When L21-30 just isn't big enough

Re: When L21-30 just isn't big enough

Rick Stansby said:
If we run at 208, then we have the potential for 34 amps per leg, but really only the sub amp is running full tilt, so we would probably be OK. I just don't want to have to keep the amps throttled back at all times. Why buy these big amps if we can't use everything they have to offer.

Maybe 4 amps per rack is a bad idea.
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I don't know if Lee is around, maybe he can check my math on this one..

But when all three phases are balanced, the maximum current P-P is sqrt(3) * P-N current (for conductor sizing). I.e. at 18A on each P-P circuit, you will be exceeding 30A line current.
 
Re: When L21-30 just isn't big enough

Rick Stansby said:
We are trying to figure out how to power our new amp racks that have 4@ Lab PLM20000Qs each. Each amp really needs a full 30A (or more), so an L21-30 won't do. We have considered using a pair of L21-30s to each rack, but there are a lot issues associated with that (no room for pass-thru on the rack-pack, custom rack-packs cost more, and we would have to run 2 cables to each amp rack). I am familiar with the 63A 3phase Ceeform connectors, but we don't see them very often in the US. If we switch to these connectors we will have to get the proper outlets added to at least one of our distros, also we will need new power cables to the amp racks.

I mention the 120V current needs, but in fact we plan on running the amps at 208v once we get the power worked out. At 208v we need about 50A per leg, which is why we are looking at dual L21-30 or single 63A Ceeform.

Is anyone here using ceeforms for amp rack power? Who made the rack-pack?

Does anyone else have any other good suggestions to power these racks? Cam seems a little bit overboard, but not buy much.

We currently use Cam, L21-30, L5-30 and edison exclusively.

P.S. I like the crown V-rack power panels.
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Rick,

We use a dual L14-30 for all of our big racks. Yes we run two cables per rack. Not a big deal though. Both cables are loomed together and are 15' long. We use a distro for each side of the stage.

We just had a new rac pac distro made from Curtis at Six 2. Dual L14-30 inputs and 4-L530 outputs. No breakers on the pack as they all terminate to there own breaker on the Distro...The price was not bad at all!
 
Re: When L21-30 just isn't big enough

Ryan Lantzy said:
I don't know if Lee is around, maybe he can check my math on this one..

But when all three phases are balanced, the maximum current P-P is sqrt(3) * P-N current (for conductor sizing). I.e. at 18A on each P-P circuit, you will be exceeding 30A line current.
Click to expand...

If all the loads are line to line, there is no neutral current. You do have to account for current flowing in each line, though. So 3 amplifiers delta-connected puts roughly the same amount of draw on each conductor as the same 3 amplifiers Y-connected. (This also means that putting 4 amplifiers line-line on the same L21-30 will put 2 hot legs at 52A.)
 
Re: When L21-30 just isn't big enough

Steve Ferreira said:
I have seen acouple of soundco's around here run 2x l14-30 per rack. I'm sure it was for cost savings as all there old racks where single l14-30.
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yeah Ultra Sound uses a lot of L14-30, and there are two going into each amp rack. That would be just about perfect for us, if we used L14-30 in other rigs, but we have almost completely phased out that connector.
 
Re: When L21-30 just isn't big enough

Scott LaRochelle said:
We just had a new rac pac distro made from Curtis at Six 2. Dual L14-30 inputs and 4-L530 outputs. No breakers on the pack as they all terminate to there own breaker on the Distro...The price was not bad at all!
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Wow Scott, that is a really interesting configuration. We might go that way, with L21-30. I never thought of losing the breakers at the rack-pack. My only concern would be the fact that our distro has the breakers linked, so if we pop one, we lose all three legs to that L21-30.
 
Re: When L21-30 just isn't big enough

Rob Timmerman said:
If all the loads are line to line, there is no neutral current. You do have to account for current flowing in each line, though. So 3 amplifiers delta-connected puts roughly the same amount of draw on each conductor as the same 3 amplifiers Y-connected. (This also means that putting 4 amplifiers line-line on the same L21-30 will put 2 hot legs at 52A.)
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Rob, that's what we figured. 17.3A per leg, 2 legs per amp, puts us at 52A on X and Y, with 34.5 on Z, plus we would put some edisons on Z. Basically we'd need 50A per leg. That is what got us thinking about the 63A Ceeform connectors.

In reality, only the sub amp is going to draw near 17A per leg.

All of this led us to the original idea of 2@L21-30 with one driving the first 3 amps and one driving the sub amp. Allowing us to run the sub amp at 208V, and split the load between 2 of the legs of the second L21-30.

Apparently this design will be very pricey for Motion Labs to build.

I'd love to go down to 3 amps per rack - to make power easier. Unfortunately that doesn't cover our amplifier needs, and we would need to figure out a way to stack amp racks in transport. We are configuring these for 4@ tri-amped zones with 4 channels of Sub. Our old racks have 3 triamped zones, passive fills and 4 amp channels for subs (14 amp channels total). So we only have 2 extra amp channels in these racks, however we will be running a larger rig off one of these racks than we can run off the old racks.
 
