Water heater efficiency?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Vitaliy, Sep 12, 2005.

  1. Vitaliy

    Vitaliy New Member

    Messages:
    73
    Location:
    Massachusetts
    Hi Everybody,

    Well, price for all energy sources is going up.
    What would be the more efficient way to run water heater?
    1. Decrease hot water temperature to acceptable minimum.
    Assuming recovery time is also acceptable and heater will
    be able to provide enough hot enough water.
    This way heat loss will be minimal during the time when
    there is no water use at all (most of the day time, except for
    weekends and holidays and night time) but heater will be
    running all the time when water is actually used.
    2. Increase hot water temperature to the allowed limit.
    In this case temperature control mixing valve must be installed.
    This approach will minimize hot water usage and heater run time
    should be less (I am not sure about this?) but heat loss will
    be higher due to the grater temperature difference.

    Theoretically (in ideal world without losses) there will not be any
    difference at all. But in our real life it must be a difference.

    What do you think?

    Thank you,

    - Vitaliy
  2. Take shorter showers, less baths, use a water heater blanket to minimize heat loss and insulate the first 8 feet of the incoming cold, the entire hot side water lines. Wash hands with cold water instead of warm. You lose a great deal of temperature loss running water till it gets comfortable.
  3. Kristi

    Kristi Tradesman Plumber

    Messages:
    176
    Location:
    Vancouver, BC
    ... and check out tankless/instantaneous water heaters... you only heat what you are actually using rather than storing and maintaining your heated water every hour of every day, year after year.
  4. Vitaliy

    Vitaliy New Member

    Messages:
    73
    Location:
    Massachusetts
    Hi Guys,

    Well, you missed my point.
    I am very happy with my current indirect water heater
    and I am not going to replace it. Heater itself and all
    related pipes are very well insulated.
    My question was:
    What is more efficient way to run this heater:
    i.e. temperature setting should be as low as possible
    or as high as possible?

    Thank you,

    - Vitaliy
  5. efficinecy

    probably the best setting for one is
    low to med whichever you find comfortable...

    another suggestion is to install shower restrictors
    to slow the flow down....

    everything else sounds like it has
    been covered already by others.
  6. Vitaliy

    Vitaliy New Member

    Messages:
    73
    Location:
    Massachusetts
    Hi Mark,

    Thank you for the answer.
    This is actually my current setting and this is what I expected too.

    - Vitaliy
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,251
    Location:
    Cave Creek, Arizona
    setting

    Besides efficiency you should consider functionality. If the heater is set at 110, for example, you would use only hot water for a shower, which would give you about 15 gallons of water before it started cooling off, and there would be no way to increase the temperature back to a comfortable setting. Set at 130 degrees, you would mix a considerable amount of cold water with it to attain 110 degrees, so that same shower with the same flow from the shower head will now give you 25 or more gallons of showering water, and when it starts to cool down, you can reduce the cold water to maintain the temperature for a longer period. If you feel the exterior of a water heater you will realize that it is relatively cool, so it is not losing temperature at a "wholesale" rate.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,316
    Location:
    New England
    One indirect tank I looked at was speced at 1 degree per hour standby loss at "normal" ambient room temperatures. If it held 40 gallons, that's about 320 pounds or about 320 btu/hour standby loss. Say your boiler is 75% efficient (low by today's standards), you'd need 400 btu to reheat that water to the set point (probably wouldn't happen until it got much lower, though). Not much at all.
  9. Vitaliy

    Vitaliy New Member

    Messages:
    73
    Location:
    Massachusetts
    Hi Guys,

    My heating system consist of Burnhum V73 oil fired boiler
    (1.05GPH, 121MBH, 82.2%AFUE) and 40 gallons indirect
    Superstore water heater with 1/2F/H temperature drop.
    Thermostat is located in the middle (by height) and set to 150F.
    At the hot water outlet temperature must be higher but I don’t
    know by how much. System is running very well. Boiler fires
    once a day (occasionally twice) and runs about 20min. We are
    very comfortable to use two showers simultaneously.
    Each shower has pressure balanced faucet so flushing toilets
    does not create temperature discomfort.
    Looks like my system is very well tuned.
    Should I try to lower temperature to 130F as HJ suggested
    or it is better not to touch things at all and leave it “as is�

    Thank you,

    - Vitaliy
  10. only if you want troubles

    if it is working good and everything is
    well tuned,

    especially with the "more special system" you got

    I would say leave it alone unless you are

    really into abuseing yourself...
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