Sizing A Swimming Pool Heat Pump
Pool heat pumps are typically matched to the number of gallons in your pool. If you dont know or arent sure how many gallons you have, measure your pool, and use this pool volume calculator tool.
Some heat pump manufacturers dont list the gallons, but list their heaters in terms of the BTU output. Most models are in the range of 50K BTUs to 125K BTUs.
50K BTU heat pumps are meant for small pools, or aboveground pools, under 12,000 gallons. It will work on larger pools, but heating will be slow and total temperature rise may not be what you desire.
Youll need to consider pool size and the desired temperature change when selecting a heat pump for your swimming pool. Other factors such as the average air temperature, humidity and wind speeds will also influence a heat pumps ability to warm the pool water. Figuring on a temperature increase of 1-1.25 degrees per hour, you can use the following equation to get an approximate heat pump BTU requirement:
x x 12 =
For example, well use a rectangular pool 14 ft. wide by 28 ft. long. During the coldest month of use, the pool owner wants to increase the water temperature by around 20 degrees Fahrenheit.
x 20 x 12 = 94,000+ BTU
If you happen to know the volume of your pool in gallons, you can also follow this general guideline for heat pump BTUs:
|25,000 gal.||140,000 BTU|
How To Calculate The Volume Of Your Pool
To calculate the volume in cubic feet you multiply the surface area by the average depth.
example : 800 x 3 = 2400 cubic feet.
Convert to gallons
Volume = 7.5 x the calculated pool volume.
7.5 is a constant used to covert the volume to gallons. )
Using our example of a square pool: 7.5 x = 18,000 Gal.
Calculate the BTUs required
For these calculations, lets consider an outdoor pool of 40 x 20 with an average depth of 3. We want to heat it from 60°F to 80°F in about 48 hours while the outside air temperature is 60°F. The wind speed is moderate. We will calculate the total required heat to increase and maintain the temperature:
First, we calculate the BTUs needed to heat the pool to the desired temperature . Next, we estimate the BTUs that are used to contain the temperature losses due to evaporation .
Total BTU = Heat up BTU + Surface BTU
Total BTU = Total heat load in BTU/hr.
Surface BTU = Heat loss from the pool through the surface mainly through evaporation of water in BTU/hr.ef
Heat up BTU = Heat load required to increase the pool temperature
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To heat the pool from cold
To heat one gallon of water by 1°F, you need 8.34 BTU. Therefore:
Heat up BTU = 8.34 x Volume x dTw ÷ H time
dTw = difference between the initial temperature and the final temperature of the pool water
H time = Time to heat the pool we use 48 hours, but a longer period will enable us to use a smaller unit
e.g. 5 x x = 80000
How Exactly Does A Pool Heat Pump Work
So how exactly does a pool heat pump transfer that heat? It simply uses electricity to pull in warm air from its surroundings, and then moves that heat to the water itself.
Not satisfied with that explanation? Were about to get technical. If youre not interested and want to move to the next section, I wont judge you.
Heres the advanced, step-by-step explanation of how a pool heat pump works. If youre ready to read on, buckle in:
1. First, the pool heat pump pulls in water from the pool. The heat pump itself contains freon, which is a colorless liquid used as a refrigerant. Chances are you have freons in your air conditioning, too.
2. Next, the pool heat pump compresses the freon until it reaches a temperature about 200 degrees Fahrenheit, 93 degrees Celsius.
3. The freon then passes from the high-pressure zone of the heat pump into the low-pressure zone. Once the freons pressure is released, it turns into a hot gas.
4. Meanwhile, the pool heat pumps fan pulls in warm ambient air, which flows over a set of evaporator coils. The hotter the temperature of this air, the more heat the evaporator coils will absorb from the freon gas in this next step.
5. Next, the freon gas flows through the evaporator coils, which cools the gas. During this process, the gas transfers its heat to the water circulating through the heat pump, which is then returned to the pool.
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Swimming Habits Vs Swimming Pool Heat Pump
Your swimming pool habits won’t necessarily impact the size of the heat pump, but they will influence the heating speed needed. Stronger heat pumps will naturally have a much better ability at quickly heating a pool. Even if you live in a warm environment, you might choose to purchase a strong heat pump to accommodate your constant use of the pool. That said, heat pumps are designed to provide resilient and reliable heating in a wide range of climates, so a standard-sized heat pump should suffice.
