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Does hot tub stop heating if it reaches certain temperature?

Does hot tub stop heating if it reaches certain temperature?

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  #1  
Old 11-02-16, 06:50 AM
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Does hot tub stop heating if it reaches certain temperature?

I have an old hot tub and I don't know what the model is but I was wondering if in general do hot tub auto shut off heating the water if it reaches a certain temperature or if it reaches the max temperature. Or, does it keep heating and heating until you manually dial down the temperature?
 
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  #2  
Old 11-02-16, 09:57 AM
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In the US most/all hot tubs have two thermostats. The main thermostat gets the most use and it cycles the heater on and off as needed to maintain the water at the desired temperature. The second safety or high limit thermostat is there in case the main thermostat fails and the heater sticks "on" or if the jets are left running continuously. When the water reaches a dangerous temperature, usually like 110-120f, it trips and in most cases all power is turned off.

Surprisingly I've seen the high limit kick more often due to the jets being left on and not a heater malfunction. It can easily happen with well insulated spas when the lid is closed. All that power from a 2 or 3hp jet pump moves the water, creating friction which results in heat. In an outdoor spa without insulation the heat can radiate away fast enough but a portable, well insulated spa just gets hotter and hotter until the high limit kicks in and kills power to everything.
 
  #3  
Old 11-02-16, 10:05 AM
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Thank you for the input. My hot tub is inside the house and also have a cover. So, I shouldn't worry too much as long as I don't turn on the jet for long periods of time, correct?
 
  #4  
Old 11-02-16, 12:01 PM
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Correct. Most spas have a timer on the jets but some also allow you to turn them on for as long as you want. Leaving it on with the cover closed is what can cause a problem. And, leaving them on with the cover off can also be a problem as it evaporates off water until the pump sucks air. Hard to believe but I've seen both problems. Usually though it's with the cover closed when someone thinks they hit the timer button and accidentally hit the manual on.
 
  #5  
Old 11-02-16, 12:27 PM
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Thanks, good to know. So, if when it trips and all power is off, will that ruin the system?
 
  #6  
Old 11-02-16, 04:40 PM
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Tripping of the high limit will not damage anything but if it trips something may already be broken. If nothing is damaged say by running the jets all day with the cover closed turning it off and letting it cool may not turn it back on. Many high limit switches have a manual reset button that must be depressed to reset the switch.
 
  #7  
Old 11-03-16, 05:05 AM
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Thank you so much for the help.
 
  #8  
Old 11-05-16, 07:15 AM
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I have one other questions. Okay, so the hot tub will automatically turn off the heater when it reaches the temperature. Will it automatically turn back on if when the water temperature drops?
 
  #9  
Old 11-05-16, 09:37 AM
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Yes, the heater will cycle on and off as needed to hold the water at the desired temperature. There is usually a window of about one degree when the heater turns on then off again which is normal. If it allows the temperature to swing much more than that it becomes more noticeable and could indicate that the thermostat needs to be checked or replaced.
 
  #10  
Old 11-05-16, 02:00 PM
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Again thank you so much for the help.
 
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