Efficient use of pool heater

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staudtlar
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My Pool: large community pool, approx. 50' X 20', in-ground, gas heater

Efficient use of pool heater

Postby staudtlar » Wed 04 Mar, 2009 13:38

I live in a condominium in Florida. We have an in-ground pool approximately 50' X 20' with a gas heater. In the winter, the nights are often much cooler than the day (around 60 degrees at night and 80 degrees in the day). The board has installed a timer that shuts off the pump and the heater at night in order to save gas. I am a retired chemist and tried to tell them that this does not save any gas. It just takes longer for the pool to heat up in the morning and the number of BTUs to heat the water is the same as if the heater had been left on all night.

Can you confirm or deny my theory?


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Larry
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Efficient use of pool heater

Postby Larry » Wed 04 Mar, 2009 15:28

We have found that turning the heater off at night allows the water to cool rapidly. The heater then has to burn at a higher rate in the morning to make up the lost heat.

The higher you turn the burner the lower the heating efficiency and the greater the heat loss from the exhaust gases.

Month on month we have found that turning the heat off at night costs an extra 10% - 20% in fuel due the this heating inefficiency. A slow steady burn is actually more economical.

Have you considered an insulating cover? That would cut heat loss (and heating costs) drastically.
staudtlar
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My Pool: large community pool, approx. 50' X 20', in-ground, gas heater

Efficient use of pool heater

Postby staudtlar » Thu 05 Mar, 2009 12:29

Thank you for your response. That is just what I thought. Unfortunately a pool cover is not an option for us because of the odd shape of the pool, the lack of deck space for a roller, and the lack of a person willing to cover and uncover.

I will forward your information to the board.
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Larry
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Efficient use of pool heater

Postby Larry » Thu 05 Mar, 2009 13:22

You might take a look at this thread about the liquid solar blanket / solar pill. It reduces heat loss and evaporation and may be a viable alternative.

Liquid solar blanket
staudtlar
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My Pool: large community pool, approx. 50' X 20', in-ground, gas heater

Efficient use of pool heater

Postby staudtlar » Fri 06 Mar, 2009 18:01

Thanks Larry. This "liquid blanket" sure sounds like it might be our answer. I will do a little research and take the info. to the board. It will be nice to have a warm swim in the morning.

I am not sure our heater has 2 stages as you implied in your answer. Do you think that would make any difference in the advice to leave the heater run day and night?
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Larry
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Joined: Thu 09 Dec, 2004 20:19
My Pool: Inground concrete 72m2
Tiled overflow pool
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Tiled deck

Efficient use of pool heater

Postby Larry » Sat 07 Mar, 2009 02:08

If the heater doesn't have a heat adjustment then the thermostat will control the heater's on/ off cycle. It doesn't make a difference.

The less you let the pool cool, the less the heater has to work. If the pool loses too much heat then the heater will have to work longer to make up the difference.
Jami

Efficient use of pool heater

Postby Jami » Wed 11 Mar, 2009 11:29

Your theory is correct. It is one in the same to either leave the heater on all night or to start again from a lower temperature in the morning except that you lose hours of warm water swimming time in the morning if you leave the heater off all night.however you may need those night hours to allow the heater to keep up with demand. I also want to make sure that when you say that they are turning off the pump at night they are not turning the pool pump off at night as it is Florida Law to keep a commercial pool constantly running. If efficiency is what you are looking for I would suggest the following:

1.) Using a blanket at night. Check with your liability insurance first and if your pool does not have gutters then you are a candidate for a liquid blanket.

2.) Replace the gas heater with a heat pump.

Please feel/free to call/email with any questions!
Last edited by Larry on Wed 11 Mar, 2009 11:39, edited 1 time in total.
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staudtlar
Pool Newbie
Pool Newbie
Posts: 4
Joined: Wed 04 Mar, 2009 13:16
My Pool: large community pool, approx. 50' X 20', in-ground, gas heater

Efficient use of pool heater

Postby staudtlar » Sat 21 Mar, 2009 20:57

Thank you Jamie for your very helpful information. You have confirmed my theory exactly and I am sure this will give me more clout. I was unaware of the Florida law, but we no longer will be in violation as our pool policy has now changed to include contiuous running of heater and pump.

As to the blanket, it looks like we are out of luck. Our insurance does not allow a blanket, and we DO have gutters so that leaves out a liquid blanket too. I guess we'll just have to pay the bill.

Our gas heater is only 1 1/2 years old. I know the Board did a lot of research before purchase. It uses natural gas which was recently made available in our neighborhood, and not propane as you may have assumed. It is supposedly a very efficient heater and I don't doubt that.


Thanks again for confirming that the laws of physics still apply to pool heaters,
Larry
Heynow999
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Efficient use of pool heater

Postby Heynow999 » Sun 24 May, 2009 07:35

Well, I think you are all wrong. It will cost more to run the heater all night.

Here's why. As the pool cools after the heater is turned off, the temperature differance between the air and pool temperature becomes less and less. If you were to look at it on a graph the temperature would fall quickly then become less steep, and eventually level off, but it would probably take several days for it to reach equilibrium with air temp. Regardless, as the slope becomes less steep, the savings would become more. The savings would be represented by the area under the less steep line and the inverse slope of the temperature rise of the heater. Kind of hard to picture without looking at a graph, but I assure you there are savings.

Also, a heater works more efficiently when there is a greater temperature difference between the incoming water and out going water, not when there is a lesser difference.

Think of it like a tankless water heater. They obviously save money and reduce energy use for the same reason.

More from a pool website.

"It's a myth that it takes more energy to heat swimming pools up when you turn the temperature down than you save by lowering the temperature or by turning off the heater. Turn the temperature down, or turn off the heater whenever the pool will not be used for several days. Experiment to determine how long it takes to heat it back up. Lowering the temperature and raising it back up again always saves more energy than keeping it at a constant temperature. "

What you need to do to achieve maximun savings on heating is to first determine when the pool will be used. For arguements sake say it is used until 9 PM then the gate is locked. The pool is then opened at 7 AM. You could proably shut the heater off at 8 PM and no one would notice. You then have to monitor how low the temperature drops on a typical night and experiment with how long it takes to reheat the pool. Turn the heater on in time to reheat it. The timer on the heater may have to be adjusted seasonally.

Best idea is to get a solar heater. I believe that natural gas prices will rise considerably in the coming years as natural gas is difficult to transport so we only have whatever gas is in North America available to us. Many governments are shutting down coal fired plants and switching to gas fired plants to generate electricity as it is cleaner. I don't belive the impact on future supplies has been calculated responsibly.

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