ballast power

[Doug Lasiter]

So you can get ballast-compatible LEDs that substitute in cleanly for fluorescents. I see a 4-foot T8 ballast-compatible LED listed as 18W. But you can also get ballast-free LEDs, that connect directly to the a/c. I see a 4-foot T8 ballast-free LED listed as 18W. But doesn't a ballast consume power? This doesn't make sense. In fluorescents, I thought a ballast took about 10W.

That being the case, you would think that a ballast-free, direct LED would consume less power than a ballast-compatible LED with a ballast attached. What's the deal?

 

[UNG]

Historically they give the tube wattage and not the total power consumed including the ballast, leaving the ballast in is just false economy with LED tubes but it makes for an easy conversion to LED without any rewiring of the fitting

 

[Deleted account]

not had Much experience with internals of fluorescent light fittings until recently.

so are you saying the LED T8 tube will work if it’s coming directly of the ballast or not.

about to start another thread regarding T8 tubes in a moment not related to this question As I don’t want to hijack the thread.

 

[timhoward]

I tend to convert the fittings as I've seen too many ballast units on the verge of being a fire risk. I took one out last week that said "Made in West Germany" on it!
I leave the capacitor in, remove the ballast, and most tubes just need power to one end. I always mark the fittings though as some LED tubes have terminals one end that are a dead short, so if someone changed one and got it wrong it would be interesting.

 

[timhoward]

so are you saying the LED T8 tube will work if it’s coming directly of the ballast or not.

Yes.

 

[Doug Lasiter]

So you can get ballast-compatible LEDs that substitute in cleanly for fluorescents. I see a 4-foot T8 ballast-compatible LED listed as 18W. But you can also get ballast-free LEDs, that connect directly to the a/c. I see a 4-foot T8 ballast-free LED listed as 18W. But doesn't a ballast consume power? This doesn't make sense. In fluorescents, I thought a ballast took about 10W.

That being the case, you would think that a ballast-free, direct LED would consume less power than a ballast-compatible LED with a ballast attached. What's the deal?

Historically they give the tube wattage and not the total power consumed including the ballast, leaving the ballast in is just false economy with LED tubes but it makes for an easy conversion to LED without any rewiring of the fitting

OK, so you're saying that a fluorescent tube marked "40W" that needs a ballast actually pulls more power than that when it is used with a ballast? Maybe something like 50W?

 

[UNG]

OK, so you're saying that a fluorescent tube marked "40W" that needs a ballast actually pulls more power than that when it is used with a ballast? Maybe something like 50W?

Yes, I can't remember the exact figures but I think it was around 10 - 15% that the ballast adds to the tube wattage for total power consumption

 

[Doug Lasiter]

Yes, I can't remember the exact figures but I think it was around 10 - 15% that the ballast adds to the tube wattage for total power consumption

Thank you. That's what I was trying to figure out. I'm replacing my 4-foot T8 ballast-driven fluorescents with direct drive LEDs, and I'm wondering what the real power impact will be. Looks to be about a factor of 2.5. Time to give those ballasts the heave-ho. These fluorescents have always been kinda flaky, and I suspect the ballast is at fault.

 

[Doug Lasiter]

so are you saying the LED T8 tube will work if it’s coming directly of the ballast or not.

If a T8 tube needs a ballast, it's not going to work without one. Period.

 

[Deleted account]

@timhoward says yes
@Doug Lasiter says no

who is right and who is wrong?

I don’t know, I only asked the question.

 

[GBDamo]

Seems a bit of a palaver, unless the fittings are unusual, it is nearly always cheaper to swap out the fitting.

 

[Doug Lasiter]

@timhoward says yes
@Doug Lasiter says no

who is right and who is wrong?

I don’t know, I only asked the question.

Which light bulbs need a ballast?

Do LED lights need a ballast? Ballasts can be confusing, and it's helpful to know which lighting technologies depend on them.

insights.regencylighting.com

"All fluoresceht bulbs require a ballasts."

That being said, I was under the impression that some fluorescents actually had internal current regulators, and those did not need ballasts.

 

[GBDamo]

@timhoward says yes
@Doug Lasiter says no

who is right and who is wrong?

I don’t know, I only asked the question.

Both, some need the ballast, some don't but you can leave the ballast in place, some you have to remove the ballast, some you have to link out the starter, some come with a dummy starter link.

 

[loz2754]

And, in case of confusion, an LED T8 tube is not a T8 fluorescent.