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Title: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 04:16:55 PM
Hi all!  We have an ETC Unison DRD 12-24-120 with 10 D20 modules.  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?
Title: Re: Help With Tripping Dimmer Breakers
Post by: g'bye, Dick Rees on August 04, 2014, 04:18:37 PM
Wiring?
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 04:25:53 PM
Wiring?

I'll have to look into it and report back.  What type of wiring should I be looking for?
Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 04, 2014, 04:27:33 PM
Hi all!  We have an ETC Unison DRD 12-24-120 with 10 D20 modules.  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?
Do they trip right away, or over time?

ETC breakers are rated at 100% duty cycle, so theoretically it should be possible to run 4 575w fixtures on one circuit.  HOWEVER, the power consumption of your bulbs depends heavily on the voltage at the fixture.  Have you measured your facility voltage?  If you trend a little high - more than 120V, you may have too much voltage at your fixtures, causing your bulbs to effectively be more than 575w loads. 

If you're having trouble, make sure you're using the 120V rated bulbs instead of the 115V bulbs.

You may also want to check your lugs in your dimming equipment to make sure that all connections are tight, and that you aren't adding to the ambient temperature in your dimmer rack with heat from loose connections.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 04:30:29 PM
I'll have to look into it and report back.  What type of wiring should I be looking for?

It looks like the red, blue and white wires inside the dimmer box are all 10 AWG.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 04:33:36 PM
Do they trip right away, or over time?

ETC breakers are rated at 100% duty cycle, so theoretically it should be possible to run 4 575w fixtures on one circuit.  HOWEVER, the power consumption of your bulbs depends heavily on the voltage at the fixture.  Have you measured your facility voltage?  If you trend a little high - more than 120V, you may have too much voltage at your fixtures, causing your bulbs to effectively be more than 575w loads. 

If you're having trouble, make sure you're using the 120V rated bulbs instead of the 115V bulbs.

You may also want to check your lugs in your dimming equipment to make sure that all connections are tight, and that you aren't adding to the ambient temperature in your dimmer rack with heat from loose connections.

It takes a few minutes for them to begin to trip.  The lamps in the par cans are GE 120V.
Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 04, 2014, 04:37:48 PM
It takes a few minutes for them to begin to trip.  The lamps in the par cans are GE 120V.
Measure your facility voltage, and if you can, put a twofer at one of your fixtures, and do a voltage measurement with the light on.  This will tell you the voltage through the whole system at the fixtures.

I don't recall if there's a way to tweak max output in the Unison, but you may be able to limit the channels that are problematic to 95%, which would likely solve the issue.  You could manually do the same thing on your board by only raising the master fader to slightly less than full scale.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 04:44:07 PM
Measure your facility voltage, and if you can, put a twofer at one of your fixtures, and do a voltage measurement with the light on.  This will tell you the voltage through the whole system at the fixtures.

I don't recall if there's a way to tweak max output in the Unison, but you may be able to limit the channels that are problematic to 95%, which would likely solve the issue.  You could manually do the same thing on your board by only raising the master fader to slightly less than full scale.

Yeah, that's what we've been doing, only using slightly less than maximum on all the faders that control the par can circuits.  It seems to only be the same two circuits that are tripping.  It takes about 1 minute for them to go.
Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 04, 2014, 04:47:02 PM
Yeah, that's what we've been doing, only using slightly less than maximum on all the faders that control the par can circuits.  It seems to only be the same two circuits that are tripping.  It takes about 1 minute for them to go.
If they trip that fast, that suggests to me that something fairly drastic is wrong.  Are you sure you don't have a couple 750w bulbs on those circuits?  Check the tightness of screws in the dimmer panel, measure the voltage in your facility to make sure you aren't running too far above nominal - both at the dimmer and at the fixture if possible, and verify that all bulbs are 575w 120v.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Cailen Waddell on August 04, 2014, 05:06:49 PM
It's also possible you have a worn out breaker on one module and or a heat issue there.  Try moving modules around (but turn off rack power before doing so for arc flash safety).  If the problem follows the module... There ya go....
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 05:07:52 PM
If they trip that fast, that suggests to me that something fairly drastic is wrong.  Are you sure you don't have a couple 750w bulbs on those circuits?  Check the tightness of screws in the dimmer panel, measure the voltage in your facility to make sure you aren't running too far above nominal - both at the dimmer and at the fixture if possible, and verify that all bulbs are 575w 120v.