Re: When L21-30 just isn't big enough

Ryan Lantzy said:
I don't know if Lee is around, maybe he can check my math on this one..

But when all three phases are balanced, the maximum current P-P is sqrt(3) * P-N current (for conductor sizing). I.e. at 18A on each P-P circuit, you will be exceeding 30A line current.
Click to expand...

Ryan,
You are correct that at 18A each, we would exceed 30A per leg.

Disregarding the 4th amp. If we put 3 amps in each rack at 208 (XY,YZ,ZX) we have the potential to draw 17.3 A per amp. That would put 17.3 amps x 2 on each leg, so a possible load of 34.6 A per leg. I am confident that only the sub amp would draw 17.3 A, so we might just squeak by. Running at 208 means we split the load of the sub amp between 2 legs, which might be beneficial.
 
Re: When L21-30 just isn't big enough

Scott,

Is that six 2 rack-pack 2 rack spaces or 3?

Another issue with these new amp racks is the fact that there isn't much room for paneling. The amps only take 8 space, and we are planning on having 12 space racks. That leaves 4 rack space for the giga-switch and the rack-pack. We would really like to keep the rack-pack at 2 spaces if at all possible.

With breakers there is no way to fit 8 on a 2 space motion labs rack-pack. Maybe losing the breakers will be the best way for us to fit in 2 spaces.

My boss is going to call Six 2 tomorrow to see what they can offer. Thanks again for the suggestion.
 
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Re: When L21-30 just isn't big enough

Rick Stansby said:
Rob, that's what we figured. 17.3A per leg, 2 legs per amp, puts us at 52A on X and Y, with 34.5 on Z, plus we would put some edisons on Z. Basically we'd need 50A per leg. That is what got us thinking about the 63A Ceeform connectors.

In reality, only the sub amp is going to draw near 17A per leg.

All of this led us to the original idea of 2@L21-30 with one driving the first 3 amps and one driving the sub amp. Allowing us to run the sub amp at 208V, and split the load between 2 of the legs of the second L21-30.

Apparently this design will be very pricey for Motion Labs to build.

I'd love to go down to 3 amps per rack - to make power easier. Unfortunately that doesn't cover our amplifier needs, and we would need to figure out a way to stack amp racks in transport. We are configuring these for 4@ tri-amped zones with 4 channels of Sub. Our old racks have 3 triamped zones, passive fills and 4 amp channels for subs (14 amp channels total). So we only have 2 extra amp channels in these racks, however we will be running a larger rig off one of these racks than we can run off the old racks.
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Some thoughts:
Can you set up the amps so that each amplifier is doing a triamp zone + sub? This'll make it easier to balance the load across multiple phases, as well as reducing the maximum draw per amplifier.

Have you given thought to putting 2 L21-30 breakouts in the rack? One breakout (the "primary") has 3 amplifiers, all as line-line loads. The second breakout has a single amplifier, plus whatever you need for courtesy outlets. If you just have the amplifier, it could be as simple as an under-populated L21-30 to Powercon. Basically, 2 racpacks instead of one. On quieter shows, you could perhaps use the loop-thru on the primary to feed the secondary. The primary breakout wouldn't need any additional overcurrent protection.
 
Re: When L21-30 just isn't big enough

Rob Timmerman said:
Some thoughts:
Can you set up the amps so that each amplifier is doing a triamp zone + sub? This'll make it easier to balance the load across multiple phases, as well as reducing the maximum draw per amplifier.
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Up to now, all of our planning has been to run one amp as a sub amp, with 3 amps for the mains. However a few minutes ago it did occur to me that we could do Sub, Low, Mid, Hi on each amp. I believe that Lab told us that you can't run at 2 Ohms on channels 3 and 4 (maybe that only applies to the older PLM amps but not the 20,000). The only issue I can think of is the fact that each amp only has 2 inputs, and we were planning on sending Left and Right to each of the first 3 amps, to allow us to pick off the correct one (depending if the amp is running mono or stereo).

Have you given thought to putting 2 L21-30 breakouts in the rack? One breakout (the "primary") has 3 amplifiers, all as line-line loads. The second breakout has a single amplifier, plus whatever you need for courtesy outlets. If you just have the amplifier, it could be as simple as an under-populated L21-30 to Powercon. Basically, 2 racpacks instead of one. On quieter shows, you could perhaps use the loop-thru on the primary to feed the secondary. The primary breakout wouldn't need any additional overcurrent protection.
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We have considered 2 rac pacs. The main issue is rack space. 2 rac pacs take 4 rack spaces. There are a lot of people working together to design these racks. Somebody else is pretty set on 12 space racks. 8 spaces of amps, plus 4 spaces of rac-pac, leaves no room for the giga-switch. We thought we might combine the functions of two rac-pacs into one chassis, but that doesn't leave any room for pass thru jacks.

