My Tankless Experiment

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

  1. week #5

    the meter is now at 3500 cu ft

    the water temp is now at 63 degrees...

    I am sort of interested in seeing how much gas
    the heater will use when the water temp crashes to
    about 45 degrees this winter..
  2. week #6

    temp is now at 60 degrees...

    cubic feet used to date 4300..
  3. Week #7

    heater has now used 5030 cubic feett

    water temp is now at 60 degrees....

    I still need to see what a cu foot is costing me


    looks to be averageing about 700 cu ft per week......
  4. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Look at your last two gas bills. Assume that 100 cubic ft is one THERM. It is probably costing you about 1.5 cents per cubic ft.
  5. thank you

    I was gonna get around to calling the gas company to
    nail that down tomorrow...

    I will be spending the day at home with a sick kid...
    so its time to catch up on my paper work


    at 1.5 cents which you claim it shoud be per cubic
    foot that only works out to about 75 bucks for 7 weeks???

    5030 cu feet x .015 = 75.45

    or about 10 bucks per week??
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,995
    Location:
    New England
    Now, with the water meter, how many gallons of water were heated? You can then figure out approximately how much was used to heat it the first time, then how much was standby losses. You have the average input temp so you know the temp rise the heater is trying to provide.
  7. I dont want to go there....

    I think That would really be cutting some fine hairs....

    That would involve putting another meter on the
    heater to measue water usage ...

    I am only looking at the average usage for a family of 4....
    a ballpark average is good enough
    I am not going to get suckered
    into turning this into a bigger project than it already is

    I dont think its necessary to figure out exactly how much
    energy it took to heat up 100 gallons of water...

    Especially when at this point it looks to be doing about
    only around a measely 10 bucks a week anyway....


    this is all very boring right now...in Week #8 but they
    seem to be passing very fast.... .


    The big hurdle is still ahead some day with the tankless
    unit ......probably next spring...

    of course I am still in the "procurement phase."

    I am still looking for one of the owners of a supply house
    around here to donate a scratch and dent one to me.......
    that will do 3 bathrooms...
    Last edited: Nov 6, 2007
  8. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    I'll guestimate,
    At 22-24% higher efficiency and the standby heat loss on a 75 gal, You'd save about $2.50-$3.00 a week.
    Approximately $140.00 a year.
  9. you got to be kidding me.....


    So Grumpy.....you have not been around for a while...
    did you get back from a vacation to Europe or some place exotic?


    I found another site that claims a tankless will save as much as 23 dollars per month to heat the water....

    it dont seem realistic to install the tankless if all you
    are going to save is a so small....

    here is the article I found from the Plum biz newsletter I get

    Are they really cost effective?
    Last week I started prying open a can of worms concerning the cost savings of tankless versus storage type water heaters. It's been over twenty years since I had my first practical lesson in the benefits of both. With the help of the engineers at PVI water heaters (I live less than two miles from their HQ) I wrote the specs for a municipal maintenance facility. The facility included crew showers which, if I remember correctly, would accommodate 8 mechanics at once. In theory, they would likely all be hitting the showers at the quitting time so we needed to provide enough hot water for all of them at once. To handle the task, we installed a 250 gallon tank type heater which only had about 100,000 btuh or so for a burner (I could be off a bit on the burner size). At first, I thought their engineers were just trying to spec a big tank but then I realized how much money we saved on the project by specifying this monster. For all I know, it could have been the key to winning the job.
    Installation costs were shaved in several ways: The flue was considerably smaller than one which was necessary for a quicker recovery unit. This was important since the roof was about 20 feet overhead. Then, there was a considerable savings on gas piping. If we had run piping for a half million btuh burner we would have been into welded pipe sizes, instead of being able to stick with screw pipe. Let's not forget that by being well under the 200,000 btuh boiler threshold we didn't have to deal with an ASME rated tank.
    The tankless market is asking us to reverse these infrastructure savings. Although there are plenty of instances where a tankless model makes good sense (I have no plans to remove them from my price book system) but, whenever the government gets involved, as in offering rebates for energy savings, then it's time to take a look at the real world that they may not have thought of. (Can you say "Daylight Savings Time?")
    So, let's say that half the population of a given neighborhood suddenly decided to go tankless. Since large segments of our population share schedules ( "rush hour" doesn't just happen on the freeway). So, what happens at 6:00 a.m. on a January morning when everyone hits the showers at once?
    Here's a simple example: Let's say a distribution branch is designed to handle a hundred homes equipped with 45,000 btuh storage type water heaters. If just 10% of those homes switched over to tankless, at 190,000 btuh each, demand could result in a 25% increase in peak energy demand. In other words, just as individual homes have to be upgraded to accommodate the peak demand of tankless burners, the municipal infrastructure could have to be upgraded in order to provide enough energy for peak usage. Fortunately, the high up front cost of converting to tankless will prevent hoards of consumers from adopting these units but that doesn't change the fact that several tankless heaters on a single distribution branch could cause problems.
    If you don't think this could happen, perhaps I should tell you about the challenges I've seen neighborhoods experience when severely cold weather resulted in every furnace firing at once. The gas company had to bring in tanker trucks of natural gas, pumping it into the local distribution system because the infrastructure couldn't deliver enough fuel gas.
    I realize this is getting a bit far fetched but these infrastructure problems would be a real headache if the population in general decided to go tankless. It won't happen, as mentioned already, but it's still evidence that tankless isn't going to solve our energy challenges.
    Speaking of infrastructure and payback. Last week, I mentioned that I had found a manufacturer boasting of 50% savings. Here's the phrase from their website in case you missed it:
    "[Our brand] tankless gas water heaters provide an endless supply of hot water on demand; only heating the hot water that is needed. This performance cuts water heating costs up to 50%."
    I asked them to help me understand the savings claim and sure enough, they have a real live case study where they replaced a 40 gal. NG water heater with their tankless unit. They had 6 months of before/after fuel costs for each water heater (I'm not sure how they gleaned that part of the data) and sure enough, they managed to squeeze out as much as 53% savings in a couple of the months. The six month average savings ended up around 45%. This is a pretty significant savings by any measure. Very impressive. But there's a hitch: That 45% savings results in a monthly dollar savings of. . .are you ready for this. . . less than $23.


