Safe operating temp for Magnetic Ballast « on: September 26, 2026, 06:04:13 PM » Author: Waxsoda61774308
I recently needed a bright light for a few hours and decided to take out my magneticly ballasted 400W MH fixture, with a custom ballast enclosure. After using it for a few hours, I measured the temp of the ballast and it was 168 degrees Fahrenheit. Is this too hot? I have recently added a fan to the enclosure but I wanted to see if that would have damaged it.
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	Re: Safe operating temp for Magnetic Ballast « Reply #1 on: September 26, 2026, 09:00:35 PM » Author: Multisubject
All of the ballasts I have also get quite hot, I feel like it's normal but I didn't measure any actual temperatures. I have a feeling this is partly due to using thinner copper/aluminum windings to save money but also partly due to the core layers being welded together on almost all ballasts, resulting in eddy currents that heat the core itself. It probably wouldn't have been damaged, but I would measure the wattage of the ballast to see if it is really high. I hear that significantly above 500W input would be not so great, though I could be wrong.
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	Re: Safe operating temp for Magnetic Ballast « Reply #3 on: Today at 12:47:18 AM » Author: Medved
The deltaT will give you ballpark what operating temperature to expect as normal (you add it to the room temperature). If you then measure something way different, it means the power dissipation is different than expected, so something does not run normal...
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	Re: Safe operating temp for Magnetic Ballast « Reply #4 on: Today at 01:58:27 AM » Author: dor123
I think that American ballasts don't mentions their dT.
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the international date format (dd.mm.yyyy).

I lives in Israel, which is a 220-240V, 50hz country.

	Re: Safe operating temp for Magnetic Ballast « Reply #6 on: Today at 02:47:56 AM » Author: SoxFtw
Quote from: dor123 on Today at 01:58:27 AM I think that American ballasts don't mentions their dT. Interesting, because most if not all of my ballasts have a deltaT written and even those made in china by Osram. Maybe it's an American thing. Quote from: Laurens on Today at 02:20:52 AM In general, they can go 65 to 75 degrees C above ambient. So that means painfully hot.  I've never had mine get nearly that hot, but it's possible. And rather unrelated but dual-purpose HPS/MH ballasts run cooler with MH lamps, but with HPS they get unbearably hot to the point you can't hold on for more than a second.
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	Re: Safe operating temp for Magnetic Ballast « Reply #8 on: Today at 04:32:21 AM » Author: dor123
My Eltam L 7/9/11.514 ballast in my NISKO PL-S 9W meltlight, gets very hot, but I think less than 100*C.
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the international date format (dd.mm.yyyy).

I lives in Israel, which is a 220-240V, 50hz country.

	Re: Safe operating temp for Magnetic Ballast « Reply #9 on: Today at 04:39:37 AM » Author: SoxFtw
I think it has to do that with the nightlight being fully enclosed and is being also heated up by the lamp running near it. Tw is 130C°/266°F so it is plenty.
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