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Thread: water very hot even on vacation setting

  1. #1
    DIY Junior Member Mark111's Avatar
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    Default water very hot even on vacation setting

    I had a new gas water heater installed about 6 months ago, Lochnivar LTN040G. This is at a house that is only being used about half the year. I turned the thermostat down to Vacation when no one was living there, but noticed that the water at the tap is still very hot (It hurts to even put my hand under it for less than a second). The plumber who installed it came right out and changed the gas valve in case that was the problem. It still gets very hot. If I fill the tub for example, and use all the hot water in the tank, the burner doesn't come on if on Vacation setting. A day or two later, the water is very hot again. If I set the thermostat to a medium temperature, the thermostat seems to work properly if the hot water is being used daily. If I leave it unused for a day or two, again it gets too hot.

    We have a 2 year-old and I am concerned with the water at the tap being so hot. Is it possible that the pilot alone is able to heat up the water so much? Is this normal behavior? I used to have a heater that kept the water relatively cool on the vacation setting and thought this was normal.

    Thanks,

    Mark

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    No, a pilot light cannot heat a WH to excessive temps. Where I live, they require all WH to have a tempering valve...you may want to consider adding one. This is adjustable, and adds cold water, if required, so the WH output never exceeds that setting. Normally, it is set to 119-120 degrees, or so. This is still hot, but at the upper end of safe. If it can be done easily, sometimes people will run untempered water to the dishwasher. This is especially important if the thing doesn't have a water heater built-in as they just don't work well with cooler water.

    It sounds like the thermostat is messed up. Or, it could be as simple as the sensor is loose or not inserted properly into its sensing well.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Junior Member Mark111's Avatar
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    Thanks. I recently installed a honeywell tempering valve on my other water heater (different house) and it works very well.

    This is the second thermostat for this heater and it still has the problem. The unusual thing is that when the thermostat is on Vacation setting and the tank fills with cold water after using all the hot, I never see the burner light up. At least not for about 30 minutes of watching for it to come on. A few days later, it is extremely hot again. Once the tank heats up, if I turn the thermostat all the way up to the maximum setting, the burner lights. The thermostat seems to be clicking on/off correctly.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    Check the manual and find out where the sensor is. Make sure it is where it is supposed to be. there may be a check procudure for it - this is often a resistance check which should vary by temperature.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    In the trades Dana's Avatar
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    Is there any reason you don't just turn off the gas to the unit rather than monkeying around with "vacation" mode when you take off? As long as it's working OK at an operational temp setting you should be fine. (I usually just set & forget the temp on vacation propery HW heaters, kill the power/fuel to it for non-use periods.)

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    DIY Junior Member Mark111's Avatar
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    I suppose I could just shut off the gas when no one is there.

    It is a brand new heater and I want to make sure that it is working correctly. I can't figure out why it is getting hot when the thermostat is turned all the way down. I just checked it today after letting it cool yesterday and it took about 12 hours to get to almost 90 degrees, 24 hours later it is very hot again. I pretty sure the main burner is not doing this. Is it possible the pilot can make enought heat to heat up the tank? This is the second thermostat/gas valve and it behaves the same way.

  7. #7
    In the trades Dana's Avatar
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    Quote Originally Posted by Mark111 View Post
    I suppose I could just shut off the gas when no one is there.

    It is a brand new heater and I want to make sure that it is working correctly. I can't figure out why it is getting hot when the thermostat is turned all the way down. I just checked it today after letting it cool yesterday and it took about 12 hours to get to almost 90 degrees, 24 hours later it is very hot again. I pretty sure the main burner is not doing this. Is it possible the pilot can make enought heat to heat up the tank? This is the second thermostat/gas valve and it behaves the same way.
    There's absolutely no way the pilot light could heat the tank to scalding levels, but if the flue is restricted at the top of the tank it can bring it up to over 110F over the course just idling over a day or so. A restriction that severe would also interfere with it's normal operation though.

    It's good practice to turn off the gas & water inputs (and power) to non-essential systems when leaving a place empty for weeks/months. A small water leak can grow into a big leak, gas leaks undetected can be lit off by standing pilots and blow the place sky high, corrosion/drips/squirrels/hurricane-damage can cause electrical fires, etc. Turning off the main gas & water valves and throwing some breakers is cheap insurance against avoidable floods, fires & explosions.

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