anyone have a tankless hot water heater? "pressure" vs. "temperature"...

  • rnch

    Posts: 11524

    Feb 18, 2011 7:02 AM GMT
    i just installed one today.

    in order to get the hot water temperature i had with my old 40 gallon tank hot water heater, i have to cut back on the volume of water going thru this new heater wayyyyyyyy back. i have the flame height adjustment knob as high as it will go.

    it seems like the higher water temperature you want the lower water pressure/volume you have to have??

    wadduathunk??
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    Feb 18, 2011 7:07 AM GMT
    The smaller ones are set for one fixture running 1.5 gal per minutes.
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    Feb 18, 2011 7:10 AM GMT
    yup, you have to realize this is supply on demand, the heater has no stored hot water so in order to have the amount needed, you have to have a high btu unit. If you only have a small unit, you may have to install them in series or get the largest unit they make.....good luck...btw..these are being installed in most new homes on the upper end and are a good idea as long as they match the demand..................Keithicon_wink.gif
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    Feb 18, 2011 1:42 PM GMT
    I had one and liked it just for the space saving (was able to turn a half bath to a full one by adding a shower where the tank was, increases home value WAY more than the heater cost). The flow issue is something I had to adjust to but good luck trying to expalin it house guests. icon_biggrin.gif
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    Feb 18, 2011 1:57 PM GMT
    If the unit is properly sized, at least in theory, a tankless can provide an adequate supply. I'm told they're fairly accepted and routine in Europe.
    But I just opted for a gas storage heater instead because of some compromises I didn't want to make for tankless.
    First, in winter when the incoming water temp is at its lowest the increased delta challenges the tankless heater and can reduce volume signficantly.
    Second, demand has to reach a certain threshold before the unit will fire......meaning if you just want a little luke-warm water to wash your hands you could be out of luck.
    I've read that tank insulation performs so well these days that the difference in efficiency isn't enough to justify the extra cost of tankless anyway (about 3-4x the cost of a tank heater).
    They can save the day if you have space issues though.
  • LJay

    Posts: 11612

    Feb 18, 2011 2:08 PM GMT
    I am considering one because of space. I am also trying to arrange a small well-insulated reserve tank to act as a buffer.

    We had a tankless heater 50 years ago when living in Florida and it did nicely for a family of five.
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    Feb 18, 2011 2:08 PM GMT


    We use a lot of these combi boilers here, but really only in new installations, in central Europe it's much more common to see gas fired instanaious water heaters which tend not be so powerful.

    Alot of people here have pumped electric instant showers that provide hot water on demand, but again even at 9.5kW if you want a really hot shower, the volume seriously diminishes.

    The best set up is a factory insulated, properly sized storage tank fed from your gas boiler, with a really powerful pump to take your skin off.
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    Feb 18, 2011 2:19 PM GMT
    Friends of mne who installed one recently also complain about the lower volume of water.
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    Feb 18, 2011 2:30 PM GMT
    anyone have a tankless hot water heater? "pressure" vs. "temperature"...

    Yes, we have an electric one by Titan. I'm not sure if you got the right capacity for your needs, and if the ability of a gas-fired demand heater is as responsive as electric, as it cycles on & off.

    Here's our experience: we have a fairly high capacity one, perhaps more than our ordinary daily requirements. It claims to support 2 showers, plus a dishwasher, clothes washer, and in our case, 3 sinks. Not that we'd have everything going at once, but the 2 showers, or a shower simultaneously with an appliance or sink certainly happens. And that's one way they rate these things, so homeowners can get a rough idea of what heating capacity they need.

    So we always have lots of hot water for as long as we want, even at fairly high flow rates, like filling a tub. In fact, it's better than a typical 40-gallon water heater tank, which as you know can run out hot water after a while.

    But what can happen is an opposite problem -- too slow a flow rate making the unit turn off, and getting cold water. Tankless units must be able to do that, sensing the flow rate through them and turning off below a certain amount. Otherwise if the water going through them slows down too much there's a risk of scalding, and even explosive steam pressure build-up.

    It happens to me (but not my partner) because I like to use a minimum amount of water flow in the shower, and also take a fairly cool shower, so the hot water blend I'm using at the tap is very low. Everything will be fine when suddenly -- ICE WATER! I've learned to keep a certain water rate setting, and then I'm OK. The other thing I've noticed for showers is the temperature tends to "hunt" around a little bit at first before it stabilizes, and then it's fine.

