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DMX fixtures themselves on relay circuits?

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Erik Walthinsen:
Our church is looking to gut and replace the old lighting systems, and as part of that I had the electrician from a local shop come out and take a look at where we're at right now.  One of the things he said was typical was to install a central relay/dimmer panel for all the lighting circuits.  Specifically, he said that it was standard practice to put all the DMX-controlled fixtures on circuits which are powered off by relays in those panels when the overall system is shut down.

The assertion was that having fixtures plugged into fixed power and left 24/7 created enough heat to prematurely kill the fixtures.  The problem I have with this concept is that the control electronics should be using a very small amount of power (on the order of a watt) when the DMX inputs read zero.  IMO if these $1000+ lighting fixtures are so susceptible to permanent heat damage from a watt of idle power, then they don't deserve the name "professional".

Has anybody else run across this claim, or seen damage caused by having permanent DMX fixtures left plugged in constantly?  Or is this a "because we always do it this way" / "we make more money installing this way" ?

Thanks!

Mac Kerr:

--- Quote from: ewalthinsen on August 17, 2022, 06:24:00 PM ---Our church is looking to gut and replace the old lighting systems,

--- End quote ---

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Caleb Dueck:

--- Quote from: Erik Walthinsen on August 17, 2022, 06:24:00 PM ---Our church is looking to gut and replace the old lighting systems, and as part of that I had the electrician from a local shop come out and take a look at where we're at right now.  One of the things he said was typical was to install a central relay/dimmer panel for all the lighting circuits.  Specifically, he said that it was standard practice to put all the DMX-controlled fixtures on circuits which are powered off by relays in those panels when the overall system is shut down.

The assertion was that having fixtures plugged into fixed power and left 24/7 created enough heat to prematurely kill the fixtures.  The problem I have with this concept is that the control electronics should be using a very small amount of power (on the order of a watt) when the DMX inputs read zero.  IMO if these $1000+ lighting fixtures are so susceptible to permanent heat damage from a watt of idle power, then they don't deserve the name "professional".

Has anybody else run across this claim, or seen damage caused by having permanent DMX fixtures left plugged in constantly?  Or is this a "because we always do it this way" / "we make more money installing this way" ?

Thanks!

--- End quote ---

This depends on the fixtures; you're correct, pro-grade fixtures don't need relays, while cheaper grade fixtures do.  The best bet is to call the manufacturer and ask, as any mid-tier or higher manufacturer tests this. 

Paul G. OBrien:

--- Quote from: Erik Walthinsen on August 17, 2022, 06:24:00 PM --- Specifically, he said that it was standard practice to put all the DMX-controlled fixtures on circuits which are powered off by relays in those panels when the overall system is shut down.

The assertion was that having fixtures plugged into fixed power and left 24/7 created enough heat to prematurely kill the fixtures. 
--- End quote ---

If they are solid state relays this isn't a terrible idea, but dimmer/electronic relay boxes absolutely not.
The problem with leaving LED light fixtures on 24/7 isn't about heat, the problem is that the internal fans will be running all that time which drastically shortens thier life, and that constant airflow will also pack more dust and dirt inside the fixture than would occur over the same amount of inuse hours... which for a church could be a small fraction of the total on time. I'd also argue that $1000/ea doesn't really get you into Pro level equipment either... especially with movers, and if that is where you are in terms of budget than putting everything on switched circuits would be a good thing in terms of maximizing the life of your investment.

Scott Hofmann:

--- Quote from: Erik Walthinsen on August 17, 2022, 06:24:00 PM ---Our church is looking to gut and replace the old lighting systems, and as part of that I had the electrician from a local shop come out and take a look at where we're at right now.  One of the things he said was typical was to install a central relay/dimmer panel for all the lighting circuits.  Specifically, he said that it was standard practice to put all the DMX-controlled fixtures on circuits which are powered off by relays in those panels when the overall system is shut down.

The assertion was that having fixtures plugged into fixed power and left 24/7 created enough heat to prematurely kill the fixtures.  The problem I have with this concept is that the control electronics should be using a very small amount of power (on the order of a watt) when the DMX inputs read zero.  IMO if these $1000+ lighting fixtures are so susceptible to permanent heat damage from a watt of idle power, then they don't deserve the name "professional".

Has anybody else run across this claim, or seen damage caused by having permanent DMX fixtures left plugged in constantly?  Or is this a "because we always do it this way" / "we make more money installing this way" ?

Thanks!

--- End quote ---
Your electrician, surprising, I know, is correct.... it IS standard practice in LED fixture installations to power them off when not in use. Not for the purpose of heat damage however. As has been mentioned by others, in many fixtures, fans are not thermostatically controlled and run all the time. Besides pulling dust and pollutants into the fixture, the less expensive the fixture the cheaper the fan that is used. Your 50,000 hour LED fixture will fail because the fan failed long before if left on constantly. There are some LED fixtures which are fanless, but usually more expensive because of massive heat sinks.

But the biggest issue is that all LED fixtures use a switching type power supply, like used in computers. These are very susceptible to being taken out by
electrical surges or transients. I have seen two commercial installations where in one case 6 fixtures were taken out by an electrical surge during a storm (just after a performance ended fortunately as the audience was making its way to their cars) and in another case where 12 fixtures died in a building only months old when a weird electrical transient occurred which also took out multiple computers. In both cases, replacing the power supply (at quite a cost in labor in addition to the part) repaired the fixture.

Solid state relays are NOT recommended in this application, only "air gap" or mechanical relays. For relevant examples of DMX controlled air gap relays, go to etcconnect.com and look up Sensor IQ Intelligent Breaker System (up to 48 relays), Foundry relay (single, 4 or 8 relays), and ColorSource Relay (single wired or wireless). I have used the ETC Foundry Mini-Panel (4 relays) in a modest church installation and although a little costly, performs well and is made for commercial use. Most dimmers which have a relay or dimmer selection feature use solid state relays and are NOT recommended for this application.

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