# Melting Pavement

Discussion in 'Lighting and Electrics' started by DuckJordan, Feb 18, 2012.

1. ### DuckJordanWell-Known Member

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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?

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

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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. ### avkidNot a New User

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You need to find a new hobby.
5. ### DuckJordanWell-Known Member

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No the number is right 3840 lol

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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
Last edited: Feb 19, 2012
7. ### tjrobbActive Member

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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.

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Zero...
9. ### derekleffewSenior TeamSenior TeamPremium Member

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One would think, given a known foot-candle reading (in this case ~221 for HPL750/115, 5&deg;@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 :
Maybe S4 PAR-EA VNSPs would be a better choice for the, alleged, diabolical deed.

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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. ### DuckJordanWell-Known Member

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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. ### techieman33Well-Known Member

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Older 5* strands with FELs would put out a lot more heat.
13. ### shibenWell-Known Member

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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 8,000&ordm;F) 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...
Last edited: Feb 19, 2012
14. ### DuckJordanWell-Known Member

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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. ### avkidNot a New User

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24,000 Amps?
Holy mother of.............

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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. ### MNicolaiWell-Known Member

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I believe he means 2.4k, or 2400A, which is 800A on three phases -- about right for moderate handful of dimmer racks.
18. ### DuckJordanWell-Known Member

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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. ### shibenWell-Known Member

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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 1200A3&oslash; 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.

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