upgrading water heater system for more capacity

Discussion in 'Water Heaters and Softeners' started by bikeboy, Apr 17, 2019.

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  1. Apr 17, 2019 #1

    bikeboy

    bikeboy

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    In the home I'm presently living there's 2- 50 gallon electric water heaters opposite ends of house; (aprox. 50ft apart). One takes care of kitchen sink and 2 full baths with a long pipe run to termination. The 2nd heater has a slightly less distant pipe run which takes care of a laundry (tub and washer) and Master bath which contain a Shower, double sink, and 84 gallon whirlpool tub. I was hoping the 50 gallon water heater taking care of the Master bath would allow the tub to fill @ aprox 120 deg. it will 2/3 fill w/ hot water. The rest needed we fill it with hot water from stove! Not convenient. Also; the other end w/kitchen and 2 baths, achieving hot water is slow and a 60 ft pipe run to termination. I considered to replace the WH for the master bath w/ the whirlpool tub w/a tankless unit for the master bath. Then I considered to just use a higher gpm Navien tankless w/ built-in circulator and just replace both water heaters. But then I thought, why not just use both existing water heaters there with a circulator; allow the 1st HTR to fill w/ cold , take hot to 2nd WH cold side, then 2nd WH hot side back too 1st WH drain valve to keep circulation using 3/4 for circuit main ? I figured I could get a 100 gallons at hand which is circulating thru both units, and use for whirlpool tub when needed. I figure the 2nd WH would be only maintaining temps as a holding tank, and both would be still be cost effective when not in unusual use. Please tell me the drawbacks of this system, or how to be connected in different way to work efficiently, tankless or other way. There's only 2 of us , so not big daily hot water demand. A diagram would be helpful.

    Thank you; and please reply.
    Howard.
     
    Last edited: Apr 18, 2019
  2. May 22, 2019 #2

    JHEARD

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    take a look at the attached file. four different ways to pipe a tankless heater(s). w/diagrams and explanation
     

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  3. May 22, 2019 #3

    JHEARD

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    Tankless units on a recirc. pump are extremely efficient compared to tank heaters. you can program the pump (depending on which one you get) to only circulate or kick on durring high usage times which can be easily programed. i see a lot of new rheem heaters going in the RTGH-RH10DVL series has a built in pump that can be programed to any time you like and a digital display on the front of the heater. you can program different times for different days etc.. there is also a setting opposite to the program setting called auto. this will collect data on usage over a 30 hour period and set the pump to run durring high use times. rheem has on demand swithch options that are hardwired and would be great for that big tub. you could hit the button like a light switch easily installed in your bathroom. you should look into the new rheem products available. if youre interested i have a lotttt more info i can give you.
     
  4. May 27, 2019 #4

    bikeboy

    bikeboy

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    Thanks for reply; I figured by plumbing the 2 electric water heaters I already have , there would be minimum material needed and a comparable operating cost and that would be a wiser choice. If going w/tankless, I'd be heating water w/ propane, not sure if one is better than the other ; I could be wrong w/ that decision, but still researching. The simpler solution would be better, cause the high demand of hot water is not used on a daily basis. That's why I was trying to find a way to tap the opposite water heater, and bring it up to WH#1 when I use the tub. either way is fine.

    Thanks for reply;

    Howie.....
     
  5. Jun 11, 2019 #5

    SGkent

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    If those are two element water heaters have an electrician or plumber make sure both elements in each tank are working.
     
  6. Jun 12, 2019 #6

    frodo

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    Just call me Macgyver Professional Supporting Member

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    Your idea is a sound one that 2 w/h can be tied together, BUT, not if they are across the house from each other
    below is a quick drawing to show the scope of work involved in tying the 2 wh together
    as noted,,the piping MUST be of equal lengths in order for the system to work properly.
    if not, water will just seek the path of least resistance and ignore the other WH, making it nothing but a storage tank
    there are different types of temp sensors. I do not like the strap on's I perfer the sensors that are inserted into the stream of the water//mo accurate
    _wye_branch_threaded.png 6''.png 2.jpg
     
  7. Jun 13, 2019 #7

    bikeboy

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    I think I understand, Since water heater #1 is closer to the tub, the draw of hot water will be greater than wh#2 , and will not allow that flow thru other circuit to combine them. The other option would be to connect the WH's in series, hot side WH#2, plumb circuits together w/ circ/ck,and timer w/temp. sensor; keep main loop insulated 3/4" back to WH#2 cold side w/ additional ck valve.

    That was my original plan, but thought I could achieve the tub fill easier. At least this way I'll always have ready hot water.

