Flickering CFLs when on inverter

RandomJoe · February 2010

I finally installed the new VFX 3648 inverter to go with the rest of my Outback system yesterday. Played with it a bit last night, but nothing much. The big test is today, to see how it does. And so far, not so great!

I have the AC In wired to grid, and when I'm using grid everything is fine. When I switch to inverter, the CFL desk lamp has an extremely annoying and random flicker! Sometimes just a single "blink", sometimes a whole series of them. Nothing actually goes *out*, it's like the flicker I would get when an incandescent bulb was plugged into the same circuit with a laser printer or copier at work. Some people never notice, it drives me absolutely insane!

Nothing much for loads right now, I just have a small subpanel that the inverter feeds, and a single breaker wired to an outlet. Plugged into that, at the moment, is the desk lamp and two low-power computers. Total load is a whopping 120W or so... Batteries are charged, system has already gone through absorb and is currently floating.

FWIW, the CFL has never flickered at all when running on my Samlex inverters. And, again, I can switch to grid and no flicker at all...

Wishing I still had the scope in my work truck, to check the waveform, but had to give it to a coworker to use. The Fluke meter does show that the voltage dips a touch when the flickering happens - it's running 120.9V normally, and when I see the flickering I'll see it go down to as low as 120.3V.

Any ideas / thoughts / suggestions? I do hope this isn't normal!

BB. · February 2010

Re: Flickering CFLs when on inverter

Do you have other loads on the inverter (i.e., inverter is not in "search" mode looking at that ~6-8 watts before it "turns on").

Also, I found that CFL's can be sensitive to oscillations in line voltage...

My "weird" story... I have CFL's in all of my main fixtures... And I had just installed a pair of CFL flood lights in an outdoor motion controlled sensor.

Eating dinner one evening just after I installed the outdoor fixture--and I noticed my pair of CFL kitchen lights flickering very rapidly (and irritatingly).

Long story short--found out that my outdoor flood light fixture and pair of 11 watt CFL floods was cycling on/off (flickering) because of the light level sensor. The sensor was near a white wall that was illuminated by the CFL floods (dark, lights on, light, lights off, repeat). Redirected the lights and sensor--and my indoor kitchen lights stop flickering too (this is all on grid/utility power). I was really surprised because the CFL floods draw so little power but yet caused my indoor lights to flicker too.

So, check if you have any loads that may be rapidly changing their current draw from the inverter.

The other CFL "blinking" problem I had--Lighted wall switch (neon lamp) had enough leakage current that it would charge a couple CFL's enough that they would blink on once every second or so... Very strange. Swapped back to the non-lighted wall switch and problem went away.

-Bill

RandomJoe · February 2010

Re: Flickering CFLs when on inverter

Just tried the computer UPS on the inverter - seems to like it okay, at least it isn't clicking on/off as some had reported theirs doing. I then plugged the computers into the battery-backed outlets and the lamp into the non-battery-backed but surge-protected section and the flickering is... If not gone, then only every-so-barely perceptible.

Perhaps the inverter didn't like the highly capacitive load, and the UPS is helping to filter that? (Reaching there, but who knows....!)

I notice the voltage has stabilized even between the inverter and UPS, it is now a rock steady 120.6V. System shows only a touch more load - 130-140W.

RandomJoe · February 2010

Re: Flickering CFLs when on inverter

BB. wrote: »

So, check if you have any loads that may be rapidly changing their current draw from the inverter.

No, the only loads are the two computers and the CFL. One computer is an Atom SFF that pulls a steady 25W all the time, the other is my MBP with LED Cinema display which was steady the time I measured it although I've never watched it closely.

The Outback system shows a pretty constant load of (then) 120W (now) 130-140W (resolution is only 10W though). DC side to the inverter is steady at 54.1V 2.5A.

Edit: Just added the fridge, so I'll see what happens when that kicks off again...

RandomJoe · February 2010

Re: Flickering CFLs when on inverter

Well, that was interesting...!

Cruising along, doing great when the UPS suddenly switched off! No alarm, no warning, just like hitting the switch. The surge-only ports (with the lights) still worked, but trying to turn the battery-backed outlets back on only caused it to trip the "Replace Battery" alarm. Moved the UPS back to grid, and it's operating just fine. Not sure why it worked fine for so long though...

Through the process of switching things around, it appears the culprit causing the flickering is the Apple system! What actually plugs in is the Cinema display, which also has a built-in charger that connects to the Macbook Pro. When the UPS quit, I plugged the computer into the surge-protected outlets along with the lights - and the flicker came back!

I now have the MBP on the UPS on grid, and put the lights back on the inverter. No flicker at all, even with a different computer on there (Asus Eee netbook that's charging its battery).

I have a surge protector somewhere, I may try isolating the Mac behind that, but not sure if that'll be sufficient. I'm wondering what Apple is doing (wrong?!) in this display to cause such trouble... Have to try the Macbook's own adapter separately, see if that does the same thing.

BB. · February 2010

Re: Flickering CFLs when on inverter

It sounds like the Mac charger is more or less an "on/off" PWM type charger--The el'cheapo CFL's I buy (~$1 each in northern California) really show any "quick" voltage variations.

I am guessing the PWM of the Mac charger is just simply causing a low frequency voltage drop in your wiring that the control circuitry in the CFL is somehow resonating with.

Placing the CFL's on a short cord closer to the Inverter (and Mac farther away on extension cord/other branch circuit) MAY help.

A surge suppressor/line filter should not help.

May have to try other brands of CFL's or try other florescent/ballast lamp combinations. Small 25 watt halogen desk lamp (vs 13-20 watt florescent).

Alternative charging/chargers for the Mac batteries...

-Bill

RandomJoe · February 2010

Re: Flickering CFLs when on inverter

I dug around and found an old Isobar surge suppressor power strip to try. And it works! Mostly. I have the Isobar plugged into the power strip that the lights are on, then the Mac is plugged into the Isobar.

It isn't perfect, and you are right, it probably has something to do with low-frequency ripple from a lightly loaded PSU. As long as I keep the power level up to a certain point, there's no lamp flicker. If I turn the power consumption of the Mac down below that point (easiest is by adjusting the brightness of the backlight) the lamps start to flicker a bit! But still not as bad as if the Mac is plugged straight into the strip with the lights.

Be interesting to see what happens when I get the rest of the circuits run, I'll try the lights on a separate circuit from the computers. The wire runs aren't very long, just through the wall, but at least where they meet will be much closer to the inverter with much larger wiring / busses.

What still gets me is that there is no flicker whatsoever when I switch the Outback system to grid. Same wiring downstream of the inverter, just using the inverter's grid passthrough instead. Is it the extra capacity of the house / grid wiring buffering things out, or is the noise generated by the Mac actually causing the Outback inverter to fluctuate output?

Flickering CFLs when on inverter

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