HVAC System / LED Dimmers Not Getting Along

[A/A Fuel GTX]

Have a customer with a new home with a high end HVAC system. DC, variable speed, etc. When the system is in the cooling mode, the LED's in recessed cans throughout the house flicker randomly. The dimmers controlling the cans are LED rated. I recall a previous job awhile back where the well pump had the same effect on LED's/Dimmers. I believe the well guy had to put some kind of filter on the constant pressure well pump to alleviate the problem. Has anyone else had this problem? TIA

 

[ramsy]

DC, variable speed, (cause) LED's in recessed cans throughout the house flicker

Try moving VSD breaker & Neutral wire closest to service/feeder, and LED sub-panel/branch wires at opposite end

 

[fastline]

I work with electronics. Personally, I'd be putting a scope on that as it will certainly identify the issue. Other reality is it's likely the dimmers as their output becomes a function of input. Small change on primary, you see it in the LEDs. many ways around this issue. None that can be defined without measurements but I've used secondary LC network to snub and support the voltage bumps. Problem is it takes calculations and such. There might be filters out there for this. I see no reason you could not deploy on primary side. Other is get better dimmers as IMO, they should be designed for exactly this.....

 

[herding_cats]

Put a line reactor on the HVAC system. Both indoor unit and condenser. Size by Amperage pull plus 20%. They have cheap LED lighting as well.

 

[A/A Fuel GTX]

I work with electronics. Personally, I'd be putting a scope on that as it will certainly identify the issue. Other reality is it's likely the dimmers as their output becomes a function of input. Small change on primary, you see it in the LEDs. many ways around this issue. None that can be defined without measurements but I've used secondary LC network to snub and support the voltage bumps. Problem is it takes calculations and such. There might be filters out there for this. I see no reason you could not deploy on primary side. Other is get better dimmers as IMO, they should be designed for exactly this.....

The dimmers are all Lutron made for LED's. So, is it my problem or the HVAC guys?

 

[A/A Fuel GTX]

Put a line reactor on the HVAC system. Both indoor unit and condenser. Size by Amperage pull plus 20%. They have cheap LED lighting as well.

 

[A/A Fuel GTX]

Do you feel this would correct the issue with certainty? The LED lamps, GE and the Dimmers, Lutron are good quality.

 

[synchro]

If a neutral is available, dimmers that use a neutral are more likely to have a higher immunity to interference.

 

[tthh]

I installed a new LED light over a mirror in a bathroom and it flickers every so slightly when the A/C compressor is on. No dimmer involved and not a cheap LED fixture. Kinda disappointed. I have yet to deal with it.

 

[herding_cats]

I am fairly certain it would. Go to galco,com and source them there. I can help you size them.

 

[fastline]

The dimmers are all Lutron made for LED's. So, is it my problem or the HVAC guys?

Do you want the fast or windy response? As I mentioned, the right approach is actually using a scope to evaluate the signal and noise, BUT ECs very rarely have experience in this area so just having a scope does not mean you will understand how to use the data.

It's 'probably' the HVAC guy's deal, but I bet you get stuck with it unless you can prove their equipment is making noise. Another reason I reach for a scope.

Other option is to call the dimmer OEM and discuss. I'm sure this ain't the first and they may have the right recipe.

There are EMI and RFI specs on the books just for this stuff.

 

[ptonsparky]

Do you want the fast or windy response? As I mentioned, the right approach is actually using a scope to evaluate the signal and noise, BUT ECs very rarely have experience in this area so just having a scope does not mean you will understand how to use the data.

It's 'probably' the HVAC guy's deal, but I bet you get stuck with it unless you can prove their equipment is making noise. Another reason I reach for a scope.

Other option is to call the dimmer OEM and discuss. I'm sure this ain't the first and they may have the right recipe.

There are EMI and RFI specs on the books just for this stuff.

Do you have a picture or two you can share? Short explanation would get you a point.

 

[fastline]

Do you have a picture or two you can share? Short explanation would get you a point.

Of what exactly? If you are asking about the scope work, I can dig in, but there are other tools, depending on the company. For instance, a Fluke power analyzer could figure this out too. A scope would never say "ah, here is your problem". This is where the experience part comes in.

What I would do is very simple. first plug into input to dimmer, eval and trap the waveform. Then just turn on the HVAC and do the same. Then kick over to Fast Fourier Transform (FFT) and look for harmonics and what those frequencies are. That will be telling.

I would also evaluate for "glitch behavior", in which a scope can see voltage changes down in nano-second scale, so if you can visually see the lights change, the evidence will be there.

Basically there is zero way a power issue like this can avoid detection of a scope.

I'd personally want to know way more about the HVAC equipment because that is telling. If ECM blower and variable compressor, there will be some SMPS that can certainly contribute to harmonic issues.

What is also possible the the HVAC is just loading the system, but something totally different is causing this. The charge/discharge of capacitors has very high instant inrush, which can cause a flicker.