How Often Should I Heat My Pool
This is all down to your preference really. Again though, it should also influence the type of pool heat pump system you buy. If you are planning on heating your pool infrequently, then you want something that will heat up fast. If you need to keep the temperature at a constant heat, then a gas system might be preferable as it slowly heats the water.
Again, if you are looking to heat it slowly then a smaller heat pump might suffice, but if you only plan on using it a couple of evenings a week, then a larger pump that heats quickly might be best.
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I Have An Existing Gas Boiler Should I Replace It With A Heat Pump Or Keep The Gas Boiler As Well
If you have an existing heater , then we recommend that you install the heat pump alongside your existing heater.
This will allow you to run both the heat pump and the existingheater if required for a rapid pool heat up, or to provide a backupheater in case the heat pump develops a fault . You can alsoswitch to your existing heater when the air temperature becomes too coldfor the heat pump to operate efficiently eg right at the end of theseason.
If you want to install the heat pump alongside your existing heater,then the water should flow through the heat pump and then the existingheater before returning to the pool for maximum efficiency
Calculation Of Sizing A Heat Pump
Believe it or not, youre half done with the sizing stuff. Now, for ensuring accuracy, you just have to use some mathematical formula. Follow these steps:
Note the average temperature of the coldest time of the year. Suppose, you live in Florida, Hence, the average temperature of the swimming season is 60 degrees.
Now, do the quick math, subtract the average temperature from the target temperature.
From above, Target temperature-the average temperature= degrees
So, the temperature increase number is 20 degrees.
Length x Width= Surface area= ft= 450sqft
Temperature increases x Pool surface area x 12= BTUs=20 x 450 x 12= 108,000 BTUs
You are done! If you calculate like this example, if a heat pump size is 108,000BTUs or more, its a good fit.
Now, know something else for having a better idea about your heat pump.
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How Should I Wire My Pool Heat Pump
I am wiring a new heat pump 50,000 btu, 208-230v ~60 hz. Plaque says 12a running current, minimum 20a circuit, max 30a.
My breaker panel for the pump is a sub panel running off the main with a 60a breaker. It currently only has a 20a circuit for the shed with one light, and one 115v receptacle, a 20a circuit for a pool light with GFI, and a 20a for the pump.
During electrician install, we asked for enough capacity to add a heater some day.
Are we good to add a 20 or 30a breaker for the new heat pump?
Am I good to just go with a double 20a with 12 gauge thn wire in a whip?
Looks like inside I’m just connecting the black and red to power and green ground. No white right? I have bare 8 awg copper to bond to the pump connector. Anything I’m missing?
Will It Damage My Heat Pump To Put It Outdoors
No, all of our heat pumps are designed to go outdoors and are weatherproof.
They will operate perfectly well in all weather conditions including heavy rain and wind etc.
We recommend that you cover your heat pump with one of our speciallydesigned winter covers during winter when the heat pump is not in use.This will give your heat pump some additional protection against theweather.
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How Long Will The Heat Pump Run For Each Day
Just like the boiler in your house, the heat pump will run for different amounts of time each day depending on the weather.
On warm summer days when the pool is up to temperature, the heat pumpmay not need to run at all. Whereas on cooler days, the heat pump mayrun for a few hours.
In extremely cold weather the heat pump may need to run for 12 hours a day or more.
When you keep a solar cover on your pool, this will give the pool some heat gain on warm days and will supplement the heat pump.
As the weather gets colder the heat pump will need to run for longer.
You can control how long the heat pump runs for each day by using a time-clock on your pool pump.
Other factors that affect how long the heat pump will run for each day include:-
- The power of the heat pump a more powerful heat pump will heat thepool more quickly and so will switch off sooner than a smaller heatpump
- How well insulated your pool is
- If you have a high water table around your pool, then this willdrain away the pool heat and cause your heat pump to run for longer toreplace the lost heat
- The pool water temperature that you require a higher pool watertemperature will need the heat pump to run for longer to maintain thetemperature
- Pool cover an uncovered pool will lose 2-3 times as much heat as a covered pool
As a guide, on warm summer days the heat pump would typically run for between 0-3 hours
The Size Of Your Pool
It probably comes as no surprise that your pools size is a key consideration when it comes to heating efficiency. A small or weak heater will take much longer to heat a large pool than a high-capacity heater.