    Other than we like it, and it does save us money.
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    Feb 18, 2011 4:53 PM GMT
    The only real problem I ever have with mine isn't the heater... it's the damned stupid "flow-control" shower fixtures that code requires. These moronic things were developed because some stupid woman somewhere scalded herself but was too dumb to turn down her water temperature. The idea with tankless heaters is that you set them at the temperature you want to shower, and use 100% hot water.

    The flow-control fixtures don't let you use 100% hot - they always dump some amount of cold into the mix. So you have to turn your heater up to create a scalding hazard in all of the other fixtures in order to get lukewarm water in your "scald-proof" fixture. I suspect they also get gummed up with hard water deposits and get screwier with age.

    I originally put in normal two-handled shower fixtures, but the building inspector made me rip them out and put in the flow-controls. Stupidly, I didn't hang on to the old ones. They don't even sell regular fixtures in my state any more. I need to smuggle in some shower fixtures from another country and re-build the showers, some long weekend.

    When it's working right though, the endless hot water from a tankless set-up is great for those who enjoy shower sex...
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    Feb 18, 2011 4:59 PM GMT
    We installed one last summer. It works great as long as there is not too much demand on it. Example; don't fill the washer, run the dishwasher and use the shower at the same time. Unless you like a cool shower. We have noticed a good reduction in our monthly gas usage.
  • rnch

    Posts: 11524

    Feb 18, 2011 5:05 PM GMT
    mindgarden said.... The idea with tankless heaters is that you set them at the temperature you want to shower, and use 100% hot water...When it's working right though, the endless hot water from a tankless set-up is great for those who enjoy shower sex...


    yes! after several adjustments of the flame height and water volume knobs i found the "sweet spot" that gives me a comfortably hot shower and acceptable shower head pressure with just the hot water knob all the way open. icon_biggrin.gif

    hoping to find out how it works for prolonged :shower sex" this weekend. icon_wink.gif
  • LuckyGuyKC

    Posts: 2080

    Feb 18, 2011 5:19 PM GMT
    if you already have a small one you best best is add a second small one in series. If you do that the second one should be able to deliver all the hot water you need. I know it's a lot of money but possibly better idea that trying to switch out your current unit for a bigger one that will have the same problem but just on a larger volume scale.

    Also - this unit should be located within 15 feet of the fixture according to most manufacturers. Generally the closer the better.

    We install a lot of them in modest new homes. People have been satisfied.
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    Feb 18, 2011 5:34 PM GMT
    mindgarden saidThe idea with tankless heaters is that you set them at the temperature you want to shower, and use 100% hot water.

    I've never heard that. Our tankless heater is set to 120 F, per the instructions on our Whirlpool dishwasher. (I set it at the kitchen sink with a candy thermometer) You probably don't want to shower with that setting.

    I believe we have a temperature control shower fawcet as well, though I didn't buy it and my partner can't recall. I believe that's part of the reason we get a little bit of "hunt" in water temperature at times with the tankless heater, as I mentioned above. In fact, it may not be the heater at all, but rather entirely the fault of the flow control device getting old, so perhaps that needs replacing.
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    Feb 18, 2011 6:15 PM GMT
    rnch saidhoping to find out how it works for prolonged :shower sex" this weekend. icon_wink.gif

    This is how I know ours produces hot shower water virtually indefinitely. icon_redface.gif
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    Feb 18, 2011 6:23 PM GMT
    kscott6671 saidWe installed one last summer. It works great as long as there is not too much demand on it. Example; don't fill the washer, run the dishwasher and use the shower at the same time. Unless you like a cool shower. We have noticed a good reduction in our monthly gas usage.


    He says, loafing in the hot tub. icon_wink.gif
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    Feb 18, 2011 6:40 PM GMT
    My landlord installed one when the original hot water tank rusted out. The issue I have is the heater is in the basement and the shower is on the third floor. I have to run the water for a few minutes before the heated water finally comes so I feel like I'm wasting a LOT of water every day...

    I have no idea if the lower electricity is better than the water wasted in the big environmental scheme of things...

