Is it acceptable to put 4x S4s on a dimmer?

[SteveB]

Excuse me for butting in, but if I may, I'll drop some info that may answer the question.
A HPL575/115 lamp is "factory rated" to draw 575 WATTS at a line voltage of 115 VAC. Given that information, we can figure operating amperage of 5 AMPS and the resistance of the filament to be 23 OHMS when hot.
Now if your line voltage is 120 VAC, the current goes to 5.21 AMPS and the wattage increases to 625 watts.
If you are one of the lucky ones with a stiff power grid and run 125 Volts, then the current will run up to 5.43 amps, and the wattage will be a whopping 678 WATTS!

I am one of the "lucky" ones, as incoming voltage varies between 123 and 127. That's one reason I like Sensor dimmers, as I can set the circuit voltage, which I keep at 115v. Most Sensor systems come factory set in the CEM/CEM+ for 115v lamps.

Now that 123-127 plays havoc with UPS's, but that's another thread.

Steve B.

 

[venuetech]

Not advisable
The dimmer is not going to be the problem. the problem will be with the cable/wiring.

The circuit breaker is there to protect the wire from going up in smoke and starting a fire.

Any imperfection in the wiring, plug/connector will over time start to cause problems.

just pick the cable up that is feeding these four units, it may not be hot but it will be very warm. carefully check each plug and connector for excessive heat.

you may not find a problem today but 4 or 5 months or more down the line.

not good, not wise.

fire safety, its your call

 

[Casey]

Yes. Of course you can run 4 - HPL 575/115 off of a single 2.4k dimmer. They were built to be used that way, and many people do so on a daily basis. I've never had any problems, but if you do run into one worst case scenerio is it will trip the breaker and you will have to run another circuit to the light.

Not advisable
The dimmer is not going to be the problem. the problem will be with the cable/wiring.

The circuit breaker is there to protect the wire from going up in smoke and starting a fire.

Any imperfection in the wiring, plug/connector will over time start to cause problems.

just pick the cable up that is feeding these four units, it may not be hot but it will be very warm. carefully check each plug and connector for excessive heat.

you may not find a problem today but 4 or 5 months or more down the line.

not good, not wise.

fire safety, its your call

I'm not sure what kind of cable you use, but in the markets that I work in primarily, the only cable I see aside from zip cord for practicals is #12 (12/3) SJO. You can easily run 2.4Kw through it. It will get warm, but again, it was designed to be used that way.

Right now I have a rig up where there are many circuits running at 2.4Kw, this is in a setup where the power (from a good generator, so it is consistent voltage) runs through about 300' of Soca, and another 50' or so broken out. No problems.


So... Yes. Of Course its OK!

 

[midgetgreen11]

I've had four sets of Strips (150W lamps, each strip w/ 4) daisy chained into one dimmer, adding up to 2.4k. Haven't had any issues as of yet.

 

[cdub260]

I'm not sure what kind of cable you use, but in the markets that I work in primarily, the only cable I see aside from zip cord for practicals is #12 (12/3) SJO. You can easily run 2.4Kw through it. It will get warm, but again, it was designed to be used that way.

Right now I have a rig up where there are many circuits running at 2.4Kw, this is in a setup where the power (from a good generator, so it is consistent voltage) runs through about 300' of Soca, and another 50' or so broken out. No problems.

Be aware that NEC Article 520 specifies the use of hard usage or extra hard usage cable on stages. SJO is junior hard usage cable and does not meet code requirements for use on a stage.

Also be aware that if your cable runs are bundled together, you are required to derate the cable to 80% of its normal capacity. This means that while a single 12/3 SO cable is rated at 20 amps, if you run several of these cables bundled together on your electrics, they are now considered 16 amp cables. Socapex is considered a bundled cable run. As such code limits you to 16 amps per circuit. There is an exception to this. There is a type of socapex that is a flat cable rather than a round bundle. I've seen it, but I've never worked with it.

And before the usual, "But I've been doing it this way for years and nothing bad has happened." explanations start, consider that just because nothing has happened, doesn't mean your doing the job in the proper manner. While it was not an incident with electricity, I had to learn this lesson the hard way. Eight years later, I still hurt.

 

[techieman33]

We do it on a regular basis, but they're generally used as wash light and never over 80% at the most so we don't worry about it.

 

[Les]

We do it on a regular basis, but they're generally used as wash light and never over 80% at the most so we don't worry about it.

I'm not saying what you are doing is wrong, but it is helpful to know that even though the lights are at 80% does not mean they are only using 80% of 2400 watts. Theatrical lights typically draw their full wattage well below 100%.

 

[SteveB]

"Be aware that NEC Article 520 specifies the use of hard usage or extra hard usage cable on stages. SJO is junior hard usage cable and does not meet code requirements for use on a stage."

My understanding is that SJ is acceptable in lengths up to 20ft, provided it's in the air and not used on deck. Which is why it's acceptable cable for use in 2-fers and breakouts, with some 6 circuit breakouts being of staggered length up to 20ft..

"Socapex is considered a bundled cable run."

"Socapex" is the name of the manufacturer of the typical (and probably most common) multi-pin connector. Multi circuit cable is the cable itself. Good installation practice is to use one wire size up from the over current rating, thus it's not unusual to see #10 wire on multi-circuit cables running to raceways, etc... that are breakered at 20 amps (Sensor D20 dimmer as example).

