Instant hot water tanks

Discussion in 'Plumbing Forum' started by Anthona, Dec 1, 2005.

  1. Dec 1, 2005 #1

    Anthona

    Anthona

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    Watched this show on tv about these hot water instant tanks. Its really complicated after reading the companys info sheet. There are so many variables and possible dangers of carbon monoxide. Has anyone used these and really recommend them? I have a 75 gal gas hot water heater now and its almost 18 years old and to my knowledge in very good condition. The problem is that i have to run the water to get hot to do all chores that need hot water. I'm constantly filling up bottles so as not to waste the cool water till it gets hot and use it on my plants. Is it cost worthy? Also, the differences of these tanks and what I read about hot water pumps that u add to your regular hot water tank. From what i understood, that along with those pumps, one has to add a gizmo to each outflow where u want the hot water ie kitchen sink, dishwasher, shower.Of the 2 which would be safer and cost effective? Thanks for any feedback. :)
     
  2. Dec 3, 2005 #2

    BillsCatz

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    Fist of all, your current hot water heater had lived well beyond it's normal lifetime -- be prepared to replace it soon. There are two types of so-called 'instant' hot water heaters. One is "point of use," which is installed right near where it's used -- isn't always practical. The other is "tanlkless," which actually heats the water as it's used and doesn't have a storage tank.

    Which would suit your needs depends on many factors -- type of fuel (gas or electric), how many fixtures (sinks, tubs, showers, washing machine) and how many of those get used at the same time. The main limitation of tankless HWH is gallons-per-minute -- the combined use of hot water by all fixtures can't exceed the GPM output of the heater. In other words, no shower while filling the washing machine, or no dishwasher and sink running while washing the clothes.

    The point-of-use, as it's name implies, is located near whatever it's supposed to supply. This doesn't always work for most people, but they will provide a constant flow of hot water to the desired fixture.

    Those are the basics, I hope this helps. Another option might be two separate 40 gallon HWH, each supplying parts of your system.
     
  3. Dec 4, 2005 #3

    Rocky

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    Here's a manufacturer of tankless water heaters. Their relatively reasonable but installation can get pricey due to the proprietary ducting system for exhaust and combustion air. They're gas fired. http://www.foreverhotwater.com/index.shtml
    Another solution to getting the hot water where it is needed without running the water for long periods of time is a recirculating system. This system involves a small pump that recirculates the water back to the water heater tank until the hot water has reached the point of use. It's most common to put the recirculating pump at the sink furthest away from the water heater tank.
    A 75 gallon tank would suggest you live in a rather large home, if not you may be heating way more water than you need. I agree with Bill, you're water heater is well beyond it's useful life. Good Luck.

    Rocky
    www.dpinspect.com
     
  4. Dec 4, 2005 #4

    Backroad boxer

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    I am putting a bathroom w/ a shower stall in my shop. This will be an infrequenly used shower, but I want to be able to have hot water when I need it. I have been toying with idea of having a instant HW system or a small water heater. Since I would like to stay all electric, the gas fired system is out. Also, the idea of keeping the small tank heated while im not using it seams to be a waste.
    Ideas?
    thanks
    Tim
     
  5. Dec 4, 2005 #5

    Rocky

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    I have seen electric tankless water systems mainly used for sinks. It's a tall order to get enough gallons per minute out of one for a shower.

    Rocky
     
  6. Dec 4, 2005 #6

    powrofone

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    There are whole house tankless hot water heaters available.
    They are a bit pricey and require large electric feeds to operate. The electric work required to install them usually negates any of thier advantages. I have done several estimates to install the necessary electric to operate the whole house tankless heaters and all but one would also require a electric service upgrade to install them. They are really more suited to new home installations where all the sub systems necessary can be calibrated and installed as required.
    Why not install a small tank style electric heater?
     
  7. Dec 4, 2005 #7

    Backroad boxer

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    I am looking to compair the difference in price, instalation and continuous amp draw between the inline heaters and a small tank. Just started getting information.
    Tim
     
  8. Dec 5, 2005 #8

    BillsCatz

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    Takagi makes tankless hotwater heaters in both gas and electirc, relaible with a good warranty.
     
