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I've a 1000 W MH ballast. Is it okay to use the wiring for 240 V on the ballast and use it on 120 V? Does it reduce the ballast to 500 W?

Here's a video for better understanding of how the bulb reacts to the connection.

ballast specs

Comparison between a 400 W & 1000 W ballast:

Ballast comparison

Current draw while running:

enter image description here

ocrdu
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The_Vintage_Collector
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    Reread your question a third time. So you want to cheat your 1000 W ballast into a 400 W one. For starters, that aitotransformer “input” side of the ballast is partially or entirely in order to overcome the working or forward voltage of the bulb, which at 1000 W may be substantial. Please compare the datasheets for both 400 and 1000 W MH bulbs and find working voltage for both. You probably do need to calculate or simulate it from there since you have several things going on: overcome Vf, too low inductance for 400 W bulb and “cheat” with input voltage. – winny Sep 14 '18 at 19:17
  • @winny Yes, exactly! I'm trying to see if it is okay to do so. Yes I've to admit that that the 240V wiring on 120V causes the light to reach to its full output only after like 2-3 mins approx. When using the 120V wiring it reaches the full brightness in like 3-10 seconds. That kinda scared me like will the bulb explode or something. I've also added the ballast comparison between a 400W & 1000W ballast. – The_Vintage_Collector Sep 14 '18 at 20:49
  • You will probably need something in-between. Can you cheat and wind a few more turns on the choke side, or add more inductance in series? – winny Sep 14 '18 at 20:54
  • I think the later option of adding an inductance is possible. Re-winding the core is a hassle. I would just get a 1000W bulb which is easier. Unfortunately, most shops now sell only MH lamps and that too only the lamp not the ballast as they say its banned and being phased out due to huge power draw. – The_Vintage_Collector Sep 14 '18 at 20:59
  • Get yourself a current clamp meter and measure the lamp current when warm and compare with the datasheet. I would expect 3.5-4 A. Too much? Add inductance. Too little, remove inductance. If you are not afraid to hack together something, you can parallel (identical) ballasts to increase the current capability and series connect them to get more inductance. – winny Sep 14 '18 at 21:46
  • @winny So, did a small current test today. At the moment I don't have a clamp meter with me. I've only a series type AC ammeter as shown in the above picture. It's reading is like 4.3A after the initial strike were the current was like 6A for a second .I'll try to borrow a clamp meter from work tomorrow and see if the reading is the same. That current seems to be what is expected from a 400W ballast it seems from the above spec chart comparison. So, should I just leave it as it is? – The_Vintage_Collector Sep 15 '18 at 12:52
  • Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/83219/discussion-between-winny-and-the-vintage-collector). – winny Sep 15 '18 at 17:40

1 Answers1

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If you are sattisfied with the result then it's OK. The higher wattage ballast means just that it has more thicker copper winding and more steel, while the inductance is the same, I think. But you also have an autotransformer that brings you the possibility to use on different suppy voltages.

To be short: I have a ballast of 1kW and I use to connect 250W lamp, fixed voltage, no autotransormer. There is no need to use lower voltage as rated unless you want to have dimmer light.

I'll admit, I was wrong. Of course the inductivity is different, so you'll get higher voltage on the smaller lamp.

Marko Buršič
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  • Nope! Inductance is less to allow more current to pass, given the same forward voltage. – winny Sep 14 '18 at 20:53
  • @Marko Buršič I've added a comparison between a 400W & 1000W ballast in my original post. With the 240V wirings in 120V supply the light takes 2-3 mins to warm up and reach full output. but when wired in the 120V mode and plugged in. The lamp quickly glows brightly like in 3-10 seconds. Kinda scarcely that will it explode on my face. I've have seen the old mercury lamp outside my house used to light up my lawn power up. It's very gradual and slow. It takes about 3 minutes to 5 mins to fully show its strength. – The_Vintage_Collector Sep 14 '18 at 20:55
  • @The_Vintage_Collector Ok, forget about it. winny has right. Don't connect ot on 240V if you don't want to blow up. – Marko Buršič Sep 14 '18 at 21:12
  • You don’t necessarily need higher voltage for higher power bulb. Say the working voltage is 102 V for the 400 W one and 114 V for the 1000 W one. At 120 V service, this would pose problems require an autotransformer but with “normal” 230 or 240 V service, you could neglect this and only see it as decreased inductance to allow higher current. – winny Sep 14 '18 at 21:43