American Chillers and Cooling Tower Systems

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Can You Convert Your Hot Tub or Spa into a Cold Plunge Pool?

Cold Plunge Chiller 🕔May 7, 2019

Can You Convert Your Hot Tub or Spa into a Cold Plunge Pool?

Cold water therapy used to be only common in professional sports and division one college athletics. With the more widespread belief that bathing in cold water not only reduces swelling and helps achy joints feel better, but by getting the blood flowing, it may also increase energy levels, speed healing and aid in weight loss. With people like Tony Robbins promoting the positive health effects of cold water therapy, we are getting more and more calls by homeowners interested in cold plunge chillers.

With more calls from homeowners, the question often arises about what type of tub to use. So, Can you convert your hot tub or spa into a cold plunge pool? Yes, you can convert your hot tub or spa into a cold plunge pool by plumbing in the chilled water supply and return water lines from the chiller into your spa.

Spa Pump

You will use your same spa pump to circulate the water through the chiller (the chiller will not run without flow). Have your pool contractor change the settings on the controller so that the pump will run without the heater. Depending on the chiller you purchase, the average flow rate through the chiller is 3 GPM / ton of refrigeration. If the spa pump is sized for more flow, then you will want to run a side stream installation (bypass) so the chiller flow can be throttled back. You also want to make sure any filtering is done before the chiller and any water treatment process is done after the chiller. We don’t want to hit the chiller heat exchanger with a large concentration of chemicals or other treatment. Doing so will cause the heat exchanger to fail prematurely.

Temperature Control

The temperature of the cold plunge will be determined by the owner of the spa. In most cold plunge pool settings that are for therapy purposes (achy joints, reduced swelling, etc.), the typical desired water temperature is between 45F degrees and 55F degrees, although temperatures above and below are also requested. The chiller will be equipped with a temperature controller.

What Size Chiller to Buy?

There are a number of factors to consider when sizing a chiller for a cold plunge pool. I have a sizing chart available by clicking on this link that gives you some general information on the chiller sized required. If you would like American Chillers to help you size your cold plunge chiller, please send an email with your contact information to and we will gladly assist you.

Can the Chiller be Controlled by Your Pool Controller?

Can the chiller be controlled by your pool controller? Yes, for sites that have swimming pools that already have a PLC type pool control system, the chiller in many cases can be connected. There are different ways of connecting the chiller to your pool controller, but one of the easiest is to preset the chiller controller to the desired water temperature, like 50F degrees, then use the pool control system to turn the chiller on/off as desired. Contact American Chillers Engineering and your pool professional for more information about connecting the chiller to your system.

Is the Chiller Suitable for Outdoor Operation?

Yes, American Chillers are built to be installed outdoors in the elements similar to an air-conditioning condensing unit and in general, is the best place to install the chiller because it keeps the heat that has been removed from the water outdoors – not in the house.

Areas that Freeze in Winter

If you live in an area that freezes during the winter and plan on using your chiller year around, then you will have to decide on whether to install the chiller indoors or outdoors or to split the chiller as the water in the system will freeze.

Indoor Installation

Installing the chiller indoors does remove the risk of freezing the water due to cold winter temperatures, but created another issue of heat. The heat being removed from the water will be rejected to the air. It needs to be removed from the air around the chiller so that the temperature in the room does not continue to heat up until the chiller is no longer able to operate. In general, the CFM of the chiller will be approximately 1,000 CFM per ton (or horsepower) of the chiller.

Outdoor Installation

Installing the chiller outdoors eliminates having to remove the heat from indoors, but now is at risk of freezing during the cold winter months. If you live in an area that doesn’t freeze, then this is not an issue for you. If you are not using the chiller in the winter, then it needs to be properly winterized by blowing out the lines.

Winterization Methods

If all water is not removed or you are not sure if all of the water is removed from the system, you may want to run a little glycol through the system. Another method is to heat trace (with heat tape) all of the water piping and heat exchanger. This can be risky. If the heat tracing loses power on a cold day, your chiller may be damage beyond repair not to mention the broken piping between the chiller and your tub. Finally, you can use the spa heater to heat the water in the system to keep it above freezing. Keep in mind, the temperature probe needs to be on the water in the chiller – not the water in the tub and your pump will need to circulate nearly all of the time when the temperature is below freezing.

Splitting the Chiller

Another excellent option for areas that freeze is to split the chiller. By splitting your pool chiller, we mean that the condenser or condensing unit will remain outdoors and the water side heat exchanger be installed indoors. This works to keep the water from freezing while keeping the hot air outdoors. The biggest consideration with splitting the chiller is distance (mostly vertical distance) between the indoor and outdoor units. A long distance or having to go up a couple of stories can create refrigerant challenges so always communicate with your salesperson when planning on purchasing a split chiller.

For more information please contact us; or 803-822-3860.