Control/Dimming Do Strand/Century Dimmer Leak?

[Footer]

In the attempt to somehow get a new lighting rig for Mrs. Footer, we have stumbled into the beginning of the meetings to have meetings about meetings. So, the people we met with today were engineers that specialize in power savings for large institutions. While walking them through all of the lamps we use (550 1k lamps in the air kind of throw those type of guys...) one guy asked if we power down our dimmers every night. Of course I said no. He then asked if I knew how much power they used while on but not in use. I know the newer racks only draw as much power as the control cards use while off. I assume that our 1970's vintage Strand/Century dimmers are the same. Am I wrong?

Can't remember the model number's, but we have 60@6k, 10@12k...

 

[David Ashton]

In the attempt to somehow get a new lighting rig for Mrs. Footer, we have stumbled into the beginning of the meetings to have meetings about meetings. So, the people we met with today were engineers that specialize in power savings for large institutions. While walking them through all of the lamps we use (550 1k lamps in the air kind of throw those type of guys...) one guy asked if we power down our dimmers every night. Of course I said no. He then asked if I knew how much power they used while on but not in use. I know the newer racks only draw as much power as the control cards use while off. I assume that our 1970's vintage Strand/Century dimmers are the same. Am I wrong?

Can't remember the model number's, but we have 60@6k, 10@12k...

dimmers of that era commonly output 10 volts at 0, not enough to light the filament but cumulatively enough to draw a fair current, especially with the low resistance of cold lamps, and should one fail and catch fire overnight it could be problematic.I always power down older dimmers

 

[derekleffew]

"Do... dimmers leak? ''
Is there a puddle under the rack?

Throw an amprobe on the feed and measure your quiescent current. If, as @David Ashton says, it's 10V, across 550 FELs that's 1032A. That can't be correct, can it?



Sent from my Nexus 7 using Tapatalk 4

 

[DavidNorth]

Using an amprobe is indeed the way to know whther you leak and by how much. The primary concern about leakage from the engineer's point of view will be from the exerience with power supplies. You've heard of vampire power draw, otherwise known as quiescent current, that common devices such as cell phone chargers and TVs create. Power supplies that are on but not used still draw current. In your case, there is a power supply in each dimmer in the rack. So in fact yes, the Century dimmers will likely be drawing more standby current than a modern rack as there is only one [or a few] power supply in each rack.

It is also highly probable that a small amount of leakage current is coming out of each dimmer with a connected load. I do not believe it is as high as calculated but again, the amprobe tells all. All SCR dimmers leak, but as these dimmers typicaly have larger SCRs and amount leakage is usually tied to the overall current rating, then again, a modern dimmer system is going to be more efficient.

Lastly, do know that most facilities outside the Americas turn their dimmer system off at night. There are various reasons for this but the primary one is safety.

Hope that helps.

 

[David Ashton]

dimmers of that era commonly output 10 volts at 0, not enough to light the filament but cumulatively enough to draw a fair current, especially with the low resistance of cold lamps, and should one fail and catch fire overnight it could be problematic.I always power down older dimmers

correction or rather clarification, I live in 240 volt land so 10v applies here, it would be 4-5 volts in 110 volt land, whatever the leakage current is it would accumulate over a year to quite a lot of wasted power.

 

[JD]

Most older dimmers do idle even with 0 input. This can add up to a heck of a lot of power. Amprobe should answer the question. A 5% idle on a 100kw system would be like leaving 5kw on 24/7 (or 27.5kw for 550kw system.) Can't say I've gone around surveying different dimmer designs on this question, but considering the cost of juice, I would check it. (The lower the idle, the less it would be.)

One other thing- If your utility's meter also measures PF, the bill could be shocking as that idle has a VERY bad PF rating.

 

[hobbsies]

Most older dimmers do idle even with 0 input. This can add up to a heck of a lot of power. Amprobe should answer the question. A 5% idle on a 100kw system would be like leaving 5kw on 24/7 (or 27.5kw for 550kw system.) Can't say I've gone around surveying different dimmer designs on this question, but considering the cost of juice, I would check it. (The lower the idle, the less it would be.)

One other thing- If your utility's meter also measures PF, the bill could be shocking as that idle has a VERY bad PF rating.

What does PF stand for?

 

[JD]

What does PF stand for?

Power Factor. Made simple, it is how well the current and voltage phases line up. Power companies often punish commercial customers for Low Power Factor draw. Since a dimmer at idle only gates current flow at the end of the waveform half, it is way out of phase with the voltage peak, scoring it as a very low Power Factor. If you go home at night and the only thing left running in the building is the dimmer racks idling, any you have an electric meter that tracks PF, the results can damage your budget.

