Control/Dimming ETC SmartBar Breakers Tripping

[bluemando]

Here is my question - information follows.

I am having ETC SmartBars tripping breakers. Is there some test I can set up to mimic a pair of 575watt lamps - to show whether the dimmer bar is or is not the source of the problem?

So that is my question and here is a description of our system and the problem we are having:

Our ETC House and Stage lighting system (Phase I) was purchased and installed in 2007 and included all the base building electrical work. We started with (5) SB6-10M-B and (2) SB4-6-B SmartBars, Ion Console; Unison Dimmer Rack, Architectural Control Unit, DMX Repeater, etcetera, etcetera - the whole system is ETC.

We had an electrical engineer review and electricial company install all new building service panels and distro for the lighting system - we defered the house lighting for some time but that's installed now. Now the only part of the system not installed as designed are wall washers and additional dimmer bars and fixtures.

All of our fixtures are SourceFour Elipsoidals and Pars with Edison Connectors. We made up Distro cables from 3/12 SO and SJO Cable and our dealer recommended using Black Cube Taps for two-fers. I am guessing that our longest cable run is 50ft with an average of maybe 25ft - we bought lots of cable so almost all the runs are a single cable. We are lamping with 575x lamps throughout.

From the start we had to limit the dimmer bars to 90% to keep breakers on the SmartBars from tripping with (2) fixtures on a 10A dimmer. As I recall, some of the dimmers loaded with a pair of 575's tripped instantly untill we dummed the bars down to 90%. The dealer said to check our cabling - but as we have no catwalks and the facility is used nearly every day of the week I failed to get to the bottom of the issue in a timely manner. But I do check the cables as I go along and have not found anything - no burned up Edison connectors or loose terminations.

We did have one L21-20P connector get hot and burn - totally our fault due to a bad wiring job. That's been fixed and I checked the others and they all look perfect.

We just purchased a pair of SmartBar 2's and they both are they too are tripping breakers when we have a pair of lights connected. Not every channel, but some are consistantly tripping.

For our facility we have the dimmer channels at 100% for long periods of time.

The only weak point in all of this in my mind would be using these cube-taps. But it seems like they are pretty common and the most they see are a pair of 575w lamps and I have not seen any evidence of a cube tap getting hot - not even once.

That is all the relevant information I can think to include. It seems that there are 3 potential sources, the extension cabling we made up, the 14amp Cube Taps (which I think are not the problem) and/or the dimmer bars. I did check the voltage to the dimmers with my meter and it reads 120V. ???

Thanks for any help with this - I would love to sort this out.

 

[Dover]

The wiring is fine. From what you said everything is working as it was intended. The SmartBar is a 1200W dimmer on a 10A breaker, and that is the cause of this problem. 2 S4 575W 115V lamps draw exactly 10A on paper [(575w*2)/115v=10a]. Any variation in the tolerance of the lamps or the breaker will cause the breaker to trip. Nothing is wrong, the SmartBar is simply being overloaded, which is why it works at 90%. The SmartBar is a dimmer per circuit per lamp type device, 1000W is probably the max load you can put on one and still guarantee that the breaker will not trip at an inopportune time.

Hope this helps
Dover

 

[derekleffew]

... 2 S4 575W 115V lamps draw exactly 10A on paper [(575w*2)/115v=10a]. ...

Yes, but how much current do those 575W 115V lamps draw when supplied with 120V? (Hint: http://www.controlbooth.com/forums/question-day/9282-acceptable-put-4x-s4s-dimmer.html and http://www.controlbooth.com/forums/question-day/9400-another-current-question.html .)

...We are lamping with 575x lamps throughout. ...

HPL 575/115X (ETC Part#RT114) or HPL 575/120X (ETC Part#RT171) lamps?
Do the breakers trip immediately or after a period of time?
Does fading up slowly from 0 to 100% make any difference?

... Is there some test I can set up to mimic a pair of 575watt lamps - to show whether the dimmer bar is or is not the source of the problem? ...

I'd be curious to see what would happen if using a single PAR64 can with a GFA 1200W 120V lamp.

 

[FMEng]

The filament resistance won't be completely linear because of temperature effects, so this could be off a smidge, but it should be close:

At 115 Volts, a 575 Watt lamp has a hot filament resistance of:

R = E^2/P, R = 115^2/575 = 23 ohms

At 120 Volts, the same lamp would draw:

P = E^2/R, P = 120^2/23 = 626 Watts

I = P/E, I = 626/120 = 5.2 Amps

Given the fact that circuit breakers aren't precision devices, and are happiest loaded to not more than 80% of their rating, no wonder they are tripping. Use fewer lights or more or bigger dimmers.

 

[Footer]

Given the fact that circuit breakers aren't precision devices, and are happiest loaded to not more than 80% of their rating, no wonder they are tripping. Use fewer lights or more or bigger dimmers.

On a standard house breaker that is true, however on dimming systems the breakers are designed to be fully loaded past the magical 3 hour mark. This is just one more reason why you should never use home depot distros.

 

[bluemando]

HPL 575/115X (ETC Part#RT114) or HPL 575/120X (ETC Part#RT171) lamps?

Originally we used 115V Lamps - back a few months we started using 120v lamps - not sure if we have any 115V lamps in service yet or not.

Do the breakers trip immediately or after a period of time?

Early on some of the breakers were poping right away and so we set the max power on the bars to 90% which seemed to help. Still, breakers trip from time to time and we try to remember to check before we replace a lamp now.

Does fading up slowly from 0 to 100% make any difference?

Have not checked that - seems they trip either right away or after a few hours.

I'd be curious to see what would happen if using a single PAR64 can with a GFA 1200W 120V lamp.

That is a good thought - I will see about making that happen.

Thanks!