Melting Pavement is being discussed in the ControlBooth Lighting and Electrics forum; Random Theoretical question... How much heat is produced through a s4 5* at a 78 foot throw also what would ...

1. ## Melting Pavement

Random Theoretical question... How much heat is produced through a s4 5* at a 78 foot throw also what would be the diameter of that spot.

Little bit of info

We are coming up with a really stupid idea, 3840 s4 5* lamped at 750 watts. all focused on the same spot. how much heat would that produce at ground level?

2. ## Re: Melting Pavement

I assume you mean 384 S4s, not 3,840. That should be a beam with a diameter about 9.3'.

3. ## Re: Melting Pavement

According to ETC the field diameter is 7.9' at a 65' throw so somewhere close to that I'd imagine. Here is a pdf to the photometrics though.

I'm not sure how to get the temperature created from those numbers though.

4. ## Re: Melting Pavement

You need to find a new hobby.

5. No the number is right 3840 lol

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6. ## Re: Melting Pavement

Originally Posted by DuckJordan
Random Theoretical question... How much heat is produced through a s4 5* at a 78 foot throw also what would be the diameter of that spot.

Little bit of info

We are coming up with a really stupid idea, 3840 s4 5* lamped at 750 watts. all focused on the same spot. how much heat would that produce at ground level?
The amount of IR energy exiting the front of a Source 4 is negligible, because of its "cold mirror" coated reflector. For precise figures, measure one and multiply by 3840.

A bigger issue is 2.88 megawatts of heat generated by 3840 750W HPL lamps. That is going to produce significant temperature rise in a space, even from 78 feet away.

Do you want to share what you're up to with us?

ST

7. Not to doubt you, Steve, but we had a S4 burn through our wood catwalk once. Mind you, it was 4" away at the time, 575W. Not entirely sure how they managed that trick.

8. ## Re: Melting Pavement

Originally Posted by DuckJordan
...all focused on the same spot. how much heat would that produce at ground level?
Zero...

9. ## Re: Melting Pavement

Originally Posted by STEVETERRY
... For precise figures, measure one and multiply by 3840.
One would think, given a known foot-candle reading (in this case ~221 for HPL750/115, 5°@78') at color temperature of 3250K, one should be able to calculate heat in calories, BTUs, or somesuch. No?

See also KnowledgeBase: Source Four Heat Ratings/ How Much Heat Does the Source 4 Emit? - Electronic Theatre Controls :
Keep in mind that S4, S4jr, and S4 PAR-MCM fixtures absorb more of the infrared light spectrum than most typical fixtures due to the cold mirror optical coating on the reflector, and therefore transmit significantly less heat to the stage. The S4 PAR-EA does not contain this feature and projects the full infrared spectrum to the stage.
Maybe S4 PAR-EA VNSPs would be a better choice for the, alleged, diabolical deed.

10. You've got to remember that while some heat comes out the front a good chunk of that is discharged out the back.

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11. I'll have to look at those threads. As far as other heat for this question its not important. Pars might be better but from 78 feet that's close to 30' circle.

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12. ## Re: Melting Pavement

Older 5* strands with FELs would put out a lot more heat.

13. ## Re: Melting Pavement

Why is it desirable to melt pavement? From 78 feet away, I can come up with some FAR superior ways to melt asphalt (that will cost a fraction of the price), and concrete is gonna need a thermal lance to melt it anyhow (around 8,000ēF) and I have a feeling that your S4s wont come close, and nothing but perhaps a very large DEW will work from any real distance. FWIW, my cutting torch CAN melt bricks, but it takes a long while to make that happen. I still doubt that you will get enough heat to really melt pavement per se... Otherwise, Synchros might work better if you just want to burn actors, but then get one of those HMMWV-mounted microwave dishes that create searing pain and no damage...

14. ## Re: Melting Pavement

not so much about the melting of the pavement, but just to figure out the temperature of 3840 source fours aimed at one spot... (btw the reason it came up, late night and found out our new building will be getting 24k amps of power into the building just for show power....