See- http://epb.apogee.net/foe/frbp.asp

 

[hobbsies]

So it's something like the median voltage demand from a building. If you have lights on and devices powered up, then PF is 100% since you're using 120V 100% of the time? If the devices are plugged in but off, and are leaking 10V over the course of the night, that median drops below 100%?

Am I understanding this correctly?

 

[JD]

So it's something like the median voltage demand from a building. If you have lights on and devices powered up, then PF is 100% since you're using 120V 100% of the time? If the devices are plugged in but off, and are leaking 10V over the course of the night, that median drops below 100%?

Am I understanding this correctly?

Not to do with voltage, but the phase relationship of the voltage to the current. You might be confusing it with "Demand Metering", where you pay a surcharge based on your peak demand.

With the exception of incandescent lamps running at full, very few items score a PF of 1 (or 100%.) Computers, florescent fixtures, HID lights, motors (especially if lightly loaded) all score lower numbers. Low PF equipment creates more strain on distribution equipment then the rated wattage would imply. A dimmer is all over the place depending on where it is set. When on at 100%, its PF is darn close to 100% as the full waveform is passed to a resistive load. As you move the dimmer down, the PF drops as more current flows in the later half of the waveform. At idle, it is as bad as it can get. (Somewhere on this board someone posted a graph.)

Commercial customers may have sliding rates based on the PF load they are putting on the utility's resources. If they can maintain a PF above 90%, they usually receive a good rate. if it drops below that, they have to pay a higher rate. You would have to check with your utility to find that number out. Better yet, don't! Check your bills. See if you are paying a PF surcharge. If you aren't then there is no need to raise their curiosity about possibly changing that!

Understanding Power Factor- http://www.oru.com/energyandsafety/electricdelivery/powerfactor/index.html

Here is the link for the previous discussion. Unfortunately, the new software did not translate the table as a table. - http://www.controlbooth.com/threads/power-factor-discussion.29414/page-2#post-261312

 

[lekobird]

In the attempt to somehow get a new lighting rig for Mrs. Footer, we have stumbled into the beginning of the meetings to have meetings about meetings. So, the people we met with today were engineers that specialize in power savings for large institutions. While walking them through all of the lamps we use (550 1k lamps in the air kind of throw those type of guys...) one guy asked if we power down our dimmers every night. Of course I said no. He then asked if I knew how much power they used while on but not in use. I know the newer racks only draw as much power as the control cards use while off. I assume that our 1970's vintage Strand/Century dimmers are the same. Am I wrong?

Can't remember the model number's, but we have 60@6k, 10@12k...

looks like a CCR 300 (Century Controlled Rectifier) @phenry should still have wiring diagrams and maint manuals... As does the Strand Archive in the UK

 

[David Ashton]

Understanding Power Factor- http://www.oru.com/energyandsafety/electricdelivery/powerfactor/index.html
this is the classic meaning of power factor, where the problem is phase shift between voltage and power, which can be corrected by capacitors, the modern situation is infinitely more complex caused by wave chopping and varying current being drawn by switchmode power supplies and dimmers during the cycle and which certainly cannot be corrected out, there are "harmonic filters" which try, but these cause all sorts of timing problems for dimmers.A dimmer on an incandescent light keeps the voltage and current in phase but causes a power factor loss by only working on a part of the cycle, distorting the wave form and causing harmonics.

 

[STEVETERRY]

In the attempt to somehow get a new lighting rig for Mrs. Footer, we have stumbled into the beginning of the meetings to have meetings about meetings. So, the people we met with today were engineers that specialize in power savings for large institutions. While walking them through all of the lamps we use (550 1k lamps in the air kind of throw those type of guys...) one guy asked if we power down our dimmers every night. Of course I said no. He then asked if I knew how much power they used while on but not in use. I know the newer racks only draw as much power as the control cards use while off. I assume that our 1970's vintage Strand/Century dimmers are the same. Am I wrong?

Can't remember the model number's, but we have 60@6k, 10@12k...

In every one of those dimmers is a linear power supply with a transformer, rectifier bridge, and filter capacitor. Each of those power supplies draws quiescent current. I think you would be surprised at the overall quiescent current of your system--it's worth measuring.

PS--It's way past time to consign that system to the dumpster. Let us know if we can help.

ST

 

[STEVETERRY]

"Do... dimmers leak? ''
Is there a puddle under the rack?

Throw an amprobe on the feed and measure your quiescent current. If, as @David Ashton says, it's 10V, across 550 FELs that's 1032A. That can't be correct, can it?

No.

ST

 

[David Ashton]

I clarified that earlier, on 240 volt systems like Strand JTM's the minimum voltage would be set at around 10v, I set enough to remember that. What the situation is on 120v I cannot know but it certainly could be substantial.

 

[David Ashton]

I forgot to mention the "preheating" function on many dimmers which greatly increases consumption especially if left on 24/7