    Thanks for reply; HR...
     
  8. Jun 13, 2019 #8

    frodo

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    Just call me Macgyver Professional Supporting Member

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    Series installation uses heaters that are not identical in both BTU input and storage capacity.
    An example might be when an expansion or addition is made in an application that will require additional hot water.
    For example, you add a new bathroom to your home.
    The existing system will not handle the demand and a new water heater must be installed. The new heater is not identical to the existing heater. In this example, series installation may be appropriate.
    When installing water heaters in series, the heater with the largest input (BTU or KW) should be the first heater in the series, at the cold-water inlet side of the system.
    Series installation draws hot water from one tank at a time. As hot water is drawn, it is taken from the last heater in the series. For every gallon of hot water drawn, preheated water is introduced into the last heater in the series and cold water is introduced into the first heater in the series.
    In a series configuration, the first heater, piped to the cold-water inlet, will do the majority of the work. The second (or remaining) heater will not work as hard because it receives preheated water, not cold water. The last heater in the series will do very little work. In the example below the installation shows a series system with a gas water heater and an electric water heater. The larger gas heater is supplying the hot water into the cold inlet side of the electric heater. When there is a demand for hot water it is drawn from the hot water side of the electric heater.

    series.png
     
    Last edited: Jun 13, 2019
  9. Jun 13, 2019 #9

    Brayan Jack

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    Its better to replace your old water heater with the tankless water heaters. This will not only save your energy bills, but their life is long due to the on-demand water heating feature. You can get hot water whenever needed and when it's not in use, there is no power consumption which ultimately ends up as lower bills. Read here how they are better and what benefits they offer to the users!
     
  10. Jun 13, 2019 #10

    Brayan Jack

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    Excellent diagram and explained it well. Keep it coming. This was highly informative and easy to understand.
     
  11. Jun 13, 2019 #11

    bikeboy

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    I considered Tankless, but since I've got 2 - 2 year old 50 gal. WH's, why not use them, also; I never considered a loss of water pressure using that method . I know WH#2 will mostly be a holding tank, till I use the tub; and WH#1 will be doing most of the work and may wear out faster. So, is there an advantage to connecting them in parallel? I have to decide cost and complexity of tankless, vs. 2 tanks I already have.

    Thanks for reply, HR...
     
  12. Jun 13, 2019 #12

    frodo

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    use timers to lead/ lag the 2 water heaters

    6am---6pm wh 1 on wh 2 off
    6pm--6am wh 2 on wh 1 off
    let the circ line that feeds wh 1 act as a passive source of tempering heat
     
  13. Jun 14, 2019 #13

    Diehard

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    While deciding on the use of a tankless, make sure you consider all pros and cons.
    More complex.
    Higher cost.
    Probably required to up size the energy source.
    Added delay for hot water to reach fixture.
    Maintenance required.
    Google reviews.
     
  14. Jun 15, 2019 #14

    bikeboy

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    What about a 3.5 kw 240V point of use water heater just for the tub , fed from the hot side of tank WH. senses and comes on w/temperature drop as tank water heater starts running out of hot water, and the small tankless makes up the difference. would that continue to provide enough supplemental hot water to fill the 85 gallon along w/ an existing 50 gallon tank heater WH ?

    THANKS FOR REPLY; HR...
     
  15. Jun 15, 2019 #15

    frodo

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    http://www.chriscollinsplumbing.com/questionsandfaqs/tanklessquestions/tanklessquestions.html

    TANKLESS

    The big question on everybody's mind has always been, do these water heaters actually work?

    Yes, they work very well, when they're installed in the right application. Now it's the second part of that last sentence that's caused a bit of confusion and also not a small amount of buyer regret.

    Tankless water heaters are essentially what's known in the plumbing supply business as a "point of use" water heater, of course no one says that publicly, what that means is that they're meant to be located very close to the plumbing fixture, whether it's a sink or shower, and to serve only that fixture or perhaps other ones located very closely.

    And that's how you find them in Europe or Japan, they're usually right located in the bathrooms themselves or often on the exterior wall nearby.

    But they're not marketed as such in the US. The "whole house tankless water heater" concept is very much an American invention, and although it works perfectly when installed in some homes, it performs very poorly in others, and almost all of this is a result of locating the unit in the basement, where water heaters usually reside.

    The reason for this is that any tankless water heater, no what matter the size, is incapable of providing hot water at the same speed as a traditional water heater. It's fairly simple to understand, with a storage or "tank" type water heater, the water is already warmed, and when you open a tap, it's headed your way, and arrives fairly shortly, at the same speed as the cold water side.

