Dirty Dimmers Waste Energy!?

[derekleffew]

I recently read in one of the Industry Periodicals about ways to make stage lighting more efficient. One of the points made was to keep optics and dimmer cabinets clean.

...this dust collection [in the dimmer rack] also diminishes output at the instruments downstream. If I have to push a channel to 90 percent to achieve the desired light level when I could have been at 80 percent, that's a simple waste of energy.

(I'm reluctant to cite the source until we've had some discussion.)

Now there are a number of perfectly valid reasons why one should keep a dimmer rack's filters and modules clean, but I've never heard of diminished output as being one of them. So the question is: Can/will dust build-up on a dimmer module (assuming dimmer, phase control) cause overheating to such a degree that it leads to a noticeable voltage drop at the fixture?

Thoughts, anyone?

[DavidNorth]

So the question is: Can/will dust build-up on a dimmer module (assuming dimmer, phase control) cause overheating to such a degree that it leads to a noticeable voltage drop at the fixture?

Thoughts, anyone?

Simple answer, no.

Longer answer. While yes, it is possible that dirty conponents and connections can cause voltage drops, but let's be honest, there are only a few parts in the current path from feeder to load and if those parts are dirty enough to cause a voltage drop, they are also emitting smoke burning the dust and dirt off. Power cubes or SCRs/Triacs and circuit breakers are not affected. Only chokes are left and they would get so stinkin' hot [literally] that this would be a larger issue than voltage drop.

Now, what was not mentioned was voltage drop due to loose connections. While not related to dirt, thermal cycling can cause feed and load screws to gradually loosen and copper wire can also thermal flow inside these connections. Regular tightening or torque checks on said fasteners [when tension clamps are not used] should reduce or eliminate voltage drop over these connections. Lack of maintenance can eventually lead to conductor failure.

BTW, just looking at connections inside dimmer racks and ignoring connectors in circuits strips and boxes is an oversight.

Next you'll ask me how often to check tightness. Not sure I can give you a direct answer as it greatly depends on use of the system. The colleges and municipalities that perform this maintenance do it about every other year. There is another option which is to use a thermal imaging camera to look through panels to see if any wiring connections are heating up [and therefore are loose]. Unfortunately, this means you have to run loads on every circuit [not how we usually work] and seeing inside dimmer racks is usually difficult.

Maybe there is something I'm blatantly missing, but I can't think of a reason why dust and dirt would create a voltage drop. Wait, maybe I've been thinking exclusively of digital dimming. It will take me some time to run through my brain catalog to think of how dust could create voltage drop issues in analog or even linear autotransformer dimmers. Goodness, I still can't think of why. Maybe JD knows?

[JD]

No.

SCRs, Triacs, SSRs are either on or off. Junction voltage drop is <1 volt. This does not change in any appreciable way with temperature.

Output is determined by when in the AC cycle they switch from off to on. (Phase chop dimmers.)

There are many reasons to keep dimmers clean, and proper cooling will extend life. Efficiency, however, is not one of them.

Of course, I must remember that this was posted by Derek, and he did not specify from what year the periodical was from, only that he read it recently. It could be true with resistance plate dimmers as confining the heat would cause the nichrome resistor wire in the plate to overheat and increase in resistance, requiring a higher setting. (Of course, Derek will than note that he specified Phase Control dimmers in his summary question.)

[DavidNorth]

Found the article. While yes, more energy is burned to keep racks cool, it's usually not because the fan is running harder to increase the cooling. Racks with thermal controlled fans are not common [even though we make one] and they might run faster but a fixed speed fan will turn harder when packed with dust trying to maintain fixed speed. The energy difference, especially compared to the overall draw of energy from lamps, is negligible.

Interestingly enough, what's not mentioned is dimmer efficiency in regards to HVAC cooling. Any high dimmer rise time dimmer is going to have more waste heat than a low risetime dimmer, which must be countered by air conditioning. Now you are burning energy twice.

I do like the subsequent comments about relative brightness. How many of us like to pop the stage with today's even more efficient tungsten lamps. I remember trying to squeeze every drop out light out of old Century and Strand ellipsoidals and would have killed for a 750W S4 years before they existed. I think we have reached a very bright level of lighting in shows and I am not without blame.

But back to the topic....

[JD]

Well, the quote that got me is:

"If I have to push a channel to 90 percent to achieve the desired light level when I could have been at 80 percent, that's a simple waste of energy."