    At $23 per month, what's the estimated payback (in months or years) for swapping out a 40 gal. Nat. with a tankless unit from your shop? For calculations, use a tankless unit that's just under 200,000 btuh max input with a remote T-Stat. Be sure to include re-sizing gas and flue piping as would be typical in your area when working up your prices then send me an e-mail with your bottom line number: At $23 per month, how many months would it for a conversion to pay itself back?
    Last edited: Nov 9, 2007
  10. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Heya Mark, thanks for noticing...feast or famine here.
    Got real busy about a month ago and been crazy since.
    As for $23 a month, it's math.
    Lets say a 40 gal tank costs $800 for install and a tankless costs $3K.
    A disparity of $2200.
    At $23 a month, thats $276 a year, $2200 in 8 years.
    I better stop ignoring those Plumbiz E-mails..apparently I'm missing out.
  11. your math is fuzzie

    that plumb biz news letter is usually pretty dry.....
    but its a good read one in a while....I glance it over

    you are sort of close to about right with that estimate but....

    the 23 a month was supposed to be the 50% high end of
    saveings the absolute most you could save useing the tankless salesmens numbers.


    of course the tankless folks are going to use the absolute highest % for saveings
    and they are going to use the absloute rock bottom numbers for installation costs too
    to get the years down on the pay back end ..... and that is all smoke and mirrors to me....

    but the Plumb biz guy also wants you to factor in
    some sort of ball park estimate for enlargeing the chimmney---and enlargeing the gas line too....

    into the overall cost and then figure out the payback from there..

    it will be interesting to see the numbers he gets back....


    they are not factoring in future maintaince to this equation to me
    its really a FUZZIE shot in the dark...
    Last edited: Nov 9, 2007
  12. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    The $3K ballpark figure is for install with a 3/4" upgrade on the gas supply, as well as the vent set-up.
    They're wall mounted, so you generally set them up on the foundation wall as close to where they'll vent outside as possible because the SS vent is expensive (around $80 for a 4' length of 4" if memory serves).

    Maintanence is another issue, but from what I hear it isn't much more than a yearly vinegar flush, which you're "supposed" to do on tank types anyway.
    Tankless have been around for many years, much like cell phones, they were originally a high end item that was too cost prohibitive for the average Joe.
  13. Week #8

    week #8 have used 5680 cu ft so far..