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    Feb 18, 2011 6:49 PM GMT
    toddstud saidMy landlord installed one when the original hot water tank rusted out. The issue I have is the heater is in the basement and the shower is on the third floor. I have to run the water for a few minutes before the heated water finally comes so I feel like I'm wasting a LOT of water every day...

    I have no idea if the lower electricity is better than the water wasted in the big environmental scheme of things...

    Wasn't the distance just as great as with the old tank, and should have taken as long to deliver hot water? Another advantage to tankless heaters is that they can often be placed closer to the fixture, than a larger water heater tank can. They still need some space, though, including surrounding air space, such as a vented utility closet where junk won't get piled up against them.

    For this reason some houses are now installing several tankless heaters, for a "zone" approach like some larger homes do with multiple A/C units. That might also appeal to landlords, who have multiple tenants in the same building. An approach I'm beginning to see here in Florida is one zone that includes all the bedroom baths, and a second zone for the kitchen and laundry, plus maybe a guest half-bathroom.
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    Feb 18, 2011 8:22 PM GMT


    On larger homes here, the new trend would is moving to under sink electric heaters in remote bathrooms with instant electric showers,

    The other option is to install centralised hot water with a secondary return and pump that keeps the water hot at the point of use, these types of set-ups eat energy and therefore the electric instant design tends to be more energy efficient.

    If your hot boiler is cutting in and out its set too high, i.e. a lower temperature with higher flow works better.

    Again if your thermostatic shower mixer is 'hunting' that usually means the water temperature of the hot water is again too high, in that it keeps overshooting the temperature and reacts by closing off the hot and so on

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    Feb 18, 2011 8:24 PM GMT
    I installed one in December. It operates on propane. I've always had one of those shower heads that increases the pressure without increasing the volume. That solves the problem, easily.

    I have a very small "cabin" and all my bathroom plumbing is on one side of a wall and the kitchen plumbing on the other side of the wall, so placement at "point of use" was simple for bathroom and kitchen, and at the same point. lol

    Mine has a setting for "winter" or "summer" which also helps.

    I like mine and can't be happier.
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    Feb 18, 2011 9:04 PM GMT
    I bought one two years ago for my condo, and when I buy a house I will get one there if it doesn't have one already.

    I bought mine because of space. A 30 gal tank proved useless. With the tankless I have never had a pressure issue, you may have gotten one too small. To compensate for your shower pressure, you can get a shower head that will increase the pressure.

    I believe they are a tax write off also.

    The great thing is endless hot water. And I converted from electric to gas, so it saved me even more. Plus the extra space.
  • rnch

    Posts: 11524

    Feb 18, 2011 9:09 PM GMT
    blackhawksfan said... A 30 gal tank proved useless. With the tankless I have never had a pressure issue, you may have gotten one too small.....


    water pressure is...adequate...barely...lost of compromises with an old (circa 1882) house!

    the natural gas line is only half-inch, dunno how old and internally crudded up the water pipe line under the house is...

    "it is what it is".

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    Feb 18, 2011 9:14 PM GMT
    Thisuserexists saidThe other option is to install centralised hot water with a secondary return and pump that keeps the water hot at the point of use, these types of set-ups eat energy and therefore the electric instant design tends to be more energy efficient.

    That is the common solution in many large office buildings and in hotels. The water may be heated many floors below in the basement, or even in a separate building, particularly where this is a campus of multiple buildings. But hot water is always quickly available at the tap because it's being recirculated all the time, a double set of feeder & return pipes near the fixture.

    But as you say, rather wasteful, even when the pipes are heavily insulated. I think in the future, now that tankless demand heaters have been developed, relying upon microchip technology, you will see fewer recirculating systems and more point-of-demand ones.
  • mybud

    Posts: 11819

    Feb 18, 2011 9:18 PM GMT
    rnch saidi just installed one today.

    in order to get the hot water temperature i had with my old 40 gallon tank hot water heater, i have to cut back on the volume of water going thru this new heater wayyyyyyyy back. i have the flame height adjustment knob as high as it will go.

    it seems like the higher water temperature you want the lower water pressure/volume you have to have??

    wadduathunk??


    Question..Dude aren't those units like 5 thousand??????
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    Feb 18, 2011 9:24 PM GMT
    Typically $2500 - $3500.

    If the pipes are old and you have hard water, there may also be an iron build up.