Tankless water heater ??
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Thread: Tankless water heater ??

  1. #1
    Join Date
    Sep 2008

    Default Tankless water heater ??

    Does anyone have any experience with tankless water heaters ? Good, bad, no, yes, gas, electric, economical to operate, practical for a home or just small office. Thanks for any advice.

  2. #2
    Join Date
    Jul 2000
    Eureka Springs, AR


    We have had a whole house on demand tankless water heater for 10-12 years. Works great. We love our Bosch unit.First one lasted 10 years. We use propane out here in the country.

  3. #3
    Join Date
    Mar 2008
    Eureka Springs (S of town)


    Bean Counter--

    We have had a tankless propane whole house on-demand system since moving into our house in January, 2008 and are very happy with the concept.

    A key factor, based on our experience, is the quality of the system. We originally installed a Richmond system I bought at a big-box outfit (Menards). Within 2 years it started having problems—oxygen sensor falsely shut the unit down, claiming low oxygen. The tech folks said to sand the end of the sensor probe. I did that several times over the next 18 months and finally decided to just replace the probe. No luck—they said it was an obsolete unit and they no longer carried parts for it—less than 4 years after the unit was built—and it was one of the first units of that model, S/N under 100.

    So we replaced it with a Rennai propane unit. We have been very happy with it. The only catch was that it had to be installed by a Rennai dealer (plumber) in order to get the 11 year warranty.. I called the only dealer in Rogers and the quote was even more outlandish than the purchase price on Amazon. When I told the dealer (North Star Plumbing) what I could buy it for on Amazon, he said “I can't even buy it for that. Tell you what—you buy it from Amazon and I'll install it.” His installation was very reasonable—it was basically a cut and paste job since the plumbing was already in place from the original unit.

    You probably already know this, but the key things to keep in mind:

    1. The higher the BTU rating, the more water you can heat continuously.
    2. The minimum turn-on flow rate is the amount of flow you need in order to get the burner to fire when you start using hot water. If you turn on a faucet at less than that rate, the burner will not fire and cold water goes through the unit unheated and is sent into the hot water pipe.
    3. The minimum continuation flow rate is the amount of flow necessary to keep the unit burning. This is typically lower than the turn-on rate.
    4. It can keep on making hot water indefinitely. If you need 50,000 gallons of hot water, it will make it. (This about the amount my daughters used per shower during their teen years. It's genetic.)
    5. As with storage hot water heaters, scale can occur, and it is much worse with hard water than soft. We run soft water and I do a simple de-scaling about every 18 months.

    The trick, if you only need a small flow of hot water, is to become used to turning on the hot water at a high flow rate (to get the unit to start heating) and then back it off. If you have water going through the heater but the burner is off you get what is referred to as a “cold water sandwich”. Example: at the bathroom sink prior to your shower, you turn on the hot water at a pretty good clip, but then back it off to just a trickle, under the minimum. Then the heater will shut off and the pipe will have a bunch of nice, hot water followed by a slug of cold water. This makes for a very unpleasant surprise when you step into the shower. All seems fine until the slug of cold water arrives. This concern applies to propane/nat gas units, but not to electric, AFAIK.

    Because we never used a standard storage water heater in this house I have no cost comparison. We use propane in our water heater, but also for the stove, grill, fireplaces, and clothes dryer so I can't effectively separate out the water heating costs. However, the basic math is: propane cost per 100,000 BTU, at today's price, $1.50/gal, is about $1.64; and Carroll Electric, $.087/kwhr, is about $2.56 (both numbers pre sales tax). Propane cost, of course, varies tremendously seasonally, and also the net cost will be affected by the efficiency of the heater you choose.

    Hope this helps.

    "Knowledge is good." --John Faber: Philosopher, Educator, Founder of Faber College (Animal House)


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