Apr 25, 2023, 1:47 PM@TechConnectify so I was watching the most recent episode by @TechConnectify about contactors. Interesting episode, and I learned a lot.
Now, in it it is said that the lights in the house dims when the AC turns on. I have never seen this in any house. Is this something that happens more often in the US which uses 115 V?
@loke I doubt it's to do with our voltage - if you've never seen this, you might be from a place where variable-speed compressors are the norm.
They're not, here. Starting to get common but still quite rare in the grand scheme. When that contactor closes, you'll definitely see a disturbance in the lights for a fraction of a second.
@loke This does make me wonder, though - have you never noticed this with a fridge kicking on?
It's a lot more subtle and these days we see it less since fridges have their own circuit in modern builds. But if you plug a fridge into a circuit that has some lights on it, you'll usually notice the lights flicker a bit when it starts.
Given that motors are still motors no matter what voltage they run on, I'd imagine this is normal everywhere.
Apr 25, 2023, 2:08 PM@TechConnectify I've never seen it in any of the places I've lived, both in Sweden and Singapore. I've never had an AC in Sweden, but in Singapore they're everywhere. In my current house I have 4 units and two separate compressors.
@loke Honestly this all goes back to how the systems start.
If you've never noticed an air conditioner come to life with a bang, then they probably have some sort of soft-starter or a variable-speed compressor.
Those are very, very rare here.
Another factor is that three-phase service in the home is unheard of, so every large compressor needs a start capacitor. That may increase apparent drop upon startup.
Apr 25, 2023, 2:50 PM@TechConnectify the ones I have in the house is the Misubishi MSY-GE18VA. I don't know if it has a variable speed compressor.
@loke Almost certainly.
Basically, if you've never noticed it go KA-CHONGGGGGGG, then it does. And given that it's a Mitsubishi, it's very unlikely to be single-speed.
My cheap Pioneer mini-split doesn't cause the lights to dim because it slowly ramps up in speed. It never goes from being silent to loud in an instant like my cheap Lennox central unit does. But mini-splits (and vari-speed units) remain exotic here in the States.
@loke @TechConnectify, I suspect that it is quite possible, a lower voltage requires thicker cables for the same power, but this means that there are also larger voltage losses than in a 220 V network. Adding that household appliances in the US do not usually have the same energy efficiency as those in the EU, which adds an extra load to the network.
@Catweazle @loke Just going to clarify in case you didn't know, air conditioners here are 240V.
Our transformers have a center tap which is earth-bonded, so instead of a single 240V phase, we get two 120V legs phase-to-neutral and 240V phase-to-phase.
The voltage drop that the air conditioner causes at startup would be identical on a 240V transformer because it actually /is/ on a 240V transformer. Whether it's more noticeable since our lights only use half of the transformer, I don't know.