Now I'm not so sure these lamps are 120v.  Here's a pic.  When I search for replacements I see them listed as 115v. The model number on the bulb is HPL575X-C.

Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 04, 2014, 05:23:27 PM
Now I'm not so sure these lamps are 120v.  Here's a pic.  When I search for replacements I see them listed as 115v. The model number on the bulb is HPL575X-C.
That can be confusing.  Here is a 120V long-life bulb:
http://bulbman.com/stage-studio-c-1_284_293/hpl575120x-p-405.html
Title: Re: Help With Tripping Dimmer Breakers
Post by: Cailen Waddell on August 04, 2014, 05:58:23 PM
There are several versions of hpl 575s.   The ones we are concerned about are the 575-115x and the 575-120x.  Generally etc dimmers show about a 3 to 4% drop in output at 100% so if your incoming voltage is 120, use a 115 lamp, if it's 125, use a 120.  The x btw indicates a reduced output long life lamp.  2000 hours versus 300 I think.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 06:02:46 PM
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.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Cailen Waddell on August 04, 2014, 06:47:36 PM
Don I don't think a unison rack will show voltages, like an etc dimmer rack does, but the advantage is a unison rack has an 8 year warranty....  Anyway, I would guess that you have low voltage.  You have a 2300w load, at 115v that is 20 amps.

2 options - ask an electrician to check your voltage, see if you are getting low voltage from the poco.  Otherwise, if you can't change your voltage, relamp with the 375w lamps. 
Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 04, 2014, 06:59:09 PM
Don I don't think a unison rack will show voltages, like an etc dimmer rack does, but the advantage is a unison rack has an 8 year warranty....  Anyway, I would guess that you have low voltage.  You have a 2300w load, at 115v that is 20 amps.

2 options - ask an electrician to check your voltage, see if you are getting low voltage from the poco.  Otherwise, if you can't change your voltage, relamp with the 375w lamps.
Low voltage in this case would be a good thing. I suspect he has high voltage.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 07:19:38 PM
Low voltage in this case would be a good thing. I suspect he has high voltage.

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.  Verdict so far:  each outlet is reading 124.7 or 124.8 volts ac.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Cailen Waddell on August 04, 2014, 07:37:38 PM

Low voltage in this case would be a good thing. I suspect he has high voltage.

It may be the end of a long day for me so I may not be thinking of this clearly, but a light bulb is a constant wattage or resistance, therefore if the voltage goes down, the current goes up, causing the breaker to trip, if the voltage is high, the current is lower, allowing the bulb to blow but not trip the breaker....

Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 04, 2014, 07:47:58 PM
It may be the end of a long day for me so I may not be thinking of this clearly, but a light bulb is a constant wattage or resistance, therefore if the voltage goes down, the current goes up, causing the breaker to trip, if the voltage is high, the current is lower, allowing the bulb to blow but not trip the breaker....
Nope. A lightbulb is a simple device - as the voltage goes up, the current goes up too. A filament's resistance is not linear, but more voltage always means more current, and less voltage means less current.

Induction motors work the way you are describing to some degree.
Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 04, 2014, 07:49:23 PM
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.  Verdict so far:  each outlet is reading 124.7 or 124.8 volts ac.
that's on the high side, and could be problematic with 115V bulbs.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Cailen Waddell on August 04, 2014, 07:52:58 PM

Nope. A lightbulb is a simple device - as the voltage goes up, the current goes up too. A filament's resistance is not linear, but more voltage always means more current, and less voltage means less current.

Induction motors work the way you are describing to some degree.

You are, of course correct, I just reread what I wrote, and yeah - it's wrong.   Anywho, I'm not sure 124vac would be enough to trip the breaker but it might.... 

To the OP, What control module is in that drd rack?  A simple edit of the config can make the rack max those dimmers out at 95% or whatever you choose....

I would still lamp down to 375 though....
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 08:06:17 PM
You are, of course correct, I just reread what I wrote, and yeah - it's wrong.   Anywho, I'm not sure 124vac would be enough to trip the breaker but it might.... 

To the OP, What control module is in that drd rack?  A simple edit of the config can make the rack max those dimmers out at 95% or whatever you choose....

I would still lamp down to 375 though....