    However, a tankless water heater has to heat the water as it's coming in, and here in Upstate NY, that means raising the temperature of incoming water that's about 40º up to 120º, that's the temperature your own water heater is probably set at, and what you're used to.

    Tankless heaters simply can't replicate that speed, and without going into flow rates, heat exchangers and countless other things that no reader really cares about, the end result is that if you have a larger two story home, and you decide to install a tankless in the basement, you're going to be waiting a full minute or more for hot water to get to a second story bathroom.

    Now for a shower, or filling a tub, that's not really a big deal. But can you imagine wanting to wash your hands and waiting a minute each time you do it? Lots of people who have converted to tankless are doing just that.

    And a larger problem presents itself when we look at the hot water supply to appliances, most modern dishwashers and clothes washers are designed to use a lot less water than those sold in the past. And what we end up with when we have an improperly installed tankless water heater is usually a washing machine or dishwasher that's already filled up and running before the hot water even gets to it. All the hot water heated by the tankless is still sitting in a pipe, you paid for it, but you won't be using it.

    This isn't a problem that just affects tankless heaters, it also happens whenever you locate any water heater too far away from the point of use. To solve that problem, plumbers usually utilize a concept known as recirculation, which involves installing a small circulator pump and either a recirculation loop or special valves that use existing cold water piping to recirculate the hot water so that there's hot water immediately whenever you open a faucet.

    Let's take a look at how we do that with a conventional water heater…

    see... wwhh1.png


    See how easy it is? Since the hot water piping is always filled with hot water you get it immediately whenever you open a tap. You can even chose between pumps that maintain your loop at a consistent temperature or ones with a timer that you can set for when you get up, or when you get home. These are really only a low head circulator pump, much like you use in a boiler, just modified a little bit.

    Now let's look at our Rinnai tankless heater, that's the one we installed in the opening picture.

    wwhh2.png
    Water going in, water going out. Nothing simpler, this is a tankless installation that provides a real benefit, the unit was located around 8' from the kitchen and less than 20' from the master bathroom, and that's the real reason that it was installed, as there was a whirlpool tub that couldn't be filled with the existing 50 gallon water heater, as well as another 40 gallon heater feeding a guest bathroom.

    That's 90 gallons of water being heated 24/7/365, and with only the owner living in the home. This is a perfect home for a tankless solution, and we're going to save this guy around 400 dollars a year in natural gas costs by doing this.

    But what if he wanted a tankless heater, and owned a larger home, and needed a recirculation option to make it worth doing? Let's look at how Rinnai and other manufacturers make us install this, it's not a choice, they cut the warranty coverage in half if you don't install it the way they want you to. There are legitimate mechanical reasons for this, as you really don't want the unit firing every time the circulator starts up. But lets virtually install this and see what it's gonna look like…




    wwhh3.png
    Good Lord, take a look at this. Now our simple tankless conversion has a 40 gallon electric water tank plumbed in series acting as a buffer tank, the energy consumption from that unit alone totally wipes out any savings from our new tankless heater. That and we now have two thermostats, two electrical elements and a circulator pump to maintain, and we still have to wire electrical power to both the new electric tank and the circulator pump.

    As a plumber, I just really can't warm up to this, no pun intended. In a scenario like this we would have taken out a traditional water heater that although isn't the most glamorous thing in the world, had probably provided hot water through it's entire service life at a reasonable purchase price and annual cost and never needed even one service call. This solution, if anyone really needed one, is just far too expensive and complicated.

    Some tankless manufacturers have listened to complaints about this problem, and responded by installing both buffer tanks as well as recirculation pumps in their water heaters. The Navien tankless heaters are a great example of this. It's not really a bad idea, but since these tanks are only about the size of a large soda bottle it really doesn't help us much with feeding those dishwashers and washing machines.

    Let's finish this off with a fast summary, I know this has been a long read.

    Tankless water heaters are a great choice when…

    • Located in close proximity to bathrooms, laundry rooms or kitchens.
    • Used to replace multiple traditional water heaters.
    • Used to supply hot water to larger jacuzzi or whirlpool tubs.
    • When installed in smaller units like condos or vacation properties, where the unit can be located close to the point of use.

    Tankless heaters are a poor choice when…

    When replacing a traditional water heater that's located in the basement, unless it's a single story home.


    Hope this helps,
     
    Rickyman likes this.
  16. Jun 15, 2019 #16

    Diehard

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    Generally speaking, recovery rates of electric water heaters is based on Temperature Rise (desired temperature minus the incoming temperature) and the heating element size. In other words the lower the temperature rise and/or the higher the Kilowatt rating, the higher the flow rate.

