Need some data

Discussion in 'Tankless Water Heater Forum' started by sjsmithjr, Feb 13, 2009.

  1. sjsmithjr

    sjsmithjr In the Trades

    Joined:
    Dec 12, 2005
    Occupation:
    Geologist
    Location:
    Knoxville, Tennessee
    I observe exactly what I should in a properly designed system - nothing of significance. Your point.

    ...and you still seem to fail to understand the difference in a storage system and a demand system when it comes to sizing.
     
  2. Ladiesman271

    Ladiesman271 Homeowner

    Joined:
    Aug 22, 2008
    Occupation:
    Care and maintenance of transformers

    Sure I do. You are just being a wise guy!

    Since the majority of gas tank type water heaters are installed in the 40 gallon size, maybe you should properly figure out the typical home hot water demand instead of overstating it. Heck, one or two short showers back to back and a 40 gallon tank heater is producing tepid water in most homes if your demand figures are accurate for the average size home.

    As a comparison, even with 40 degree incoming water temperature I can get over 120 GPH of 120 degree hot water out of my modest tankless unit (125,000 BTU maximum).

    Like Mr. Rat said a hundred times, if you have a high hot water demand lifestyle (AKA 4 to 5 bedrooms - 3 full baths - simultaneous showers required), then you need to size your system to meet the required simultaneous demand.


    You should also note what it says in the previously linked to Minnesota summary. You, the "plumbing instructor" and his "friends" should revisit the so called and undocumented simultaneous use requirement of "the code".


    Summary

    • When looking at a new water heater, be sure
    to compare the energy efficiency of different
    models by checking the Energy Guide label.
    Choose an EF of at least .64 for natural gas
    and propane, and an EF of at least .93 for
    electric.

    • Buy the smallest size you can. Don’t try to
    buy a water heater so you can shower, and
    wash clothes and dishes all at the same time
    without running out. Instead, plan your hot
    water use. This is especially important if you
    have a large family.


    • Locate the water heater as close as possible to
    where the largest volume of hot water is
    used. Since heat is constantly lost through hot
    water pipes, the shorter the pipe runs the
    lower the heat loss.

    • Insulate the water pipes and install heat traps
    if your water heater does not have one.

    • Take easy, low-cost or no-cost measures to
    avoid waste in using hot water.


    Copy of original Minnesota summary with typical flow rate chart:


    [​IMG]
     
    Last edited: Feb 16, 2009
  3. Ladiesman271

    Ladiesman271 Homeowner

    Joined:
    Aug 22, 2008
    Occupation:
    Care and maintenance of transformers



    That may in fact be terrible advice. The larger units have a higher minimum flow rate and may turn off in the middle of "low flow" demand situations.

    I hope that you guys do not do HVAC installations!
     
  4. sjsmithjr

    sjsmithjr In the Trades

    Joined:
    Dec 12, 2005
    Occupation:
    Geologist
    Location:
    Knoxville, Tennessee
    I can assure you I am not. The plumbing system in my home is neither undersized nor is it oversized. It is appropriate for it's intended demand I am not limited to as to simultaneous fixture use. My water heater is not oversized. My observations are not qualitative but quanitative.

    Tankless manufacturers recommend that units be sized for the coldest parts of the year, meaning that at least part of the time they are oversized.

    As you seem to take issue with the opinions most professionals regardless of field as well as qualified instructors, would you mind sharing your particular area of expertise and qualifications?

    Just curious.
     
    Last edited: Feb 16, 2009
  5. Ladiesman271

    Ladiesman271 Homeowner

    Joined:
    Aug 22, 2008
    Occupation:
    Care and maintenance of transformers


    It sure is!;)
     
  6. sjsmithjr

    sjsmithjr In the Trades

    Joined:
    Dec 12, 2005
    Occupation:
    Geologist
    Location:
    Knoxville, Tennessee
    Be specific; which residential units have this problem? What are their minimum flow rates in GPM for a given temperature rise? Even a Rinnai R98 works at 0.6 GPM/50F rise. Even if minimum flow were a problem, one could install two smaller units, albeit at a greater initial cost.
     
    Last edited: Feb 16, 2009
  7. Master Plumber Mark

    Master Plumber Mark Sensitivity trainer and plumber of mens souls

    Joined:
    Feb 6, 2005
    Occupation:
    Sensitivity trainer.. plumber of mens souls
    Location:
    indianapolis indiana - land of the free, home of
    its all smoke and mirrors....

    Ladies man, you are truely an intellegent person
    and I stand in awe of all your knowledge....


    Why are beating a dead horse and having a fun time
    trying to pull everyones chain.. I dont understand...

    you are trying to make tankless something akin to
    space shuttle technology.....

    its simply a bathroom,
    and everyone of them in the USA is different ......

    get it???


    ok lets try to factor in all the variables......

    lets try to equate the flow rate when grandma takes
    a healthy shit and flushes the toilet while you
    are showering with the tankless...


    Now lets factor in a well, and now lets factor in
    pressure balanced shower faucets....


    Now factor in grandmas bowel movement not going down
    all the way with one flush...and she flushes three times
    to get that stubborn nasty hard turd to go down....


    then she jumps into the other shower and attempts to
    take a bath while you are in the other bathroom


    so whats the pressure drop going to be..?????

    man I can see that curve drop in my mind right now..

    so whats going to happen to the guy showering if the tankless is undersized??? ....