CMeD control module.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Cailen Waddell on August 04, 2014, 08:10:14 PM
Yeah - if you copy your config to a disk and email it to the factory, they will probably be happy to just adjust the max output of the dimmers with 4 pars.   Or if you have a factory tech in the area call them....

Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 08:13:51 PM
Yeah - if you copy your config to a disk and email it to the factory, they will probably be happy to just adjust the max output of the dimmers with 4 pars.   Or if you have a factory tech in the area call them....

Can I adjust that level using the menu features on the unit?  I've been through the manual and can successfully display the config for each circuit and I understand the Test submenu and the Set All submenu.

I'm scratching my head on how I get the data off the 3.5" floppy and into an email and then back to a 3.5" floppy though.  :)  I can't believe I'm on Amazon looking at 3.5" floppy USB drives to plug into my mac.  I feel so old.  lol
Title: Re: Help With Tripping Dimmer Breakers
Post by: Cailen Waddell on August 04, 2014, 08:16:36 PM

Can I adjust that level using the menu features on the unit?  I've been through the manual and can successfully display the config for each circuit and I understand the Test submenu and the Set All submenu.

Not that I am aware of...  Has to be done in light manager, which I haven't used in 4 years so I'm not even 100% that it can be done there. 
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 08:44:51 PM
If they trip that fast, that suggests to me that something fairly drastic is wrong.  Are you sure you don't have a couple 750w bulbs on those circuits?  Check the tightness of screws in the dimmer panel, measure the voltage in your facility to make sure you aren't running too far above nominal - both at the dimmer and at the fixture if possible, and verify that all bulbs are 575w 120v.

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.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 09:24:09 PM
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.

Ok.  Maximum fader values for each troublesome circuit are:

Circuit 1-8
Circuit 4-7
Circuit 3-10 (continues to be intermittent)
Circuit 9-5

Wow!  I can only raise the fader for circuit 9 to 5?!  Can 124.7 volts really cause that drastic of an end result?
Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 04, 2014, 09:37:05 PM
Ok.  Maximum fader values for each troublesome circuit are:

Circuit 1-8
Circuit 4-7
Circuit 3-10 (continues to be intermittent)
Circuit 9-5

Wow!  I can only raise the fader for circuit 9 to 5?!  Can 124.7 volts really cause that drastic of an end result?
I continue to suspect that you have more wattage on some of your circuits than you think you do.  Are you sure all of your bulbs are the same?  Are you absolutely sure you only have 4 fixtures per circuit in question? Do you have access to a current clamp so you can measure the current of each circuit?  In my experience (not with ETC dimmers) I have accidentally had 3KW of lights on a 20A dimmer and it works for 30-60 seconds.  It seems unlikely that only slightly more than 2.4KW would trip with the dimmer to a setting of 5.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 09:50:28 PM
I continue to suspect that you have more wattage on some of your circuits than you think you do.  Are you sure all of your bulbs are the same?  Are you absolutely sure you only have 4 fixtures per circuit in question? Do you have access to a current clamp so you can measure the current of each circuit?  In my experience (not with ETC dimmers) I have accidentally had 3KW of lights on a 20A dimmer and it works for 30-60 seconds.  It seems unlikely that only slightly more than 2.4KW would trip with the dimmer to a setting of 5.

I'll have to use a lift to verify each bulb (that'll take a couple days but I will verify it).  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.  When I raise a fader I only get the correctly assigned lights in groups of 4.  I can trace back the hot and neutral leads from the lights themselves into the drd.  Is there any way I'm missing something that would lead to having more lamps on a circuit than I actually have?
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 10:06:24 PM
I continue to suspect that you have more wattage on some of your circuits than you think you do.  Are you sure all of your bulbs are the same?  Are you absolutely sure you only have 4 fixtures per circuit in question? Do you have access to a current clamp so you can measure the current of each circuit?  In my experience (not with ETC dimmers) I have accidentally had 3KW of lights on a 20A dimmer and it works for 30-60 seconds.  It seems unlikely that only slightly more than 2.4KW would trip with the dimmer to a setting of 5.