    So I'd say you're probably better off with the two 50 gallon water heaters in series, where the KW rating of the 2nd unit is likely around 5 KW and it already has close to 50 gallons of heated water stored.

    I think you'll find that slowing down the flow rate slightly will give you what you're looking for.
    If you call a water heater manufacturers engineering dept and ask them if you were to purchase (2) 50 gal electric water heaters and connected them in series, if you could fill your tub with 85 gallons with (your desired temp) of water. They know pretty much how much of that 50 gal of stored water is actually usable, at a specific temperature, and at a particular flow rate.
     
  17. Jun 15, 2019 #17

    frodo

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    the 2 heaters in series
     
  18. Jun 15, 2019 #18

    Diehard

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    Why is that? Is it an efficiency thing? What is the reason?
    Of course the OP has (2) 50 gal units of unknown BTU values. So you would be saying that he can't do it unless he gets a different 2nd water heater.:eek:

    EDIT: I think I have the answer to my question. I believe I found the source of your statements/comments. Yes it does say, "Series installation uses heaters that are not identical in both BTU input and storage capacity."
    It doesn't say that they MUST NOT be identical.
    I'm pretty sure the reason it was stated that way was solely because it is more efficient to hook them up in parallel but if they are not identical in both BTU input and storage capacity, THEY CAN NOT be hooked up in parallel. Get it?
    You can probably verify that by calling Rheem/Ruud whom I believe was the source of those statements.
    TECHNICAL SERVICE DEPARTMENT
    Technical Service Bulletin
    1-800-432-8373
     
    Last edited: Jun 15, 2019
  19. Jun 16, 2019 #19

    frodo

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    Just call me Macgyver Professional Supporting Member

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    It says parallel is to be used when the 2 heaters are the same. Series is to be used when the 2 heaters are not the same. The language is clear to me.
    one system [parallel] draws from both heaters
    one system [series] draws from one heater, and uses the largest heater as a tempering tank.
    You can hook up the water heaters any way you wish, and they will work, These are just recommendations for getting the best efficiency out of the system



    INSTALLATION - SERIES AND PARALLEL

    The installation drawings in this bulletin are typical. Check local code requirements for vacuum breaker devices and cold-water inlet check valves. If you install a check valve in any of these systems, you must install a thermal expansion tank. There are two methods of manifold installation: series and parallel. Manifold means to pipe together with several apertures that make multiple connections. That is what manifolding is all about. Think about the intake and exhaust manifolds on a car. The carburetor sprays gasoline into the intake manifold (think of this as the cold water supply line). After the fuel is ignited by the spark plugs, the hot combustion gases are pushed out of the engine through the exhaust manifold (think of this as the hot water supply line). The intake and exhaust manifold on a car is an example of a parallel design.

    Parallel Installation Parallel is what i recommended in the first answer I gave

    Parallel installation uses heaters that are identical in both BTU input and storage capacity. Normally, parallel installation is used when there is a demand for large quantities of hot water over a short period of time, such as filling a large garden tub or back to back showers. Equipment being equal, two or more heaters connected in parallel will deliver more hot water than the same heaters connected in series. In a parallel configuration, the hot water ........................

    Series Installation

    Series installation uses heaters that are not identical in both BTU input and storage capacity. An example might be when an expansion or addition is made in an application that will require additional hot water. For example, you add a new bathroom to your home .The existing system will not handle the demand and a new water heater must be installed. The new heater is not identical to the existing heater. In this example, series installation may be appropriate. When installing water heaters in series, the heater with the largest input (BTU or KW) should be the first heater in the series, at the cold-water inlet side of the system. Series installation draws hot water from one tank at a time. As hot water is drawn, it is taken from the last heater in the series. For every gallon of hot water drawn.............
     
    Last edited: Jun 16, 2019
  20. Jun 16, 2019 #20

    Diehard

    Diehard

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    That's correct, Series is to be used when the 2 heaters are not the same. BECAUSE they cannot be in parallel.
    But 2 WH's that ARE THE SAME
    CAN BE EITHER WAY. Think about . Why would they have to be different.

    I won't even try to get it through to you any longer. If you don't get it now, you better call the the people that wrote it.

    You keep using a lot of words but are not saying anything different. I can't even make myself read that stuff you're writing. If you don't understand the basic concept, no amount of incorrect examples is going to change anything. You seem to keep repeating stuff from the article you read but obviously don't get the basic concept.

    Do us both a favor and please call the manufacturer. Peace!
     

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