Are Theatrical Relays Really Necessary In LED Based Systems

[brucek]

Dimmers on full is not the same as a relay. Some LEDs can handle the difference better than others.

Point being, a dimmer module ALWAYS is passing through the choke and a SCR, where as a relay is chokeless...and air gaped.

 

[121 Gigawatts]

You also have to evaluate the cost of failure. If that breaker that wasn't designed for switching duty does fail, it's probably going to fail to turn on. At that point you're either going without whatever it powers, or making an emergency electrician hire to swap it out--possibly after hours and on a weekend...

I've never used one to failure, so I can't say for sure whether it would gradually become intermittent and give you a little warning that it's on the verge, or if one day it just won't latch on without much warning.

One problem with using non SWD breakers constantly as switches is it can diminish the primary resson a cct. breaker exists at all - to protect against overload and short circuit. Edison fuses however, AFAIC... would be fine, just give 'em a twist!

 

[JonCarter]

You also have to evaluate the cost of failure. If that breaker that wasn't designed for switching duty does fail, it's probably going to fail to turn on. At that point you're either going without whatever it powers, or making an emergency electrician hire to swap it out--possibly after hours and on a weekend...

I've never used one to failure, so I can't say for sure whether it would gradually become intermittent and give you a little warning that it's on the verge, or if one day it just won't latch on without much warning.

Over my 60 years in doing electrical work in theatres and other places I've used breakers (and seen breakers used) as switches umpteen times with rarely any failures, either failure to function as switch or failure to trip on a short. Besides, changing a breaker, either plug in or bolted, is a 10 minute job w/a couple screwdrivers (and maybe your flashlight if you wanna pull the main), and one should always have a few appropriate branch circuit breakers in one's kit on any job.

 

[Jay Ashworth]

Oddly, I don't see that anyone addressed, here, *why you put relay modules in a dimmer rack*, if you have one, as opposed to all the other ways you can do this.

It's because *that's where all the wiring from your grid terminates*.

In, as MNicolai says, new work, there are lots of solutions.

If you have a grid already, and a big Sensor/CD/etc rack already wired to it, it's old work, and *those are the pigtails you're gonna plug your LED fixtures into*, so even at the cost of relay modules, it's more expensive to *pull new copper out to the grid*... and so that's the answer you pick.

 

[SteveB]

Over my 60 years in doing electrical work in theatres and other places I've used breakers (and seen breakers used) as switches umpteen times with rarely any failures, either failure to function as switch or failure to trip on a short. Besides, changing a breaker, either plug in or bolted, is a 10 minute job w/a couple screwdrivers (and maybe your flashlight if you wanna pull the main), and one should always have a few appropriate branch circuit breakers in one's kit on any job.

I have seen 60 year old circuit breakers fail due to age. They will switch off manually but not trip when needed. I recall a contract electrician attempting to locate a breaker in a panel somewhere in the building by dead shorting a hot wire to ground in hopes that in some panel, somewhere the breaker would have tripped. It didn't despite repeated attempts. Old stuff.

 

[JonCarter]

Dead-shorting a circuit to find out what breaker it' is IS NOT the recommended way to find out! If a panel isn't properly marked, book some time with an assistant and a few test lights, find out and mark things properly.

 

[SteveB]

Dead-shorting a circuit to find out what breaker it' is IS NOT the recommended way to find out! If a panel isn't properly marked, book some time with an assistant and a few test lights, find out and mark things properly.

Oh hell no it's not. I watched this in amazement. They did not own a trace kit. They were the first electrical contractor hired on out big renovation and subsequently fired when I found them ignoring the plans and failing to run a neutral with every hot wire (dimmed circuits), they were doing as neutral for every 3. They were gone a week after I complained.

 

[121 Gigawatts]

Oh hell no it's not. I watched this in amazement. They did not own a trace kit. They were the first electrical contractor hired on out big renovation and subsequently fired when I found them ignoring the plans and failing to run a neutral with every hot wire (dimmed circuits), they were doing as neutral for every 3. They were gone a week after I complained.

Just need a Fox & Hound. But I'm not the only electrician with a u-blade 120v cord cap wired to a 30a HD toggle switch... but then again I also still test for 120v using my thumb and index finger, and because of callouses I have to lick them first.

 

[Malabaristo]

Besides, changing a breaker, either plug in or bolted, is a 10 minute job w/a couple screwdrivers (and maybe your flashlight if you wanna pull the main), and one should always have a few appropriate branch circuit breakers in one's kit on any job.

In many jurisdictions, basically any electrical work (outside of a single-family home that you live in and own) is required to be done by a licensed electrician. Yes, it's a simple task, but not one you can legally do without that license (unless you're sure your jurisdiction doesn't require a license for that type of work).

