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480VAC Indicator Panel LED

Posted: Wed Oct 17, 2007 7:45 am
by jollyrgr
I would have thought something like this would exist but so far cannot find it. I need LED based panel indicator lights. Yes, these exist. But I need them for 480VAC. The highest voltage I can find is 280VAC. I did see some replacement lamps for incandescent based devices but they want $100 each bulb! I would need a dozen.

Does anyone know of 480VAC LED panel lights?

Posted: Wed Oct 17, 2007 10:55 am
by Dave Dixon
I did a quick look through some catalogs with no results. You may have some luck with Dialight. Their LEDs only go to 230VAC in the Newark catalog, but Newark doesn't carry everything that they offer.
Would neon be acceptable? That might be easier and cheaper - not that I have looked into it! Best of luck,

Posted: Wed Oct 17, 2007 11:21 am
by haklesup
What are those besides a normal 1.7V LED and a diode and resistor for the voltage you need. Looks like you'll need to spec the diode and resistor yourself. (maybe these don't even have a diode)

At $100 per bulb, you could easily buy a transformer for each lamp and use a lower voltage indicator and still save $. That may be the safest solution anyway. There may be a safety spec out there somewhere prohibiting live 480V at a control panel which is why you cannot find the rated indicators.

As Dave suggested, Neon bulbs would probably be the best for this application needing only a resistor to adjust voltage and using almost no current.

You could also use a 480V relay to switch a low voltage loop for the indicators.

Posted: Wed Oct 17, 2007 10:57 pm
by jollyrgr
If I were doing this for myself I would use a wall wart and low voltage LEDs. But this is in a data center and is the external wrap around for an enterprise (100 kVA) UPS. This cannot be a "home brew" item or I'd not even have posted.

The UPS wrap works in this manner.

From a main panel in a mechanical room there is a breaker that feeds a "bypass" panel. In the bypass panel there are two breakers. One that is fed from the output of the ordinary breaker, one that is fed from the UPS feed. Under normal data center operations the breaker being fed by the UPS is closed in the bypass panel. The breaker for the external wrap is open in the bypass panel. It is also opened in the mechanical room. When you want to wrap the data center power you make sure the bypass breaker in the data center is open. You then go to the mechanical room and close the bypass feed breaker. Three green lights on the data center bypass panel then light to show there are three good phases available at the input to the bypass breaker. You now take the UPS into internal bypass. (UPS Internal bypass shuts down the inverter and passes utility power straight through. The UPS parallels utility power and its inverter output momentarily then shuts down the inverter.) Once the inverter is shut down and the UPS is in internal bypass you CLOSE the bypass breaker paralleling two feeds. You then open the UPS breaker in the bypass panel. (Normally both breakers are closed for all of 15 seconds at most.) You can then kill the feed to the UPS and work on it cold. (For those wondering. Yes, if you were to close the bypass breaker while the UPS was on inverter and not in internal bypass bad things would happen. UPS would blow up and be destroyed. Fire would likely result. The person closing the breaker would likely die. There is a lockout key arrangement to prevent this.)

Our data center is setup such that there are two 100KVA UPS units. Most of our servers, switches, etc. have dual power supplies and one goes to each of the UPS units. When the external wrap (bypass) was put in, so were three green lights on each bypass breaker to indicate when the external wrap breakers were closed in the mechanical room. I argued for lights on the breaker from the UPS. But since the lights on these would burn 24/7/365 the expense of having an electrician to replace these bulbs every few months was not justified. LED versions were over $100 each ($1200 total) so this was not considered either. The bypass breaker lamps would only be lit for a couple hours a year so those were installed.

This past week we had to do our routine maintenance where we test the shunt trip of the HVAC and UPS units. To test this without accidentally dumping the data center we put both UPS units into external wrap. When we were about to go back to UPS power we went down our checklist to bring up one UPS. But by accident we started to perform the switching procedure on the wrong bypass panel. The breaker from the UPS was closed in the temporary parallel situation. Again both breakers are normally closed for about 15 seconds. Had then next step been performed (opening the bypass breaker) we would have dumped 80KVA of load in an instant as the input to the UPS breaker was cold. We should have been on the other panel.

Thus my request for having lights indicating the UPS breaker has power will be granted. But since this is something I wanted, everyone has pointed the finger at me to find the parts. There cannot be an ongoing expense of paying electricians to change the bulbs as they burn out. Once installed it must always work. LEDs are the most logical solution. But as I'm finding out, it is not an EASY fix as it is quite expensive.

Posted: Thu Oct 18, 2007 3:30 am
by MrAl
Hi there,

Did you try connecting two of the 280vac lights in series?
If you dont want the light from both of them, hide one inside the case.

