Using a wood fired hot tub heater in Winter

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Can you use a wood fired hot tub heater in the winter? The answer is yes, however precautions must be taken so that the system does not freeze. A winter hot tub is one of the most enjoyable experiences as the body is submersed in hot water while the crisp winter air surrounds us. The Nordic culture is famous for its hot outdoor pools and hot tubs. A hot tub after a good winter sport such as alpine skiing helps to ease the sore muscles and a great part of any winter sport.

Heating a hot tub in the winter has two elements that need to be considered. The first is that the starting temperature of the water is colder than in the summer and will require more time to bring the hot tub up to operating temperature. The second part is that there is a change the heater may freeze when turned off. To use a wood fired hot tub in the winter you will need to spend a little more time watching your heater and feeding it wood. When the tub reaches operating temperature you will want to keep a low fire going or a bed of coals to keep the heater producing a minimum amount of heat. This will be determined by the outside temperature as to how much of a fire you need, the colder it is outside the quicker the hot tub will lose its heat. Finding the right balance where the amount of energy going into the hot tub is equal to the energy loss is something that comes from experience. No one likes a cold hot tub and at the same time too hot of water means you will only be able to experience a short soak before your body over heats.

In most cases the recommended water temperature is between 102 and 104 F. In fact in all electric hot tubs made in North America, the max regulated temperature for safety purposes is 104 F. Wood fired heaters can get much hotter than that so caution is needed as temperatures over 104 F can be a health risk.

Preventing the heater from freezing – Our heaters are great for any season however in the winter you must take care to avoid a chance of freezing. This means that when you are done hot tubing you need to either drain the tub or use port plugs or valves to isolate the heater and drain the heater. Generally a warm insulated hot tub can keep its temperature for days before it would eventually freeze. However there is no insulation on the heater and as such it will lose its heat energy quickly and could freeze. If you plan to use a hot tub over a period of days, then after each use you should:

  1. Ensure the fire is 100% extinguished
  2. Isolate the heater from the tub with port plugs or gate valves
  3. Drain the heater
  4. When you go back to heat the tub the next day you many only need a short fire to bring the tub back to operating temperature.
  5. DON’T FORGET TO REMOVE THE PLUGS OR OPEN VALVES PRIOR TO STARTING A FIRE

Aux Heater – A back up electric heater can be added to the hot tub to keep the unit from freezing. We use Balboa EFX Heaters that are small 1.5 Kw inline heaters. Generally these will not keep a hot tub at operating temperature during the winter but will stop the system from freezing. They are a great accessory for those that want to do lots of winter hot tubing with a wood fired heater!

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