Interesting LED call

Status
Not open for further replies.

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
Had a call about blinking 2?4 LED lay-ins our guys recently installed. Noticed they were trying to dim them incandescent dimmers. Told them that was the problem.

Told me they first tried LED dimmers and had the same issue. The now installed incandescent dimmer is what the luminaire manufacture recommended.

They also told me when they called the manufacture back to say the issue hadn't been resolved they where told they needed a 'super neutral'.:blink::lol:

This was an open office space with 20 fixtures on a 4 wire MWBC. I took the 3 ungrounded conductors and spliced them up to one breaker. Bingo, no blinking.

This goes against rational reasoning so I figured a heads up was in order.



 

cadpoint

Senior Member
Location
Durham, NC
The line diagram of the controller looks scarier than your description!
Seems the math makes it safe....

Cree now has an additional wire off a ballast and out of fixture for low voltage dimming if required.
 

hardworkingstiff

Senior Member
Location
Wilmington, NC
The line diagram of the controller looks scarier than your description!
Seems the math makes it safe....

Cree now has an additional wire off a ballast and out of fixture for low voltage dimming if required.

So you bring in a hot, neutral, and a dimmer leg or do you just wire the dimmer leg to correct wire and don't connect to the normal hot? (I hope that makes sense).
 

Electric-Light

Senior Member
So you bring in a hot, neutral, and a dimmer leg or do you just wire the dimmer leg to correct wire and don't connect to the normal hot? (I hope that makes sense).

The dimmer wire is now the only hot, the original (usuall) is just capped off!

Per their instructions!

What "original"?

Phase cut dimming causes harmonics and poor power factor regardless of what you're dimming and it(and Light Emissive Decorations in general..) sucks donkey nuts. It's mainly for household use.

Three wire dimming that uses, neutral, switched hot and "dimmed" hot does not carry power over the dimmed hot. The dimmed hot is only used to signal the ballasts.
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
Update

Update

Went back to the same facility today as our guys installed more of the same fixtures and dimmers in other locations. Installers pulled in a dedicated neutral for the circuit and the new fixtures still were blinking.

I moved the circuit in question from A phase to C base and blinking stopped.

Go figure.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Went back to the same facility today as our guys installed more of the same fixtures and dimmers in other locations. Installers pulled in a dedicated neutral for the circuit and the new fixtures still were blinking.

I moved the circuit in question from A phase to C base and blinking stopped.

Go figure.

Sounds like some feedback or harmonics on the one phase.
How many lights on a dimmer?
Maybe this is why they make 0-10v dimming and 3 wire dimmers.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I think you probably needed an electronic low voltage dimmer not a magnetic one as shown. Or perhaps just an electronic dimmer but not Lv
 
Last edited:

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
The LED dimmers are CL dimmers not the same as electronic dimmers

The Standard Lutron LED DVCL-153 Is not the most compatible dimmer around. Works with many but not most.
Leviton has been the most compatible yet. ( I don't like the form factor though) Give and take I guess.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150316-2343 EDT

There need to be better generic names for different types of dimmers.

A two wire dimmer meaning one that has only one hot input wire and one hot output wire and has no neutral (visible or implied) is not a good dimmer for anything. But millions have been made and used, and the users tolereate or don't know what the limitations are. I have tolerated a problem for 48 years.

My two GE two wire dimmers from 1965 have never had a component failure and have been on for 50% or more hours of those years. Only load over that time has been incandescent. The problem is that I set them at a very low light level most of the time. If there is a momentary power loss the dimmer does not restart. One has raise the dimmer setting level somewhat to to get a restart, and then back it down.


What I generically call a three wire dimmer is one that requires a neutral. With a neutral, then power for the electronics is available whether there is a load or not. Restart after loss of input power is no problem and exactly the same setting is retained. For many different loads the load has no affect on the dimmer. A low power factor inductive load can present problems.

Dimmers that do not use a Triac or SCRs will have different results with different loads.

The type of dimmer and load will determine whether any dimming is possible, and what problems might occur when some degree of dimming is possible.

The Cooper website for a SF8AP is totally worthless.

You must determine what AC waveform will provide effective dimming control of a particular load. Use of loads that have their own internal dimmer are likely going to be your best choice. I believe the most desirable type would be one that used PLC (Power Line Communication) or RF transmission of data to an addressable fixture.

Bench testing of dimmers in combination with the expected load is important to observe how the items work together. Use a scope to study waveforms and how dimming is controlled.

When your load is a rectifier followed by a capacitor input filter (what some LEDs will be), then there has to be some sort of internal dimmer control (really means current control to the LED) that senses the turn on or off phase angle to control LED current, or phase shift turn on has to be from 90 to 180 degrees. . There are a multitude of ways that dimming control of an LED light can be accomplished. But most LED light manufacturers are going to do something to make use of phase shift information for dimming, but have a good part of the sine wave available for power transfer to be compatible with existing phase shift dimming controls.

Inductive or capacitive loads are quite likely to have major problems with two wire dimmers.

.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
The Standard Lutron LED DVCL-153 Is not the most compatible dimmer around. Works with many but not most.
Leviton has been the most compatible yet. ( I don't like the form factor though) Give and take I guess.


