dimming fluorescent lights

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480sparky

Senior Member
Location
Iowegia
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You either need to change out the ballast, or change the ballast & run additional wiring.
 

480sparky

Senior Member
Location
Iowegia
Thanks Sparky,

I was thinking about trying to dim a standard electronic ballast.

Jim

The purpose of the ballast is to supply the lamps with a consistent voltage. Using a standard dimmer on a standard fluorescent ballast is counter-productive.

If you did, and started turning the dimmer 'down', the lamps will remain lit. At a certain point, they lamps may dim slightly (10% or so), after which they will simply go out as the ballast is not capable of supplying the needed voltage because there's not enough voltage coming in.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
100603-1917 EST

Ravenvalor:

Ordinary 4 ft fluorescent bulbs have two pins at each end. Connected between the pins is a thermionic emitter (filament). In a cold state there will not be enough electrons emitted to provide much current thru the gas and therefore light. Some ballasts provide current thru each filament to provide heat and thus electron emission and light. Some provide a high enough voltage to cause a discharge and the subsequent current self heats the filaments.

In a dimmable ballast there is a moderately separate constant current thru the bulb filaments independent of the current thru the bulb to make available electron emission and then current thru the bulb is adjusted to adjust lamp intensity.

Buy the correct type of ballast to allow dimming.

.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Hello,

Does anyone know of an affordable way to dim 120volt 4' fluorescent fixtures?

Thank you,

Jim

I don't know if your standard household dimmer acts in the same way as a theatrical dimmer, but if it does you can dim a 4' fixture as long as you have a standard incandescent bulb on the same dimmer. I have no idea how, I just know that it works.
 

Ravenvalor

Senior Member
Dimming Fluorescents

Dimming Fluorescents

This is an interesting topic, one that I have been hoping to wrap my brain around for a long time.

Gar wrote - "Ordinary 4 ft fluorescent bulbs have two pins at each end. Connected between the pins is a thermionic emitter (filament). In a cold state there will not be enough electrons emitted to provide much current thru the gas and therefore light. Some ballasts provide current thru each filament to provide heat and thus electron emission and light. Some provide a high enough voltage to cause a discharge and the subsequent current self heats the filaments.

In a dimmable ballast there is a moderately separate constant current thru the bulb filaments independent of the current thru the bulb to make available electron emission and then current thru the bulb is adjusted to adjust lamp intensity.

Buy the correct type of ballast to allow dimming."

I was wondering if by first turning the dimmer up to full power and then turning it down I could keep the filament warm enough to discharge. I believe that your answer will be no.

Gadfly wrote - "I don't know if your standard household dimmer acts in the same way as a theatrical dimmer, but if it does you can dim a 4' fixture as long as you have a standard incandescent bulb on the same dimmer. I have no idea how, I just know that it works."

I was also wondering how burning an incandescent lamp in the same dimmer as the fluorescent lamps would help it to dim.

Thanks for a great topic.

Jim
 

Hameedulla-Ekhlas

Senior Member
Location
AFG
Hello,

Does anyone know of an affordable way to dim 120volt 4' fluorescent fixtures?

Thank you,

Jim

Smoking!


There are a number of methods available for fluorescent dimming. Some are open to the industry as a non-proprietary technology, while others are to an extend proprietary to a specific manufacture. Dimming methods are:

1- Digital dimming
2- analog dimming
3- DALI protocol


for more information read this book

"Lighting Controls Handbook By Craig DiLouie"
 

Ravenvalor

Senior Member
non-proprietary dimming technology.

non-proprietary dimming technology.

Smoking!


There are a number of methods available for fluorescent dimming. Some are open to the industry as a non-proprietary technology, while others are to an extend proprietary to a specific manufacture. Dimming methods are:

1- Digital dimming
2- analog dimming
3- DALI protocol


for more information read this book

"Lighting Controls Handbook By Craig DiLouie"

Thanks for the tip. I will look the book up.
 

dbuckley

Senior Member
Does a standard 2 - lamp, 4', t8 or t5 qualify as a "more capable ballast"?
Having thought hard about the ballasts I've seen over the years than can be dimmed, and discarded the idea of trying to list the connection possibilities, it finally occured to me that every dimmable ballast I've seen has written on it words to the effect of "dimmable ballast".

All of them also have more connections that a standard ballast, maybe two hots (one diimable, one non-dim), or a 10V pot input, or a button input, or DALI or DSI bus inputs. So a standard mag ballast with just two terminals, or an electronic ballast with just hot and neutral inputs and no other inputs, all these can't be dimmed.

There is one time a standard mag ballast can be used, and that is when there is an auxilliary transformer that supplies heater current, so you have two ballast-looking things per fitting, but it's many many years since I've seen one of these setups; by the 80s the magnetic dimmable ballasts had the standard choke plus a heater transformer in one casing.

The modern equivalent (I believe) uses a bunch of electronics to improve the dimming over the old magnetic dimmable ballasts. Possibly the leader in this field is the Varintens product from some German or Swiss company, that can dim over the full range of 0-100%, which most fluoro dimming solutions cant - they get rough at the bottom end.
 

Ravenvalor

Senior Member
heater

heater

Having thought hard about the ballasts I've seen over the years than can be dimmed, and discarded the idea of trying to list the connection possibilities, it finally occured to me that every dimmable ballast I've seen has written on it words to the effect of "dimmable ballast".