    I might have a Rheem tankless with a scratch
    and dent on it in a few weeks.....
  14. markotah

    markotah New Member

    Messages:
    3
    Location:
    Connecticut
    Tankless Units

    Fact: One product is not good for all applications!
    Tankless electric is only a good choice for point of use small sink applications especially in colder climates. Gas on the other hand is not new and has been in Europe for over 40+ years. (far longer than tank type pv units). In the northeast a tankless unit can cost 1/2 as much to operate. Comparing to a 75 gal 70K tank type heater you only have 70% of usable water. Call it 53 gals and a recovery of about 70 gals per hr. Total 123 gals. Take a Rheem 199,000 BTU unit (and all manufacturers are equal on the same BTU) 40* incoming water and 117* supply temp and you will have 4.3 gpm continiously or 258 gals per hr. You need to calculate the peak flow but if you fill the whirlpool someone can jump right into a shower and still have h/w. If you need a higher fill rate you can twin units together for higher demands. I have 2500 sq ft homes in a subdivision in CT and no complaints with a single units. I have larger homes where we have twinned units and the end users are happy. The key thing is to know what you will receive for flow with the coldest incoming water. READ LITERATURE CAREFULLY! Most of the 7.4 or 6.9 gpm you see are @ 45* rise. ALSO be aware of larger units over 200K. Most states require an ASME rating on units over 120 gal or 200K. This can be an issue with both the inspectors but more importantly your insurance carriers.
    Last the warrantys on most tankless units are better than the standard tank warranties.
  15. markotah

    markotah New Member

    Messages:
    3
    Location:
    Connecticut
    3K ballpark

    You need to qualify the install. If your customer has a chimney and is not runnining out of h/w payback may not be there. But if you have a new installation and are considering a PV or DV tank type unit the tankless is that much difference in price assuming you can mount on an outside wall. The DV units take all combustion air from outside which is better. The Nat Gas Code states you need 50 cu ft of area for every 1000 BTU. A 60'x20'x8' room only has 9600 cu ft and you would need 10,000 cu ft for 200,000 BTU.
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    21,995
    Location:
    New England
    Where I live, in the winter, the incoming water can be 33 degrees. a 45-degree rise isn't even warm! I'm surprised you can get by with that in CT. If you have a boiler, I still think an indirect is the way to go.
  17. wait till this winter

    I am wondering how cold the water will be around jan 15th in INDY...

    My guess is it will be down around 35 degrees too.....

    Thats cold water....and I honestly dont think one of the
    tankless can even hope to deliver the same heat that
    my 75 gallon can......

    right now the out going hot water temp is set at.....130 deg

    the cold incomming is 60 deg....

    I am useing about 650 cu feet a week at 60 degrees

    wondering how much more cu feet it will take to
    keep up when the water crashes ...


    Sittingat home today with a kid witht he flu today
    thnk I will call teh gas company today and
    get info on the cost per therm
    Last edited: Nov 12, 2007
  18. Waterloo

    Waterloo New Member

    Messages:
    5
    I hate plumbing

    Had a flex water heater pipe leak on me today. I tightened it up too much and split the gasket. Of course, I only put the water heater in yesterday. At least my sweat connections have held...

    When I moved into my home, the previous owner (who had the house built) had installed two electric tankless water heaters (SETS) - one 22KW and the other 11KW. I could heat up 3 gallons a minute by 75 degrees. Or, more likely, 4.5 gallons per minute by 50 degrees. We didn't need that much water heated, so the second one (11kw) got turned off.

    However, the darn thing took time to modulate to find it's set point, and since it always comes on "full blast" then modulates down, it ends up tripping it's resets. So, every week or two you end up downstairs resetting them.

    It's not too bad for just yourself. You get to know how the thing works, and how you have to run the shower for a bit to let it equalize. But when relatives show up and try to take showers, they end up fighting it constantly. It gets too hot, so they reduce the amount of hot water. Then it gets too cold, so they increase the amount of hot water. Of course, it's 30 seconds to get to their shower from the tankless, and the tankless can take 15-30 seconds to find it's setpoint. It also can be challenging for a dishwasher.

    This brings me back to why I hate plumbing. I kept the tankless SETS heater. The output of it now goes into a standard electric water heater. I now get a constant temperature out of the faucet. And, by having the tankless in front of it, I doubt anyone at my house will ever have a cold shower.

    Overall, I love the concept of the tankless design. But the temperature fluctuations drove me (and everyone else) nuts. I'm sure gas ones are different (I read that they reduce output flow to maintain temperature), but the electrics really need to be considered pre-heaters.
  19. Thats sounds like lots of fun

    I would put up with that kind of trouble or
    about one week.....

    those electric tankless would be out in the trash...

    It sounds like you threw out a couple of
    tankless water heaters over the weekend
  20. Waterloo

    Waterloo New Member

    Messages:
    5
    Nah - they're too expensive to throw out. It just feeds into the tank now. I don't ever have to worry about running out of hot water. I could take a 4 hour shower if I wanted to....
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