Converting from domestic (tank) to tankless water heater

Discussion in 'Home Repair' started by djenka2, Aug 18, 2006.

  1. djenka2

    djenka2 Guest

    I've just finished building brand new house and I put standard domestic
    Hot Water heater with tank. Now I see that Takagi and other
    manufacturers makes tankless water heaters and they are not that much
    more expensive than standard domestic ones. My question is, if I ever
    decide to get rid of domestic ones can I put Takagi tankless water
    heater instead eventhou I was told It will be bloody expensive because
    my mecanical room is not on outside wall, it is in the middle of the
    house. Does that make any sense to you?

    Thanks!
    djenka2, Aug 18, 2006
    #1
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  2. That's exactly what I intend to do in the primary zone in my house.
    Everything is there except the 110v outlet, and there is one I can
    daisy chain from within 5'. I may not be the final authority on this,
    but an air intake from the attic is there, gas connection, cold water
    in pipe, hot water out pipe, vent pipe, blow-off pressure valve drain
    pipe. What else would you need?. I see it as a direct exchange
    Eric in North TX, Aug 18, 2006
    #2
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  3. "djenka2" <> wrote in message
    news:...
    > I've just finished building brand new house and I put standard domestic
    > Hot Water heater with tank. Now I see that Takagi and other
    > manufacturers makes tankless water heaters and they are not that much
    > more expensive than standard domestic ones. My question is, if I ever
    > decide to get rid of domestic ones can I put Takagi tankless water
    > heater instead eventhou I was told It will be bloody expensive because
    > my mecanical room is not on outside wall, it is in the middle of the
    > house. Does that make any sense to you?
    >
    > Thanks!
    >


    I'm not an expert on these but I understand it is not a direct replacement
    for a standard water heater. The gas line should be larger is what I've
    seen (like 1" or more....not sure on that). Better keep investigating
    before purchasing!
    James \Cubby\ Culbertson, Aug 18, 2006
    #3
  4. djenka2

    Pete C. Guest

    djenka2 wrote:
    >
    > I've just finished building brand new house and I put standard domestic
    > Hot Water heater with tank. Now I see that Takagi and other
    > manufacturers makes tankless water heaters and they are not that much
    > more expensive than standard domestic ones. My question is, if I ever
    > decide to get rid of domestic ones can I put Takagi tankless water
    > heater instead eventhou I was told It will be bloody expensive because
    > my mecanical room is not on outside wall, it is in the middle of the
    > house. Does that make any sense to you?
    >
    > Thanks!


    Changing from tank to tankless should not be particularly expensive if
    the two heaters are the same fuel type. If you have an electric tank
    type and install an electric tankless or have a gas tank type and
    install a gas tankless.

    If you have an electric tank type heater and no chimney or exterior wall
    nearby, switching to a gas heater, whether tank type or tankless will be
    expensive.

    Pete C.
    Pete C., Aug 18, 2006
    #4
  5. The Takagi requires special stainless venting, probably the largest
    expense in an interior installation. I seem to recall wholesale
    materials cost of our exhaust stack components was over $400 for a
    somewhat long run from an interior room.

    Larger tankless heaters require a lot of gas. The gas guys mistakenly
    ran a 1/2" line when plumbing for ours, it needed a 1" line because of
    the length of the run, otherwise 3/4" would have been OK.

    --
    is Joshua Putnam
    <http://www.phred.org/~josh/>
    Updated Bicycle Touring Books List:
    <http://www.phred.org/~josh/bike/tourbooks.html>
    Joshua Putnam, Aug 18, 2006
    #5
  6. djenka2

    m Ransley Guest

    With power venting my tankless Bosch can run maybe 25ft, or longer.
    Replace it you will save maybe 25% easily. They are full btu
    replacements if you size it right, but the cost is 2-6x that of a tank.
    I left my old tank in place as a tempering tank for the cold incomming
    water.
    m Ransley, Aug 18, 2006
    #6
  7. James "Cubby" Culbertson wrote:
    > "djenka2" <> wrote in message
    > news:...
    >
    >> I've just finished building brand new house and I put standard domestic
    >> Hot Water heater with tank. Now I see that Takagi and other
    >> manufacturers makes tankless water heaters and they are not that much
    >> more expensive than standard domestic ones. My question is, if I ever
    >> decide to get rid of domestic ones can I put Takagi tankless water
    >> heater instead eventhou I was told It will be bloody expensive because
    >> my mecanical room is not on outside wall, it is in the middle of the
    >> house. Does that make any sense to you?
    >>
    >> Thanks!
    >>
    >>

    >
    > I'm not an expert on these but I understand it is not a direct replacement
    > for a standard water heater. The gas line should be larger is what I've
    > seen (like 1" or more....not sure on that). Better keep investigating
    > before purchasing!
    >
    >
    >

    My 1988 Kenmore gas 40gallon has a 40,000 BTU input.

