ECN Forum
Posted By: JohnnyB fuse selection for HID lights - 12/10/02 05:09 AM
I did a call on a 7-400 watt 277v metal arc HID lights that went out. Turns out one smoked and was pulling 50amps for 30 seconds or so before tripping. I find wire nuts laying in loose in boxes and the one that smoked. I take it out of the circuit and the lights work for an hour or so and then my partner is like "you smell something?" Sure, another one bit the dust, so I'm going back with a bunch of transformers and stuff, but I want to fuse the fixtures. They have a 1.7 amp rating, but they pull more than that on startup, right? Is the fuse selection like that of a motor? Size for inrush with a duel element fuse? They are all warehouse lights I got to do of a lift.3WYSAUFE1T
Posted By: Trumpy Re: fuse selection for HID lights - 12/10/02 06:14 AM
Johnny,
My advice to you would be, check out the wiring first-off, secondly check that you have the right sized control gear.
I assume that you are talking about Metal-Halide HID lighting?.
If not, could you please advise as to what type of lighting gear you are using.
With MH, the start current is the hardest part on the circuit wiring, we recently installed 48 250Watt lowbays in a shop, we had a multitude of problems.
Need extra advice, just reply!.
Posted By: j a harrison Re: fuse selection for HID lights - 12/10/02 07:12 PM
We as a company install a lot of HID fittings
High Pressure Sodium, Metal Halide, Mercury Vapour, and some low pressure Sodium for car parks,

The thing that puzzels me is the loading and the current draw you are saying, it sounds as though that the installation is incorrect as the approxiamte loading on 230v ac with a loading of 2800watts @ 12.17 amps.

You getting a reading of 50 amps is rather to high, my advice is that you check the following;

cable type, size, and integrity (damage etc)
lamp type,
control gear (ballast, ignitor,capacitor)
wiring of control equipment
integrity of CB (is it suitable for this type of load)

if these all match then check the supply loading,

I am curious to know the outcome so please keep me posted.

John H
Posted By: resqcapt19 Re: fuse selection for HID lights - 12/10/02 07:57 PM
I thought that the starting current for most HID ballasts was less than the running current. I has been on all of the fixtures that I have installed in the last few years. Even with the lower starting current, the inrush is still high, but not as high as incandescent.
Dual element fuses are often installed at about 150% of ballast load to prevent the circut breaker from trippin when there is a ballast failure.
Don
Posted By: HotLine1 Re: fuse selection for HID lights - 12/11/02 01:31 AM
For what it's worth..
400 watt, 277 volt, Advance ballast specs are:
Operating amps; 1.7 Input watts, 454

400 watt Lumark Hi-bay...
Starting Amps....1.40
Operating Amps....1.70

Based on the above, I would fuse at 3 amps maximum, midget fuse, 480 or 600 volt.
There are fractional amperage fuses available (2.25; 2.50) but they are pricey..

PS: Don, the sources for the above info are Advance Catalog, and WWGrainger catalog...
Another good source is Venture Lighting, they must have a web site.

John


[This message has been edited by HotLine1 (edited 12-10-2002).]
Posted By: JohnnyB Re: fuse selection for HID lights - 12/11/02 04:10 AM
The way it’s wired are two rows of lights hanging in the web joists in a warehouse? Two 20amp single pole breakers supplying 277 two each row. 8 lights in two rows. One hot lead to each row and the neutral leads to each row are tied to one neutral back to the panel. I don't have the specs of the fixtures in front of me to post, but I think my replacement transformers are coming in tomorrow and I may be on the job by thurs or fri. I will be the guy on the lift and lowering to another guy who will be ripping them apart and changing ballasts and stuff. When I took the fixture that smoked originally out of the circuit and got all the other lights to work I measured approximately the correct amp draw per string; 1.7 amps per fixture, and then I started to work on a hanging heater for a hour or so then another one smoked. I'm thinking that the guy who operates the warehouse kept resetting the breaker and watched the lights hum and go out; all the while it was pulling 50 amps through the primaries on these lights??

The wire gauge appers to be sized correctly. The neutral must be sized to the total amp of both circuts,right? The thing is I am asuming everthing worked before as it was designed so I haven't, as yet, double chected wire size and run and all that.

Would a loose wire nut cause adverse condition for premature failure of a fixture? On electrical motors their is a +or-/min and max voltage rating. I didn’t see one on the fixture, I'm wondering if this first fixture blew from high volts.

[This message has been edited by JohnnyB (edited 12-10-2002).]
Posted By: j a harrison Re: fuse selection for HID lights - 12/11/02 07:23 PM
lokking at the way this circuit is wired, i personnally would rewire both sets back to the distribution point (if the client want to bear the cost),

I have spoken to on of my work mates and he suggests that the above is the best way to do things and also you say you are changing the control gear (ballast) within the fittings,

this is a good idea, but you still havent let us know what type of HID the fittings are.

Having the lot drawing 50 amps is high, very high.
I wish i was closer as i would like to see the installation for myself.

keep us posted as to what happens.


