HVAC specialist Derek Cole explains why lights dim when your AC unit starts: the compressor's startup draws a large inrush current. He also covers variable-speed motors, duct leakage that bypasses filters, and how balancing dampers control airflow to different rooms.
Hey, on this episode we're talking about balancing the air in your home. My lights are flickering and what's going on with that? And every time I check my filter, it's clean. You ask your comfort and energy questions and they get answered. This is the Ask Derrick Cole Show. Hey, this is Derrick Cole and this is episode 36. Of the Ask Derrick Cole Show, and today they had me in the warehouse. So you see stuff here, here, all around me, which is fine because it's what we do, it's how we roll. So, yeah, stomach's feeling a little better. I'm sure y'all wanted to know about that. And I'm good. Y'all good?
Good.
Let's roll. All right. Question number 1. Wait a minute. Okay.
What is variable speed?
Very good question. That was kind of loud. Variable speed. So I think I mentioned last episode about thinking about miles per gallon when you're thinking about runtime. Variable speed is kind of the same way. If you— your system, or the older systems, have just one speed on, 100% ready to go. So it would be equivalent to you driving out of your driveway and then hitting it to 55 as soon as possible. So is that more efficient or is it more efficient for you to actually slowly gear up and speed up to get to your speed? So variable speed's kind of that same dynamic for your system. So most variable speeds are two-speed systems. So you have a variable speed indoor motor. So it's only going to run on high speed when it has a big demand. So if it's really hot, really cold outside, and you need that extra power to get to 75, whatever the set point is, it's going to get there with the high speed. But 60% of the time, roughly, it's going to run on low speed. So that will save you a lot of money because we're sizing your house at 3 tons, for example, on a 95-degree day. Well, how many of those do we actually have during the summer? You know, we might have a few weeks of 90s and then we're in the 80s and 70s and So nighttime gets down to 70, so variable speed and two-speed systems really save you a lot of energy because you're not running on high speed, turn it off, high speed, turn it off. You're running on low speed most of the time, high speed when you really need it, and then you're turning it off.
Does the design of new residential heat pumps cause lights to flicker in the house?
The answer would be no, and let me tell you why. The reason the lights are flickering in the house is because there is an issue happening in the house. J-Ru, who said— who said she's having this problem in her house, so I didn't answer her question until I answered it here first. What happens is when that unit first comes on, that is the most power it pulls. Starting that compressor. It's kind of like starting your car. You know, is it more efficient to turn the car on, turn the car off, or is it more efficient to run it for the period of time? It's more efficient to run it. Uh, it kind of goes back to episode 30— was it 35 last time? 35, where I talked about, uh, stop and go. Same situation there. It's more efficient for the compressor to run. It pulls less amps, less power cost you less money to run than does to start. So our solution in most of those situations is a compressor saver, which will actually lower that start capacity so you will not have the dimming lights anymore. So a compressor saver is what I would try first, but I would also try checking the amperage on startup to make sure you're not pulling too much power because then that is a sign it's probably fixing to go out and that's going to be a problem as well. So you're looking at a couple of different issues here. So flickering lights is not normal. That shouldn't be happening. No, it's not possessed. Not possessed. Not normal. It's a sign that you're pulling too much power. That's what it's a sign of. That's why the lights are flickering, because you're like, whoa, and then you're running and it doesn't flicker, right? It just— when it starts, so boom.
All right, number 3: I have never changed my filters. Every time I check them, they look like the day I bought them. Is that good?
Where it's going or what's being sucked into the unit is unfiltered air if your filter is clean. So you're having a duct problem more than you're having a filter problem. So the air is escaping through the duct or the cracks. You have some leaks, the ductwork has some leaks, and you're getting basically by the filter, the air is still getting to the unit, it's just not conditioned clean filtered air.
How do I balance the air being supplied to each room of my house?
All right, that's a good question. So when we install a duct system, we actually install balancing dampers because they do need to be adjusted every now and then. So that is the route you need to take. If there is no dampers on your runs from the trunk line, then it's not really possible to do it. So that is why we install on our duct systems with the lifetime warranty, by the way, we install balancing dampers with those so we can control the airflow in each room because sometimes you want a little more, a little less. You know, the kids are blowing on it, turn down a little bit. My wife's okay, a little more. So that way you can control the airflow. So yeah, good question, but unless you have those dampers in place, it's not really possible. All right, so that's episode 36. 36. I don't know why I can't remember. 36. The good news is I'm not 36 yet, so that's a positive note. We shot this in the warehouse, so I think that kind of worked. Not too bad. Not too bad. Got some, some stuff here, but it's pretty cool. So yeah, check out all the episodes and send your questions in, #AskDerekCole, and we will get them on the show.
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