 Hi, I'm Nate Adams, welcome back to the Electrify Everything course. This is module 2 of part 5, so we're talking about the HVAC in your home. This is by far the most complicated piece, because as we discussed in the Everything But HVAC section, all the other pieces are appliances that are a simple changeout. They are their own self-contained system. Now your HVAC is a system in a system of systems, which is otherwise known as your house. So where everything else is basically an appliance changeout, HVAC is not that dissimilar from an organ transplant. So the good news is, some systems you can get away with, although typically old school furnaces just didn't care what you did to them. So you can put them in really poorly and they'd work okay, like they may not be great, there may be a bunch of issues, but they'd kind of chug along. But as we have moved to newer equipment, we have to be much more careful with it. I joke that the old school equipment is like a big football player, you know, you throw a guy on his back and he just keeps on running, where the newer equipment is much more sensitive and oftentimes it's kind of like a prima donna soccer player where you touch them and they fall on the ground writhing. So we have to be cautious with how we use the new, more advanced HVAC equipment. So that's what this piece is about. So we're going to talk about important HVAC details and these are going to be a couple of things you're not going to hear about a ton, but they're very important in this. So we're going to talk about resistance heat, static pressure, and surge protection. And here's where we are in the syllabus. So we are looking at the important details of HVAC that were in part five. So you may have heard that resistance is futile when it comes to backup heat. This is where we definitely want resistance. It's not futile. It's really useful. And this is going to be counter to a whole lot of things that you've heard. But resistance is a key tool for a whole bunch of different reasons. And then we'll come back to the grid side of things later. So a couple of things that it's useful for. So if your compressor goes out, which happens, things break. You still have heat because you have the backup heat or it's known as emergency heat or grid heat or the toaster. This is like construction where everything has eight names so we can all be confused. But we're still talking about the same thing. You're going to hear a lot of different words for this, a lot of different phrases. It's also really useful for extra cold days. So when you are beyond what the heat pump is capable of putting out, you can supplement it with resistance heat. Now a bad control will turn off the heat pump and go straight to resistance. That's not what we want. We want to supplement. So think of it as a boost underneath. That's how it should be used. And a lot of controls will do that, but you oftentimes have to set them up. Resistance is also really good for dehumidification, which we'll come back to in a little bit. If your ducts are too small and can't handle the airflow that is needed, you can use resistance to supplements. And basically you can get more heat through the same ductwork. So we're going to talk about static pressure. And the last piece is if you plan to insulate later. So basically your house right now is kind of a corn crib. It's really leaky, but you've got plans to insulate it later. You want to size your equipment for where you're going, not where you are today. So you can make up the difference there with resistance heat. So I say all of this to say, don't fear resistance heat. And that's going to grate on a lot of nerves. I'm sorry, but this is what is best for consumers. It is not necessarily what's best for the grid, but there's a lot of headroom on the grid. This is mainly a discussion for cold climates, where we get into territory that heat pumps are great. So like when you start getting below 20 degrees, they start losing output a little bit or some models do. But when you get below zero, everything starts to have some form of a drawback. So sometimes systems will be games where they will purposely overdrive the compressor. They'll put more power into it than they normally would to maintain the output. But regardless, when we get below zero, things start getting more difficult. Heat loads are going up and then output of heat pumps is going down, which is problematic. So anyway, resistance is a really useful tool for all of these things. So don't fear it. We're going to talk more about that. So here's a key thing to understand. So one of the common items of pushback we get is, well, but the heat pump doesn't have enough power. I'm going to freeze. What's going to happen? And it's, you know, boogity boogity. People are worried about it. Here's how the math works on that. So say you have a three ton heat pump. That means it's 36,000 BTUs per hour, which, by the way, we find a lot of houses. That's what it takes to heat them at their design temperature here in Cleveland, which is five degrees. If you have a 15 kW or kilowatt resistance backup strip, that works out to 51,000 BTUs per hour. So you take 15,000 watts, multiply it times 3.4. That's about where you are in BTUs. So for most heat pumps, so if we're going to talk about 18 sear units, which is typically where most of your communicating equipment is, it's going to be 18 or 20 sear. They are putting out about half of their full power at 10 degrees Fahrenheit. So give or take might be 45, might be 55, but we'll just call it half. So you're getting about 18,000 BTUs of heat. Meanwhile, what the house needs to heat it has gone up. So like you may have to make up for the other 18,000. Say it has a three ton heat load. You have to make up for that with some resistance. But what you have at that point, the total available output at 10 degrees Fahrenheit is the 18,000 BTUs plus the 51,000 for the resistance. So you have 69,000 BTUs per hour of heat available at that point. Keep in mind, 60 and 80,000 BTU furnaces are common. So you have the equivalent output of a furnace if you need it. So if ever you want to warm the house up quickly, you can. It's just not particularly inexpensive because resistance isn't cheap to run. But in general, when it's being used for backup underneath, so just bumping what's needed. So the heat