S4 max ambient temperature for max lamp life?

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Cross posted to PSW: http://forums.prosoundweb.com/index.php/topic,167532.msg1545856.html#msg1545856

ETC Source 4 (S4) 575w fixtures
Ceiling Cove = 6ft x 1.5ft x 2.5ft (L x W x H)
Air conditioned room year round.
The current coves have a grate that opens to the attic. Venue wants to close that off so that the attic heat doesn't get into the room.

Concerned that the increase in ambient temperature (can't escape to attic) will decrease the life of the lamp.

ETC says best practice is to have constant airflow to "increase the life of the lamp" though they have no study to support this claim.

My problem with thinking ambient temperature determines life of lamp is that the ambient temperature is so small compared to the temp of the lamp as to be inconsequential. https://what-if.xkcd.com/155/

http://www.calculator.net/btu-calculator.html

Temp controlled Fan option:
https://www.amazon.com/dp/B000M4W2DM/?tag=controlbooth-20
 

Amiers

Renting to Corporate One Fixture at a Time.
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Well heat rises. So I don’t see the attic heat pouring out like they think it will.

I think they are super over thinking it.

If they are super worried and feel like spending money they can put in a bathroom fan to suck air up to the attic. Could go so far as to thermostat control it even. Might save a days worth of lamp life.
 
Joined
Feb 18, 2012
Location
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Well heat rises. So I don’t see the attic heat pouring out like they think it will.

I think they are super over thinking it.

If they are super worried and feel like spending money they can put in a bathroom fan to suck air up to the attic. Could go so far as to thermostat control it even. Might save a days worth of lamp life.
Agreed. I said plug the holes and I doubt you'll see any noticeable lamp life difference. There might be a statistical difference, but it's going to be small.

Mostly the humidity/temp close to the ceiling is an issue causing mold buildup. They're trying to get the AC bill down as they're having to keep the room cooler all the time.
 

JohnD

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They might also want to address the ventilation in the attic space. Usually you want an inlet for fresh outside air coming into the attic at a lower elevation and the hotter air venting outside at the highest elevation. Having good attic ventilation can also extend the life of the roofing.
 

FMEng

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I think excess heat will drastically shorten the life of the instruments. I have similar ceiling boxes with Strand Lekos, and have observed the following over 25 years of operation. I doubt the heat affects lamp life much but it does kill the ellipsoidal reflector. Some of ours had discolored reflectors, damaging the light output and color temperature. The oxidation of the reflector surface is hard to see, but the effect is obvious. Once I noticed the trend and allowed more air flow through the box, the problem subsided. More heat also shortens socket life.

The best compromise would be motorized dampers run by a hydraulic bulb thermostat. When the lights start heating the box up, the thermostat opens the dampers. Any competent, commercial HVAC contractor should be able to do the installation, and it should not cost more than replacing a few toasted Source 4s.
 

Les

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Agreed. I said plug the holes and I doubt you'll see any noticeable lamp life difference. There might be a statistical difference, but it's going to be small.

Mostly the humidity/temp close to the ceiling is an issue causing mold buildup. They're trying to get the AC bill down as they're having to keep the room cooler all the time.
An interesting study would be to see which is a bigger drain on the AC system - open hole where cool air can escape, or introducing these fixtures' heat in to the room, considering it previously vented in to the attic.
 
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An interesting study would be to see which is a bigger drain on the AC system - open hole where cool air can escape, or introducing these fixtures' heat in to the room, considering it previously vented in to the attic.
10hrs per week of 2k BTU/ fixture * 14 fixtures = 280k BTU's

vs

Attic venting 24/7 BTU + 50% (wild guess) light BTU?

Who knows?

They might also want to address the ventilation in the attic space. Usually you want an inlet for fresh outside air coming into the attic at a lower elevation and the hotter air venting outside at the highest elevation. Having good attic ventilation can also extend the life of the roofing.
Attic is vented properly as per commercial building standards. Over on my PSW post Tom states that the 350℉ creates some convection currents already. Is it enough? (rhetorical)

I think excess heat will drastically shorten the life of the instruments. I have similar ceiling boxes with Strand Lekos, and have observed the following over 25 years of operation. I doubt the heat affects lamp life much but it does kill the ellipsoidal reflector. Some of ours had discolored reflectors, damaging the light output and color temperature. The oxidation of the reflector surface is hard to see, but the effect is obvious. Once I noticed the trend and allowed more air flow through the box, the problem subsided. More heat also shortens socket life.

The best compromise would be motorized dampers run by a hydraulic bulb thermostat. When the lights start heating the box up, the thermostat opens the dampers. Any competent, commercial HVAC contractor should be able to do the installation, and it should not cost more than replacing a few toasted Source 4s.
Nice points.

Temp controlled fans would probably be the next step. They're cheap and easy to implement.
 