John H
Posted By: Wirenuttt Re: fuse selection for HID lights - 12/12/02 12:16 AM
Am I reading you right, you have one neutral tieing 16 HID fixtures back to the panel and 2 hot coductors going back. So you're sharing a nuetral?
Posted By: JohnnyB Re: fuse selection for HID lights - 12/12/02 05:24 AM
Sorry, 8 total fixtures...two rows of 4 fixtures each with the two hot legs and one shared neutral back to panel. The transformers are kits multi tap with a cap. Like 120/208/240/277 with a capacitor in series with the lamp, no igniter. The same as what was in the fixtures 400watt M59. I started to change them out today, haven’t found anything conclusive as yet, although, I swear I keep finding loose wire nuts without evidence of direct short to the box. Like,.. I go to take a box cover off and a wire nut falls out. What the fu#!.
Posted By: j a harrison Re: fuse selection for HID lights - 12/12/02 06:37 PM
I think that you should run the neutrals back one at a time, you should not share a neutral between the fittings,

i gather these lamps are Metal Halide with integral ignitors ??

i have never come accross this fault before but i am waiting to find our why.

Wirenuts do sometimes come loose as these fittings will vibrate a little depending on how secure to control gear is within the fitting and the fittings to the position they are mounted.

keep us in touch with the progress.

John H
Posted By: Scott35 Re: fuse selection for HID lights - 12/12/02 07:17 PM
Johnny B:

Just wanted to toss a little information in this thread regarding your scenario.

1st off, the wirenuts probably fell off due to these factors:

<OL TYPE=1>

[*]Constant vibration of the Core resonating the entire fixture and conductors,

[*]Heat build up added to the vibrations, causing expansion and contraction,

[*]Wirenuts probably weren't installed correctly to begin with, amplifying the above situations.
</OL>

Seen many Wirenuts which have fallen off due to the scenarios above - along with Wirenuts that fried to dust!

If the connection between the Autotransformer's output and the Reactor's input becomes faulted, this will draw excessive current.
This fault can be from a fried winding or a direct ground fault due to a loose Wirenut falling off, allowing the connection to contact the grounded fixture.
This fault will be limited by the Reactance of the "Primary" circuit, so currents will not act like a direct fault does [with the sparks show and trip breaker real fast].
Depending on the point of the fault, the circuit may not even draw an abnormal overcurrent / overload.
However, if the overload current is 2 or more times that of the designed operating current - and it flows continuously, this will barbeque the coil[s] and the core.

Now if the Reactor circuit becomes faulted - such as a short circuit, this will only load the complete Ballast upto the rated input current flow. This will end up frying the Reactor coil after continued use, since the Reactor is producing lots of heat [the True Power - in Watts - is dissipated in the Reactor coil, not the lamp].

Your example of 50 Amps is not uncommon for shorted Autotransformer sections on CWA / HX Ballasts.

Circuit wise, the Multiwire circuit is fine. The Wire size should be large enough to keep the voltage drop as low as possible.
Don't forget about increased Ambient temperature in these areas! That's one more adjustment factor to use for conductor sizing.
Balancing three lines across one common grounded conductor may be done with an increased common conductor size - to help out with the Harmonics which most likely will pop up.
Harmonics can get generated between components of one fixture and components of another fixure[s]. If a Capacitor from one Ballast can resonate the primary coil on some other Ballast, this will cause currents to flow between the two luminares.

Just a little THD info!

Next, the Ballast circuitry you described is for a Constant Wattage Autotransformer type Ballast [known as "CWA"].
With the CWA Ballast, the Starting current is closely equal to the running current - meaning the level of current flowing will be almost the same no matter if the lamp is starting or operating for 1 hour.
With Hi Reactance ["HX"] and Straight Reactor ["R"] type Ballasts, the Starting current varies from the running current.
These normally have 1.25 to 2x the starting current level [125% to 200% + or - of the running current for starting]. One has lower starting current, other has higher starting current.

One last item would be regarding Capacitors.
Power Factor Caps which have become open or shorted will cause the Ballast to draw higher line current [>150%].

Your Luminare specs should be something like this:

[1] 400 Watt M59 Metal Halide lamp [mogul base / 350 volt lamp].
CWA Ballast - "Quad" Input
120 VAC [4.0 Amps],
208 VAC [2.3 Amps],
240 VAC [2.0 Amps],
277 VAC [1.7 Amps].
Capacitor = 24 MFD @ 400 VAC.

Select a 4 Amp 300 VAC Fuse for protecting this Ballast.

For HID Ballast Schematics to check over, refer to HID CWA Ballast Schematics in the Technical Reference section.

For other Schematics, see the Menu For Technical Reference Section to find additional Schematics via links.

Good luck.

Scott s.e.t.
Posted By: Bjarney Re: fuse selection for HID lights - 12/12/02 08:14 PM
A few vaguely related comments.

ISTR the referenced fuses are primarily intended as an auxiliary overcurrent device for 277V light fixtures—intended to be mounted in a 7/8-inch knockout on the fixture housing. http://www.bussmann.com/products/Electronic/Group8.asp

Re Johnnyb’s comment of “…Two 20amp single pole breakers supplying 277 two each row,” note that aside from any harmonic currents, in the case of the common neutral conductor serving only two phases of a multiwire branch circuit, the neutral will see full phase current for two equal phase currents. If two circuits were routed with individual neutrals in a common raceway, the “over 3 conductor’ derating would have to be applied.

