How many Smartpack wall mount racks can I LAN together

[Esoteric]

Its the breakers that need to be down-rated. Most breakers/electrical systems are designed to hold their max load for a total of 3 hours. After that, they will theoretically trip. If you intend on loading them endlessly, you can only load them up to 80% of their max power. So, as Steve said, a 40 amp breaker becomes 32 amps. It has nothing to do with the method of connection to the service panel. You can get continuous load breakers that will allow you to use 100% of the power 100% of the time, however cooling needs to be taken into account.



The point is you will only be able to load up the system to the 225a amount. Use all 20amp modules you will be able to load 33 circuits fully. If you go beyond that, your disconnect trips. However, in a traditional setting this is really not a problem. ETC did a study a few years back and found that most modern venues put no more then a 1500w load on most dimmers. Therefore, at the "average" load, you can load up 54 dimmers, getting you really closed to that 60 mark. Bust down to 575 watt lamps and you will never hit it. The same thing is done in houses all the time. Most house have a 100 amp service. However, they might have 150 amps of distrobution. They assume that at no time will you be running the dishwasher, hot water heater, a/c, and have every single outlet in the house fully loaded at the same time. Its the same concept.

You are correct on the top, but on the bottom:

They want all 62 circuits to get their own dimmer. So 62 20A circuits puts me well above the 225A breaker (It puts me in the 450A range). And, as an installer, I do not feel comfortable with doing that on a 225A breaker. Their current setup runs off of 24 20A dimmers and they still have room left over.

But what happens 3 years from now when they add equipment and someone new comes in who doesn't know the rack is limited, and maybe the breaker doesn't trip in time and a fire starts.

Not something I want anyone looking anywhere near me for.

That being said, does anyone have the part number on this 10A dimmer?

 

[derekleffew]

You are correct on the top, but on the bottom:

I'd argue the opposite, but we'll let that go for now. The "ETC Survey" alluded to can also be found via the wiki link cited:

... See NEC 2011 520.27(C), and also the article at Dimmer feeds--How much power is enough? - ControlBooth .

... And, as an installer, I do not feel comfortable with doing that on a 225A breaker. Their current setup runs off of 24 20A dimmers and they still have room left over.

But what happens 3 years from now when they add equipment and someone new comes in who doesn't know the rack is limited, and maybe the breaker doesn't trip in time and a fire starts.

Not something I want anyone looking anywhere near me for. ...

While I understand your concern (and it may be very valid in a non-professional setting) reduced feeders are used all the time. Did you read Steve Terry's Power Play article linked to above? There's currently a thread with this same debate on LightNetwork.

Taking the other side, if you install only 10A dimmers, what happens if/when the user decides (s)he wants to use some 2K Fresnel s or cyc light s, or just has to two-fer two 750W lamps on one circuit?

 

[Esoteric]

There won't be any 2K Fresnels or cyc lights (this is a church installation). In addition I don't think I would call this a "professional" setting. 90% of the users are volunteers.

Yup, I read the article. Doesn't mean I agree. We always do feeders at least 25% larger than needed. In this case it makes me very nervous to do simply the full feed.

Anyone have a part number on the 10A Sensor Module?

 

[Esoteric]

I would love to hear from someone at ETC. I don't see a D10 listed on their site. But I do see a 10A module listed.

 

[sk8rsdad]

But what happens 3 years from now when they add equipment and someone new comes in who doesn't know the rack is limited, and maybe the breaker doesn't trip in time and a fire starts.

Two things:

• 3 years from now they will be bringing in LED fixtures and get no where near the theoretical maximum.
• A fire won't start because the main breaker will trip when it is overloaded, even though individual branch circuits won't. At no point in the system is the wire undersized for the load. The weakest link is the breaker, not the rack.

Take for example my venue where we have 2 Sensor 48s (89 D20s, 6 R20s, and 1 D50) fed by a 400a service. It is theoretically possible for somebody to connect way more than 400a load, but it is highly unlikely. That would be one heck of a lot of instruments for my venue. It is also highly unlikely the entire rig would be running at full power at any point during a show.

