Subject: Sizing branch breakers

Is there an easy way to determine what size branch breaker to use?

Yes, a good rule of thumb is 1600 watts of audio per 20 amp breaker. Two 400 watt stereo amplifiers or one 800 watt stereo amplifier will run forever on a 20 amp circuit breaker without any nuisance breaker trips.

Subject: Breaker nuisance tripping

Do all 20 amp circuit breakers respond to inrush surges the same way?

NO! Circuit breakers have widely varying trip responses depending on their intended use. For most audio power amplifiers you need breakers with a HM rating. The High Magnetic rating allows a substantial inrush current, about double, for the first 100 milliseconds to eliminate nuisance trips. Nuisance trips are common on circuit breakers not rated for High Magnetic duty.

For instance, a standard Square D QO120 breaker will trip with as little as 120 amps in the first cycle compared to 240 amps for a QO120HM.

In Square D, the HM rating is only available for 15 and 20 amp breakers.

The 30 amp QO breakers sustain inrush currents of 300 amps for the first 10 cycles @ 60 Hz, sufficient to light up most of the largest power amplifiers without nuisance tripping.

Subject: Multi Pole Breakers

We are using powered loudspeakers that may be powered by 208v. I see you have 2 pole motorized breakers (MB-220) Do I need 2 breaker drivers for a 2 pole breaker?

No, they are the same as a single pole. Each step on a MS-12 sequencer board can drive two breakers, be they one, two or 3 pole.

Each MS-12 board has 6 steps capable of driving 2 breakers per step.

The MB-220s are becoming more popular to power “flown” powered loudspeakers running on 208 or 240v to reduce wire and conduit size/cost. Each MB-220 contains one motor for actuation of both poles.

Subject: How much power will panel supply?

How much power will a 3 phase, 225 amp main breaker supply?

Assuming most audio gear is 120 volt, a 225 amp, 3 pole main breaker will deliver 225 amps in each leg forever.

Code dictates that breakers be derated to 80% of their indicated handle current.

Example: 225 amps per leg x 3 = 675 amps x 80% derating = 540 amps @ 120 volts.

The continuous power rating is 540 amps x 120 volts = 64,800 watts or 64.8 KVA

Audio systems typically require a high inrush current to charge the power supply capacitors and then only need high current to keep the capacitors charged when a sustained high output is encountered. A conservative approach for audio systems is to figure a maximum duty factor of 50% so the panel could power amplifiers requiring up to 129,600 input watts. The actual audio output power will be contingent on amplifier efficiency.

Subject: Bolt on breakers

I have a specification that calls for bolt-on breakers. Can we use bolt-on breakers in the MSLC 341 Sequencing Load Center?

No. The load centers have insufficient room to accommodate bolt-on breakers. The bolt-on tabs require an additional inch between the two breaker rows. If bolt-on breakers are required use the MSP or MSPH Sequencing Panelboards. The MSPs will accept bolt-on or snap-in breakers. The MSLCs only accept snap-in breakers.

Subject: RMS Symmetrical Short Circuit Current Rating

How do we get a Sequencing Load Center with an interrupt current higher than your standard 25kAIR main breaker rating?:

Short answer:
Replace the standard (25kAIR) QDL main breaker in our MSLC & MSP 341 panels with a QGL main breaker rated at 65kAIR. The model numbers change to MSLCH and MSPH series.

Long answer:
Sometimes a large capacity transformer feeding a sequencing panel will deliver more than 25,000 Amperes to a dead short, requiring a higher main breaker interrupt current rating than the standard 25kAIR (Square D QDL series) offered in our MSLC 341-xx Load Centers.

All of the MSP 341 Panelboards have a 65kAIR main breaker (Square D MHG or MJG series) to satisfy this requirement.
(see Acrobat-15w

Your MB Motorized Breaker series and BMB Motorized Breaker series only have a 10kAIR rating. What happens if they sustain a 65,000 Ampere capacity short?

All of our panels are “Series Rated” by Square D. Example: A Series Rating on a QGL main breaker indicates that the 65kAIR main breaker and 10kAIR branch breaker, QO or QOB, combination have been tested and certified to UL. Both breakers may trip but safety will not be compromised. Acrobat-15w

Subject: ZipOn ??

