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.