Tankless Water Heater Problems

Discussion in 'Tankless Water Heater Forum' started by BlackDogKurt, Sep 1, 2009.

  1. BlackDogKurt

    BlackDogKurt New Member

    Messages:
    1
    We are the second owners of a 9-year old house with an oil burner furnace and baseboard heating. There is no water heater tank and the hot water is heated by the oil burner furnace.

    In 2007, we had to replace the power vent blower motor, which cost us over $900 with labor. The repairman said that the motor probably wore out faster than normal because of the fact that it was running so frequently and year round, every time water was heated. He suggested that we might want to consider switching to a tanked water heater since he could not guarantee how long the new motor would last.

    This year, the transformer on the furnace needed to be replaced, which cost a few hundred more. In addition, we have found that the water does not get hot enough in the winter if more than one of the three heat zones in the house is heating at the same time. We were leaning to live with this inconvenience (I assume our tankless water heater is undersized…???), but now, in the past few months, the temperature of the hot water suddenly does not get very warm ever, and it is not even winter yet. I am afraid that there is something new now wrong.

    Having now spent over $1,000 on the boiler in the past few years, and being wary of the power vent blower motor going again in the next few years, and now with the new problems with the hot water, I am seriously wondering if it does make sense to switch to a tanked water heater to reduce the wear on the boiler parts.

    I know that tankless water heaters are more efficient overall, but I am afraid that in our case, it is becoming a major money pit. As I am previously unfamiliar with tankless water heaters, I am looking for other opinions or suggestions before making a decision though.

    Thanks!
  2. Dana

    Dana In the trades

    Messages:
    2,783
    Location:
    01609
    You have in internal coil on the boiler for the HW which is probably limed up a bit making it VERY inefficient, and the boiler is probably firing on every zone call, compounding the wear & tear and cutting into the efficiency as well.

    For the about the same installed price as a tankless you can kill several birds with one stone and reconfigure the heating zones to run of a "reverse-indirect" tank like the TurboMax, or ErgoMax, or Everhot EA series, which are essentially a heating-system buffer tanks with internal heat exchangers for the domestic hot water. By slaving the boiler to serve the tank-only and letting the zones sip off the tank as-needed, getting the DHW through the internal heat exchanger in the tank it minimizes the number boiler firings, and guarantees a minimum burn length for the boiler, increasing it's operational efficiency by double-digit percentages(!).

    Configured this way it basically CAN'T short cycle, since at a minimum it needs to heat up the mass of the water in the tank by the hysteresis designed into the tank's aquastat (usually 8-12 degrees F). This is several times the mass of the water in the boiler itself.

    See: http://www.ergomax.com/New-Tanks.htm

    http://www.tfi-everhot.com/pdfs/TFI_EAseries.pdf

    http://www.thermo2000.com/pdf/en-US/manu/turbomax.pdf

    Another advantage to this approach is that you can run the baseboard temps at almost arbitrarily low temperature (whatever you set the tank temp to), which lowers the distribution losses in the heating system (usually good for ~3% fuel savings for every 10F you can drop the temp). If you've tightened up & insulated the place since the heating system was first installed, it could be that you'll could drop the baseboard temps from 170-180F to 140-150F without getting cold, providing a more even temperature & greater comfort at lower operating cost.

    Even if the boiler craps out, you want to change fuels etc. the tank will last for decades (at much lower maintenance than a tankless), and it's not-sensitive to heating source- any boiler will do, and efficiency benefit will be similar with gas or propane fired boilers as well. They're not cheap, but it'll save wear & tear on the boiler with better annual efficiency than a tankless + boiler, or a boiler + priority-zoned indirect.
  3. flamefix

    flamefix New Member

    Messages:
    71
    Location:
    Exeter, England
    As Dana says from reading through the advice is a buffer store which distributes heat to either the heating or the hot water.

    Another method is to fit a 3 port zone valve or two two ports and direct the flow from heating to heating a coil in an indirect cylinder for hot water storage.
    Make sure you tie the return from the cylinder back into the pipe just beofre it goes into the boiler or you'll get reverse circulation in your system.

    Not knowing your boiler you may have a storage facility in the boiler or a straight plate heat exchanger on the boiler directly heating the cold water when demand is placed on it. The plate is probably limescaled or clogged. and replacement is advised although if limescale you could flush it and descale it.

    Interested to know a bit about the boiler as $900 for a new blower( I'm assuming just the motor that drives the fan to force the air into the burner and turn the oil pump) is wow strong money. Think I'll fly over and offer my services for a month then retire ;)

    $600 here would buy you a complete burner unit.. like this.
    http://www.rielloburners.co.uk/index.php?section=99&page=1185
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