 

[STEVETERRY]

Just need a Fox & Hound. But I'm not the only electrician with a u-blade 120v cord cap wired to a 30a HD toggle switch... but then again I also still test for 120v using my thumb and index finger, and because of callouses I have to lick them first.

Actually, this is not funny. Since I surmise from your profile that you have about 20 minutes of experience in this industry, I suggest that you refrain from promoting unprofessional and potentially life-threatening techniques on this forum, which has a wide audience--some of whom lack the experience to turn on their BS filter when reading your posts.

Here's a novel piece of advice: stop trying to be funny and listen to the experts on this forum and you might learn something.

ST

 

[n1ist]

"Over my 60 years in doing electrical work in theatres and other places I've used breakers (and seen breakers used) as switches umpteen times with rarely any failures"
I once opened a 400A 3ph breaker only to have one phase remain hot. Once it was replaced, I tried to close it again (not connected to anything, of course) only to have it disintegrate with a bang. Glad I didn't try to close it hot. It was a 60 year old Frank Adams breaker that likely hadn't been touched in 60 years.

 

[FMEng]

The internal failure of a circuit breaker, from frequent operation as a switch, can be completely hidden while presenting an unsafe condition. For example, a breaker with badly worn contacts may not show any obvious signs, but those contacts can arc and burn. I've seen a breaker with a hole burned in the case from failed contacts. A damaged breaker could cause a buss to buss or buss to ground short, which would be catastrophic.

 

[tjrobb]

I saw a 100A breaker fail, weld itself to the bus, and melt neighboring breakers and bus. Ended up a full panel replacement. (To be fair, the new panel is much prettier).

I also saw, in my face, an unseen 20A circuit fail to trip ANYTHING (including the main) when I discovered it the hard way- grounding it to an electrical box. Not even the main tripped.

 

[121 Gigawatts]

I saw a 100A breaker fail, weld itself to the bus, and melt neighboring breakers and bus. Ended up a full panel replacement. (To be fair, the new panel is much prettier).

I also saw, in my face, an unseen 20A circuit fail to trip ANYTHING (including the main) when I discovered it the hard way- grounding it to an electrical box. Not even the main tripped.

Often a "bolted short" doesn't pass enough current to trip a main. Which is why I honestly believe that all major equipment utilize fused disconnects, which are pretty common in large-motor control centers, because a locked rotor or a bogged down motor might not trip it's protective breaker's trip curve before the motor windings melt down, and rewinding a motor isn't cheap.

 

[121 Gigawatts]

Actually, this is not funny. Since I surmise from your profile that you have about 20 minutes of experience in this industry, I suggest that you refrain from promoting unprofessional and potentially life-threatening techniques on this forum, which has a wide audience--some of whom lack the experience to turn on their BS filter when reading your posts.

Here's a novel piece of advice: stop trying to be funny and listen to the experts on this forum and you might learn something.

ST

Sorry I said that tongue in cheek, my bad.

 

[Jay Ashworth]

In many jurisdictions, basically any electrical work (outside of a single-family home that you live in and own) is required to be done by a licensed electrician. Yes, it's a simple task, but not one you can legally do without that license (unless you're sure your jurisdiction doesn't require a license for that type of work).

It's always been my understanding that *anywhere in the US*, you have to be a licensed electrician (not necessarily a licensed contractor; different people, different goal) to work on anything except a single family home that you own and live in, as you suggest... and that this is driven by *fire insurors* more than anything else.

It's not any sort of accident that the National Electrical Code is NFPA (National Fire Protection Association) 70, nor that the Underwriters who have the Laboratories are all *insurance* underwriters; in the US at least, the underlying prinicpal is "insurance carriers not having to make payouts", it's not by any means altruism, nor reverence for life.

 

[SteveB]

It's always been my understanding that *anywhere in the US*, you have to be a licensed electrician (not necessarily a licensed contractor; different people, different goal) to work on anything except a single family home that you own and live in, as you suggest... and that this is driven by *fire insurors* more than anything else.

It's not any sort of accident that the National Electrical Code is NFPA (National Fire Protection Association) 70, nor that the Underwriters who have the Laboratories are all *insurance* underwriters; in the US at least, the underlying prinicpal is "insurance carriers not having to make payouts", it's not by any means altruism, nor reverence for life.

In my experience on multiple projects in NYC, the contractor had a licensed eletrician on site, but many members of the electrical crew were not licensed. As long as the person with the license was watching what they all did, all good. I was never in a position to question if person A had a license or not, so it was often speculation based on what I could ascertain from observing how they worked. I do know that on all the projects I saw, NOBODY official from the city ever inspected rough in or finished work.