15. ## Re: Melting Pavement

Originally Posted by DuckJordan
not so much about the melting of the pavement, but just to figure out the temperature of 3840 source fours aimed at one spot... (btw the reason it came up, late night and found out our new building will be getting 24k amps of power into the building just for show power....
24,000 Amps?
Holy mother of.............

16. ## Re: Melting Pavement

I think that takes spare capacity to a whole new level.
We can do a concert for 100k people down here on about 1000A/ph so 3000A total. Convert for voltage difference and that's still only 6000A, a quarter of your feed.

Beware that you'll probably have a fairly hot mains voltage on those feeds because they aren't under much load...
This may cause unwanted effects on your equipment longevity

17. ## Re: Melting Pavement

Originally Posted by avkid
24,000 Amps?
Holy mother of.............
I believe he means 2.4k, or 2400A, which is 800A on three phases -- about right for moderate handful of dimmer racks.

18. ## Re: Melting Pavement

nope 24k Amps 24,000 Amps, This would never be used fully Most shows only require 1500 amps but its a possibility. Again all theoretical...

19. ## Re: Melting Pavement

Originally Posted by DuckJordan
nope 24k Amps 24,000 Amps, This would never be used fully Most shows only require 1500 amps but its a possibility. Again all theoretical...
Crap. Thats a large amount. However, it is useful to ask: how big is the building and what is being done there? ESC certainly uses several times that, and I can imagine a large conference center would have this sort of system in place... Also, if you have, say, several theaters, each with an 800 A Company Switch AND a couple of dimmer racks, it gets eaten up. Figure if you have a mainstage w/ a 1200A3ø switch (large but they might be planning for a large amount of extras) and say 4 Sensor 3 96 racks, a couple studio spaces w/1x Sensor 3 96 rack each, and maybe a conference center with a couple 600A company switches, thats 24000A. Overkill? Probably. More likely, the designer added up all the circuits, figured they would be on max load, then went ahead and figured out how much power to push in. So yeah, I don't actually think its terribly unreasonable, especially if generators are hard to come by in the area. Although needing your own substation might negate the savings on that, but whatever.

20. ## Re: Melting Pavement

Well our air compressor is on a 600A 3PH disconnect. We have a 400A 3PH company switch onstage, a handful of 80A 3PH scattered in the cats. Not sure what feeds the dimmer racks or audio equipment. Not sure what the standard utilities use. Lots of 277V for lighting. I imagine our Air systems run on 208V and 480V.

24kA is a lot of current, that's for sure.

If you are insistant on melting things consider carbon arc equipment. Or an oxygen concentrator and a large stock of cutting lances. You could build one hell of an electrolysis system and create a LOT of Hydrogen and Oxygen and build an awesome torch.

21. ## Re: Melting Pavement

Originally Posted by 65535
If you are insistant on melting things consider carbon arc equipment. Or an oxygen concentrator and a large stock of cutting lances. You could build one hell of an electrolysis system and create a LOT of Hydrogen and Oxygen and build an awesome torch.
I do not think a Carbon Arc unit would be nearly as efficient as a giant cutting lance. IIRC, OxyHydro is not a great torch system for most cutting applications, and it might not even burn as hot as Acetylene... A cutting lance is your best bet. Molten Iron, Magnesium and Aluminum in the presence of pressurized oxygen.

Edit: Max temp of an Oxy-Hydrogen flame is 2800ēC, Max temp of an Oxy-Acetylene flame is 3500ēC. I believe that you can actually get an oxidizing flame in excess of 3500ēC, but it is generally not great for welding or cutting applications.

22. ## Re: Melting Pavement

If I understand everything now, I don't think he's really wanting to cut anything, someone just did the math after they found out about the 24,000A and realized they could theoretically have that many lights turned on and wanted to find out the temp if they ever were to really have a situation like that.