Take for another example, it is always possible to connect a bigger load to that 15 amp receptacle near your computer. That's why they put the circuit breaker in the circuit.

 

[Esoteric]

Yeah, but sometimes the breaker fails and then your house catches on fire.

 

[starksk]

I would love to hear from someone at ETC. I don't see a D10 listed on their site. But I do see a 10A module listed.

We do have a D10 Module as an option, but it is a custom module. There is not a standard part number because it is not often made.

I now return you to your debate on the use of 20A modules underloaded versus 10A modules fully loaded.

 

[derekleffew]

Not so fast there, Kirk.

In what application would the L10 Dual 10A Low Wattage Dimmer Module be used?

EDIT:
http://www.etcconnect.com/community/wikis/products/fluorescent-dimming.aspx :

ETC in the past produced some forward phase modules that handled low loads better, known as the L10(110V) and AL5 (277V). The L series used MOSFET and IBGT technology to more accurately dim low wattage loads. Due to dimming control improvements in the Unison DRd rack and Sensor CEM+ control modules, these modules were discontinued as they were no longer needed.

So that's a big NO to the L10!

------

And if the D10 is a "custom module, not often made," does that make it more expensive than a D15 or D20?

 

[starksk]

Not so fast there, Kirk. In what application would the L10 Dual 10A Low Wattage Dimmer Module be used?

I see you found the answer as I was replying...

And if the D10 is a custom module, not often made, does that make it more expensive than a D15 or D20?

I honestly do not know. Because it is a custom module, its list price is P.O.A....

(I now? return you to your previous debate)

 

[SteveB]

Additional to the issue of whether to use a 10 amp or 20 amp dimmer is going to be the wiring.

I could be wrong but I believe the NEC requires a 20 amp minimum rated branch circuit wiring be used for theatrical systems ?. As well you are probably going to use 2P&G pin connectors ?. So zero cost savings at that end.

If the D10 is custom, I'm betting all they do is swap the breaker to a 10 amp breaker, which is what they did for a 15 amp dimmer for the old NYC house lighting circuits. Everything else stays the same, SSR's and chokes and you don't get any add'l dimmers in the rack by downsizing.

And if you go the SmartPack and still need to install wiring rated to 20a or better, as well as 2P&G, what do you save over a 20a Sensor rack, except possibly a lower cost for the SmartPack wall unit.

One option might be to swap the 40amp 3 pole breakers for an 80 or so, letting you use a 12x2.4kw Sensor. It's not unusual to see a CB panel have space for a different sized breaker. We did this when we renovated a black box that had 4 - TTI 6x2.4kw packs fed on 40a, 3 pole breakers and we swapped the 4 40a breakers for 2 - 80 amp 3 pole breakers. It was pretty cheap.

 

[Esoteric]

I have to get 48 dimmers. They already have distribution in place. So 12x2.4kW doesn't help anything, that is only 1/4 of the amount of dimmers the project needs. I would have to do 48x2.4kW which would require a 300A breaker.

 

[sk8rsdad]

I have to get 48 dimmers. They already have distribution in place. So 12x2.4kW doesn't help anything, that is only 1/4 of the amount of dimmers the project needs. I would have to do 48x2.4kW which would require a 300A breaker.

I know it has been said before but I feel like pounding my head against a brick wall

It's OK to have engineering guidelines that say you can attach a maximum of 2.4kW to any individual circuit to a maximum of whatever the main breaker will sustain. It is done all the time. Heck, even shoebox dimmers do it.

 

[Esoteric]

You can keep saying it again and again, but my ME won't do it, and my lawyer advised me that there could be liability issues if the system was not used properly and damage resulted. So, I am not going to do it.

