tenax
09-02-2006, 09:13 AM
had an old teledyne laars 150,000 btu heater up until a month ago (by old, i mean 23 years..it served us well) so i replaced with a 125,000 laars jandy heater. my thinking in going with smaller size was largely based on size of my pool, what charts told me i would need for the temperature rise i wanted and the expense difference between a 125K and the next step up which is 175K.
my pool is about 430 square feet and based on that size, i figured the 125K to be more than adequate as i never did have to "crank" up the old one. the new heater is more efficient as well. my goal was a 1 degree rise in temp per hour.
my actual experience is i am getting on average, less than a 1 degree rise per hour. why? because the charts i read prior to my post purchase research did not tell me when they are referring to temp rise, they are relating it to air temp, not the current pool temp.
for example, yesterday afternoon when the air temp was about 70, my starting pool temp was 63 farenheit (into cooler nights now but still warm days...between 65 and 85 is the forecast for next week) my heater up until 10pm was able to rise the temp about a degree per hour. by 10pm, the outside temperature was 59 and this morning it is 40 degrees) the pool temp has risen only 5 degrees in 8 hours so about .5 degrees per hour overnight.
over 17 hours, the pool temp has risen 12 degrees so about 2/3 of a degree per hour average. not quite my target.
now, that also does not account for wind and evaporation as it was calm last night and i do have a solar pool cover on (thank god)
the better charts i've run into will factor in windspeed, not "ideal" heating conditions but i'm assuming do not take into account having a pool cover or not. they also will show the btu rating needed for "startup" which is longer of course than "maintenance". they also will state the heatup time is over a 24 hour period.
the main thing i'm concerned with is being able to get the pool up to swimming temp for the whole season (basically mid may to mid september for the pool season in my area)
it turned out i think that i was lucky that the 125K will be "adequate" for the task, but that's based on the big factor of conditions generally being perfect. low to no wind, pool cover on, no desire to push the season further than mid september.
i totally did not take into account that while we still get hot days in late august and september, overnights the temperature has dropped from double digits to single every night.
to summarize,my tips if you use a heater would be:
a) take air temperature overnight into account. a big factor.
b) buy a pool cover. right now, there's many online pool stores that have "fall deals" on. good time to buy.
c) consider carefully if your goal with a new heater includes wanting to extend the season for your pool.
d) remember, the charts are based on air temp rise, not current pool temp. if the pool temp is 71 and air temp is 59 and you think, well, my heater is rated to give me up to a 20 degree rise in 20 hours and my pool temp is 71..heck, i'll be at 85 in 16 hours..don't bank on it.
e) take into account the least desirable conditions...colder weather, wind, no cover..and plan heater size based on that..then you'll KNOW that you're heater will be more than adequate in the generally ideal condition "summer" season.
my greatest fear would be buying a heater that will not bring my pool to desired swimming temp (in our case, 85 works) when i want it to.
my heater will do what i need it to do, but barely knowing what i know now. in hindsight, i would have bought the 175K.
live and learn!
my pool is about 430 square feet and based on that size, i figured the 125K to be more than adequate as i never did have to "crank" up the old one. the new heater is more efficient as well. my goal was a 1 degree rise in temp per hour.
my actual experience is i am getting on average, less than a 1 degree rise per hour. why? because the charts i read prior to my post purchase research did not tell me when they are referring to temp rise, they are relating it to air temp, not the current pool temp.
for example, yesterday afternoon when the air temp was about 70, my starting pool temp was 63 farenheit (into cooler nights now but still warm days...between 65 and 85 is the forecast for next week) my heater up until 10pm was able to rise the temp about a degree per hour. by 10pm, the outside temperature was 59 and this morning it is 40 degrees) the pool temp has risen only 5 degrees in 8 hours so about .5 degrees per hour overnight.
over 17 hours, the pool temp has risen 12 degrees so about 2/3 of a degree per hour average. not quite my target.
now, that also does not account for wind and evaporation as it was calm last night and i do have a solar pool cover on (thank god)
the better charts i've run into will factor in windspeed, not "ideal" heating conditions but i'm assuming do not take into account having a pool cover or not. they also will show the btu rating needed for "startup" which is longer of course than "maintenance". they also will state the heatup time is over a 24 hour period.
the main thing i'm concerned with is being able to get the pool up to swimming temp for the whole season (basically mid may to mid september for the pool season in my area)
it turned out i think that i was lucky that the 125K will be "adequate" for the task, but that's based on the big factor of conditions generally being perfect. low to no wind, pool cover on, no desire to push the season further than mid september.
i totally did not take into account that while we still get hot days in late august and september, overnights the temperature has dropped from double digits to single every night.
to summarize,my tips if you use a heater would be:
a) take air temperature overnight into account. a big factor.
b) buy a pool cover. right now, there's many online pool stores that have "fall deals" on. good time to buy.
c) consider carefully if your goal with a new heater includes wanting to extend the season for your pool.
d) remember, the charts are based on air temp rise, not current pool temp. if the pool temp is 71 and air temp is 59 and you think, well, my heater is rated to give me up to a 20 degree rise in 20 hours and my pool temp is 71..heck, i'll be at 85 in 16 hours..don't bank on it.
e) take into account the least desirable conditions...colder weather, wind, no cover..and plan heater size based on that..then you'll KNOW that you're heater will be more than adequate in the generally ideal condition "summer" season.
my greatest fear would be buying a heater that will not bring my pool to desired swimming temp (in our case, 85 works) when i want it to.
my heater will do what i need it to do, but barely knowing what i know now. in hindsight, i would have bought the 175K.
live and learn!