All of them also have more connections that a standard ballast, maybe two hots (one diimable, one non-dim), or a 10V pot input, or a button input, or DALI or DSI bus inputs. So a standard mag ballast with just two terminals, or an electronic ballast with just hot and neutral inputs and no other inputs, all these can't be dimmed.

There is one time a standard mag ballast can be used, and that is when there is an auxilliary transformer that supplies heater current, so you have two ballast-looking things per fitting, but it's many many years since I've seen one of these setups; by the 80s the magnetic dimmable ballasts had the standard choke plus a heater transformer in one casing.

The modern equivalent (I believe) uses a bunch of electronics to improve the dimming over the old magnetic dimmable ballasts. Possibly the leader in this field is the Varintens product from some German or Swiss company, that can dim over the full range of 0-100%, which most fluoro dimming solutions cant - they get rough at the bottom end.

You know more about this fascinating topic than I. An earlier post in this thread was educating me on the necessity of heat at the filament. Heat that is not there when a regular ballast is not dimmed. I am wondering if I could run 120volts through the filament as well as the voltage that is coming from the ballast?
 

iwire

Moderator
Staff member
Location
Massachusetts
All of them also have more connections that a standard ballast, maybe two hots (one diimable, one non-dim), or a 10V pot input, or a button input, or DALI or DSI bus inputs. So a standard mag ballast with just two terminals, or an electronic ballast with just hot and neutral inputs and no other inputs, all these can't be dimmed.

There are electronic ballasts that can be dimmed with only two connections and the correct dimmer.

I ran across these before on a service call, I opened things up and said 'Here is your trouble some idiot used a dimmer on these ballasts'. Once I talked with the ballast company they confirmed I was the idiot and that their ballast could be dimmed using specific electronic dimmers.

I have also heard some Edison base CFLs are dimmable.
 

dbuckley

Senior Member
I am wondering if I could run 120volts through the filament as well as the voltage that is coming from the ballast?
Nope,. the filament doesn't want anything like 120V across it; I cant remember the voltage but its quite low.

I've drawn a rough schematic of how the old school fluoro dimming worked; note the filament transformer with two seperate windings to keep each end of the tube warm, and yest still allow the mains voltage (limited by the ballast) to appear across the tube.

There are electronic ballasts that can be dimmed with only two connections and the correct dimmer.
Actually, I guess these days that is entirely possible, as there are, as you note, CFLs that are dimmable, with just two wires.

The way the dimmable CFLs work is quite interesting; all electronic CFLs start by rectifying the mains to DC, and use that to subsequently power the inverter that drives the tube. And as it stands this sort of CFL doesn't dim at all well.

But the later incarnations of some of the ICs that are the heart of the inverter can analyse the incoming mains waveform, and from the shape of it deduce what setting you've got on the dimmer that the lamp is powered through, and use that knowledge to control the lamp output. A very neat bit of lateral thinking there by somebody...
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
There are electronic ballasts that can be dimmed with only two connections and the correct dimmer.

I ran across these before on a service call, I opened things up and said 'Here is your trouble some idiot used a dimmer on these ballasts'. Once I talked with the ballast company they confirmed I was the idiot and that their ballast could be dimmed using specific electronic dimmers.

I have also heard some Edison base CFLs are dimmable.

I thought the same also, until I looked at a dimming system for a chapel were doing, the manufacture sent literature with it saying it was dimmable with thier specific dimmer. We are dimming LED's on this job too, they are backlighting the cross with the LED's, so we have a dimmable driver that uses a three wire flouresent dimmer to input the dimming. I figure it must be for retrofits were the original fixtures were fluoresents.
 

Electric-Light

Senior Member
Hello,

Does anyone know of an affordable way to dim 120volt 4' fluorescent fixtures?

Thank you,

Jim

What's affordable?

Why are you trying to dim?

How much dimming range do you need?

How many fixtures?

There are two major categories. power-line phase control dimming or auxiliary control dimming.

If you're installing or retrofitting using existing two wire system and you're not doing too many, then the power-line phase control(i.e. Advance Mark 10 or Lutron Tu-Wire ballasts) is the most affordable type.

If you have a lot of fixtures or this is a new install, 3-wire dimming that uses dimmed hot as third rail for control purpose(best dimming range) or low voltage control 0-10v(industry standard, best control system selection and the wire pair can also be used for DALI in the future).

Below 10% is more or less useless for energy savings. You hit the floor at 25% or so energy consumption @ 10% output and anything below has negligible effect on power usage and it is mostly for aesthetics. Ballasts that dim below 10% cost more.

So, keeping 25% energy consumption floor in mind....
square root of measured light output is perceived output
or perceived^2 is measured output.

Ballasts are rated in measured output.

10% measured output ballasts are the ones spec'd for incentive and energy saving work. They "feel like" they dim to 32% (sqrt 0.1). Some newer ones go down to 5% (feel like 22%), but whatever you do, don't mix and match ballasts. No harm, but the fixtures will look like cow patches if you do. They don't feel like they dim anywhere near as much as incandescent lamps.

You can get 5-10% ones in 0-10v, Lutron style (3 wire) or power line phase control.

The only 1% ones I know of are Lutron Hi-Lume and they only come in 3-wire control or 3-wire/DALI hybrid and they dim to feel like 10% of full output.

Whatever you choose, you have to get a special dimmer. You can't use an incandescent dimmer even with the 2-wire type and expect each dimmer to cost $50-100 ea.
 
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