  9. Dec 6, 2005 #9

    Rocky

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    I installed a tankless water heater today. It's a 240 volt 9500 watt water heater that will produce 2 gpm at a 27 degree temperature rise. This means you will get 2 gallons of water per minute that will be 27 degrees hotter than what is was before it got heated. This unit draws 40 amps.

    Rocky
    www.dpinspect
     
  10. Dec 14, 2005 #10

    2pyrs

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    In other words, no shower while filling the washing machine, or no dishwasher and sink running while washing the clothes.

    This is wrong with the newer units sold today that can run more then one area, but as said price high. If you are looking for a nice shower then you may want to consider a unit just for it and still use tank for the rest of the house, you may be able to down size your now tank. As to cost to run tank less unit you have to look at your over all consumption, keeping in mind the tank-less unit only runs when used unlike tank unit that has to come on to maintain it’s level of warmth even when not used. Installation is not that hard with some units but it can get complicated if you chose one of the one’s that is computer ran and have to do a whole new set up, exhaust, water line, gas, electric. As with any gas run unit there has to be safety taken in consideration at all times so unless you feel comfortable DIY I would recommend having a pro do the work. Cost could be as little as $1,000 to $2,000 depending on the unit and installation.
    You’re now unit is up there in years but I have seen them older when maintained. If waste of water is your concern you might want to consider one of the units sold for recirculation of the cold water back to your tank. They just had a show on TV with Ed the plumber showing the different types sold and how to install some of them.


    2pyrs
     
  11. Dec 16, 2005 #11

    rabadger

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    Sounds like your problem is with the distance from the tank to the fixture. Your may be able to have a return loop installed with a circulator for less money. The curculator will keep the hot water in the line so you don't waist all the cold trying to get the hot.
     
  12. Feb 24, 2006 #12

    PAULYBOY

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    Is this true of all tankless heaters? If so, then here in the midwest where the winter tap temparature of cold water coming into the house goes below 70, then the water wouldn't even be hot enough for a shower, right?
     
  13. Mar 31, 2006 #13

    onyx

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    I also installed a tankless water heated in place of my 50-gallon unit - short story - I de-installed it the next day and put back my gas- 50 gallon unit.
    Long story -
    The bosch aqua-star 125 tankless was 'supposed' to be enough for 1 shower or bath at a time but only gave luke-warm water at a very low rate. For example, my hot water tank can flow 6GMP to the bathtub until the tank runs cold. The tankless can flow 2-3 GPM of much cooler water forever. The endless flow does no good if it takes 45 minutes to fill the tub.
    Good for washing hands or a quick rinse off in a fishing cabin, but not nearly enough flow for a regular home even one shower at a time. I also understand
    in colder climates where the incoming water temp is very cold the temp rise is more of a problem. I still am intrigued with the Idea of tankless, because my wife will let the hot flow 'till there is none left, but to get a system large enough for adequate household use would cost many thousands of dollars as opposed to a few hundred for a standard water heater.
     
  14. Jan 27, 2008 #14

    apsinkus

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    Onyx, sounds like you got wrong size tankless heater.

    Benefits from tankless come with proper sizing. Any system, no matter how efficient, will be useless if not properly sized.

    Half of Europe has been running tankless for several decades now. You think they would continue using that type of heading if it was not up to snuff.
     
  15. Jan 27, 2008 #15

    apsinkus

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    Take a look at say one of the Rinnai exterior-mounted tankless. For $1400 MSRP you are getting up to 9.4GPM.
     
  16. Mar 16, 2008 #16

    apsinkus

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    Sounds too high, unless they are gutting all your gas infrastructure. Also, Canada is notorious for awesome incentives (e.g. geothermal, PV, and other systems get much larger rebates than in US), check what you will get back.
    Rinnai and Bosch are probably two most known companies for tankless. Europe and Japan is full of Rinnai units that have been working for long long time.
    Shop around a bit more. I no longer trust Sears for anything. They used to be OK, but now you get Kmart service for much higher prices.
    Also, maybe you should just find a good gas man or plumber who has experience installing these and than just buy the Rinnai unit online. As long as it is installed by a licensed pro, you should be OK with warranties. For you climate though I would stay away from externally mounted ones.
     
