Straight Talk About "On-Demand Tankless Water Heaters by A.O. Smith

Discussion in 'Tankless Water Heater Forum' started by SewerRatz, Feb 10, 2009.

  1. SewerRatz

    SewerRatz Illinois Licensed Plumber

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    The following is some questions and answers about tankless water heaters. I think this will be a great help to all that are considering a tankless unit.
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  2. SewerRatz

    SewerRatz Illinois Licensed Plumber

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  4. SewerRatz

    SewerRatz Illinois Licensed Plumber

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  5. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

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    You had me saying "NO" at tankless :D
     
  6. SewerRatz

    SewerRatz Illinois Licensed Plumber

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    Just a note to those that think A.O. Smith doesn't want to sell you a tankless water heater. That is false, what they want you to do is make an informed choice when you are considering a tankless unit. They want people to realize here in the USA we take the amount of water we use at once for granted, and if you install a single unit in a high demand situation the water will not get hot enough to be satisfactory. Which is why they point out it could be costly to replace your tanked heater with a tankless unit.

    For some homes two units are needed to provide you enough hot water for those peak usage times. Below is a pic showing how two units are installed. Just a note if you are just washing your hands only one unit fires up, the only time the second unit will turn on is when you exceed the flow rate of the first unit to get the desired temperature.

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  7. SewerRatz

    SewerRatz Illinois Licensed Plumber

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    Another note about the cost of installing tankless units is gas pipe sizing. Most Tank units only use 1/2" piping due to BTU ratings which the most common is 40,000 BTU's. Tankless units on low flow mode usually draws 25,000 BTU's and full flow mode can go as high as 199,000 BTU's, some units can go higher but they must follow boiler installation codes once they go over 200,000 BTU's. Well in most cases you will need to tap off the main gas supply coming into the home with a 3/4" line to the tankless unit, if you have to install multiple units as this next picture you will see they ran 1 1/4" pipe up to the units then reduced it down to the 3/4" to the units, This insures that when all three units fire up at their 199,000 BTU's they will get enough gas to run at that setting. So this is the other part of the expense that A.O. Smith is talking about.

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  8. dimprov

    dimprov New Member

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    How loud are the tankless units? I don't think I ever found reliable decibel information.

    David
     
  9. SewerRatz

    SewerRatz Illinois Licensed Plumber

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    They are no louder than a power vent water heater. I never went and measured the decibels. I will try to research this a bit and post it here when I get the answers.
     
  10. SewerRatz

    SewerRatz Illinois Licensed Plumber

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    Ah yes, my local plumbing supply hands that out to homeowners that come in asking about tankless heaters. I am going to make jpgs of them 4 pages and post them here in this thread too. I like to see this thread stay on the facts of tankless heaters instead of a battle ground like the other threads ended up becoming. Thank you Redwood for posting this PDF
     
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  11. SewerRatz

    SewerRatz Illinois Licensed Plumber

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    Thanks Redwood for the pdf to Bradford Whites testing of Tank Vs Tankless water heaters. Also if you want to view these larger click on the page you want to view. These images where made from the pdf file Redwood posted

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  12. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

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    I dunno to possibly save that .15 a week I might be tempted :rolleyes:
    I was hoping to see long term test to allow for scale buildup
     
  13. gregsauls

    gregsauls Homeowner

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    I'll let you know this August (1st year anniversary) when I do my first descale how hard it was and how bad :rolleyes: the system was hosed up....:eek:
     
  14. Ladiesman271

    Ladiesman271 Homeowner

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    I was going to point out how they stacked the deck in that test and have commited a few "code" violations, but those issues have been beaten to death in other threads.

    The NG and electric costs are also way out of date!
     
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  15. SewerRatz

    SewerRatz Illinois Licensed Plumber

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    That is from 2005 so yes 4 years out of date. But still some information explaining some of the issues.
     
  16. dimprov

    dimprov New Member

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    Hi Ladiesman271,

    What's the decibel level when measured at 1 meter? That's the usual distance for taking noise measurements.

    David
     
  17. gregsauls

    gregsauls Homeowner

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    My Rinai R75lsi is what I would say to be about 50-55db....with 50 db being Normal conversation and 70 db being a Vacuum cleaner.
     
  18. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

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    WHAT!! ??

    So you mean with better insulation in the tank models recently the gap is even closer!! :D
     
  19. dimprov

    dimprov New Member

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    Ladiesman,

    Your original post said 10 feet, which is more like 3 meters.

    Why not just measure it at 1 meter?

    The HVAC guys measure it at greater distances because they're trying to distort reality by saying their unit is, say, 50db, and then asterisk it to say "oh, by the way, it was measured at more than 30 feet away".

    Sounds measurements at more than 1 meter are a red flag.

    David
     
  20. sjsmithjr

    sjsmithjr In the Trades

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    To add to what David posted, you should also take your measurements using the Decibel A filter; dbC is typically only used to measure very high SPLs.

    FWIW, they even had a discussion of tankless technology on the Sound&Vision forum, where Ladiesman271 is equally well loved...

    But wait, Laddiesman271's knowledge base doesn't stop at plumbing and home audio, he also does HVAC. Here's what one professional member had to say about him over on hvac-talk.com: "This loud mouth ain't even a tech and hes giving hvac advice. I checked all his posts and his claim to fame is just putting links to HVAC source information. No solid input of any other kind." It's worth signing up just to check out his posts!

    I don't feel so special anymore...
     
    Last edited: Feb 13, 2009
  21. sjsmithjr

    sjsmithjr In the Trades

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    If you could demonstrate that you actually know what you're talking about I would.

    The A weighting curve approximates human frequency response at low to moderate SPLs. dbC would be appropriate if the SPLs were over 100dB.
     

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