heat time

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gregg123

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Sep 15, 2008
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I am heating my pool for a party today. I turned it on last night at 2am. The outside temp is 60 and the pool water was about the same. I wanted to heat the pool to about 83.
Question, my Jandy LXI 4000 has a "pool heat" and "spa heat" button. I put it on "pool heat" and after 5 hours the water temp is now 73. If I push the "spa heat" button, does that give a faster heat or is it the same as "pool heat"?

I have manual valves so they are set to pool. Are both setting the same amount of heat?
 
I think spishex miswrote. Pool mode and spa mode will both heat at the same rate. The two different modes simply give you two different final temperature settings, like presets on a car radio. The heater always runs at it's maximum heating rate when the water is colder than the current target temperature.

It takes a tremendous amount of heat to heat a pool. Pool heaters are frequently several times the size of the furnace that heats a single family home. You are getting almost 3 degrees an hour, which is fairly good. I would guess that you have another four or five hours to go.
 
While heating the pool I had a thought. Rather than running the cooler bottom of the pool water through the heater then out the returns why not heat the spa to a 100+ and let that spill over into the pool. By the time the heated water from the returns make it out a few feet they have cooled off. If you have all that concentrated hot water pouring in the pool, wouldnt that heat it faster? Any thoughts?
 
No that won't help. The heater is most efficient when it is heating very cold water by just a couple of degrees, so drawing cold water from the main drain is the ideal setup. Also, you would also lose heat to the environment more quickly from the spa while it was at the higher temperature.

Heat is produced by the heater at a more or less uniform rate, typically somewhere between 100,000 and 400,000 BTUs per hour (depending on the heater). Each BTU can raise 1 pound of water 1 degree. A gallon of water is about 8 pounds. That means that it takes about 80,000 BTU to raise 10,000 gallons of water by one degree.

You have 25,000 gallons and were trying to raise the water temperature by 23 degrees, which means you needed about 4,600,000 BTUs. Actually you needed significantly more than that, since heaters are not perfectly efficient and heat is lost from the pool to the environment all the time. In practice it could easily have taken 6,000,000 BTUs. A 400,000 BTU heater (a large heater) would take 15 hours to produce that much heat. So really you were doing very well.
 
Here's an example of my heat time for our pool party this past weekend
We have a Starite Max-E Glass 400K BT. Temperature of pool 16K gal. pool was 59 degrees with a solar cover on. We started heating the pool at 2am and it arrived at our set heated temperature of 84 degrees at noon. In a nut shell it took 10hrs to heat it 25 degrees. Solar cover cover was in place during the warm up too. Propane reading at start was 78% after heat it was 30%, expensive swim day...
HTH

JasonLion that was great information, I wish I had this information a few weeks ago.
 
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Between 2 and 3 degrees an hour is very impressive.
I would be thrilled if I were you.

My IGP gets about a degree per hour if I am lucky. And I can't really complain about that cause it gets there as long as I time things right.

Does your heater have a digital thermostat? If not, it is possible to rig it up with a digital "refrigerator" thermostat. You can then set the temperature to a specific degree. Once it gets there, your pool temperature will stay consistant and probably cost you much less in the long run since it doesn't have to heat the pool over 20 degrees in one shot.

Just make sure you have a firemans switch.
 
We've noticed that heating our 20x40 pool from full cold (60ish) to 75+ takes most of a day. That's with the natural gas heater running all that time. Our gas bill goes up around +$200 for that month, then levels back down to +$100 or so if we keep it at 70ish and 78ish Friday-Sunday.

We keep a solar cover on most of the time.
 

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Piney said:
We've noticed that heating our 20x40 pool from full cold (60ish) to 75+ takes most of a day. That's with the natural gas heater running all that time. Our gas bill goes up around +$200 for that month, then levels back down to +$100 or so if we keep it at 70ish and 78ish Friday-Sunday.

We keep a solar cover on most of the time.
Click to expand...

Where are you located?
 
3 degrees an hour is about what I get too... Mine is hooked to our natural gas and I've been extremely surprised by how cheap it is to operate... several times over the winter I heated the pool from 50ish to 80ish on weekends where we had warm weather... I would just turn the heater on the night before and it'd be warm the next morning. I've never seen my bill increase by more than about $30 though... Keep in mind, I didn't leave the heater running all weekend, usually just to heat it up initially, and then a few hours Sunday morning to re-capture what was lost overnight. A buddy of mine thinks my gas meter is broken.
 
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