A general rule of thumb is that you should increase your pool heater size by 50,000 British thermal units for every 5,000 to 10,000 gallons of water your pool holds. If you live in a cold climate, you may need to increase that to 100,000 BTU.
Make sure to ready my article on what size pool heater you need to figure out the right size for your pool.
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How To Properly Size A Pool Heat Pump
Heating or warming up a swimming pool with a pool heat pump is different from heating or warming it up with a traditional pool heater. What are traditional pool heaters? These are your electric pool heaters and heaters that use natural gas. The main difference for these types of heaters is that with your traditional pool heaters, theyre actually actively producing heat to warm up your pool, which is why their output is measured by BTUs . Pool heat pumps on the other hand simply transfer the heat from the air to your water, so computations and numbers like BTUs can be a little bit off as it is directly affected by the temperature of the air. The colder the air surrounding your heat pump, the less heat is being transferred to the water and vice versa.
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A common question that consumers ask us when shopping for swimming pool heat pumps is: How big does my heat pump need to be? You should have a trained swimming pool professional size your swimming pool heat pump, as its size will depend on many factors. There are, however, general formulas we provide to our customers to approximate heat pump size. We explain how to use these formulas in this article.
Heat pumps are sized according to required BTU per hour of the swimming pool. Consumer often make the mistake of purchasing under-sized units units with insufficient BTU output per hour. Under-sized units must run longer in order to heat swimming pools. These longer run times translate to decreased efficiency and higher operating costs. Use the following instructions to approximate the BTUs per hour your heat pump will require.
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Calculate Your Surface Area
When you are determining which size pool heater to buy, the first step is calculating your pools surface area. A lot of pool owners assume that you use your pools gallon size to determine your heater size. In fact, there are some websites that DO use the number of gallons. If you have a pool with a large surface area, the heat has more space to escape and subsequently, more water to heat. As a result, the heater needs to be large enough to compensate for surface area and the pool size.
To calculate the surface area of your pool, multiply the length times the width.
For example: If your pool is 15 x 30, then your surface area is 450 square feet.
Related:Pool volume calculator.
What Is The Difference Between The Digital And Analogue Models
Analogue units use a simple knob to set the required temperature whereas digital models have a digital panel where you set the required temperature.
Once the required temperature is set on either types, the heat pump will then automatically maintain the pool at the required temperature.
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What Is A Heat Pump Pool Heater
Heat pump pool heaters work almost like a reverse air-conditioner. Instead of exchanging warm air for cold air, they put all of that heat generated in the process into the poolâs water.Unlike an air conditioner, pool heaters do not need to work so hard for instant results. They implore a slow and steady technique that draws less power and costs you less money. For this reason, heat pumps have the highest coefficient of performance or COP rating of all types of pool heaters. Want proof? Every hotel that has a heated pool uses a heat pump to save on their pool heating efforts.âA study done by the U.S. Department of Energy on pool heaters ultimately recommends using heat pumps as they perform the best and draw less power. After the study was published, the number of heat pump pool heaters sold in Florida alone grew by a staggering 480% year over year. Hotel chains rushed in to save thousands per year on pool heating.
Other Pool Heating Considerations
With a heat pump pool heater, maintaining your water temps will reduce the amount of electricity that you will use. Here are some recommendations:
- How often do you use the pool?â – You should aim to only leave your pool uncovered a maximum of 2 hours per day. If you are using your pool for more than 2 hours consider that you will be losing heat and will need to keep your pool heater on a bit longer.
- What months do you use your pool?â – Heat pumps work best in warmer temperatures, so lucky for us here in Spain a heat pump will work perfect all year round. Keep in mind that if you are using your pool in January or February, you will need to run the pool heater for about a week or 10 days to bring that water temp up to a swimmable level.
- How much are you willing to pay?â – Heat pumps are a much cheaper option than a gas pool heater. Weâve found that they are half the price at least. But heat pumps do cost a bit more up front. The savings in the long run make gas pool heaters a very expensive option when compared to a heat pump.
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