JD

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I assume that the HVAC vents are in the normal ceiling section, and that there are no ceiling fans that push air down. Under those circumstances, there is a natural heat gradient in any room with the floor being coolest and the ceiling being hottest. Without a mixing element, AC can coexist with hot air near the ceiling. I don't see a significant cost savings for the venue to close them off unless there is a positive pressure above the ceiling forcing the hot air downward.
 

BillConnerFASTC

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Is the ceiling the thermal and barrier or the roof? If the ceiling, then obviously those ceiling vents from room to attic should be sealed and insulated, and I suspect the lighting cove will be overall cooler. If the building is generally a swiss cheese with no continuous thermal and air barrier, it doesn't matter much.
 

JD

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North Wales PA
They are hung almost below the coves so I don't think it will affect them as much, especially as there will be a ceiling level swirl from the HVAC vents. Small vent fans (like a bathroom vent) connected to thermostats in the boxes, set at 100 degrees would help and save them money by removing the heated air from the room.
A bigger problem might be the bases of the movers, which contain the electronics, being subjected to preheated air. May cause early failures in those electronics.
 

BillConnerFASTC

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I have to disagree with John. You would save more energy dollars and have less mold problems by sealing the ceiling which, based on photo, is the thermal barrier. By venting or exhausting air from high inside, your sucking warm air in some other place and its saturated. As it enters and cools, the moisture condenses from it.
 

FMEng

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The pictures change my opinion. I think the S4s have enough air movement to be fine. I would worry about the mover, though. At the least, hang it lower so that the electronics are where there is more air movement and lower temps.

I am skeptical about the bathroom fan idea. Not only do they tend to be noisy, but the motor bearings would be subjected to the temperature of the exhaust air. They won't last long under those conditions because permanent lubrication isn't really permanent.
 

JD

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North Wales PA
I am skeptical about the bathroom fan idea. Not only do they tend to be noisy, but the motor bearings would be subjected to the temperature of the exhaust air. They won't last long under those conditions because permanent lubrication isn't really permanent.
I used the work "like" because of the noise issue, but there are plenty of small vent fans and some duct booster fans that run pretty quiet. Object would be to dump the air from the box if the temperature got above X degrees. Still, I suspect nothing needs to be done about the S4 fixtures because they are hung low. Capacitors drying out in the electronics of the movers over time would worry me.
Here's another thought, see if someone in the HVAC department could run some 3 inch flex-duct from the AC ducts and vent them into the boxes. getting a little air moving around may prevent the heat buildup without adding any noise.
 
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Here's another thought, see if someone in the HVAC department could run some 3 inch flex-duct from the AC ducts and vent them into the boxes. getting a little air moving around may prevent the heat buildup without adding any noise.
Ohh that's a good idea!

Aight, glad my gut reaction was along the correct lines.

I'll inform them covering the holes won't hurt the lights, but adding some cooling specifically for the movers might be a good idea :)

Thanks everyone!
 

Chase P.

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San Francisco
What about a couple of little brushless fans? They're nearly silent, cheap as chips on Amazon, and compact enough to fit almost anywhere. Get the 120v versions, and they could go on the same power as the mover, thereby only being on when it is.

They'd do a fair bit to just keep the air moving, same as the 3"duct idea, but without calling in an HVAC contractor.
 
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RonHebbard

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If you dump chilled air into those coves, aren't you going to have condensation problems?
@Jay Ashworth For a number of years I played IA Head Electrician in a 750 seat venue in Hamilton, Ontario, Canada. The auditorium was heated and cooled by 3 rooftop units; one for the balcony, one for under the balcony and the third for the remainder of the main floor. Large diameter round, uninsulated, ducts were routed across the full width of both ceiling coves. The Artistic Director was a serious penny pincher who'd only turn on the air about 30 minutes prior to doors. I always found it "interesting" when the the three separate systems worked against each other with two attempting to cool the auditorium while the third did its darndest to heat and / or vice versa. Your comment about condensation recalled a memory. When the auditorium was hot and stagnant and the Artistic Director fired up the three air conditioners, they'd blow chilled air through the warm uninsulated overhead ducts and water would immediately begin condensing on the exteriors of the ducts then running down around their exteriors and dripping off their bottoms in rows of what amounted to rain saturating two rows of soft seats below. Not exactly what patrons were hoping to find when they folded down their seat cushions and sat in their wet seats then found water dripping on their heads. The larger dual balconied road house in town had lined ducts which never appeared to exhibit this problem. They were also larger diameters moving greater volumes of air at slower velocities.
Toodleoo!
Ron Hebbard
 

JD

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North Wales PA
If you dump chilled air into those coves, aren't you going to have condensation problems?
Shouldn't. As air heats up, it drops in humidity so it would be a drying effect. Now if hot moist air were entering a cool pocket, then there would be a problem.
As Ron mentioned above, the condensation occurred on the outside of the ducts as hot air cooled on the chilled metal.