Powering 250W MH bulbs with 400W PFO ballast?

[bigjohn]

I am shopping for a dual 250 W MH retro for my tank, and I have located a good deal for a dual 400W PFO ballast. I don't think it would be a problem to power smaller bulbs on an oversized ballast, but I have never heard of anyone doing it.

Comments please???

[Ranran]

I do not think you can run a 250 in a 400 ballast.
You could always ask pfo yourself over on RC.
Randy

[bamann345]

You cant run different watt bulbs and ballasts. They have to match up. A 250 watt bulb will not handle the 400 + watts delivered to it on startup, I think it would explode.

[bigjohn]

I posted over at RC and haven't gotten a complete response yet.

I have no experience with MH lighting, so I do have a lot to learn. It seems to me that is the output voltage on a 400 W ballast is the same as a 250 W ballast it would work because the current (and power consumption) would be controlled by the type of bulb connected.

Is the voltage output the same??

[cyberchef]

Do not use a 250W bulb in a 400W balast. It can be dangerous. Bulbs and ballasts have to match, sometimes even to get specific enough to match specific ballasts with specific bulbs.

[bigjohn]

Thanks for the quick reply!! I am not trying to start an argument, but the EE in me wants to learn more.

I can understand that electronic ballasts have to be tuned for specific bulbs, because of the way they transform the voltage.

However, the PFO ballast appears to be a transformer, which I assume steps down the voltage so the bulb can draw more amps (heat/light energy).

I can only afford to do this once so I will follow your advice, but if you can enlighten me I would appreciate it.

Thanks,
john

[cyberchef]

Sorry I'm not an electrician or an electrical engineer... But I do know that you cannot power a 250W bulb with a 400W ballast... LOL