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Joined: Oct 2000
Posts: 2,723
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Broom Pusher and
Member
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.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Joined: Apr 2002
Posts: 2,527
B
Moderator
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.

Joined: Dec 2001
Posts: 201
A
Member
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.

Joined: Dec 2001
Posts: 201
A
Member
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!

Joined: Nov 2002
Posts: 267
W
Member
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.

Joined: Dec 2001
Posts: 201
A
Member
Why is a HVAC Tech troubleshooting lights, anyway?

Joined: Apr 2002
Posts: 2,527
B
Moderator
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).]

Joined: Apr 2002
Posts: 7,381
Likes: 7
Member
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


John
Joined: Feb 2002
Posts: 33
J
JohnnyB Offline OP
Member
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?

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