How to Determine Required Size of Electric Heaters

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In order to determine the required size of an electric water heater, it helps to first take a reading of first hour usage. Discover how old water heater valves will use more water than newer ones with help from a master plumber and heating specialist in this free video on electric heaters.

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Video Transcript

There's questions of people have when it comes to water heaters and of themselves. One of the important aspects, one of the first aspects that you go to when you're thinking about water heating in a house, new house or even if you're replacing one in the house is sometimes sizing the water heater. How do I determine what size water heater I need? One of the first steps you do, you go to being a plumber is I go to first hour usage on something. Typically residential like this, we just go to first hour ratings. To pick that up there's a lot of different tools you can do. First one obviously is you can get your local plumber involve, your local service technician and they can help you out if you have questions on it; but there's a lot of helpful sites online that you can go to. Just type in your Google search bar, sizing your water heater and there's different, different calculators that you can use on that level. Keep in mind that older houses have older valves that typically use a lot more water than newer ones and most to your sizers will indicate; hey, you need to think a little bit more water because if it's pre-1992 the house shower, typical shower valve will probably use up to 30 gallons or if it's a Roman tub, it will use up to 30 gallons per minute. So those calculations really can make a difference in what your water heater's first hour rating is. One of the things that I wanted to point out to you is the first hour rating is always on every single water heater. You'll always see a yellow tag that's called an energy guide. The energy guide has all kinds of information on whether it's electric or gas and how many therms it will use; how many kilowatts it will use and kind of the average on what's it's going to cost you every year. It also has a little number on it where it says capacity first hour rating. That's where you design your water heater to. So then we come back to the actual going to the design of the system itself. Hypothetically, we're going to put, kind of a design together to give you something to go by. You got a, a shower that you got; one shower which is a typical past 1992 at 18 gallons per minute. So you put that in; say you take two showers in the morning because there's two of you and you've got two kids. One of the kids uses another bathroom and let's say, you've got a third bathroom for another kid. The next one is going to be 23 gallons, straight across. You've got 36 23 and then you've got bath three at 11 1/2 gallons. You kind of cut it into thirds on those levels past what you've got. Your, let's say you do the clothes wash in the morning; run a load of clothes; that's a 40 gallon usage and you always count that towards the hot side. People might not use hot but they may, it's one of those things that you just count it as part of the system as you do it. The other thing, let's say; we're, we take, we do a shave. Everything we do in addition to; I'm a guy, I shave every morning, so you've, you shave your face as well, that adds another 2 gallons to it. Basically, it takes a process of; I don't know, two to five minutes and you run about 2, 2 1/2 gallons out in that process time and we wash our hands because we fed our dog that morning. So we come up with a total gallonage of a 124.5 for our first hour of recovery. That's what we need to kind of point our design to because if that's a typical morning for us, we need to make sure that our water heater can handle that. This water heater in, in that capacity wouldn't be the right size because it's got a first hour rating of 87 gallons. What's that, what that means is it will do 87 gallons of hot water recovery in that first hour. Even though the tank itself is not an 87 gallon tank, it's only and I believe this is an 80 here. This is, yes, an 80 gallon tank; it will do 87 gallons in that hour because we have stocked heat in here that's residual from it being completely good and warm, up to our temperature. So it does the first hour rating of 87 gallons which would be small for our system for what we're designing. We would probably on electric water heater; we want to step to a 120 gallon and it would probably take up where we need to be 'cause there's size ranges that you have to go to. Your, your only specific like to 40 gallon, a 50 gallon minute steps up; I think you can do a 66 gallon, then you do 80, then 120 and then they go commercial from there. But you size it to the first hour rating and that's how you come in to it. Another thing people wonder about or worry about is sometimes, let's refer to this bathroom, you don't get hot water real soon. You let it run and run and run and you're worried about water usage on top of it. You got five minutes before you get any hot watered and you want to get in the shower or get things done. There's a couple of things that you can do on that level. The main one that I would recommend is probably doing a recircline. What that is is tying another; this is something that you'll most likely need a certified technician for as well; but this, this will give you an idea what you're going to have to do. You'll run another water line off of your hot water side over to the furthest point in your sink and in that loop, right here, you'll put a little pump that's got a little timer on it 'cause if you get up at 5:00 and like to take your shower at 5:00, make it come on at 4:15 and get that loop getting hot. That way when you come to your sink and turn it on, you got instant hot water. It's kind of like having a separate little tank up underneath your sink right there at that point; that's another thing that we'll go to and kind of talk about 'cause kitchens have that a lot. Now in that process, it's, it's a, you cut into this line; you shut the water system on; you cut into this line and you run a new loop all the way over. A lot of times it involves removing dry wall and things like that. There are newer systems out there that you can ask your certified technician what, what, you know, what options you have that are, are not so home invasive. But they change things as far you know, your cold water and inside of your bathroom and your comfort zones. Now since we're on the subject of getting instant hot water; they, they do make little tanks that are one gallon called instant hot tanks that you can put underneath your kitchen sink. It involves putting another tap on your faucet; they don't necessarily tie in to your hot water system, but they do produce a 190 degrees water right there.


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