Replies

1. 
   WayneL5 | Jul 09, 2006 03:27pm | #1

   Lots has been written here about them.  It is a frequent question.  Check the archives for the many threads on this.

   The summary is that such units are quirky and you have to be willing to accept a change in your habits to put up with them.  They don't run out of hot water, so they are good for back to back showers, but the maximum number of outlets that can be operating at once is limited.  You can't get a little bit of hot water because they need a minimum flow to kick on (if you use a gas fired unit).

   They save energy, but the initial cost is higher, so the payback is quite long, in the neighborhood of ten years.

   Hard water can shorten the life of the units due to mineral buildup within the heat exchanger.

1. 
   davidmeiland | Jul 09, 2006 05:50pm | #2

   >>The summary is that such units are quirky and you have to be willing to accept a change in your habits to put up with them. 

   Very minimal changes to our habits... nothing that was difficult to accept. 

   >>They don't run out of hot water, so they are good for back to back showers, but the maximum number of outlets that can be operating at once is limited. 

   Ours will run the washing machine, the shower, and someone washing dishes at one time.  

   You can't get a little bit of hot water because they need a minimum flow to kick on (if you use a gas fired unit).

   Ours will run the vanity faucet alone, which is very low flow.

   I would encourage anyone to get a tankless. The space and gas savings are immediately noticeable.

    

1. 
   etherhuffer | Jul 09, 2006 06:33pm | #3

   When we remodeled our rental/mother in law/basement we looked and did the numbers. They made sense at 400 a unit but 2000 up? You are into VW diesel economics. You save pennies every day but pay thousands more up front and have huge repair costs. The economics don't make sense.

   I have a relative in energy efficiency for large buildings. She notes that passive solar preheaters for the water tank is really a better choice. The amount of sun most places get year round is actually enough to work, even here in Seattle. These are passive loops or small pump run loops. There is a heat recovery drain system too called the GPX heat recovery unit to capture waste heat from drains.  The downside is these things cost a lot to install in old construction. The upside is they are passive, and require not a lot of maintenance.

   The tankless makes sense if you have space limitations. We solved our problem by spending money on appliances that heat their own water. Our Asko washer is more expensive but truly saves us a lot of water and does not draw from the tank.

   After watching years of these posts, I think the solutions are absoutely individual to the person and the property and the economics of local energy costs. Use a sharp pencil before you decide.Those who can make you believe in absurdities can make you commit atrocities- Voltaire

2. 
   frenchy | Jul 09, 2006 10:06pm | #4

   mclearn,

    2400 for the unit itself?  Hmmm, the chain places sell them for about $1100 including (usually)  the special exhaust flue..  The other aspects of this are you need to plumb a gas line to them and you'll need to have enough of a water supply.

          I will say the units I've seen working have operated just fine whenever a water faucet is turned on..  The cold water that runs is totally dependant on the length of the water line feeding it..  If all the faucets are grouped together you get hot water right away.   If some are at opposite ends of the house they will take a long time to get hot..  Same as with a tank type heater..  There are ways around those issues but they aren't cheap or easy..

    Durability?   The newer designs appear to solve the issues with regard older designs.    One brand I've seen a great deal of negative reporting is the Bosch brand,  on the other hand Japanese brands seem to have excellant reputations.. With American brands somewhat in the middle..

    I just went thru the same process myself.. In the end I surprise! surprise!, choose a large electric tank water heater..

     I live here In Minnesota Gas and electric costs are a wash per therm with our recent additions of wind power, the efficent use of Nuclear power and several extremely well managed coal plants. Electric costs should remain relatively modest while future costs of gas promises to be steeply increasing..

    IN the end what made the differance to me was that the air used to operate the burner comes from inside the house.. it's already heated and then sent outside..  The flue is a 4 inch hole  that is open 24/7/365 pulling heat from inside the house and letting it go even if the unit isn't on..  When it's below zero a 4 inch hole is a serious amount of heat to let go outside 24/7/365.  When it is on the air used for combustion goes up the exhaust flue sucking more air from inside the house. That creates a low pressure area in the house sucking cold air in to replace it...

    

       

1. 
   mrsludge | Jul 10, 2006 07:21pm | #5

   We ended up going with a tankless Noritz.  One thing not mentioned is the ability to mount a tankless on an exterior wall and avoid the venting issues.  I still have to heat trace and insulate our exterior piping, and then we'll see how it fares through next winter.  But that gave us the ability to locate it adjacent to the two bathrooms it serves, without taking up any real estate or conditioned air inside.  We still have an older tank heater on the other side of the house, but a cutoff valve on the piping dedicates it for the kitchen and laundry (and can be opened if either heater fails).

2. 
   mclaren | Jul 11, 2006 05:26am | #6

   Thanks for the feedback.

   Maybe I wasn't as clear as I should have been.

   Our house is 80 years old and the water tank and boiler for the radiant heat

   is at one end of the house. The kitchen and bathrooms are at the other.

   I'm in the Baltimore area and our rates for electricity and gas are going up

   dramatically. The thought was to hang the tankless on the basement wall

   below the kitchen/bathroom area for a shorter run. To do that a larger water

   line needs to be run 22' from the meter to the heater and a larger gas line

   run as well. The quote from the plumber included that additional work as

   well as the unit itself.  The onetime shot on the unit would be offset somewhat

   by the tax incentive ($300 me thinks) and more efficient operation.

   Plus! not having to wait 5 min for the water.

   But, again its a large expense as opposed to the traditional type.

   Mclaren

1. 
   ruffmike | Jul 11, 2006 08:06am | #7

   I don't know if it is an option for you, but I've had a tankless boiler (Trinity) that is a coheater. Does our radiant flooring and domestic water. 3 showers at once no problem.  We love it.                            Mike

       Trust in God, but row away from the rocks.

1. 
   mclaren | Jul 12, 2006 05:57am | #8

   Just replaced the boiler two January's ago.

   It was 35 degree's and dropping........

   So, I'm really just looking at the water heater.

   Thanks for the feedback tho..

   M