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Thread: lower temperature on hot tub while away?

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    lower temperature on hot tub while away?

    Would it be a good idea to lower the hot tub temperature if you're going to be away for 5 days?

    If so, lower it to it's lowest level?
    8,000 gallon, in ground, fiberglass pool with a cartridge filter.

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    Re: lower temperature on hot tub while away?

    I would not lower it and it has no advantage. As long as the cover is on it does not take much to maintain the heat. It will likely cost as much or more to bring it back up to temp. I was gone for 10 days and left mine set as is.
    Barrier Reef Pacific1-Pacific color 37'9" X 14'1" fiberglass IG ~ 17,500 gallons, FHPM1.0-2 Jandy FloPro pump, Jandy Aquapure 1400 SWG, Waterco Multicyclone 16 pre filter, Jandy CV580 filter, 3 PAL-2000 RU LED lights, 1 skimmer, 2 main drains, 3 returns, 2" rigid pvc suction and return plumbing, BBB method, TF100 Kit

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    BravoRomeo's Avatar
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    Re: lower temperature on hot tub while away?

    If that were true, it would mean in-ground spas should be kept hot all the time... Or that turning your house heat back for vacation wouldn't save energy. Every day you don't add energy to an energy-loosing system is money in your pocket.

    I did calculations on my tub and found that turning it down even for a long weekend away saved me about $2, and that accounts for the cost of heating it back up. Longer vacations save even more.

    Keep in mind that a hot tub is not perfectly insulated from the environment. It is always loosing heat. That is why your pump/heater has to come on periodically. The bigger the difference between the tub temperature and environmental temperature, the faster the heat escapes! Thus, turning the tub back saves energy in two ways: you aren't feeding the constant energy leak for the duration, and the cool tub looses less heat (until is finally reaches equilibrium). Heating the tub back up replaces the heat that was lost, but you still get to keep the money you saved by allowing the tub to be cooler.

    Downsides? You have to wait for the tub to heat back up, which may take several hours. If the power goes out for several days while you are away and it is below freezing out, a hotter tub lasts longer before freezing, but I would think it would take a major catastrophe and severe cold temps to be a problem.

    Upsides? You save money, and chlorine lasts longer at cooler temperatures. Before I switched to a SWCG, I would shock the tub to 14ppm and turn the temp down before leaving for a long weekend. When I got home, there would still be a decent residual. The $2 I saved paid for a cup of coffee at least.
    Spa: 2001 Hot Spring Jetsetter, 215 gallon Dichlor/Chlorine
    When I'm not soaking, I just might be flying!

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    Re: lower temperature on hot tub while away?

    I disagree. For a 5 day away period it makes no sense to turn the heat down.
    Barrier Reef Pacific1-Pacific color 37'9" X 14'1" fiberglass IG ~ 17,500 gallons, FHPM1.0-2 Jandy FloPro pump, Jandy Aquapure 1400 SWG, Waterco Multicyclone 16 pre filter, Jandy CV580 filter, 3 PAL-2000 RU LED lights, 1 skimmer, 2 main drains, 3 returns, 2" rigid pvc suction and return plumbing, BBB method, TF100 Kit

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    Re: lower temperature on hot tub while away?

    This is from my spas manual

    Electrical Power Efficiency
    Your new spa comes equipped with an electric heater.
    Following the directions listed below will ensure the
    most efficient operation:
    NOTE: This method is only for spa usage under two
    hours a week.
    Keep the spas operating temperature 5?F below
    the desired usage temperature when not in use.
    One or two hours before use, set the temperature
    to the desired temperature.
    If the spa usage exceeds two hours a week, the
    set temperature should remain at the desired
    usage temperature.
    Allowing the water temperature to lower more than
    10?F below the desired usage temperature and
    reheating it prior to usage will cause the heater to
    operate longer than it normally would maintaining
    the desired temperature. Doing this will increase your
    operating cost and makes your heater work more
    than necessary.
    -Kevin
    X-Pert Pool Service
    x-pertpool.com
    X-Pert Pool on Facebook and @XPertPoolServic on Twitter
    22,000 gal / 16' x 32' / Vinyl / Hayward s244t /Pentair SuperFlo 1 hp

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    Re: lower temperature on hot tub while away?