 

[shiben]

I happen to agree with Esoteric on this one. Its called minimizing risk, and with a 90% volunteer situation, you just dont want to run that risk, even if its tiny, that someone does something stupid and ends up burning the place. In a different thread we discussed BillESC? getting sued for selling some lifts that got blown over by wind. I wouldnt want to be the one who could be on the end of a "you installed a product that didnt trip before the main building breaker and that caused a fire due to some oddball situation". Spend 15 minutes on the dodgy technicians FB page and see how many times you find breakers taped to the open position so that it wont throw. I have seen it done in about 6 venues for various reasons, the one I left in a hurry and didnt touch anything more was "because it keeps popping". So I think Esoteric has the right idea here, make the system as safe as possible, then you can simply say "I installed the safest possible system available". Of course, hes gonna do it, and in a year and a half, we are gonna get a new guy on here from Dallas posting "some **** moron put 10A dimmers in our rack at my church, and I need to get a 2k Fresnel on one circuit. I thought about plugging it into 2 outlets, will this maim/kill anyone?"...

 

[Gern]

You can keep saying it again and again, but my ME won't do it, and my lawyer advised me that there could be liability issues if the system was not used properly and damage resulted. So, I am not going to do it.

Cool. Then its settled.
Either you:
1. Pay for the 10A dimmers. This sounds like what you'll end up doing.
2. Pay for the larger service, and use 20A dimmers.
Find out what your AHJ says.
My stage 31 Strand racks @ Paramount have 606 dimmers equalling a total of 26,400A.
The dead front switchboard has a 2500A breaker allowing me to only pull 7500A before it trips. The breaker is there to prevent over amping. When I (and the rest of my fellow 728 S.E.L.T.'s) feed a 1200A temporary distro box on set with anything smaller than 4/0, we are aware of the cables limitations. We do it all the time.
I can see how you could doubt any thing I say, but I don't understand you doubting Steve Terry and the National Electric Code, if your AHJ says it is acceptable.

 

[derekleffew]

...Spend 15 minutes on the dodgy technicians FB page and see how many times you find breakers taped to the open position so that it wont throw. I have seen it done in about 6 venues for various reasons, the one I left in a hurry and didnt touch anything more was "because it keeps popping". ...

NEC 2011 240.80:

Circuit breakers shall be trip free and ...

From TRIP-FREE/NONTRIP-FREE CIRCUIT BREAKERS :

A trip-free circuit breaker is a circuit breaker that will trip (open) even if the operating mechanism (ON-OFF switch) is held in the ON position.

While you have your code book out, again I'll point you to NEC 2011 520.27(C) . There's no changing Esoteric's mind on this, and that's fine, but I encourage others to read Mr. Terry's and others' wisdom expressed in the Light Network thread "Install Question".

 

[Esoteric]

I happen to agree with Esoteric on this one. Its called minimizing risk, and with a 90% volunteer situation, you just dont want to run that risk, even if its tiny, that someone does something stupid and ends up burning the place. In a different thread we discussed BillESC? getting sued for selling some lifts that got blown over by wind. I wouldnt want to be the one who could be on the end of a "you installed a product that didnt trip before the main building breaker and that caused a fire due to some oddball situation". Spend 15 minutes on the dodgy technicians FB page and see how many times you find breakers taped to the open position so that it wont throw. I have seen it done in about 6 venues for various reasons, the one I left in a hurry and didnt touch anything more was "because it keeps popping". So I think Esoteric has the right idea here, make the system as safe as possible, then you can simply say "I installed the safest possible system available". Of course, hes gonna do it, and in a year and a half, we are gonna get a new guy on here from Dallas posting "some **** moron put 10A dimmers in our rack at my church, and I need to get a 2k Fresnel on one circuit. I thought about plugging it into 2 outlets, will this maim/kill anyone?"...