Actually, that setting of 5 is probably misleading.  I only arrived at those values by turning the circuits in question all the way up, letting them trip, backing the fader down 1 increment and then resetting the breaker.  I can then gently raise the level of circuit 9 by increments of 1 and it won't trip until I get back to 9.  There must be something different in the application of power between the all at once method and the raise it slowly method.  At any rate, all circuits in question continue to trip.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Josh Daws on August 04, 2014, 10:06:44 PM
has anyone considered de-rating?? a TBH im a little out of practice here as i've hadn't had to deal with this and electrical isn't my forte, but i have been taught by electricians when ive done installations and larger live event setups is to not load up more than around 80-90% of your max allowance to allow for de-rating...

for example i have a 16AWG 100ft AC cable connected to a 575w Source 4. the actual power because of distance maybe close to 650w as the current required to operate at 575w @ 120v is actually more.

but you should never load your circuit to near max.

if someone more qualified reads this and if my information is misleading or wrong, please feel free to educate me, and correct me!...
Title: Re: Help With Tripping Dimmer Breakers
Post by: Josh Daws on August 04, 2014, 10:08:14 PM
and this would also confirm tom's theory as well about have more wattage on the line...
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 04, 2014, 10:20:05 PM
Wiring?

Tracking back wiring I've learned that the wires used are 600 volt/12AWG.  If I'm reading the letters on the wire correctly.  They can be seen in the photo I posted.
Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 04, 2014, 10:29:02 PM
has anyone considered de-rating?? a TBH im a little out of practice here as i've hadn't had to deal with this and electrical isn't my forte, but i have been taught by electricians when ive done installations and larger live event setups is to not load up more than around 80-90% of your max allowance to allow for de-rating...

for example i have a 16AWG 100ft AC cable connected to a 575w Source 4. the actual power because of distance maybe close to 650w as the current required to operate at 575w @ 120v is actually more.

but you should never load your circuit to near max.

if someone more qualified reads this and if my information is misleading or wrong, please feel free to educate me, and correct me!...
Standard thermal magnetic breakers need to be de-rated - such as in a general purpose service panel.  ETC uses special magnetic breakers in their dimmer racks that are designed for 100% duty cycle at the nameplate rating.
Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 04, 2014, 10:29:33 PM
Tracking back wiring I've learned that the wires used are 600 volt/10AWG.  If I'm reading the letters on the wire correctly.  They can be seen in the photo I posted.
I'm confident that your wires are fine. 
Title: Re: Help With Tripping Dimmer Breakers
Post by: John Fruits on August 05, 2014, 09:35:48 AM
I don't know if this has been suggested, but have you called ETC?  They have a reputation for some of the best technical support in the industry. 
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 05, 2014, 12:39:58 PM
I don't know if this has been suggested, but have you called ETC?  They have a reputation for some of the best technical support in the industry.

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. 
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 05, 2014, 01:20:03 PM
Here's a link to the thread I created on Control Booth.  http://www.controlbooth.com/threads/help-with-tripping-etc-dimmer-breakers.36014/

I think I'm going to pursue lamping down starting with 1 fixture per group of 4.  If this wattage reduction eliminates the trips than that will be the best solution.

If we want to move to a 5k dimmer we would have to buy a 230volt DRD unit because the 120volt model isn't compatible with the 5k module, upgrade the building wiring to 6AWG/600 volt/55AMP and purchase new dimmers.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco CFCRC on August 05, 2014, 01:28:13 PM
Does anyone even make a 375 watt 120 volt lamp?  Or am I going to have to use a 375 watt 115 volt lamp?
Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 05, 2014, 01:54:47 PM
Here's a link to the thread I created on Control Booth.  http://www.controlbooth.com/threads/help-with-tripping-etc-dimmer-breakers.36014/

I think I'm going to pursue lamping down starting with 1 fixture per group of 4.  If this wattage reduction eliminates the trips than that will be the best solution.

If we want to move to a 5k dimmer we would have to buy a 230volt DRD unit because the 120volt model isn't compatible with the 5k module, upgrade the building wiring to 6AWG/600 volt/55AMP and purchase new dimmers.
I suggest current measurement before going to extremes here - 4 575w fixtures should work, or at least be able to work with  a 90%-95% module max.  If you're way off this, something is wrong.

Rather than putting in 5KW dimmer modules (which I'm not sure are even legal without 20A branch circuit breakers which would get you back to your same problem), it seems like going to 3 fixtures per dimmer would be a better intermediate solution - if you can live with 375w bulbs instead of 575w bulbs, it would stand to reason that you should be able to live with 3@575w, depending on beam angle needed.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Don Lomonaco on August 05, 2014, 07:20:16 PM
The following is a reply from the Control Booth forum that bears attention.  I'm going to check into these points and report back.


