# Multi Tap Ballast



## MDShunk (Jan 7, 2007)

They stuff a small Chinese kid with a meter inside every ballast.


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## user4818 (Jan 15, 2009)

More than likely with an electronic power supply. That's the beauty of integrated circuitry.


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## erics37 (May 7, 2009)

PFM. That's how all electricity works.


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## Chris Kennedy (Nov 19, 2007)

MDShunk said:


> They stuff a small Chinese kid with a meter inside every ballast.


They are crafty SOB's.


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## BBQ (Nov 16, 2010)

Chris Kennedy said:


> They are crafty SOB's.


That is so if the ballast fails they know whose hands they have to smash with a hammer.


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## Chris Kennedy (Nov 19, 2007)

BBQ said:


> That is so if the ballast fails they know whose hands they have to smash with a hammer.


LOL, they still do that?


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## Dennis Alwon (May 9, 2009)

I believe most laptops are the same. They will work on either 120V or 240V- it magically knows.


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## cultch (Aug 2, 2011)

Those are not what we call multi tap ballast tho. We refer to them as intelivolt ballasts. Might just be us but multi taps have multiple taps.


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## micromind (Aug 11, 2007)

There are two circuits in a multi-volt power supply, the power circuit and the control circuit. 

The power circuit will operate on any voltage that's higher than the output, but lower than the maximum rating of the IGBTs, SCRs, triacs, or whatever they're using to switch with.

The control circuit begins with an AC to DC converter, plus a regulator of some sort. This is what will smoke if the input voltage is too high. This circuit cannot be a switching supply, because in order for a switching supply to work, it has to have a control voltage.

Thus, the control circuit begins with simple diodes. It's more costly to make a regulator that will accept a wide range of input voltages, so manufacturers tend to stick with single voltage inputs unless the market dictates otherwise.


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## Control Freak (Mar 8, 2008)

Almost all I see now is multi voltage. We call them universal ballasts. Very common in NYC. 

When I hear multi tap it refers to fixtures with multiple leads coming off of different taps for different voltages from 120v to 480 v. Usually high bay type high pressure sodium with the metal protective cones


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## oww-is-that-hot? (Jun 26, 2011)

BBQ said:


> That is so if the ballast fails they know whose hands they have to smash with a hammer.


Ha, they must go through hammers like crazy then


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## bobelectric (Feb 24, 2007)

Md, That made my day!


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## timjimbob (Jul 21, 2011)

Some multivoltage ballasts "remember" their input voltage and cannot be reused at a different voltage after initial installation. Model # will let you know if this is the case.


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## Southeast Power (Jan 18, 2009)

electricalwiz said:


> If you have a multi tap ballast in a fluorescent fixture when all you have is a black and white coming of the ballast. How does the ballast know if you are sending 120, 208, 240, or 277 volts to it.


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## McClary’s Electrical (Feb 21, 2009)

timjimbob said:


> Some multivoltage ballasts "remember" their input voltage and cannot be reused at a different voltage after initial installation. Model # will let you know if this is the case.


Very true, don't test the light in your garage, then go hook it up to 277, you'll let the magic smoke out.


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## GDK 13 (Oct 6, 2009)

mcclary's electrical said:


> Very true, don't test the light in your garage, then go hook it up to 277, you'll let the magic smoke out.


WOW...never knew that.


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## kaboler (Dec 1, 2010)

mcclary's electrical said:


> Very true, don't test the light in your garage, then go hook it up to 277, you'll let the magic smoke out.


Yes TY for teaching me something.


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## Shockdoc (Mar 4, 2010)

mcclary's electrical said:


> Very true, don't test the light in your garage, then go hook it up to 277, you'll let the magic smoke out.


Not true, I temped out a room of 2x4 troffers off a 120 volt extension cord and later wired them to a 277volt circuit. Worked fine, no magic smoke.


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## McClary’s Electrical (Feb 21, 2009)

Shockdoc said:


> Not true, I temped out a room of 2x4 troffers off a 120 volt extension cord and later wired them to a 277volt circuit. Worked fine, no magic smoke.


 
As the original poster said, "some ballast" remember voltage.


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## Shockdoc (Mar 4, 2010)

mcclary's electrical said:


> As the original poster said, "some ballast" remember voltage.


True, amazingly I had Home depo 3 light multivolt troffers.


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## kaboler (Dec 1, 2010)

Maybe it goes up but won't come back down?


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## macmikeman (Jan 23, 2007)

I haven't seen any lately but before they used to have latching multivolt ballasts. It would latch at the nominal of the system whether 120 or 277 v.
Once latched to the higher level, then it got stuck there. 


One surge from the poco for 120 systems and ballasts generally were rendered worthless. (except they could become used for 277v replacements). Thats why you don't see them around now.


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## Scott Paullin (Dec 17, 2011)

*Multitap ballasts*



electricalwiz said:


> If you have a multi tap ballast in a fluorescent fixture when all you have is a black and white coming of the ballast. How does the ballast know if you are sending 120, 208, 240, or 277 volts to it.


I would think they have resistors for that purpose


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## Gaterhater (Nov 15, 2011)

MDShunk said:


> They stuff a small Chinese kid with a meter inside every ballast.


Haha!


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## Gaterhater (Nov 15, 2011)

mcclary's electrical said:


> Very true, don't test the light in your garage, then go hook it up to 277, you'll let the magic smoke out.


You know I've heard that many times but never actually seen it thankfully. I guess it wouldn't be wise to keep tempting fate!


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## Scott Paullin (Dec 17, 2011)

When wiring up commercial exit lights to unknown voltages always wire to 277v first, if it's 120v it won't smoke the sign


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## Scott Paullin (Dec 17, 2011)

*McLary's electrical*

I once saw my 18v DeWalt battery sitting in the drill case go up in smoke


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