I agree The CL are not perfect that is why I suggested the electronic dimmers with the neutral setup- not the magnetic one
 

Electric-Light

Senior Member
150317-2116 EDT

Dennis:

Can you describe how the dimmer you are referring to works? And do you know why it is better?

Lutron has a description of each of their types at
http://www.lutron.com/en-US/Education-Training/Pages/LCE/DimmingBasics.aspx
.

The C-L dimmers are intended for non-linear loads like dimmable CFLs and LE Decorations to avoid drop outs, failure to come on, pulsation and beating.

The potentiometer maybe used as direct acting passive analog input or it could simply be an input to embedded controller. The more universal modern ones use an embedded controller which is designed to address things like dead-band.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
150317-2116 EDT

Dennis:

Can you describe how the dimmer you are referring to works? And do you know why it is better?

Lutron has a description of each of their types at
http://www.lutron.com/en-US/Education-Training/Pages/LCE/DimmingBasics.aspx
.


No, I can't to be honest. I know that the CL dimmers don't always work on all LED's . In fact Lutron will not even guarantee that a specific LED will work on their dimmers unless they are one of the ones that they have listed on their site.

I also know that sometimes even with the listed ones we have had an occasional issue. When the CL don't work we have tried the electronic LV dimmers- not magnetic- and they have worked successfully.

I know that the Halo undercabinet LEDs will not dim properly with a CL dimmer but they work fine with the Electronic LV dimmers-- of course these are quite expensive
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150318-1343 EDT

From looking over the Lutron site I believe that a CL dimmer is a "forward phase shift" that requires a neutral connection. What this means is that the dimmer is a delay to turn on type of phase control and that it uses a neutral so that the electronics is is powered from hot to neutral independent of whether or not a load is present or the type of load.

This type of dimmer would always turn on at a controlled phase point, unless some very inductive load was present, and would turn off at the next current zero crossing. The current zero crossing is load dependent. For an inductive load this will lag the voltage zero. For a capacitive load it occurs when the capacitor voltage equals the source voltage. This means leading a voltage zero crossing.

Whether CL type function, meaning requires neutral, is combined with types of functions is not clear but almost required in some cases.

A magnetic dimmer is one where an attempt is made to keep the average DC current near zero to prevent magnetic core saturation. Either forward or reverse phase control could be used, but Lutron only shows forward.

With capacitive loads, meaning a rectifier with a capacitor input filter, either forward or reverse phase control could be used, but for other reasons reverse might be preferred.

It is jungle out there relative to the various dimmers and their loads. Just because someone says it is dimmable does not mean that it is or works very well.

Incandescents dim very well with adjustable voltage AC or DC or phase shift control. Zero to 100% with properly designed equipment. Ideally a fluorescent or LED can dim from 0 to 100% with correct circuit design. But most actual devices won't and there are varying degrees of performance.

Experiments need to be performed on the components to be used before installing the various items. Also to be considered is how wiring and layout affect performance.

.
 

Electric-Light

Senior Member
150318-1343 EDT

From looking over the Lutron site I believe that a CL dimmer is a "forward phase shift" that requires a neutral connection. What this means is that the dimmer is a delay to turn on type of phase control and that it uses a neutral so that the electronics is is powered from hot to neutral independent of whether or not a load is present or the type of load.

Not all of the CL dimmers have a neutral. The ones that use toggle or touch pad do to power the embedded controller and associated electronics. The most basic CL slider type dimmer does not.

Ceiling fan controllers, regular incandescent dimmer, CL LE Decora/CFL dimmers are all the same in principle, but it's the small touch that makes or breaks their functionality. (Calibration curve, trim, linearity etc tailored to specific usage)

This type of dimmer would always turn on at a controlled phase point, unless some very inductive load was present, and would turn off at the next current zero crossing. The current zero crossing is load dependent. For an inductive load this will lag the voltage zero. For a capacitive load it occurs when the capacitor voltage equals the source voltage. This means leading a voltage zero crossing.

Whether CL type function, meaning requires neutral, is combined with types of functions is not clear but almost required in some cases.
See above response.

A magnetic dimmer is one where an attempt is made to keep the average DC current near zero to prevent magnetic core saturation. Either forward or reverse phase control could be used, but Lutron only shows forward.

No. There is a specific warning against mixing reverse phase and a transformer load.

It is jungle out there relative to the various dimmers and their loads. Just because someone says it is dimmable does not mean that it is or works very well.

Incandescents dim very well with adjustable voltage AC or DC or phase shift control. Zero to 100% with properly designed equipment. Ideally a fluorescent or LED can dim from 0 to 100% with correct circuit design. But most actual devices won't and there are varying degrees of performance.

Experiments need to be performed on the components to be used before installing the various items. Also to be considered is how wiring and layout affect performance.

.

I think it helps that incandescent consume considerable more power than their relative output (i.e. 10% light ~50-60% input) that it stabilizes the triggering electronics.


It is a jungle out there with LIGHT EMITTING DECORATIONs
 
Status
Not open for further replies.
Top