    Yup
    Barrier Reef Pacific1-Pacific color 37'9" X 14'1" fiberglass IG ~ 17,500 gallons, FHPM1.0-2 Jandy FloPro pump, Jandy Aquapure 1400 SWG, Waterco Multicyclone 16 pre filter, Jandy CV580 filter, 3 PAL-2000 RU LED lights, 1 skimmer, 2 main drains, 3 returns, 2" rigid pvc suction and return plumbing, BBB method, TF100 Kit

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    BravoRomeo's Avatar
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    Re: lower temperature on hot tub while away?

    Here are numbers from the last time I turned my tub down for a four day absence:

    Starting at 104F (weather in mid 40's with light and variable winds)
    Turned set point down to minimum (80F)
    When I got back, 96 hours later, my 215 gallon tub was at 87F
    That works out to about 36 kWh saved
    Heating the tub back up took about 8 hours, at 1500W, that is 12 kWh.

    I pay 8.5 cents per kWh, so that saved me $2.04. That number only increases the more days the tub is left without heat input. At some point the thermostat would kick in at 80F to maintain that, but again, less heat is lost to the environment at lower temperature differences. Also, the 24hr circulation pump throws this off a bit... That is 70W, but that also ultimately ended up as waste heat in the water. In the summer, HS tubs have a summer mode which disables the circ pump for 8 hours a day, allowing me to save a nickel a day.

    These may not sound like impressive savings, but in this modern world we have lots of little things that nickel and dime us and add up to hundreds, if not thousands of dollars a year. I make the relatively small effort to reduce recurring expenses like that when it doesn't impact me much... $2 saved say 25 times a year is $50. Easy. That is a nice dinner out!

    I should add a couple, er, number of things here:

    1) when in doubt, always follow the recommendations in your tub's manual

    2) your mileage may vary... I have a very well insulated tub, moderate weather, and inexpensive electric rates.

    3) I use a conversion factor of 2.44 to derive Watt-hours saved per gallon per degree of temperature drop (Fahrenheit) per day. Multiply times 1000 for kWh. I came up with that one day crunching number of BTU and raising temperature of one pound of water, etc, etc. So far my logs pass the sanity test and match up with what I observe on my power usage meter.

    4) Check out WattVision and The Energy Detective for ways your can monitor your home electricity consumption. I use WattVision which seems to work well enough for this purpose. TED looks more sophisticated, but required space in the panel for installation, which I don't have enough of. Even cheaper and just as effective is to learn to read your electric meter and track kWh over time. You can do pretty darn well with just keeping a simple log or spreadsheet.

    5) I could be wrong. Wear safety glasses.

    [edited to correct units]
    Spa: 2001 Hot Spring Jetsetter, 215 gallon Dichlor/Chlorine
    When I'm not soaking, I just might be flying!

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    Re: lower temperature on hot tub while away?

    Quote Originally Posted by X-PertPool
    Allowing the water temperature to lower more than
    10?F below the desired usage temperature and
    reheating it prior to usage will cause the heater to
    operate longer than it normally would maintaining
    the desired temperature. Doing this will increase your
    operating cost and makes your heater work more
    than necessary.
    This part from the spa owner' manual is just plain bunk. Maintaining a higher temperature always takes more energy than letting it cool down to a lower temperature and maintaining that lower temperature and then later on heating it back up. The reason is that at the lower temperature there is slower heat loss so less energy to maintain it. Now the difference may not be very much unless the time at the lower temperature is reasonably long but the above quoted statement is just plain wrong.

    Imagine the extreme case of stopping heating it at all and letting it drop to the ambient temperature for years and then deciding to heat it back up. Are they seriously wanting us to believe that maintaining a temperature 10F below the desired temperature the entire time uses less energy? This just proves that one cannot believe everything that a spa manufacturer says.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: lower temperature on hot tub while away?

    Although my specific hot tub has various time settings. It can not heat when the pumps are running in high speed (unless you switch a jumper). Maybe this has something to do with it. For instance it has to run the filter pump to heat the water so if it's below 10 degrees the pump would keep itself on until it reaches the desired temp. Maybe they are taking this into account. It's highly customizable, allowing you to only heat when pumps are running and vice versa. Personally I just leave it the my desired temp since I don't plan out using the tub hours in advance so if I did keep it low it wouldn't be hot when I wanted to use it.
    -Kevin
    X-Pert Pool Service
    x-pertpool.com
    X-Pert Pool on Facebook and @XPertPoolServic on Twitter
    22,000 gal / 16' x 32' / Vinyl / Hayward s244t /Pentair SuperFlo 1 hp

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