One idea was to put 2@L21-30 inlets on a single rac-pac, and then build a bunch of L21-30 Y cords for times when you don't have 2 outlets available.
 
Re: When L21-30 just isn't big enough

OK, if we're at the point of possibly using two rac-pacs for four amps, then that is a really good reason to split single big racks into dual 6-space racks. Here are my reasons:
  • You don't need a rackmount switch for 4 or 5 ports. I figure the rack will need two external ports (in and out) and one for each amp. That's four ports if you're doing two amps per rack, and no rackspace wasted since you can tuck a regular compact switch in the back virtually anywhere.
  • All I/O panels can go in the back or on the side, taking up no more rack space than the amps and the rac-pac alone.
  • Assuming that each amplifier can run solidly on a 30-amp 120 volt circuit, then an L14-30 in and through per rack is perfect. For big shows, every rack gets its own circuit. At smaller or quieter shows, the loop out can be chained to the next rack to share a circuit. No custom two-fers or splitters needed! Just use existing jumpers!
  • 10/4 or 8/4 is already bigger than any wire I want to be coiling. Going 10/5 or 8/5 or even bigger just makes me sad inside, and makes your wallet cry even more...and copper is outrageous these days.
  • There is no reason for two separate racks to take up any more space than one big rack. You can set the racks up to stack, maybe going 3 high, with a wheelboard for the bottom rack. Alternatively, the wheels could be attached to every other rack and they could always stack two high.
  • More smaller racks also obviously weigh less each. This might be a plus if you have a bad load-in or stairs or something terrible, where each rack had to be carried in. Smaller racks can also be tucked in extra space pretty easily, where a 12U loaded amp rack is going on the floor of the truck with no exceptions.
  • Each pair of amps is already 8 channels, which is enough to to a LOT. Especially considering how much power they're putting out per channel, it might be more flexible to have more smaller racks than one big rack for many shows: if each side of speakers only needs 8 channels to run, you can run one rack per side rather than sending a 100' NL8 across the stage and suffer all that loss. Also, since each amp gets two inputs, then running sub-low-mid-high per amp makes sense: you can either do aux subs on one input and the rest of the rig on the other, or do a stereo biamped rig, or two biamped wedge mixes, etc. Not really anything to do with power, but certainly makes L-R amp racks look better than all on one side.
  • With more smaller racks it's easier to pick the 'size' needed for a specific show. If someone wants to rent a pair of PLMs, but you need 24 channels for another show, then you can take 3 racks and leave one for the rental. That flexibility is significantly lacking with fewer bigger racks.
 
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Re: When L21-30 just isn't big enough

Rick Stansby said:
Scott,

Is that six 2 rack-pack 2 rack spaces or 3?

Another issue with these new amp racks is the fact that there isn't much room for paneling. The amps only take 8 space, and we are planning on having 12 space racks. That leaves 4 rack space for the giga-switch and the rack-pack. We would really like to keep the rack-pack at 2 spaces if at all possible.

With breakers there is no way to fit 8 on a 2 space motion labs rack-pack. Maybe losing the breakers will be the best way for us to fit in 2 spaces.

My boss is going to call Six 2 tomorrow to see what they can offer. Thanks again for the suggestion.
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Rick,
We did 2 rack space. As far as breaker being linked in the distro, unlink them. There is no reason for those to be linked with 120 volts...Someone correct me if I am wrong? When the breaker is linked I think of a device using 2 hot legs 240v.
 
Re: When L21-30 just isn't big enough

Scott LaRochelle said:
Rick,
We did 2 rack space. As far as breaker being linked in the distro, unlink them. There is no reason for those to be linked with 120 volts...Someone correct me if I am wrong? When the breaker is linked I think of a device using 2 hot legs 240v.
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Rick also when you call curtis at six-2 tell him you want to to my design. SCL Sound Systems...
 
Re: When L21-30 just isn't big enough

Ryan Lantzy said:
Multi-phase connectors must be fed by a multi-pole breaker that is linked.
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Please explain. It's a single phase connector. 2 hot legs.
My theory, and I could be a total idiot, is 2 amps in a rack fed by 1 L14-30. L14-30 hot leg number 1 goes to amp 1, L14-30 #2 goes to amp 2. If amp one has a problem it trips the breaker, not taking out amp 2.
 
Scott LaRochelle said:
Please explain. It's a single phase connector. 2 hot legs.
My theory, and I could be a total idiot, is 2 amps in a rack fed by 1 L14-30. L14-30 hot leg number 1 goes to amp 1, L14-30 #2 goes to amp 2. If amp one has a problem it trips the breaker, not taking out amp 2.
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Read up on MWBC's. Lots of qualified people have given good explanations. I'm on my phone now but can post some links later.
 
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