is this good practice? In my own opinion it is better to always leave headroom on a circuit. It also helps extend the life of the SSRs.
Regarding wire gauging- He's right, long runs require you to up-gauge. Is this part of your problem? No. If anything, the thinner wire adds series resistance to the loop lowering the current slightly.*
Now, if you start seeing breakers trip with 3 lamps @575, then you have a problem!

*Note: True for resistive loads such as conventional fixtures. Not true for switching power supplies or electronic ballasts, which may actually compensate for the long run by drawing more current.

 

[Don Lomonaco CFCRC]

I'm leaning towards buying two new D20 modules and wiring the 575's 3 to a circuit rather than 4. That's a solution I should have listed in the original post.

I'm very much inclined to agree that headroom needs to be present in every design no matter what the manufacturer specs are.