Steve B.

 

[David Ashton]

only using 80% of 2400 watts. Theatrical lights typically draw their full wattage well below 100%.[/QUOTE]
A properly set dimmer will only draw its full current when at full, but it is very non linear so at 80 on the dimmer you are drawing maybe 90% of your current,
and the main reason is the non linearity of the resistance of the lamp with heat.

 

[coldnorth57]

20A (2400W) dimmer. Four fixtures with HPL575/115 lamps. Discuss.

NO the breakers in the dimmer pack are reated for 2400watts ....but their true running load is 2000watts ...80% that is the continuse laod but for short time they can ruun at fulll load of 2400 watts

 

[Les]

Originally posted by coldnorth57
NO the breakers in the dimmer pack are reated for 2400watts ....but their true running load is 2000watts ...80% that is the continuse laod but for short time they can ruun at fulll load of 2400 watts

ETC Sensor dimmers are Listed for 100% loading, 100% duty-cycle operation. Four x 575W is no problem.

Some dimmers with thermal breakers can only be loaded to 80%, or 1920W on a 2400W dimmer.

You need to determine the rating of your dimmer to answer this question.

ST

What dimmers are you talking about, coldnorth57?

 

[rmarston]

No, not acceptable to run four 575W S4s on a 2.4KW rated dimmer. Good design practice says the dimmer rating should be derated by some amount. 20% derating will allow 3 S4s to operate even under voltage transient conditions. Why gamble with failures during a production caused by loading a dimmer to close to its rating.

 

[philhaney]

No, not acceptable to run four 575W S4s on a 2.4KW rated dimmer. Good design practice says the dimmer rating should be derated by some amount. 20% derating will allow 3 S4s to operate even under voltage transient conditions. Why gamble with failures during a production caused by loading a dimmer to close to its rating.

I, too, was told by an electrician that you're not supposed to load a dimmer more than 80% of its rated capacity. On the other hand, if SteveTerry says his dimmers are rated for 100% load, I believe him.

 

[STEVETERRY]

NO the breakers in the dimmer pack are reated for 2400watts ....but their true running load is 2000watts ...80% that is the continuse laod but for short time they can ruun at fulll load of 2400 watts

No, the breakers on most theatrical dimmers are fully magnetic units that are listed for 100% load 100% duty cycle. A 20A dimmer like ETC Sensor is rated for 2400W continuous.

Please see the attached article for more on this

ST

 

[STEVETERRY]

I, too, was told by an electrician that you're not supposed to load a dimmer more than 80% of its rated capacity. On the other hand, if SteveTerry says his dimmers are rated for 100% load, I believe him.

The difference is that a Sensor dimmer (and some other manufacturers' theatrical dimmers) are UL Listed for 100% loading, 100% duty cycle. Please see article attcahed to another post in this thread for an explanation.

ST

 

[STEVETERRY]

Be aware that NEC Article 520 specifies the use of hard usage or extra hard usage cable on stages. SJO is junior hard usage cable and does not meet code requirements for use on a stage.

Also be aware that if your cable runs are bundled together, you are required to derate the cable to 80% of its normal capacity. This means that while a single 12/3 SO cable is rated at 20 amps, if you run several of these cables bundled together on your electrics, they are now considered 16 amp cables. Socapex is considered a bundled cable run. As such code limits you to 16 amps per circuit. There is an exception to this. There is a type of socapex that is a flat cable rather than a round bundle. I've seen it, but I've never worked with it.

And before the usual, "But I've been doing it this way for years and nothing bad has happened." explanations start, consider that just because nothing has happened, doesn't mean your doing the job in the proper manner. While it was not an incident with electricity, I had to learn this lesson the hard way. Eight years later, I still hurt.

1. Junior hard service cord is acceptable in Art 520 venues for twofers, adapters, and breakout assemblies--subject to the limitations of 520.68 and 520.69.

2. If you bundle cables together you may be subject to more derating than 80%, per table 400.5. However, if you meet the requirements of table 520.44 for borderlight cables (multicables), you are subject to a different derating and ampacity table. The key requirement of 520.44 is 50% diversity in loading or number of energized circuits.

3. Socapex cables are not bundled cables--they are a specific cable type with a specific ampacity and temperature rating that may be determined by table 520.44 if the diversity requirements are met.

Does everyone on this thread have a copy of the NEC? If not, you know what to do!


ST

 

[cdub260]

1. Junior hard service cord is acceptable in Art 520 venues for twofers, adapters, and breakout assemblies--subject to the limitations of 520.68 and 520.69.

2. If you bundle cables together you may be subject to more derating than 80%, per table 400.5. However, if you meet the requirements of table 520.44 for borderlight cables (multicables), you are subject to a different derating and ampacity table. The key requirement of 520.44 is 50% diversity in loading or number of energized circuits.

3. Socapex cables are not bundled cables--they are a specific cable type with a specific ampacity and temperature rating that may be determined by table 520.44 if the diversity requirements are met.

Does everyone on this thread have a copy of the NEC? If not, you know what to do!


ST

Thank you for the corrections Steve Terry.

I did not have my NEC Codebook with me when I wrote my post, so I had to generalize from memory.

Just one of the dangers of posting while on vacation.