My Tankless Experiment

Discussion in 'Tankless Water Heater Forum' started by Master Plumber Mark, Mar 1, 2007.

  1. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    You've got 10 more degrees to match my worst case temps last year - it hit 33 degrees incoming. Under those conditions, I think a tankless would not keep up. The things are generally designed around 50-degree, worst case, incoming water; you're already below that, and it tends to be worst around the end of Feb (at least here).
  2. This guy has got me beat already

    Just when you think you have seen it all

    Whole looking for pics of water heaters for this years yellow page add, I stumble on this tankless information....

    he has me beat hands down.....
    and has in my opinion
    gone off the deep around 7 grand here.......

    but their is a lot of very valuable information....

    check out the two Rennai tankless heaters he installed

    and the two electric heaters..

    he certainly has me beat.....
  3. drakeDenver

    drakeDenver New Member

    Tank vs Tankless cost calculator (mattox)

    That mattox site that you linked to has a really easy to use calculator. Basically, the colder your incoming water and the more usage (more people in the house etc...) the shorter the payback period for a tankless (except there is no field for higher tankless maintenance costs).

    Myself, I requested an estimate on a Rinnai on Friday. It has an energy factor of .84 One tanked HWH I saw had an energy factor of .63

    I am considering the AO Smith Vertex because the manufacturer says it could be simultaneously used hot water and for space heating (like radiators). I am thinking about moving my washer/dryer to the currently unheated garage and make the utility room (heated by existing furnace) into a second bathroom.

    One web document mentioned the department of energy testing procedure uses hot water "draws" that aren't like real world usage. It will be interesting to see how this thread's poster does with his experiment (more realistic).

    I agree with the plumber who said "one product is not for everyone". Customers that neglect maintenance will always pay more, no matter what product they have.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    My boiler runs at a minimum of .94 and heats my indirect WH tank...

    Personally, I don't see how a tankless would pay for itself faster if the incoming water is colder...the maximum temperature output just drops along with the input once it reaches its limits. It takes the same amount of heat to raise x gallons y degrees, whether it is being done in advance or in-line. Obviously, the efficiency of the heat delivery will affect the total costs. There are tank type heaters that are quite efficient.

    Most tankless can only produce their maximum rating and flow with incoming water at around 50-degrees. Many places of the northern US have water approaching freezing for part of the winter...this has one of two results on a tankless: either an unacceptablly low output temperature or a severely limited volume. Neither of those issues occur with a tank type heater. Some may put up with that low flow, but those who use hot to fill a big tub, or for certain loads of clothing in the washer just may not want to put up with the limitations or the costs to provide the desired flow.

    Even with that difference in efficiency, countering with the difference in purchase and installation costs, it would take quite a number of years for the typical user to come out ahead.
  5. my summer tankless experiment

    [​IMG] [​IMG] [​IMG] [​IMG]

    yes that is 3/4 inch toung and groove real cherry panelling on the walls from 1966

    well the summer floods came about a month ago and put about 6 inches of water in our downstairs walk out home

    my heater never flooded out but the gas meter for my tankless experiment
    did get half submerged.... it was a sealed meter and still seems to be chugging along...

    the only good thing about it ,
    is I got good flood insurance

    of course this little set back will not deter me in my endeavor to
    prove which heater is more economical
    Last edited: Jul 4, 2008
  6. dave148

    dave148 New Member

    This may have already been mentioned, but I didn't have a chance to read every
    post in the thread. When I looked into the tankless, I rejected it for a few reasons:

    1. The "whole house" units don't click on until 0.5-0.75 gpm. So hot water to
    a lav can be a problem.

    2. If the power suddenly goes out, the water turns instantly cold once the
    supply line to your shower is used up. This also applies to the gas units
    with the electronic controllers (all the good ones as far as I can tell)

    3. Theres no reserve for serges. So Even with the Takagi flash T-H1 @199KBTU/Hr
    and 95% efficiency, I could bearly run two showers here over 7100 ft elevation,
    and any intermittent (washing machine, dishwasher, lav...) use during the two
    simultaneous showers would drop the temperature of the showers.

    I looked into combining the Takagi with a small tank to eliminate most of the
    above problems, but instead of all that mickey mousing around, I just went
    ahead and bought a 199KBTU/Hr Polaris (high efficiency, 50 gallon, urethane

  7. Cass

    Cass Plumber


    May I suggest a Zoeller Aquanot 2 battery back up sump pump.
  8. and pump it where???? thats a cute idea.....

    basically the home is a walk out bi- level on the creek.
    and the water came into the home from 3 sides.........

    the home should have been built about 3 feet higher

    I am considering putting up a burm or pour a wall perhaps about 5 feet out and then install a pit out on the patio to
    pump the water back over the wall....

    this is the second time it has flooded , once in 66...

    so do you just gamble on it or not????
  9. sounds like you had one

    sounds like you already fought the battle of the bulge with a tankless and had nothing but troubles...

    any other experineces you care to share??
  10. dave148

    dave148 New Member

    Re: Tankless

    >sounds like you already fought the battle of the bulge with a tankless and had nothing >but troubles...

