Powering an ETC Smartpack without 60a direct

[Kent.B]

OK, so I've been reading the forums... forgive me if this has already been addressed... I'm trying to hook up an ETC Smartpack (both the SL1210 and SL620 models).... I've got a variety of lunch boxes that can give me 30a dedicated through edison or twist lock... but I know the dimmers want that 60a input through cams or the equivalent... Is there ANY POSSIBLE WAY to break up that 60a input either 2 or 3 ways over multiple breakers...? I originally ran three lines across a 3 phase setup to 3 dedicated 20a circuits, but experienced major flickering, jumping, etc. Is there any other way at all to run this thing single phase and have multiple 20 or 30 amp inputs to fulfill the power requirements here? THANK YOU to anyone who might be able to help!!!!

And/Or maybe this is the solution...

But does anybody have an update to this outdated link:
http://www.etcconnect.com/docs/docs_downloads/manuals/SmartPack_Portable_Setup_Guide_revD.pdf

 

[venuetech]

http://www.etcconnect.com/WorkArea/DownloadAsset.aspx?id=10737460902

 

[JChenault]

I am not aware of any to safely / legally use multiple 20/30 amp twist locks or Edison's to do what you want. Now I do see how you could use (say a single 30 amp circuit to power the dimmers, but you would be limited to a total of 30A over all dimmers of 30 amps

How are you powering your lunch boxes? My understanding is these Re usually powered by 3 phase 4 wire or single phase three wire. Why not just use that?

 

[Kent.B]

Thank you so much! Yeah, I didn't think there was any legal / safe alternative, but I REALLY appreciate the help! Each lunch box is powered with a 50a single phase 3 wire twist lock... I've got 2 separate phases spanning 6 outs at 50a each (with the third phase dedicated to sound...) feeding 6 lunch boxes each with 30a outlets. I can try a 50a direct connect, I just know they want 60... Thank you again! Really appreciate it.

 

[JD]

Well, they don't really "want" anything. All draw will be determined by whatever load you place on the packs. For example, if you put a 1kw par on each of the 6 channels, then your draw (at 120 volts) would be 25 amps on each of the two hot legs (assuming single or by-phase configuration two hots, neutral and ground.) If you were only loading each of the 6 channels at 575 watts, then your load would be 14.3 amps. A 30 amp supply breaker can provide a continuous 24 amps (30 x 80% for de-rating), so you probably would not have a problem at 1kw per channel. A 12 channel pack, you would double the numbers. (28.6 amps with 575 watts on each.) In this case, you would be pushing things if you turned everything on at the same time and left it on as you are operating too close to the rated 30 amp circuit without the headroom for the de-rating.

That said, often when packs are benched for service, the whole pack is plugged into a single 15 amp circuit while tests are being made. Only when the pack is fully load tested for thermal problems as a final step do they have to have a source that will stand the load. Point is, the pack itself draws less than an amp for operation. All the rest of the current is based on what is plugged into the outputs.

ETC specs the pack based on a full load on each channel and that is the basis of input breaker and wiring statements. Generally, on portable packs, that is a solid recommendation. Rack systems get based on practical loading by calculating diversity, which is a whole other subject

 

[RickR]

FYI the 60A rating is for single phase. When using 3 phase they max at 40A. So if you get 30A to them you really aren't losing much, as JD points out.

 

[Scenemaster60]

This whole situation seems unorthodox to me. There are a number of ways that it COULD be made to work reasonably safely but I am uncertain as to whether any of them would actually meet codes.

Since you say that one phase is dedicated to sound (I'm not sure how useful that kind of isolation really is since you're still coming off of the same panel and transformer, but that's another story…) Is there a possibility of getting a proper 4 wire 60 amp 120/208 outlet installed? For that matter, the installation a 50 amp 4-wire range outlet would be also be an option and the outlet and cords that you need would be standard issue and relatively inexpensive.

Or, as you mention you could wire them directly into the panel making sure that your 60 amp breaker was connected to the proper "lighting" phases. You will also need to make certain that you are using 4 AWG cable if you want to use the full 60 amps safely. If you downrate to 50 amps you can use 6 AWG cable safely.

You say that they want 60 amps. What kind of loading is being anticipated? As mentioned above the racks only NEED 60 amps if they are going to be fully loaded. If, for example, all of the the 20 amp dimmers in a pack are being loaded to 2300-2400 watts then there could be a problem. If they are only being loaded at 1500-2000 watts average then 50 amps will serve just fine.