@Shiben, it also sounds like they don't have to ask what else is in the building since Duck said it's 24,000 just for show power. Meaning presumably it's all theirs and no need to worry about whatever power the building needs or is getting.

23. ## Re: Melting Pavement

All I have to say is that I'd hate to see the electrical bill produced by this experiment if it were to really happen. Heck, I'd hate to see how a theatre can pay for that electrical bill in general if it isn't a larger conference center.

24. ## Re: Melting Pavement

This is all well and good, but did I miss the part where this was somehow practical, useful, or anything?

Don't get me wrong I'm laughing along with everyone else :D man this is the kind of stuff we did in high school all the time. Obviously in lower quantities.

25. ## Re: Melting Pavement

Haha, this sounds like something my Dad's friend did at his frat house. Apparently the house was a few stories tall and had a courtyard in the center. So one day his friend pennies some guy on his floor into his room (locks him in his room). Then he plugged a microphone into his stereo and directed everyone else on the floor to take the mirrors off their walls and direct the sunlight at so-and-so's room.

Holy crap, that's pretty crazy electrical service.

26. ## Re: Melting Pavement

Originally Posted by shiben
I do not think a Carbon Arc unit would be nearly as efficient as a giant cutting lance. IIRC, OxyHydro is not a great torch system for most cutting applications, and it might not even burn as hot as Acetylene... A cutting lance is your best bet. Molten Iron, Magnesium and Aluminum in the presence of pressurized oxygen.

Edit: Max temp of an Oxy-Hydrogen flame is 2800ēC, Max temp of an Oxy-Acetylene flame is 3500ēC. I believe that you can actually get an oxidizing flame in excess of 3500ēC, but it is generally not great for welding or cutting applications.
Max temperature for the arc temperature of plasma devices like carbon gouges I have seen quoted in excess of 25kC. That's 25,000C.

Thermic lances may produce more heat, but in terms of raw temperature plasma wins.

Also a thermic lance doesn't put the power available to use, carbon arc and other plasma devices do.

Another thing, once you get a material hot enough pure Oxygen reacting with the material creates enough heat to cut through that material, once started the reaction doesn't require the lance but to deliver the Oxygen to the cut.

27. Practicality I want to bad roast a cow... This is an event center space.

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28. ## Re: Melting Pavement

Originally Posted by 65535
Max temperature for the arc temperature of plasma devices like carbon gouges I have seen quoted in excess of 25kC. That's 25,000C.

Thermic lances may produce more heat, but in terms of raw temperature plasma wins.

Also a thermic lance doesn't put the power available to use, carbon arc and other plasma devices do.

Another thing, once you get a material hot enough pure Oxygen reacting with the material creates enough heat to cut through that material, once started the reaction doesn't require the lance but to deliver the Oxygen to the cut.
Truth. Plasma would be hotter.

Originally Posted by DuckJordan
Practicality I want to bad roast a cow... This is an event center space.

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Win?

29. ## Re: Melting Pavement

Wouldn't it be substantially easier to... i don't know, put a heating element under the pavement onstage, and just bring up a lot of light on it, but actually melt it from below?

Also you realize the off-gassing is going to be terrible, and pavement doesn't melt as much as it catches on fire

30. Hmm, most switchboards are maximum 6000A per phase. Your setup intrigues me. (Switchgear may go higher, but I can't recall.)

31. Switchgear can be had at higher ratings, and exponentially higher cost. I too am curious about the specifics as it seems somebody forgot about applying a diversity factor.

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32. ## Re: Melting Pavement

Originally Posted by tk2k
Wouldn't it be substantially easier to... i don't know, put a heating element under the pavement onstage, and just bring up a lot of light on it, but actually melt it from below?

Also you realize the off-gassing is going to be terrible, and pavement doesn't melt as much as it catches on fire
Concrete or something will melt into a lava of some sort...

33. ## Re: Melting Pavement

Yes but I'm from the east coast so 'pavement' just translated as asphalt to me which will stink and burn.

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