Hahahaha... You know, 10 years ago I was that guy!!! I couldn't understand things like budget considerations, so I would spout off "well, they should have pulled new wire in from the main service, blah, blah, blah." *lol*

But yes, we have gone over the limitations of such a system. And I also went over the possibility of putting in a larger rack on a smaller service, but I told them I wouldn't do it (because of the liability issues) so they would have to find someone else. They agreed on 10A dimmers.

And I can't imagine why they would want to use a 2K Fresnel in a space with 15'-20' throws. Except to melt singers faces off.

And no, I am not ignoring their thoughts. They are great thoughts, but it isn't their company that might have to pay out a giant settlement because the system was improperly installed. There is theory and then there is real life. I know it is only a 5% chance, but that would bankrupt my company. Heck, the attorney's fees to defend myself would put us behind the 8 ball for a while.

 

[DavidNorth]

The feeds would not be unsafe, they are defined in the NEC, there is no risk of fire. Either solution is completely acceptable and I hope all can see that. You can feed 96 dimmers with a 20A breaker and if you put more than a few lights into the system, the only thing that happens is that the 20A feed breaker trips. Nothing is unsafe but it certainly is inconvenient when a show is being lit.

Do some math. Tell me how in the world you would ever take standard theatrical fixtures and create a 2400W load. This is difficult to do. At three 750W units, which is 2250W, you are still only at 18.5A. Over a 96 dimmer system, this is 600A but yet the nameplate rating of the rack is 800A. Unless you are loading up everything and turning it all on at the same time, 400A is plenty.

I think it makes sense to use the feed that is in place at 40A because of cost. Fully loaded 12 channel SmartPacks are going to pull 40A, 3 phase but the breaker will be able to supply 32A. You are still technically overloading the system, but, because the wire is of the NEC prescribed size, there still will be no fire. Oh, and there is no way you are going to fully load it.

Same situation....just a matter of choice and cost. Again, none of the solutions are bad, dangerous, or fire-inducing. There is no magic here.

David

 

[Esoteric]

The feeds would not be unsafe, they are defined in the NEC, there is no risk of fire. Either solution is completely acceptable and I hope all can see that. You can feed 96 dimmers with a 20A breaker and if you put more than a few lights into the system, the only thing that happens is that the 20A feed breaker trips. Nothing is unsafe but it certainly is inconvenient when a show is being lit.

Do some math. Tell me how in the world you would ever take standard theatrical fixtures and create a 2400W load. This is difficult to do. At three 750W units, which is 2250W, you are still only at 18.5A. Over a 96 dimmer system, this is 600A but yet the nameplate rating of the rack is 800A. Unless you are loading up everything and turning it all on at the same time, 400A is plenty.

I think it makes sense to use the feed that is in place at 40A because of cost. Fully loaded 12 channel SmartPacks are going to pull 40A, 3 phase but the breaker will be able to supply 32A. You are still technically overloading the system, but, because the wire is of the NEC prescribed size, there still will be no fire. Oh, and there is no way you are going to fully load it.

Same situation....just a matter of choice and cost. Again, none of the solutions are bad, dangerous, or fire-inducing. There is no magic here.

David

There is a third possibility. The breaker doesn't trip, the wire heats up and causes a building fire. ;-) Breakers have failed in the on position before, I have replaced several.

But you are absolutely correct, I would not put the Smartpack dimmers on the system if the wire gauge could not handle the 40A load. So that even if the breaker fails you are still pulling the load intended for that wire.

All I know is the lawyer said that there was a good chance that system set up like that could be argued that it was setup incorrectly and would bring about liability issues that would cost either a settlement or a long, drawn out court case.

Neither of which is good for business.

So, before you install a system like that, consult your insurance agent and your lawyer.

 

[DavidNorth]

Well, then I trust you will replace all the 40A breakers and wire in the system before it is energized so that you will avoid the possibility of fire. No telling whether they are still really in good shape or not. I'm sure your lawyer and insurance agent will agree.

Dude, I am completely on your side in your specific installation and application.

For all the other readers on this forum, I hope that you will read Steve's article and contact me if you have questions.

David