Anyone who does lighting in situations where they are using portable dimmers plays this game all the time. As soon as you connect more that 50 amps of load you can also play the slightly more dangerous (not in terms of safety but in reliability) game of being REALLY careful in your cueing such that you never have more than 50 amps of load operating at any given time. This is not inherently unsafe since if you go over the 50 amp limit for more than a few seconds you'll trip the main breaker. I would personally not do this as an electrician unless I was also going to be the board op. for all rehearsals and performances.

 

[JChenault]

Thank you so much! Yeah, I didn't think there was any legal / safe alternative, but I REALLY appreciate the help! Each lunch box is powered with a 50a single phase 3 wire twist lock... I've got 2 separate phases spanning 6 outs at 50a each (with the third phase dedicated to sound...) feeding 6 lunch boxes each with 30a outlets. I can try a 50a direct connect, I just know they want 60... Thank you again! Really appreciate it.

The above is not making sense to me. iIf you have a single phase three wire (plus ground), you have two hot legs that are 180 out of phase with each other - and thats the power that is coming into the building.

If you have 'Two separate phase with a third dedicated to sound " ( Which sounds wrong as you would not get any noise isolation with such a set up) you have a service feed of three hot legs that are each 120 degrees out of phase with the other. And that is determined by the power feed into the building.

Now I can theoretically see how someone Might have both kinds of service in their building - but it seems highly unlikely.

I think you need to make sure what your feeder poser consists of.

 

[n1ist]

More confusing, you say "50a single phase 3 wire twist lock". Is it really three wire, or is it 4-wire in a California connector (where the shell is ground)? If you are feeding a distro for anything other than 208V, make sure you have both a neutral and ground.

3-wire (HHN) is useless (and not code) for anything other than ranges and dryers.
3-wire (HHG) is only useful for 208V/240V loads like some movers and strobes, or for feeding a stepdown transformer for reduced voltage drop on long lines.
3-wire (HNG) is 120V single phase, and must feed a distro with overcurrent protection to break it out to 120V/20A circuits.
4-wire (HHNG) or 5-wire (HHHNG) is most common for feeding a distro.

You can certainly wire up 2 phases of a 3-phase circuit to a range outlet or equivalent; that's done in many large apartment buildings. The only issue is that you will have 208V instead of 240V, and your range won't get as hot...

Time to break out a meter and see what you really have.
/mike

 

[Kent.B]

You're absolutely right. It was 4 write AWG cable. The dedicated leg for sound wasn't intended for noise isolation as much as it was for amperage calculation. We're dealing with a situation in which power is extremely limited. There's no possible way to get isolated power to sound as a stand alone setup within the budgetary constrictions we're dealing with... so what we did was just set aside one leg just for sound and video so that they could calculate their power draws and lighting could deal with theirs. I ended up using the four wire AWG to a 50a connection and then profiled the dimmers to downgrade the output.... it seemed to work OK so far. Thank you so much for your help.

 

[TJCornish]

This issue is the reason I don't use SmartPacks. I had a 1210 many years ago and it was a nice dimmer, but it sat in that odd spot of "not really big enough to be called a real dimmer rack but too big to be used on smaller shows." I've since gone to Leprecon ULD packs http://www.leprecon.com/products/product/9 which are much more flexible, and at similar cost to the SmartPacks (2 Leprecons vs 1 SmartPack).

As others have said, there's no safe way to use multiple Edison plugs to run the SmartPack - it must be run with a multi-phase input with common OCPD. Using one Edison plug per phase and jamming all of the neutral wires under the lug may appear to work, but there are significant issues - won't work with GFCI circuits, the neutral lug isn't designed for multiple conductors, a H/N reversed receptacle on one of the legs will create an unintended light show, and code requires that power be cut with only one switch/breaker/plug, among other things.

 

[JD]

Ahhh... Going to echo that point about connecting the neutrals together. It is an invitation to a fire. There are always slight variances in the resistance of cables, bough on by variations in length as well as variations in drop resistance in connectors. By nature, power will find the path of least resistance. It may look like 4 neutrals are in play, but 80% of the current may be flowing through one of them! Worst, there is no visible indicator that this is happening until the heating starts.