    When a simpelton like me sells a water heater

    the first thing I ask is how many people are presently living in the home,
    and how old everyone is living in the home....

    if they have a few children about 9 years old....
    I KNOW that the demad will be going up in about two years .
    ..


    and I KNOW that the 40 gallon heater will not suffice.
    ..

    so we usually go one size larger for the varaible of

    larger increased demand when the childred become pre-teens in a few years

    so they buy a 50 gallon..





    Now all I state....

    if you are putting in a tankless, I simply suggest
    you oversize the unit for future issues and other variable factors....
    like grandma and pressure drops....



    but this is just too damn simple for you.....

    isnt it???..
     
    Last edited: Feb 17, 2009
  8. Redwood

    Redwood Master Plumber

    Joined:
    Dec 15, 2007
    Occupation:
    Service Plumber
    Location:
    Connecticut
    Yea I was wondering when You were going to post the meaningful Data you were asked for...

    Slipped out of another one eh? [​IMG]
     
    Last edited: Feb 17, 2009
  9. nhmaster

    nhmaster Master Plumber

    Joined:
    Jul 30, 2008
    Occupation:
    Tech. Instructor
    Location:
    S. Maine
    flow rates and demand aside why not address the real folly of tankless heaters and that is that the average savings is a crappy 4% over conventional tank heaters with the installed price being 2 to 3 times that of a tank type heater. That's a lot of money to save very little floor space. Why not address the common problem of long wait times for the water to get to the faucet or how if you just crack a faucet the unit will not fire or how the temperature and pressure fluctuate enough to keep quite a few pressure balanced valves from operating correctly. better yet ask anyone from Europe that has grown up on these things what they think about tank type water heaters when they come over here for a visit?
     
  10. gregsauls

    gregsauls Homeowner

    Joined:
    Nov 10, 2008
    Occupation:
    IT
    Location:
    Texas
    Folks, here's what 15 or more pages of debate boil down too. Several (ie, more than 2) DIYers have installed tankless systems in their homes and are happy with them. Plumbers around the country are installing them successfully (ie. no manufacturer recalls). A few "boys" here hate them for highly biased reasons.

    Bottom line, don't let NHmaster install one in your home as he can't cope with it. And don't let Rugged in your home or you may be "scammed" out of a water heater that is under warranty.

    Now for more FUD (and dumb pictures) from the "boys".
     
  11. sjsmithjr

    sjsmithjr In the Trades

    Joined:
    Dec 12, 2005
    Occupation:
    Geologist
    Location:
    Knoxville, Tennessee
    In the interest of being fair and unbiased, let's not forget that many of those DIY'ers voided their warranties in the process.

    Let's be clear, I don't hate tankless water heaters. My interest in tankless water heaters and the sizing of hot water systems comes from the current (and growing) interest in obtaining LEED certification for new construction projects. I am not so jaded either way as to not consider all of the factors: installation, parts, service, warranty, functionality, fuel consumption, and water consumption. I also have to consider cost.

    The green that consumers and organizations seem to be interested in the most are the dollars in the present worth calculations.
     
    Last edited: Feb 18, 2009
  12. Master Plumber Mark

    Master Plumber Mark Sensitivity trainer and plumber of mens souls

    Joined:
    Feb 6, 2005
    Occupation:
    Sensitivity trainer.. plumber of mens souls
    Location:
    indianapolis indiana - land of the free, home of
    Un-believer----

    we are all boys and simpeltons,
    dont you understand???

    we have not seen the light yet......

    Getting a tankelss heater is like converting to a new faith or religoin....


    it is literally like blind faith,
    sort of like some other fanatic religions out there...


    you have to take that leap of blind faith,

    and then never question your faith.....ever again





     
  13. nhmaster

    nhmaster Master Plumber

    Joined:
    Jul 30, 2008
    Occupation:
    Tech. Instructor
    Location:
    S. Maine
    No matter what wisdom issues forth from these two cretans the fact is that the average annual energy savings is a wopping 4%. So in a way I suppose I am thankful that there are those out there so pig headed and ignorant that they would gladly spend 2 to 4 times the cost of a conventional water heater. God bless capitolism. :eek:
     

    Attached Files:

  14. Redwood

    Redwood Master Plumber

    Joined:
    Dec 15, 2007
    Occupation:
    Service Plumber
    Location:
    Connecticut
    Yes, God bless capitolism.

    and,

    "Never Give a Sucker an Even Break." ~Otis Criblecoblis~ 1941
     
Similar Threads: Need data
Forum Title Date
Tankless Water Heater Forum Do I need dielectric unions for a circulator pump? Sunday at 9:11 AM
Tankless Water Heater Forum New Tankless, need Recirc Mar 22, 2020
Tankless Water Heater Forum Need help replacing tank gas water heater with tankless Oct 15, 2018
Tankless Water Heater Forum Eternal tankless redirect needed Jul 9, 2018
Tankless Water Heater Forum Minimum flow needed to light has increased, Noritz NRC1111-DVNG Jun 8, 2018

Share This Page