    Read the specs for the gas tagaki, its BTU input is several times larger.

    In terms of gas usage, the tankless will be the largest single consumer
    of gas in your house by a LARGE margin at any instant of time. Granted
    it only runs when hot water is flowing so its total gas use is not that
    great. But when its on, it uses ALOT of gas.

    Whole house Electric tankless is similar. Dedicated circuits must be
    installed.

    To go from natural gas traditional to natural gas tankless, you will
    need the following
    1. New gas line installed from meter or from the distribution line
    in your house.
    2. Stainless steel exhaust installed thru the roof (can't share with
    furnace, and this baby is HOT)
    3. new 115V circuit.

    The costs of the install may well rival or exceed the costs of the
    equipment.

    For example, I see a competitor's tankless electric. Depending on
    capacity, they recommend minimum wire size of 6 guage, and 60 to 180AMPs
    of circuit breaker capacity (60A, 2x40A, 2x50A, 2x60A, 3x50A, or 3x60A)
    Robert Gammon, Aug 18, 2006
    #7
  8. djenka2

    m Ransley Guest

    In the manual my Bosch states it can be run to a chimney, so it can
    share it with a furnace. My 117000 btu unit uses and was sized to use
    the existing Ng pipe. Of course the large 190000 btu units use alot more
    Ng.
    m Ransley, Aug 18, 2006
    #8
  9. djenka2

    Guest


    > Changing from tank to tankless should not be particularly expensive if
    > the two heaters are the same fuel type. If you have an electric tank
    > type and install an electric tankless or have a gas tank type and
    > install a gas tankless.
    >


    WRONG!

    Both the gas or electric tankless consume many times the fuel gas or
    electric used by a tank type while they are operating.

    figure a upgrade to 200 amps just for a electric tankless, plus a
    second main for regular home power uses...
    , Aug 18, 2006
    #9
  10. djenka2

    Guest

    Why are you choosing a tankless?

    First they cost so much more than a standard tank the energy payback
    exceeds the probable life of the heater:(


    You MAY need to upgade your electric service, if the tankless is
    electric, or your gas service, tankless consume LOTS when they are on..



    In the winter a standard tanks heat loss goes to help heat the
    building, so its not really lost, this probably cuts your energy saving

    by 1/2 kinda dependent on local temperatures.


    good your aware low flow may result in cold water, like washing
    hands....or using a spray wand on dishes.


    exceeed max flow and cool shower is result.


    Of course the UNLIMITED hot water may result in longer showers
    ultimately consuming more water sewer and heating fuel....


    People who have owned a tankless say there are two great
    days.............


    the day its installed and the day its replaced by a standard
    tank........


    so why are you buyng a tankless?
    , Aug 18, 2006
    #10
  11. djenka2

    Guest

    If you have a power failure with a standard gas or electric tank you
    have HOT water ayt least whats in the tank

    A power failure in a tanklless either gas or electric means instant no
    hot water:(

    just what you need first thing in the morning:(
    , Aug 18, 2006
    #11
  12. djenka2

    m Ransley Guest

    I dont need AC with my Bosch it has battery pilotless ignition.
    Powerventing is an option for me.
    m Ransley, Aug 18, 2006
    #12
  13. djenka2

    m Ransley Guest

    Hallerb, my Bosch 117000 btu unit has a payback of 4 yrs, I save 20$ a
    month, in summer my total Ng bill is now 6$ and that includes cooking
    and Ng dryer. I used a 1/2" pipe, no additional work. Tankless are the
    way to go, to bad few know the facts.
    m Ransley, Aug 18, 2006
    #13
  14. djenka2

    Pete C. Guest

    "" wrote:
    >
    > > Changing from tank to tankless should not be particularly expensive if
    > > the two heaters are the same fuel type. If you have an electric tank
    > > type and install an electric tankless or have a gas tank type and
    > > install a gas tankless.
    > >

    >
    > WRONG!
    >
    > Both the gas or electric tankless consume many times the fuel gas or
    > electric used by a tank type while they are operating.
    >
    > figure a upgrade to 200 amps just for a electric tankless, plus a
    > second main for regular home power uses...


