Ballast Turns Off After Several Minutes?

Can anyone solve this mind-bending problem --- please?

Voltage = 120vAC.
Ballast = Electronic MH1100MV-LFS-VK, single (medium-base) screw-in lamp.
Lamp wattage = 70watts.
Number of lamps in an open fronted fixture = four.
Mounting = open under carriage, with all four ballasts mounted on a perforated 16" inch metal (horizontal housing assembly, three inches above all four lamps).

Ballast Characteristics:- If there is any interruption of power - (maybe thermally protected, I don't know?) - then the power has to turned off at the breaker for several minutes, then turned on again for the lamps to strike, and light again.

What is happening:-
Arrive at job.
Sometime one, sometimes two lamps are out.
Turn breaker off.
Wait approx. 15 minutes.
Turn power on.
All lamps strike.
All lamps come up to full luminosity.
Approximately four to eight minutes after full luminosity, one, sometimes two lamps extinguish.

I've changed all lamps, and all ballasts.
Sometimes it is O.K. for a couple of weeks, maybe a month, then the same thing starts happening -- One or two of the lamps extinguish, while the other two stay lit.
When I turn off the power at the breaker, then turn it on again, all four lamps strike, and light, again. The minutes later go out again -- or maybe stay on for an unknown amount of time, but eventually go out. Hence, a continual return call is generated.

Half of the lighting crew has been on this one, and several electricians to date, and the fault keeps on turning up like a bad penny. Now I've inherited the doozie.

Today I replaced two out of the four bad ballasts, and their lamps. I stripped all connections and re-did them. I continuity tested all medium-base sockets, and installed two new 70watt HID lamps. (Note:- These fixtures are 6ft. convex shaped circular shaped units, with four 70watt medium based HID lamps located at the center, and eight 18" fluorescent Bi-ax tubes spaced around its perimeter.

The fixtures are located 30ft. AFF, (above finished floor), and can be lowered by a slave motor that take forever to cover the distance to working level, and to add insult to injury, they are above a working escalator, in a busy Barns and Noble book store -- what a pain!

If anyone can help, I will be eternally grateful, and we will hire you on the spot!

Any ideas...

Yours truly,

Stumped???
 

rt66electric

Senior Member
Location
Oklahoma
Bad wiring

Bad wiring

I have had similar difficulties

A large pole light with four 1000watt MH heads would regularly burn out ballasts.
troubleshooting results determined that the feeder wires were undersized for the distance and voltage drop, To expensive to trench and re-pull, Decided to diconnect two heads, and they have been burning for five years and going.

I suspect low voltage caused by either a bad connection at a wirenut, or fixtures wires too small to handle the load,
OR....
overheating issuses, try to cut/drill more ventilation holes.
 

mopowr steve

Senior Member
Location
NW Ohio
3 things,

By chance are they multi tap ballasts wired to incorrect voltage?

Is the heat at that level 30' up to much for the fixtures, kicking out thermal switch, check with manufacturer what max ambient temp they can be installed in.

You can get defective lamps right out of the box too, may have a bad batch.
 

kwired

Electron manager
Location
NE Nebraska
Have you checked operating voltage, and possibly temperature at the ballast when it has been running?

Make sure you don't have a compromised neutral on a multiwire branch circuit someplace, or you will likely have issues because of improper voltage.
 

stars13bars2

Senior Member
you have some bad lamps that can't sustain the arc, but they are so close to the lamps that don't drop out that they can't cool down to restrike.
 

mirawho

Senior Member
Location
Sun Valley, CA
Not that it should make a difference, but electronic ballasts can be finicky. The ballast you are using is for a 100W Metal Halide lamp and you are using 70W Metal Halide lamps. Why not use the 70W electronic ballasts with the 70W lamps?
 

cadpoint

Senior Member
Location
Durham, NC
...By chance are they multi tap ballasts wired to incorrect voltage?

Based on their own web site I input your spec's "
MH1100MV-LFS-VK"

Accordingly the MH100 needs a 100 watt lamp, not a 70 watt lamp...

http://www.espentech.com/
 

kwired

Electron manager
Location
NE Nebraska
Not that it should make a difference, but electronic ballasts can be finicky. The ballast you are using is for a 100W Metal Halide lamp and you are using 70W Metal Halide lamps. Why not use the 70W electronic ballasts with the 70W lamps?
I missed the fact it was a 100 watt ballast. It is probably over driving the lamp and this is probably overloading the ballast and it cuts out on thermal overload.

Unless a ballast would happen to be rated for more then one lamp size/type - they are designed to drive a specific lamp at a specific voltage and current level.
 
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