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.
Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 05, 2014, 08:20:57 PM
The following is a reply from the Control Booth forum that bears attention.  I'm going to check into these points and report back.


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.
Don, with respect, you're starting to go in circles here, and more information is only helpful if it's accurate.  Reading TFM, we see that the ETC modules are "fully rated for continuous duty" http://www.etcconnect.com/Products/Dimming-Switching/Unison-Dimming/Dimmer-Modules/Features.aspx

These are not subject to 80% derating, and the whole 575w thing was designed specifically about being able to have 4 of these on a 20A circuit.

You mentioned earlier that you already have #10 wire - there isn't a problem there.  Most of this post you copy is dubious at best, and not particularly germane to the equipment you are using.  He's wrong about having 124v at the bulb (you won't - dimmer modules have a voltage drop of 4 volts or so), and wrong about de-rating the ETC breakers (though probably correct about the main breaker).

If you truly want to find out the root issue, you will need to do some measurement of voltage and current, and stop guessing.  If you just want to make the problem go away, your choices are either to lamp down to 375w bulbs (not my personal choice), or reallocate and use 3 fixtures per circuit.

I'm still suspicious that you have either a mixture of 750w bulbs or 115v bulbs, and that if you measure the current, it will be more than 20A.
Title: Re: Help With Tripping Dimmer Breakers
Post by: Josh Daws on August 06, 2014, 07:43:06 AM
i thought i wrote about de-rating somewhere....lol

anyways there is always going to be some de-rating. continuous duty means that it is designed to be able to operate at 20a continuously (see link and scroll down http://www.qualifiedhardware.com/glossary (http://www.qualifiedhardware.com/glossary)...it doesn't mean that at the lamp end that you are able to fit 20a. unless someone has installed larger breakers.

and as i've stated previously stated you should keep your loads to around 80% max, and this then allows for overdraw of the amperage due to de-rating.

however yes there is a voltage drop. 124v is a little high IMO, especially if you are using non-dim fixtures. however as long as you are reading 120v at the fixture end you are fine.

my advice is to either lamp down, or go to 3 fixtures...

Title: Re: Help With Tripping Dimmer Breakers
Post by: TJ (Tom) Cornish on August 06, 2014, 08:52:54 AM
i thought i wrote about de-rating somewhere....lol

anyways there is always going to be some de-rating. continuous duty means that it is designed to be able to operate at 20a continuously (see link and scroll down http://www.qualifiedhardware.com/glossary (http://www.qualifiedhardware.com/glossary)...it doesn't mean that at the lamp end that you are able to fit 20a. unless someone has installed larger breakers.
Josh - continuous duty 20A means that you can draw 20A forever without tripping the breaker.  This means exactly that you can you can supply 20A worth of lamps on this dimmer.  Whether the OP is over or under 20A is the issue.

Your earlier post:
Quote
has anyone considered de-rating?? a TBH im a little out of practice here as i've hadn't had to deal with this and electrical isn't my forte, but i have been taught by electricians when ive done installations and larger live event setups is to not load up more than around 80-90% of your max allowance to allow for de-rating...

for example i have a 16AWG 100ft AC cable connected to a 575w Source 4. the actual power because of distance maybe close to 650w as the current required to operate at 575w @ 120v is actually more.

but you should never load your circuit to near max.

if someone more qualified reads this and if my information is misleading or wrong, please feel free to educate me, and correct me!...
You have several errors here, and they have already been addressed in this thread.  Adding cable length does not increase the power consumption of a light bulb, it reduces it. 
Title: Re: Help With Tripping Dimmer Breakers
Post by: Stephen Swaffer on August 09, 2014, 08:18:28 AM
A $100 clamp meter would give you your answer in 30 seconds or less.  Trying to solve this without one is like stumbling around  in the dark looking for something-the first thing most people do is find a light.

If your time is worth anything, the investment will pay for itself.

Not allowing for derating should have one of two results-dimmer lamp for same output at dimmer or overheated wires in the conduit/wiring,  not a tripped breaker.  I have seen on a number of occasions where a loose connection on a breaker of fuse will cause it to blow at less than rated current, but it sounds like that possibility has already been eliminated.