What else might work is a 24k, 10 watt resistor if you dont mind
about 5 watts of heat. Set it up for half wave rectification with
an appropriate rated diode (1N4007 for example) and another
diode in reverse parallel to the LED. The LED will see an average
of 10ma forward current and the resistor will use up about 5 watts.
Use with a high brightness LED.

Another idea is to put a power resistor in series with the 280vac
light you purchase. You'll have to see how much current it
draws in order to determine the right resistor value and power

Still yet another idea is to set up a triac circuit with a fixed
conduction angle. This would be a little more elaborate however.

Posted: Thu Oct 18, 2007 6:13 am
by ecerfoglio
Three phase indicator lights are ussually wired in a "Y" configuration (live to neutral) and so they receive only 58% of the line voltage. (58 % = 1/square root of 3 is the relation between "line" and "phase" voltages)

In a 480 VAC system the phase voltage would be 277 V.

Just wire the three (277V) lamps as a "Y" or "star", connecting the star's centre to the neutral. If there is no neutral available, and the line's neutral is refered to earth it can be connected to earth. (in both cases, each lamp will indicate the status of the phase it is connected to).

If there is no neutral available, and the neutral is not connected to earth, and the 3 lamps are identical, then the star's centre may be left without connection. But in this case, the only "valid" status will be "All OK" (3 lamps on) and "All off" (3 lamps off). If only one phase fails the other two lamps will be dimmer, and if two phases fail the 3 lamps will be off.

Posted: Thu Oct 18, 2007 9:06 am
by dacflyer
is it possible to use "current transformers"..the small power they create could be fine for leds ?

i have something like this on my water heater, as a remote indicator to let me know which element is on and it also tells me that they are working..
and theres no tapping into the power its also safe.

Posted: Thu Oct 18, 2007 7:48 pm
by jollyrgr
ecerfoglio wrote:Three phase indicator lights are ussually wired in a "Y" configuration (live to neutral) and so they receive only 58% of the line voltage. (58 % = 1/square root of 3 is the relation between "line" and "phase" voltages)

In a 480 VAC system the phase voltage would be 277 V.

You are right! Problem solved. Thanks!

Posted: Fri Oct 19, 2007 7:28 am
by jollyrgr
Retract my D'OH.

My original thinking of Phase to Phase was right. Then ecerfoglio posting of Phase to Neutral seemed like a perfect solution; until I presented it to the electricians. Both responded that there is NOT a neutral available and that they want to monitor Phase to Phase as originally thought.

They do like the transformer solution and will be exploring that. We shall see.

Posted: Fri Oct 19, 2007 8:29 pm
by Externet
A neon optocoupler will turn leds on, and safely.
You can even make them with superglue and a photo diode attached to a neon bulb driven by your 480 V
I made some a while ago to detect telephone ringing pulses, wrapped in black shrink tube to isolate from external light.
Miguel :grin:

Posted: Fri Oct 19, 2007 9:11 pm
by dyarker

That may work, but see 1st paragraph of jollyrgr's 18 Oct post. This needs to be a real pro job.

I think three transformers with 480V primaries is the way to get an "inspectable" installation. The secondaries would depend on panel indicators chosen.


Are 120V panel indicators less expensive than 280V?


Posted: Fri Oct 19, 2007 9:25 pm
by Externet
Right, Dale ! :sad:
There are some tiny potting boxes where the thingy can be embedded in black epoxy yielding the 'pro look' :grin: with 4 leads protuding for pc mount or for mounting the box to a panel.

Posted: Fri Oct 19, 2007 10:29 pm
by dyarker
True, but it would still be a one-of-kind made up part. This needs to be maintainable by any licensed electrician with off-the-shelf parts (or at least custom parts ordered from established manufacturers) rated for the purpose. It shouldn't depend on jolly or someone else being able/willing to hand fabricate replacements which would have no rating at all.

100KVA, 480V, 3 phase, in a commercial environment, is no place for hobby shopping; no matter how well it works and looks.

I'm not trying to slam or flame you. Your ring detector is inovative and clever. But that is a one-off for your own purpose, and ring voltage isn't likely to do serious damage no matter what happens to your circuit. For Jolly's project building codes, insurance companies, etc, etc, are involved.


Posted: Sat Oct 20, 2007 3:45 pm
by Crowbar
How about a standard 480VAC xfmr style panel indicator with an LED replacement for the incandescent bulb? Most of these operate off of 12 or 24 VAC and an LED replacement is readily available.

Posted: Sat Oct 27, 2007 4:57 am
by Lenp
If the indicator isn't 'cast-in-stone' to be an LED what's wrong with a neon?
Use a commercial quality front panel relampable holder for a bayonet based neon, and a series dropping resistor for the current limiting. Although the resistor will probably last forever you could hang it on a terminal strip to give you peace of mind. The neon will last for years, offering quick change and low cost! This is method is commonly used and several manufacturers make a 120V neon holder with an internal resistor.

Don't complicate the simple!