That's the one that knocks it into the "foul ball" territory.

[DavidNorth]

Agreed.

[DrPinto]

I recently read in one of the Industry Periodicals about ways to make stage lighting more efficient. One of the points made was to keep optics and dimmer cabinets clean.

(I'm reluctant to cite the source until we've had some discussion.)

Source discovered (thanks Google)

The article stated that the author is a "lighting designer and sustainability advocate". What the heck is a "sustainability advocate"? The best I can figure out is that he's an environmentalist, unless the term has another meaning in the entertainment industry.

[Pie4Weebl]

Well, the quote that got me is:

"If I have to push a channel to 90 percent to achieve the desired light level when I could have been at 80 percent, that's a simple waste of energy."

That's the one that knocks it into the "foul ball" territory.

Then again it seems he combines the dirty rack with dirty optics, and having optics covered in haze juice and dust WILL have an impact on intensity.

[Pie4Weebl]

Source discovered (thanks Google)

The article stated that the author is a "lighting designer and sustainability advocate". What the heck is a "sustainability advocate"? The best I can figure out is that he's an environmentalist, unless the term has another meaning in the entertainment industry.

Sounds like he has a product to sell you that avoids these issues

[derekleffew]

... What the heck is a "sustainability advocate"? The best I can figure out is that he's an environmentalist, ...

AKA, "myth of global warning"-proponent.

(ducks and runs)

[STEVETERRY]

I recently read in one of the Industry Periodicals about ways to make stage lighting more efficient. One of the points made was to keep optics and dimmer cabinets clean.

(I'm reluctant to cite the source until we've had some discussion.)

Now there are a number of perfectly valid reasons why one should keep a dimmer rack's filters and modules clean, but I've never heard of diminished output as being one of them. So the question is: Can/will dust build-up on a dimmer module (assuming dimmer, phase control) cause overheating to such a degree that it leads to a noticeable voltage drop at the fixture?

Thoughts, anyone?

Very simply, no. (See David North's explanation).

Since David got there first, I will have to content myself with an other addition to the List of Big Lies.

1. This won't hurt a bit
2. The check is in the mail
etc,etc
4. Dirty dimmer racks lower output, turning a control setting of 80% into 90%.



ST

[MPowers]

To Echo what Steve said, but about the mention of resistance dimmers, this coming from someone who spent MANY hours and a LOT of shows in the 50's and 60's running both piano boards with 3K and 6K plates and a lot of (auto-transformers) Luxtrol 6/7 and Altman 6 pacs, the amount of dust needed to affect the output of those units would put the operator about waist deep in fluff. Perhaps, if we let our imaginations run wild and add a high concentration of some conducting material to be mixed in with the dust, it could affect performance.......by shorting across contacts and burning up the dimmer. Changes in intensity prior to failure would be nil as the very nature of the units, a series of contacts and a wiper type of tap, effectively clean the contact path each time the dimmer intensity changes. In addition most resistance boards and auto-transformers were mounted with the plates or master coil in a vertical position so any debris would tend to fall off even before the wiper helped clean it.

[MPowers]

Now that the Myth of dirty dimmers affecting intensity has been "BUSTED" , that doesn't mean that we should ignore house keeping. Dust can affect air filter and air flow which will cause problems. It is also bad practice in general to allow dirt and debris to accumulate in any area, like there are no dusty grids, storerooms and such in any of our theatres :-) .

[STEVETERRY]

Now that the Myth of dirty dimmers affecting intensity has been "BUSTED" , that doesn't mean that we should ignore house keeping. Dust can affect air filter and air flow which will cause problems. It is also bad practice in general to allow dirt and debris to accumulate in any area, like there are no dusty grids, storerooms and such in any of our theatres :-) .

Excellent point.

ST

[derekleffew]

Many off-topic posts have been moved to http://www.controlbooth.com/forums/o...-big-lies.html .

[TimMiller]

No dirty dimmers don't waste energy, they do the exact opposite they conserve it. Here is how it works..... Let your racks get all piled up with dust clogging up the ventilation, the rack will go into over temp and shut down or start to blink the lights thus reducing power consumption and conserving energy.

[Mitch]

From an electrical P.O.V. Getting dirt on your connections won't really effect it to much. Like mentioned above, loose connections can cause problems and if dirt/dust were to get between you conductors then that could cause problems.
Best Luck, Mitch