I know you have ZipOff for fast shutdown. Do you have a ZipOn function? The fire marshal wants access to the arena paging system within 15 seconds of a cold start. How quickly can we activate a system of 80 circuits?

We never thought of it as a ZipOn, but we can accomplish that function. The MS series modular sequencer flexibility makes this fast turn-on function possible. The MS series STEP RATE may be set at 1/8, 1/4, 1/2 or 1 second.

80 circuits would require two MSP or MSLC 341-48 cabinets. Each cabinet holds up to 41 motorized breakers. Each cabinet has 4 daisy-chained, 6 step sequencer boards. Each step controls two motorized breakers, so we have 24 steps per cabinet.

By installing both the 1/4 and 1/2 second STEP RATE jumpers we can set the step rate to 1/8 second. Each of the two cabinets with 24 steps, will take 3 seconds to turn on. (24 steps x 1/8 sec. = 3 sec.)

By using only 6 of the 15-second design target, there will still be some time that may be used for front end settling by setting the delay between steps 1 and 2 of the first board to 4 or even 8 seconds.

A variation would be to turn on each step at 1/4 second with a settling time delay of 2 seconds for a total turn-on time of 14 seconds. (48 steps x 1/4 =12 sec. + 2 sec. settling time = 14 sec.)

For larger systems, we can turn on up to 5 sequencing systems in parallel to keep the turn-on time to a minimum. For instance: A stadium has a small MSLC panel in the control room with 24 circuits. With a 4 second settling time delay it requires 5.5 seconds to turn on. (12 steps x 1/8 sec = 1.5 sec + 4 sec. settling time = 5.5 sec.)

By series-parallel connecting the daisy chain connections to five MSLC/MSP 341-48 panels we can turn on a 229 circuit system in 8.5 seconds. (Front end MSLC = 5.5 sec. + five parallel connected MSLC or MSP 341-48s, each requiring 3 sec. [but sequencing simultaneously] = 8.5 sec. total turn-on time)

See the Series-Parallel Hookup Diagram located in
Acrobat-15w (page 5) (3.3MB)

Subject: I only need 2 more circuits – Do I have to buy another sequencer board?

I have a MSLC 341-36. It feeds two different sound systems that are completely independent. For the larger system I need 26 circuits, two more than two boards will sequence. Can I double connect two more?

No, not safely. The control relay and its power supply will be overloaded, shortening its life and compromising the performance in a low line voltage situation. But wait… there is a way.

If the third board is not fully loaded you can use 2 or 4 circuits from it. Using the auxiliary breaker function, you can swipe the drive capability for 2 or 4 circuits.
See Acrobat-15w

Subject: Controlling the LynTec sequencer from a Crestron touch screen interface.

I’d like to put an image of the SS-2 ON and OFF switches on a Crestron screen and have the ON button flash during the sequencing. Is this easily done?

Yes. Download Acrobat-15w It contains a link for the jpeg button images. There are 3 actual size images: A lit ON button, and an unlit ON button that may be positioned on top of each other. By alternating them using the +5v Logic Output from the sequencer, the ON button will flash in sync with the SS-2 ON switch. The third image is of the OFF switch that is never lit.

Subject: Inhibit first few circuits from Kill and HurryOff to save DSP boot time.

For our nightclub application the Fire Marshall requires immediate shutdown of the sound system at his command or when the fire alarm is triggered. Our club has the Kill line connected to the fire alarm. When the fire alarm contacts close, Kill shuts everything down including the DSP.

The club experiences many false alarm pulls, turning off the club audio. The long boot time of the DSP exacerbates the audio dead time, pissing off the patrons. Is it possible to leave the DSP on somehow during the Kill function?

Yes. You can inhibit Kill and HurryOff to early sequenced circuits by setting a delay after those front end circuits of 4 seconds or more. [Units shipped after 6/04, revision 17 up. Use on FIRST/TOP board only]

When Kill or HurryOff are triggered, (hold down OFF button for 2 seconds to invoke Kill), all of the circuits after the ≥ 4 sec. delay will shut down leaving the front end on. Another OFF button stroke will complete shut down.

Your fire alarm shutdown will then only shutdown to the DELAY point leaving the DSP untouched. As soon as the fire alarm clears, the power amps above the DELAY point will automatically resequence on, giving your patrons what they paid for.