    He said he just built the house so it's highly unlikely to have less
    than a 200A electric service to begin with. Not many homes would need
    dual 200A service (split 400A) just to handle the house and a tankless
    water heater.

    Pete C.
    Pete C., Aug 18, 2006
    #14
  15. Living in an area with power cuts regular like, I sure appreciate the
    natural gas water heater I use. No electric needed. And a hot shower
    in the morning is nice when the power is off, and the portable heater
    isn't doing the job.

    --

    Christopher A. Young
    You can't shout down a troll.
    You have to starve them.
    ..

    <> wrote in message
    news:...
    If you have a power failure with a standard gas or electric tank you
    have HOT water ayt least whats in the tank

    A power failure in a tanklless either gas or electric means instant no
    hot water:(

    just what you need first thing in the morning:(
    Stormin Mormon, Aug 18, 2006
    #15
  16. djenka2

    Guest

    m Ransley wrote:
    > Hallerb, my Bosch 117000 btu unit has a payback of 4 yrs, I save 20$ a
    > month, in summer my total Ng bill is now 6$ and that includes cooking
    > and Ng dryer. I used a 1/2" pipe, no additional work. Tankless are the
    > way to go, to bad few know the facts.


    last time I checked the energy guide label a regular hot water tank
    barely uses 20 bucks of gas per month, so please explain how you save
    20 buckjs a month? unless you convered from electric to gas
    tankless....?
    , Aug 18, 2006
    #16
  17. wrote:
    >
    >> Changing from tank to tankless should not be particularly expensive if
    >> the two heaters are the same fuel type. If you have an electric tank
    >> type and install an electric tankless or have a gas tank type and
    >> install a gas tankless.
    >>
    >>

    >
    > WRONG!
    >
    > Both the gas or electric tankless consume many times the fuel gas or
    > electric used by a tank type while they are operating.
    >
    > figure a upgrade to 200 amps just for a electric tankless, plus a
    > second main for regular home power uses...
    >
    >

    I agree with both assertions above.

    tankless whole house hot water heaters are the largest single consumer
    of energy in your house while they are running.

    The difference for gas is 40,000 BTU input that runs several hours a day
    to keep 40 gallons at 125F vs 198,000 BTU input that runs maybe 30
    minutes a day.

    And yes, an extra 200Amp circuit will have to be run from the local
    utility JUST to supply the tankless Electric as so few of us will have
    more than 200Amps already installed, much less as spare capacity. But
    keep in mind 200Amps is for the largest of the tankless units. The
    smaller ones can get away with 50 to 60Amps, and we MAY have the spare
    capacity for that in our breaker panel.
    Robert Gammon, Aug 18, 2006
    #17
  18. djenka2

    m Ransley Guest

    I used to use 26-30 a month for Ng for cooking, HW and dryer in summer
    with a tank, now I use 6$ Ng a month in summer, cooking and dryer use
    have not changed, standby loss and heating 40 gallons cost is greater
    than you think.
    m Ransley, Aug 18, 2006
    #18
  19. djenka2

    m Ransley Guest

    rgamon, when you say a tankless is the single biggest user of gas, that
    is untrue for many users. Ng tankless have true modulating gas valves.
    My 117000 bosch runs from apx 30000 btu to 117000 btu, I have never
    needed or used 117000 Btu even with 35f incomming water, I have never
    set it to high and have hot showers. Now in summer even the lowest
    setting is to warm for me. The bigger Takagi goes even lower to maybe
    15000 btu, Tankless only use the energy needed to reach the temp
    desired. Tankless have a much higher "Energy Factor" a true rating, than
    tank.
    m Ransley, Aug 18, 2006
    #19
  20. djenka2

    Pete C. Guest

    m Ransley wrote:
    >
    > I used to use 26-30 a month for Ng for cooking, HW and dryer in summer
    > with a tank, now I use 6$ Ng a month in summer, cooking and dryer use
    > have not changed, standby loss and heating 40 gallons cost is greater
    > than you think.


    A comparison chart on the Bosch site:

    http://www.boschhotwater.com/StartP...ies/EnergySavingsChart/tabid/349/Default.aspx

    Shows a pretty large difference between tank and tankless for gas water
    heaters.

    For the electric however:

    http://www.boschhotwater.com/StartP...125/EnergySavingsChart/tabid/399/Default.aspx

    There is very little difference. It would appear that stack losses from
    the tank type gas heater are the largest factor. Heating a large volume
    of water isn't an issue when you can insulate it well as in the electric
    models.

    Pete C.
    Pete C., Aug 18, 2006
    #20
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