pump runs all the time flat out, which is a machine. They're fine doing that. And then you bump underneath like a lot of these. It's not going to be 15 kW or nothing. When you're looking at the higher end equipment, it's going to be two or three stage, so it's going to be a seven or 15 kW or the equipment that we like using will be a five, 10, 15 kW. So it will only engage as much as it needs to hold the set point. But key thing is you have the same output as a furnace. And what all that means is if you hear someone freaking out about, oh, this is going to be cold with the heat pump. We're not going to be able to heat the house. What's going to happen? What was me? Or my favorite line from Ghostbusters. Cats and dogs living together. Mass hysteria. You're going to be fine. You're going to freeze. You're not going to freeze. There's really no danger of that at all. And I can tell you that having done a bunch of these and gone through a couple of ugly cold snaps, we had a two week cold snap in early 2017. And I was sweating bullets. And you know what? Everybody's house held temperature thanks to back up. Now, the other thing where it's really nice for is what's called reheat dehumidification. And so when you're in shoulder seasons, spring and fall, say it's 75 degrees outside, but it's a very high dew point. It's very humid. So this is more of an East Coast thing than a West. But there's a whole lot of humidity that needs to be removed. But there's very little heat to be removed, which is very problematic. So reheat dehumidification is a great way to deal with this. And what happens is you run air through the air conditioner coil. You get cold but dry air. So 95 percent relative humidity may sound wet. That's relative, though. So dew points, what we want to look at. And then you add heat back in with the resistance electric. So it comes out the other side warm and dry. Or room temperature and dry, rather. And there's much more on this in the next section, which is on what we call bad ass HVAC and the six functions of HVAC. So you're going to learn more about what the math looks like underneath this because we hear a lot about, oh, let's get to use a ton of energy. We're all going to die. No, it's going to be OK. There's some climates where it may. But there's going to be other solutions that need to come into play there. But this is a really nice and purely controls based change that can be made to most heat pumps, because any heat pump that has resistance heat has the capability. It has the physical capabilities for doing reheat dehumidification. It just needs to be allowed in software. So this is a useful thing that resistance can be used for as well. And I already mentioned that the other pieces of ducts are too small or you plan to insulate later. Now, this is the big objection that I get at this point. What about the grid? First off, if rate structures don't change, I don't care about the grid. Nor do HVAC contractors care, nor do homeowners care. Incentivize that change it. But there's two key things to note here. Pretty much all northern grids are summer peaking today. So I've heard from a number of different people on a number of different grids that the grids today can handle 20 to 40 percent electrification as they stand, no changes whatsoever. And we talked about in the scaling electrification video how even if we are electrifying every single new piece of residential HVAC that comes out, that is five percent a year. And Jesse Jenkins was kind enough to have me in one of his classes with a grid planner and I asked him point blank, you know, how quickly can the grid grow? And he said up to four percent, no problem. Five percent, we start to sweat, but it's still potentially doable. We're talking about somewhere in the range of five percent here per year. And this allows electrification with today's products and today's grid. So this is a useful thing. Now, long term, if you've been watching me for long, I came into this world through the installation side and then the air sealing side. So I think about the building shell, how leaky is the boat that is your house. And so long term, we can do shell upgrades, which reduce how much heating a house needs. So insulation and air sealing or as batteries get cheaper, we put batteries on houses and that will help cover the early mornings on the cold days where we have issues. So in general, this problem is at least a decade out. And in the meantime, the grid is a living creature. This is what grid planners are for. Let's make them sweat. I mean, I joke that I want to break the grid. I want to make the grid planner sweat. I want my name, which is already four letters, to truly become a four letter word to grid planners. Like this is our job, folks. Let's move. Let's get this out there. And resistance is one tool to get us there. So don't freak out about resistance. It is a tool. It's not something we have to use all the time. But do not cast it out. That is a very dangerous thing to do for a whole bunch of different reasons. So I'll leave it at that. So I just wanted to really dig into the resistance for this little module. And then next time we're going to talk about the other two pieces, which are static pressure and. Shoot, don't you love it when you forget what was in your own presentation? Static pressure and surge protection, which is really critical for inverter HVAC equipment. So this is part of the Electify Everything course. So if somebody happened to send you here or you found this because I tweeted it or something like that, please sign up to take the rest of the course. It's free. There's a ton of information here. And I mean, that's we've done a bunch of these. We've done a bunch of thinking. We're building a system for doing this that HVAC contractors can use. So, I mean, you can also pay me by the hour. If you want to. But there's an awful lot of learning here that you can come up to speed for free for free. So that's you're pulling the cart in the right direction. Because as I've talked about before, it's a very narrow path to residential electrification. So things like resistance, he are going to be part of that path. So again, I'm Nate Adams. Please sign up for the Electify Everything course if you haven't already. And I will see you for the next one. Thank you very much. Have a great day. Bye bye.