  17. Mar 29, 2008 #17

    thebobo

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    I just finished installing a Rinnai C53i as a DIY project. I chose Rinnai because I only have 2x8 joists in my small house, and their zero clearance vent allowed the vent system to run through my limited joist space.

    When I was shopping around, the best price I could find was on eBay, where the unit was $600 plus $50 for shipping. It is however a commercial unit, which lacks a bypass between the hot and cold side (My understanding is this is required in some areas as an anti-scald feature). Also, the temperature range of the output is adjustable between 120-180 degrees F, whereas the residential unit has a "colder" range, with a lower limit of 100.

    I bought a valve/pressure relief kit and termination kit locally which came to around $200. Plumbing parts for the gas and water lines came to about another $100. I'm also participating in the Canadian ecoEnergy program, so the $300 incentive will make the project quite cost effective. With the incentive, it's cheaper than a power vent tank system.

    I'm happy with the system save one issue. It takes significantly longer for the hot water to get up to target temperature than with my old tank, in the form of an 8 second or so ramp-up time while the heat exchanger warms up (this is timing it right out of the heater). On the plus side, the draft inducer in the unit is no louder than a modern fridge, and only runs for about 5 seconds after flow ceases. The digital thermostat is neat. Temperature of the water is stable even with variable flow. I can run a hot shower and faucet no problem with our rather frigid water here in Edmonton. I did not however try pushing the system yet to its limit.

    Since I previously had an old, electric tank, I'm also looking forward to the energy cost savings. I would certainly do it again, but would consider a holding tank and recirculation system next time to speed delivery of the hot water.
     
  18. Mar 29, 2008 #18

    glennjanie

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    If you add a holding tank or recirculation system you defeat the whole purpose of a tankless water heater. They are to replace the tank full of water that has to be kept hot even while you are gone on vacation (as an extreme example) and your tankless would have to kick on as many times if it is trying to keep the hot water to the faucet at all times.
    It is better to have multiple tankless heaters than to try to circulate and hold hot water; keeping the tankless very near the point of need.
    Glenn
     
  19. Mar 30, 2008 #19

    thebobo

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    Glenn, there's a couple of ways of implementing a recirculation system with a tankless heater. In the one I find appealing, the holding tank is small (2-5 gallon), and is heated electrically. The water is circulated out of and back into this tank, so the tankless heater doesn't turn on just to heat the recirculated water. The tankless heater sits between the holding tank and the water supply, so it turns on when a faucet is opened.

    The manual for my unit has schematics on both the system you're talking about and the one I just described. Check out the drawings starting on page 31 here: http://www.foreverhotwater.com/documents/1110101.pdf.

    Ideally, yes, multiple tankless heaters at or close to each point of use would be most efficient, but the capital cost for that would be high.

    It's certainly a compromise. You get standby loss with the tank and the hot water loop, plus the cost of running the pump. On the other hand you get hot water at the tap much faster, reducing water waste, and the holding tank buffers the tankless "cold water sandwich" effect.
     
  20. Mar 30, 2008 #20

    Square Eye

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    Good Golly,

    I have a standard gas water heater located centrally in my home. It recovers so fast I wouldn't even consider a tankless. The water loop is a good thing, I don't have it but if you have a large family where the water is being used often, the heat loss would be minimal in relation to the normal usage.

    I still believe insulating the hot water pipes all the way to the outlet is worth doing. It seems to me that tankless water heaters would be most efficient in a home where the bathrooms and the kitchen are close together. BUT the same could be said for a standard water heater. Waiting for the hot water to get hot at the outlet is such a waste of water... Then again, heating water and keeping it warm while no one is using it is a waste of energy. Which is more expensive? Which weighs more on your mind?
    A tankless water heater in a home with a circulating tank is kind of like buying a super efficient truck, like the Chevy hybrid, to pull your 275 horsepower bass boat to the lake.
    Why spend the extra money for such efficiency just to cancel it out in your system?
     

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