    >any other experineces you care to share??

    All battles were on paper. Fortunately I figured out what the problems would be
    before I made a purchase.

    However, here is one calculation you might be interested in: The claimed financial
    advantage in a tankless over a tank system is standby loss. Using the 1% per hour
    specification of the Polaris, the standby loss should be:

    50 gallons * 8lb/gal*60 degF / 858 (btu/ft^3)*(0.01 loss)*$.0073 = 0.00160/hr
    = 4 cents/day

    This is using the price for gas, and the density of gas here in Colorado Springs.

    Now maybe we shouldn't believe American's numbers for the Polaris, so let's
    check that estimate against the envelope loss on a cylinder the size of the
    heater with 2" urethane insulation:

    Assuming R-value of 12 F ft^2 hr/BTU (2" of urethane):
    Surface area of 22" diameter x 68" (??) tall cylinder:
    3.14*22*68+2*3.14(11)^2 = 3385 in^2 /144= 23.5 ft^2

    If 60 degrees across insulation,
    23.5 ft^2 /(12 F ft^2 hr/BTU) = 2 BTU/HR

    Current Cost of gas $0.0073/ft^3
    $0.0073/ft^3 * (ft^3/858 btu at 7000') =$8.51E-6/btu
    * 2 BTU/HR *24 Hr/Day =$408.4 E-6/day = $0.0004/day

    Maybe 2" of urethane was too agressive. If the R value of the insulation
    is reduced to only 2, the envelope loss is still only 2.5 cents/day!

    Since the Polaris spec gave 4 cents/day, I'll assume most of the heat loss
    is actually through the hot pipe, and not through most of the cylinder

    So using the worst number we came up with above, we see only about a
    $15/year savings in the months we are *NOT* heating the room the water
    heater is in. If we are heating the room anyway, then we lose nothing by
    adding some heat from the water heater. Counting only half of the year,
    we get about an $8/year savings for the tankless compared to an equally
    efficient (burning) tank system. Most of the tankless systems are not high
    efficiency systems. By the way, this is comparing two systems that are in
    standby 100% of the time. If you actually use hot water in hour house,
    the $8/year number will be smaller.

  11. Sounds Great

    As our great and all knowing president George Bush once stated

    it all sounds like "fuzzy math " to me.....

    that is why I have just installed a simple gas meter
    directly to my 75 gallon Bradford White heater.....

    no more "fuzzy math" for me....
    I am just going by the numbers for the month or year....

    but now I am very reluctant to install that tankless heater,
    now that I have a flooded out downstairs home and have
    other projects more pressing on my mind....

    Its all beginning to become a blur of " fuzzy work." this summer.
  12. ted01

    ted01 New Member

    Tankless costs

    I'm a plumber in Park City,Utah.I live at 6500 ft.I have a lot of customers sold on the "green" tankless units.I refuse to install them.The water comes into the houses at around 40 degrees,and we have very hard water.Plus,we're in a high desert.I haven't seen any coments on how much water is wasted with a tankless WH.Why not put a recirc pump on the water heater tank?Instant hot water.Insulate the hot water pipes in the house that you can get to.Drain the sediment from the WH tank every once in a while.And change the annode rod.The tank will last longer and you'll have a lot of hot water.I installed one Rinaai tankless,and the factory rep said to come out and check it(customer's request),he charges $60 an hour,plus travelling time both ways.They needed a new electric panel to have enough power for the tankless.And they're very unhappy with the unit.Too expensive.But the tankless people seem to have a great PR machine.All of the "green" customers I have want one.I tell them to call another plumber.
  13. people are flocking to green

    You are probably doing the right thing,,.refueseing to install them.

    their are a few companies in our town that install them for about 3500.
    and they dont care how they perform....

    tankless people have a great PR machine.... .
    Last edited: Sep 27, 2008
  14. nhmaster

    nhmaster Master Plumber

    S. Maine
    I believe the average pay back period for tankless water heaters is somewhere around 15 years. I also believe that the majority of them will have to be replaced it the end of that time. like most "green" technology the hype is far more important than any actual savings. Here's the big factor though. Those folks that could really benefit from technology that would ACTUALLY save them some money can rarely afford the price of the equipment or the installation. Some scrape and borrow to purchase these products only to find that they have in reality saved nothing at all and in fact are now paying more if finance charges are added into the equation. These things are nothing new. Paloma and ELM have been on the market for years. We hated them then because they were service nightmares and did not live up to expectations. Why are we so in love with them now? Same crap, different day.
  15. damm, a year has passed......

