Fujitsu Heat Pump Causing Lights to Intermittently Flicker
I am seeing intermittent flickers on my LED lights like I have a compressor kicking on dropping the voltage. They happen every 5-20 minutes at random intervals. I believe they are coming from my two heat pumps. I don’t remember having the lights flash this summer but with more daylight and being relatively new to the home maybe I just didn’t notice. I only see it on my eco-smart LED bulbs. Anything with a built in LED: bath vanity, basement can light, undercabinet strip lights etc. I do not see the occasional flicker. I systematically turned breakers off to determine which one is contributing to the voltage drop. Both heat pumps cause the flicker but my 1 ton (12RGLX) causes it to happen more often but it is also running much harder than the 1.5 ton 18RGLX on my main floor. It doesn’t appear that it directly correlates with the heat pumps starting up, my amp draw on Emporia Vue show steady state running.
Questions:
1) Do I have a problem with both heat pumps?
2) Do I just need to start shopping for new bulbs?
3) Any recommendation on cost effective power monitor to track voltage loss?
4) Could this be related to the defrost cycle?
5) Any other thoughts?
*I have a new house as of July 2023.
*200 amp service
*Basement heat pump: Fujitsu ARU12RGLX (indoor), AOU12RLFC (outdoor) 20 Amps
*Main Floor heat pump: Fujitsu ARU18RGLX (indoor), AOU18RGLX (outdoor) 20 Amps
*I checked anything with a compressor by turning off one breaker at a time.
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Replies
Those heat pumps are tiny. Also as you know by monitoring the Emporia they do a soft start at about 100 watts, then they ramp up to 2kw or thereabouts and then after 5 mins or so they drop to whatever they think is appropriate based on outdoor temp and then modulation starts at about 1kw or less for your units.
Defrost is 3-5 minutes at 2kw or thereabouts.
My take is your main service frequency is off or you have other main service problem (undervoltage comes to mind)
Troubleshooting this stuff can be tricky. I do suspect that these types of issues are being noticed more frequently now with the move to LED bulbs and the uptick in heat pumps.
A few things you might look into for starters:
- Get an electrician to give your panel a once-over. I did this recently and found a terminal connection that had become loose. They could also verify that the connections at your mini-splits are sound and that the wires are properly sized. They should also verify that your house is properly grounded and that there is nothing funky about the grounding (for example, they should verify that you don't have any sub-panels with the neutral and ground tied together.)
- In my jurisdiction, I told the utility I was having voltage supply problems and they sent someone out for free who did a load test at the meter. Basically, that verifies that there are no upstream problems from the utility (pole transformer all the way to the meter box.)
After you check all the basics, it gets trickier. You are looking for a complicated problem (something that happens very quickly and/or harmonics) so I don't think you will have much luck using consumer grade equipment to monitor what is happening. I found this thread on reddit to be interesting. It talks about installing a line reactor or Electro-Magnetic Compatibility filter. If you start going down that route, I'd suggest working with an electrical firm that has some commercial/industrial experience.
https://www.reddit.com/r/ElectricalEngineering/comments/11xgq0r/inverter_heat_pump_causes_electrical_noise/
Sounds like the minisplit is causing some noise or voltage drop on the AC circuit, which could cause the LED driver to jitter temporarily. Different LED lights and different brands have different types of drivers and different levels of LED drive sophistication for efficiency, so what you're seeing may only manifest on a specific type of LED bulb.
I would also vote for loose connection somewhere. I had a corroded clamp on one of the phases of my overhead power feed and caused all kinds of strange problems.
Could also be a badly bonded neutral or bad ground somewhere. The issue might not also be with the heat pump but the ground to your dimmers/LEDs.
Akos I had the same thought as well and had typed out almost the same words then I happened to if reread this line in the original post “ I only see it on my eco-smart LED bulbs.” If the problem is a poor connection every load in the home would see the voltage dip and many would have reduced performance in some way. Then I read this line” It doesn’t appear that it directly correlates with the heat pumps starting up, my amp draw on Emporia Vue show steady state running.” That sound even less like a poor connection.
His Emporia Vue monitors the line voltage but I can’t tell if it logs the voltage, does it?
If the only symptom is from a single make and model of LED light bulbs I might replace the bulbs.
Walta
Try higher quality LED bulbs eg. from Philips. LEDs are susceptible to fluctuations in voltage which might be happening here. An inverter heat pump shouldn't have a "startup surge" like traditional A/C, but its normal power draw might cause momentary fluctuations in line voltage.
Thanks for the good feedback. I only see it one specific bulb type that creates a flicker. Unfortunately, I have a lot of that style bulb installed. I’ll try buying a better bulb and see what that does. Addressing power quality seems like a pain. Through work I have seen many negative impacts on harmonics and power quality causing premature failure. I went all in on a fully electric house. I hope I don’t see earlier failures on my equipment. Thanks again for all the help!
Do you have a way to log your voltage with Emporia Vue or a UPS?
Have you measured the Voltage when the lights flicker?
When you open up most Philips bulbs you do not tend to find any complex circuits nothing harmonic frequency’s could bother see attached photo.
Maybe I missed it but why are you so convinced the HPs have anything to do with the flickering?
Walta
I measured voltage of both phases coming in and they were the same. The flicker only last a moment and does not happen again, anywhere from a few minutes to 20 minutes. I have never tried measuring voltage right after the flicker. Emporia Vue does not appear to log voltage.
I systematically turned off any circuit with a motor one at time until the flickers stopped. I can turn off my freezer, refrigerator, heat pump water heater, inverter driven well, dishwasher, etc and still get flickers until I turn off both hvac heat pumps. I’m not sure why but the 1 ton unit causes significantly more flickers than the 1.5 ton unit. I’ll pick up some new bulbs and try them tomorrow. That is the easiest place to start. I’m open to other ideas as well.
Last week I checked a few spots for looseness on wiring.
1) disconnect for 1 ton heat pump
2) wire terminations at 1 ton heat pump
3) 20 amp breaker for 1 ton heat pump
I didn’t check the fan assembly inside yet because it is a pain to get to. The contractor put it too close to the wall so I need to cut a hole through the dry wall to gain access. He installed it before the drywall went in and forgot to leave an access door.
I didn’t check anything for the 1.5 ton since I can still get flickers when the breaker is turned off to that unit.
Quick update, I was able to get an industrial Fluke Power meter to measure volts, amps, and harmonics. I measured for a week and did all kinds of variations of circuits on/off. After downloading the data to my computer I didn’t see any red flags that I could correlate to the flickers.
Switching to a Phillips LED, which corrected the flickers. I assume I still have a small drop in volts from my heat pump but the improved bulb does not have the momentary flicker.
It was interesting watching as I turned on my circuits with LEDs, the THD on the neutral of my panel started to increase drastically. After some reading this appears to be normal for caused by LED drivers.
Thanks for the help.