LED lights constantly flicker when heat pump is running

Question

A few months ago we had our gas furnace replaced with an air source heat pump, using our existing ducts in our single level 3 bedroom house. As part of this update our electrical service was upgraded from 100 to 200 amps, and the panel was replaced with a new one. The heat pump is on its own dedicated circuit running from our panel to a junction box outside next to the heat pump.

Since this update, whenever the heat pump is running and either cooling or heating, most of the dimmable lights in our house flicker the entire time the heat pump is running, not just when it starts up. The flickering is VERY pronounced, not a quick blip but more like a haunted house.

Almost all of our lights are dimmable and all are LEDs. I understand there are lots of compatibility issues with LEDs and certain dimmers, but this issue impacts so many different types of lights and switches that it seems to be an issue with our electrical service or the way the heat pump is wired in. The flickering wasn't present before, with our old panel and 100 amp service – certain lights would occasionally flicker a bit at certain dim levels, but not constantly like they do now.

The bulbs we are using were made by a wide variety of manufacturers (at least 7 different manufacturers), a mix of cheap and expensive bulbs in lamps, par20 cans, and LED lighting fixtures, using Lutron Caseta, Leviton sliding dimmers, Ikea lamps with built-in dimmers, etc. The bulbs were all sold as dimmable, and marked as dimmable on the bulb.

Our HVAC contractor has been back about 6-8 times to try to identify and fix the issue with the flickering lights, with no luck so far. On a recent visit they brought some replacement bulbs and seemed to think we should simply replace the bulbs that are flickering, but I don't want to do that since it impacts most of the lighting in our house and I don't want to have to live with this nuisance for the next 20 years. Also it seems like a flaky power supply might not be good for our other electronics. (computers, a/v)

What can I do to identify and diagnose this issue, and prove that it's an issue beyond the symptom of flickering light bulbs? I have a multimeter but don't have much experience with it; can I use it to measure the voltage drop on the other circuits in our house when the heat pump is running? Is it normal for the voltage to drop and stay down or fluctuate the entire time the heat pump is running, or just when it first ramps up? Is a voltage drop the thing I should be looking for, or is there something else I should try to measure as well?

Our HVAC contractor has been taking responsibility for this issue so far but after spending maybe 30 hours of staff time on it and running out of things to try I'm worried they might just blame it on our bulbs and give up. I'd like to be able to present them with evidence that something's wrong, aside from the flickering bulbs.

Our power company has also come by to confirm the supply wiring is OK, and replaced a badly corroded neutral connection but that didn't help either. The original wiring in our house is about 30 years old and we replaced almost all of the lighting and switches about 5 years ago.

Edit: important detail I neglected to include: the HVAC company were the ones who did the electrical service upgrade and all the related wiring. They also added a 'flicker free breaker' from Siemens on the heat pump circuit to try to remedy the flickering.

Answer 1

The HVAC company brought you bulbs because they want you to go away. That's fine; unless they are the ones who did the service upgrade, this probably isn't their responsibility. It's more likely that you still have a poor neutral connection or some other significant electrical installation problem. However it is also possible that the heat pump is defective in a way that is causing all sorts of noise across your system. You won't be able to spot that with a multimeter.

If I were in your spot, I would be calling around local electricians looking for one who could do power quality analysis at my house. This will probably cost you a significant amount of money, but it's the only way you are really going to nail down what is causing this flicker. They should be able to show up with a power quality analyzer. You could rent one, but without the experience to use it you'll not know what to do with any data that you gather. You need someone with significant electrical troubleshooting experience to really dig in here.

Answer 2

An HVAC company doing an electrical service upgrade? Get a licensed electrician in there and have them give the system a once-over. There are many things to mess up, and HVAC outfits are notorious for playing fast and loose with Code.

First, get some real incandescents and replace some of the LEDs. No not permanently, just for testing. "Looks like an incandescent but is actually a halogen inside" are close enough. Incandescents are truth tellers because they remove all the LED weirdness especially the "train full of dumpsters that was on fire before it derailed" that is the state of the art of screw-in LED dimming. If you have a group of lights under control of one switch, replace exactly one of them with incandescent and see if that makes the LEDs behave. Does a room full of incandescents also shimmer? Then we can distinguish a real power problem from LED nonsense.

I'm not an LED hater. Lots of dimming technologies work great with LED, like 0-10V, PWM or powerline coding. But those are not compatible with screw-in Edison bases.

You should probably buy a Kill-A-Watt home energy monitor. It's cheap. It's a safe and foolproof way to get voltage readouts without sticking probes in slots (what could go wrong lol). You can also plug in a pure resistance heater like a space heater or toaster and compare the "watts" (the power actually used) and "VA" (the sine-wave that must be delivered to serve that power). On a resistive load they should be identical. If they're not, your power isn't a sine wave!

You should also hit the books on North America's split-phase power system and how panels are phased. That way you will be able to monitor both "legs" of power separately.

My hunch is they may have done something dumb with neutral or grounding, and created a Lost Neutral scenario in which your voltages float around (or rattle when an inverter drive is nearby). Lost Neutral is a hard one to detect because stuff "works" by and large.

Other than that, this sounds like some sort of a bodge, like miswiring or failing to upgrade the service conductors when doing a 200A heavy-up. There are too many possibilities to name, really.

Answer 3

We have also been having the same issue with led bulbs while our heat pump is running but we do not have any dimmers. Anywhere we have an led bulb, we have a constant flicker, or the bulbs will dim while the heat pump is running. In 2 different rooms we have an issue where if the heat pump is running and the lights are turned on, one bulb will not light, or will come on dim once is does come on. If the lights were on before the heat pump kicked on then they will operate normally but may flicker a bit.

I myself checked everything out myself including the heat pump, no voltage drops, no loose connections anywhere, and if i found anything suspect I tightened it or replaced. Finally I threw in the towel. We had an electrician come out and verify everything in the house is fine. He replaced the heat pump breaker but that did not change anything.

We had an hvac tech come out and speak with Bosch (the heat pump manufacture) and the support tech said they just had a class on this that they have had complaints with variable speed compressors causing led lights to flicker. He had the hvac guy run some tests on the compressor and said it is operating normally and that the only answer is to try some new bulbs. It does not cause issues with incandescent lights. I swapped some old bulbs in areas we have noticed the issues and voila no flicker. Problem is you cant find them anymore, except on rare occasions in small quantities and they are now more expensive then name brand leds.

Answer 4

Moovair, Bosch, and many other manufacturers are all a Midea unit re-branded. I can confirm Midea made a design change to one of the boards on some of their heat-pumps (3t and 4t) to address this exact issue. The contractor should be able to replace the "Inverter" board under warranty, which in many cases (assuming it is not a wiring/panel issue) will solve the flickering.

Answer 5

Try a higher end lamp like Phillips dimmable. These have worked for me in the past for similar issues.