    I started the experiment on Sept 16th 07.....

    the gas meter was on 0000000

    now the date is Sept 28th....08.......

    Looks like I have been sleeping at the wheel

    anyway the meter is now at 41521.00

    so basically my 75 gallon gas heater used

    41,521 cu feet for one whole year.....

    I went over the mark by 12 days.. ...too bad..

    now all that is necessary is to figure out how much
    I pay for a cubic foot of Indiana...

    and I can tell you about what it cost me for the year..

    and then divide by 12 and tell you howmuch it cost per month...

    time flies when you are having fun.....

    now I got to bring myself to installing a Takagi in my home and
    let it run on the meter for a year...............

    Last edited: Sep 28, 2008
  16. Ladiesman271

    Ladiesman271 Homeowner


    That is 415 CCF, or 425 therms for hot water.

    As a comparison I used 1085 therms for space heating of my home last year inluding hot water (tankless with pilot) with a 50 year old gas furnace (in New England).
  17. Handymaner

    Handymaner New Member

    What the *&^!! I read all 11 pages, and it ends like this?? Any updates? I would be very interested in any outcomes.
  18. zl700

    zl700 DIY Senior Member

    Wrong calcs

    In all fairness, if you needed a water heater, the price of the standard tank and install should be deducted from the install price of a tankless before the payback is calculated. Then it works out to about 7 years which is accurate.

    But remember the #1 reason for buying tankless today is not savings but endless hot water by people who are sick of cold showers, and # 2 is space required, followed by energy savings as 3rd.

    Interviewing plumbers shows it's the older generation that has difficulty accepting the new technology, becuase of difficulty in learning and understanding it.

    Get with it, tankless is here to stay and growing.

    To compare, why did you get a flat screen TV? That 25" would work just as well to watch the evening news.

    15 year payback is what tank manufactures spread around.
  19. well , the heater finally crashed

    this thread has been dead and gone for a long time....

    last night my 75 gallon heater finally started leaking and
    today I had to replace it with a new 75 brad white..
    it was a 2005 unit and only lasted 7 years.... not too good

    anyway the GAS METER has been churning away since I started this
    experiment way back on sept 16 2007

    here is the final reading off that meter.....199122 therms units were used
    to heat my water for basically 4 1/2 years...

    ... so now all I got to do is count the days and divide by the number of therms

    time flies when you are busy

    I am sorry that I let this little experiment go dead

    the meter is now installed on the new FVIR ICON heater and I wonder
    how many years that one will last......
    Last edited: Jun 2, 2012
  20. Ecosmart

    Ecosmart New Member

    MIami Gardens, Florida
    Tankless Experiment ?

    You need to make sure you size your gas tankless correctly, otherwise you will not be able to run simultaneous applications, like 2 showers going at the same time. All gas tankless water heater manufacturers advertize flow rates in the 6 -8 gallon per minute range. Read the small print - these flow rates are based on a 35 degree rise, so in your case with inlet water temperatures of 45 degrees, anything smaller than a 180,000 BTU model will not work for you. If you are told 140,000 BTU is more than enough, then the salesman or installer is not doing you justice. Here is why... If oyu buy a gas tankless rated at 140,000 BTU, Energy Star Rated, the Energy Efficiency being that of 82% it means that the 140,000 max BTU is really that of 114,800. If you want to figure out what this 114,800 represents as it pertains to Temperature rise and flow rates, here is the formula. Convert the 114,800 to KW by dividing 114,800 / 3414 (1KW=3414 BTU) = 33KW. Now that you know the KW you can figure out the temperature rise of the unit. Take 33kw and convert to watts (1kw=1,000 watts) so 33KW = 33,000 watts, then divide by 147 (this is the wattage needed to raise 1 galon of water by 10 degrees in an instantaneous basis) ( its actually 1470, but divide by 147 so you won't need to carry the decimal).

    33kw x 1,000=33,000 watts / 147 = 224 (this is the tamperature rise at a 1 gallon per minute flow rate) Now take the 224 and divide by the actual flow rate you need, say 2 showers simultaneously. Keep in mind that all US made shower heads are rated at 2.5 GPM at 80 psi, with normal residential water pressures in the 55-60 psi they really only put out about 2 gpm. So 2 showers running at the same time with an inlet water temperature of 45 degrees as you mentioned will only come out at 101 degrees, (244 temp rise at 1 gpm / 4 gallons of flow = 56 temp rise + 45 inlet = 101. Get my point, the advertized 7 to 8 gallon per minute flow rates are not accurate. In your case you need at least a 65-70 degree rise so your outlet hot water is at least in the range of 110-115 degrees and for this you need to have at minimum a unit rated at 180,000 which is only going to supply a max BTU output of 147,600, enough to run 4.8-5 gallons per minute or 2 showers at the same time.
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