In this episode of the Ask Derek Cole Show, host Derek Cole is joined by HVAC comfort expert William Skipper to address three homeowner‑focused HVAC safety topics. First, they discuss carbon‑monoxide (CO) detectors, emphasizing that most manufacturers recommend replacement every seven years (with newer models offering a ten‑year warranty), the importance of checking battery backup, and proper placement—low on the wall or floor level in a hallway near bedrooms—because CO is heavier than air. Second, they tackle how a homeowner can verify a furnace technician’s claim of a cracked heat exchanger. They explain that tiny hairline cracks often require a heat‑exchanger inspection camera or visual inspection guided by manufacturer‑specific failure points, and they advise documenting findings with photos or video, disabling the gas supply, and marking the unit to prevent unsafe re‑activation. Third, Skipper defines superheat and its counterpart subcooling, describing superheat as the additional heat added to refrigerant after it vaporizes, which ensures the compressor only sees vapor and avoids liquid slugging, while subcooling is the opposite process used in heating mode. The conversation blends practical safety advice with technical HVAC concepts, aiming to empower homeowners to make informed decisions about their comfort systems.
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Hey, on this episode we talk about superheat. We have a special guest, William Skipper, to answer that question. We talk about how do you know if there's a crack in your heat exchanger and do CO detectors really have a lifespan? You ask your comfort and energy questions and they get answered. This is the Ask Derrick Cole Show. Hey, this is Derrick Cole. Welcome to episode 51 of the Ask Derrick Cole Show. And it's been quite a few good days in a row. No rain, sun shining. And by the way, the special guest today is the comfort expert other half, William Skipper. So let's get into the program.
All right, how often should a CO2— how often should a CO2 detector be replaced and do they go bad?
So yeah, they do go bad and they need to be replaced. 7 years is what most manufacturers recommend. Every 7 years it needs to be replaced. Some are coming out these days with a 10-year warranty, so depending on when it was purchased is going to, you know, anything this year would probably be a 10-year warranty. Anything before This year would be every 7 years. You do want to check your battery backup in that and make sure it's working. I would change those out before the season starts every year just to make sure you're good to go. Kind of the same rotation you do like smoke detectors or things like that. So check that, make sure. But yes, it does go bad. It's very important to have one and not only to have one, but to have it in the right place because we go to a lot of homes where that CO detector is part of the fire alarm or the smoke alarm and it's up on the ceiling and that's not where you want it to be. CO is very heavy and it will fall, so you want it as close to the floor as possible. So if you plug it into your receptacle at the floor level, that's where it's recommended. It's also recommended to be in a hallway where the bedrooms are. That way at nighttime, if you're asleep, you do hear it going off and you can wake up because CO is one of those things you do not want to play with whatsoever. It's deadly, odorless, you don't smell it, you don't know it's coming, so you need that detector. Anytime you have any combustion item in the home— gas, water heater, dryer, heating and air— Anything like that, you need to have a CO detector.
I've had furnace companies inspect my furnace in the past and tell me that there's a crack in the heat exchanger and the furnace needs to be replaced. I could not see the cracks but assume that you need magnification to see them. Is there a way as a homeowner that you can tell whether it's true or whether they're just trying to scam you?
A couple things should be done in that situation. If it's a very small hairline crack, You're probably not going to see it unless you have a heat exchanger camera and go in there with a light and find it. There are books as well on heat exchangers depending on the manufacturer. You know, a Carrier heat exchanger fails differently than a Goodman heat exchanger does. It has different spots in which it's prone to fail, so that's obviously the spot they're looking at. A picture can be taken with these devices. Even the cameras we have, you can actually bring a screen to the homeowner and say, "I'm going to go, keep watching the screen, you're going to see it. I'm going to go to the furnace and I'll show it to you." So that can be done, that should be done, that way you're confident in what they find as well as if they do find a crack in the exchanger, it is going back to CO, it is a danger. And it should be disabled. We disable all of ours because it is a safety hazard because the possibility of CO coming into your house is not worth the risk of not turning it off. So we turn it off, kill the gas to it, put a sticker on it. That way if a company comes behind us, they know that we found a cracked heat exchanger. Now I've had these phone calls before where companies do come behind us. I'll give you a good example. I had one last year. Company came behind us, couldn't find the crack, couldn't find the holes, and the technician told me, did he take the top off the unit? And I said, did you take the top off the unit? The guy said no. I said, well, if you take the top off, he's got a marker around where the crack is. So it depends on who's doing the second opinion. I mean, this guy wasn't even going to take the top off the unit. He was just going to say it was good to go, turn the gas back on. That's nothing to play with. I mean, you're playing with lives and you're playing with CO, something very dangerous. So you want to be sure that the heat exchanger is good before you activate it. And if there's any kind of problem, you need to see the evidence of that problem before. Then that gives you peace of mind and you say, yes, even though I can't physically see it from looking right here, I can't really see the crack. I know that with the camera he found a crab because I saw a photo, I saw the video, and I know what I got.
Hold on one second. I think it's getting ready to turn off, but it shouldn't because I deleted the card.
How was that?
It was good.
That was a real phone call too.
I don't—
I mean, it shouldn't shut off.
Okay, you want to restart it?
What is superheat?
Superheat is— well, we have to get really, really technical here, so William is the technical man. So William, what is superheat?
Superheat is a process that we use in the HVAC industry to help charge units, to make sure that they're properly charged. The actual definition of superheat is the amount of heat that is added to refrigerant after it has changed its state from liquid to a vapor. We use— what we do is we want to make sure that that refrigerant has changed its state completely into a vapor because the compressor itself is only designed to pump vapor, not liquid. If we get liquid back to the compressor, we can get what they call liquid slugging, which actually can break internal components in that compressor and shorten the life of that compressor. So it is actually the amount of heat added to refrigerant after the refrigerant has changed state. There is also a term they call subcooling, which is the opposite of superheat. You do that in the— one in the heat, one in the cooling season. That's how you change your— you charge your unit properly.
Yeah, so I mean, what does that mean to a regular homeowner as far as— I mean, it's something, something we use basically to make sure everything's working the way it should be working.
That's right.
Yeah, so that's all there is to it. I think superheating, subcooling is reverse. I think superheating's in the cooling and subcooling is in the winter, so it's opposite of what you think it might be.
Correct.
So that's fun. All right, so that's it. Uh, episode 51. You notice we kind of switched shots here, a little technical situation. So now we're filming old school with a phone. Is that old school? I don't think it— I don't know. Um, yeah, episode 51 in the books. William Skipper, thank you for being here.
Thank you.
Good job. Uh, we will see you next time. Make sure you hashtag any question about home energy air conditioning, heating. Any question you have, hashtag it #AskDerekCole and we'll get you on the show.