About wire nuts in fixtures—one installation error while connecting a smaller stranded {id est, 18AWG} conductor to a larger solid {id est, 12AWG} conductor, if the small strands do not “lead” the larger solid conductor, the connection will likely not be secure and have a tendency to come apart.
Posted By: ayrton Re: fuse selection for HID lights - 12/12/02 08:34 PM
It amazes me how such a simple install can be so messed up. In the past five years, I personaly have installed over 700 lowbay and highbay fixtures (matal halide ranging from 250-400w) and NEVER heard of fusing the individual lights or had a problem. 1 20a 277v breaker with eight lights should be fine. And I think you said there is two rows of four, each row on a 20 a breaker. Should not share a neutral either. There is no point. Could share a ground. How are these lights controlled? Is it a standard 277 rated switch, or a contactor? Sounds to me like it was a poor installation to begin with and you have bad connections. Plus some of the fixtures have been energized, but the lamp is not lit, which will kill a light eventually.
Posted By: ayrton Re: fuse selection for HID lights - 12/12/02 08:39 PM
Let me know how the lights are switched. Do not get to carried away with measurements just yet. These threads can dazzle you with all kinds of spectacular bullshitt, but won't help you find the problem. Think simple! 9 times out of ten it is!
Posted By: Wirenuttt Re: fuse selection for HID lights - 12/12/02 08:47 PM
Remember those old wirenuts you couldn't take off. I think they were scotchlok made by 3M. Sounds like these lights could use something like that. Not sure if they're still made. I remember the old timers saying they were the best because you can't remove them.
Posted By: ayrton Re: fuse selection for HID lights - 12/12/02 08:50 PM
Why is a HVAC Tech troubleshooting lights, anyway?
Posted By: Bjarney Re: fuse selection for HID lights - 12/13/02 12:22 AM
W-nuttt, you had to pinch 'em with your Kleins a bit before they would back off—then toss ‘em for they were not reusable. Worked at a couple of sites where they were used exclusively—case closed, end of discussion.





[This message has been edited by Bjarney (edited 12-12-2002).]
Posted By: HotLine1 Re: fuse selection for HID lights - 12/13/02 02:44 AM
ARYTON:
FYI, we install "fuses" in HID fixtures when the job spec calls for them. I feel it's good practice, as when a ballast develops a short, you don't loose the whole circuit....the fuse at the bad ballasted fixture blows...saves a lot of "troubleshooting" time. (It also helps a whole lot on parking lot pole lights!)
John
Posted By: JohnnyB Re: fuse selection for HID lights - 12/13/02 04:51 AM
Just finished today, got all the lights working, put a new gas valve in the unit heater and probably scored my boss a garage door fix job. I will answer all...

Fixture;
HPS
TH 400M 277 HC5 HSG
PRI volts 277
PRI amps 1.75

(Just like this first schematic https://www.electrical-contractor.net/ubb/Forum15/HTML/000019.html )

Bulbs; M400/C/U
(I installed core and ballast kit 71a6071-001D multi tap CWA)
Breaker; (They are switched at breaker but run 24/7 I think)
Interrupt rate max RMS symmetrical amps type BDQ
14000 A 277 HACR
14000 A 125 HID

The run is #10 and aprox 2-300 feet MTW

Panel; 480Y/277 3Phase 250amp

I could draw the cable diagram and it would be clearer, but I haven’t posted pix here yet and I got to learn the setup. What I found was another loose wire nut in the end of the furthest string and the two fixtures one upstream one downstream primary windings on transformer smoked. I also found the neutral going back to the panel pulled out of the wire nut in a 600 box and lost in the conduit, so I do not know how these lights were working without the neutral leg. I suppose the wires could have been grounding out on the conduit enough to complete the circuit. So I'm sure all this poor installation was the cause of all this. I'm sure it was poor installation because all the loose connections were in the 600 boxes and the fixtures are connected by a cord with box connectors (isolated from vibration). I had a new guy trainee/helper that’s like one of those guys that yeses you to death, "OK go do that while I do this,...you know how to do that?...OH..Ya ya ya right right right". I fused everything because I don’t want to have to try to find smoked ballast with a lift again, now if one smokes it will only be that one and it will not take half the warehouse out with it. I used inline type fuse holders and I put them in the boxes because they were the only ones I could get at the time, and as it turns out it was a good thing because the guy I was with who I showed how to wire the things more than once wired a short in the last fixture we did and sure enough I had to go back up and get it and show him.

Now why is a HVAC tech doing electrical, because I'm working for a commercial maintenance contractor? Maintenance can mean a lot of things. I prefer to stick to HVAC because that is where I have all my technical training but I got to do what I got to do for the family. The HVAC biz here is very competitive and I'm trying to start up a HVAC biz for my boss now, but in the mean time I do whatever for $$$, like a prostitute.

One thing I'd like to know is can I have cut my trouble shooting time down significantly with a megger?
© ECN Electrical Forums