Pool heat pump - How many BTUs?

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On Sat, 25 May 2013 10:14:31 -0400, snipped-for-privacy@attt.bizz wrote:

Harry lives in England He is not sure what summer is. That is why so many of his countrymen come here to Florida ;-)
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On May 25, 3:37 pm, snipped-for-privacy@aol.com wrote:

If you are going to have a high coefficient of performance, the evaporator will need to get cold.
http://en.wikipedia.org/wiki/Air_source_heat_pump#Usage The outdoor section on some units may 'frost up' when there is sufficient moisture in the air and outdoor temperature is between 0°C and 5°C (32°F to 41°F)[citation needed]. This restricts air flow across the outdoor coil. These units employ a defrost cycle where the system switches temporarily to 'cooling' mode to move heat from the home to the outdoor coil to melt the ice. This requires the supplementary heater (resistance electric or gas) to activate. The defrost cycle reduces the efficiency of the heat pump significantly, although the newer (demand) systems are more intelligent and need to defrost less. As temperatures drop below freezing the tendency for frosting of the outdoor section decreases due to reduced humidity in the air.
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You really are the village idiot. You're own source above talks about icing up when the outside air is 32 to 41F. We're talking about a pool in FLORIDA. You really think people in FL are going to heat a pool on the rare occasions that it's in the 30s outside so that this is a real issue? Even in more northern climates, very few people heat pools when it's in the 30s and those that choose to, simply wouldn't use a heat pump anyway because it's not intended for, practical, good at those applications. Good grief!
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On Sat, 25 May 2013 11:37:29 -0700 (PDT), harry

If it is 5c, ain't nobody getting in the pool ... unless they are from Canada. Then they say "Toasty eh" Florida are inside wearing a parka.
In real life it gets below 40 here one or two days every 2 years.
I have resistive electric heat and I doubt it has run 100 hours in the 30 years I have lived in this house. It was not on this year at all. That is hardly worth putting in any other kind of heat.
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On May 25, 3:14 pm, snipped-for-privacy@attt.bizz wrote:

nit that puts out 141,000 BTUs (50 amps/6.4KW), would heat the pool quicker and require less time on, thus use, in theory, less electricity - but it's about $500 more expensive than the small

ouple days per week.

IIt's down to air temperature and humidity and the temperature of the refrigerant gases.
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On Sat, 25 May 2013 11:27:55 -0700 (PDT), harry

TropiCal) puts out 112,000 BTUs (40 amps/5.8 KW). I'm thinking that a larger unit that puts out 141,000 BTUs (50 amps/6.4KW), would heat the pool quicker and require less time on, thus use, in theory, less electricity - but it's about $500 more expensive than the small

how long it will take to break even on this with running it for only a couple days per week.

Idiot! Who is swimming when the air temperature is near freezing? You probably would; no brain = no pain.
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On Tue, 28 May 2013 09:30:39 -0400, snipped-for-privacy@attt.bizz wrote:

Canadians
BTW here is the electric bill for a small commercial pool with a 7.5 ton heat pump.
date...........................days..........KWH..... 05/07/2013    32     2776    $275.92    Electric Bill 04/05/2013    29     3634    $358.36    Electric Bill 03/07/2013    28     3906    $384.64    Electric Bill 02/07/2013    30     4562    $442.98    Electric Bill 01/08/2013    32     4645    $450.90    Electric Bill 12/07/2012    30     4210    $428.26    Electric Bill 11/07/2012    30     4117    $418.96    Electric Bill 10/08/2012    31     2637    $270.97    Electric Bill 09/07/2012    31     1793    $186.52    Electric Bill 08/07/2012    29     1672    $174.41    Electric Bill 07/09/2012    32     1847    $191.92    Electric Bill 06/07/2012    31     2205    $228.44    Electric Bill 05/07/2012    31     3693    $377.66    Electric Bill 04/06/2012    30     2803    $287.19    Electric Bill 03/07/2012    29     3877    $394.43    Electric Bill 02/07/2012    29     4746    $481.20    Electric Bill 01/09/2012    33     4771    $483.70    Electric Bill 12/07/2011    30     4098    $433.17    Electric Bill 11/07/2011    31     4124    $435.87    Electric Bill 10/07/2011    29     1711    $185.12    Electric Bill 09/08/2011    34     2021    $217.31    Electric Bill 08/05/2011    28     1670    $180.97    Electric Bill 07/08/2011    31     1838    $198.44    Electric Bill 06/07/2011    32     1897    $204.57    Electric Bill
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On Tue, 28 May 2013 17:45:50 -0400, snipped-for-privacy@aol.com wrote:

Outside?

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On Fri, 24 May 2013 07:42:42 -0700 (PDT), " snipped-for-privacy@optonline.net"

out 112,000 BTUs (40 amps/5.8 KW).  I'm thinking that a larger unit that puts out 141,000 BTUs (50 amps/6.4KW), would heat the pool quicker and require less time on, thus use, in theory, less electricity - but it's about $500 more expensive than the small

it will take to break even on this with running it for only a couple days per week.

This house has two 150A service panels. It's not unusual at all, here. No swimming pool.

If gas is the only option (obviously not), they're in deep water (which they are).
http://www.ft.com/intl/cms/s/6829d914-c39c-11e2-8c30-00144feab7de,Authorised lse.html?_i_location=http%3A%2F%2Fwww.ft.com%2Fcms%2Fs%2F0%2F6829d914-c39c-11e2-8c30-00144feab7de.html&_i_referer=http%3A%2F%2Fwww.drudgereportarchives.com%2Fdsp%2Fsearch.htm%3FsearchFor%3D6%2Bhours#axzz2UGyVyWPK
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On Wed, 22 May 2013 18:46:55 -0700 (PDT), snipped-for-privacy@gmail.com
Pool heat pump - How many BTUs?:

It is worth the extra cost. Go for it. You will be glad that you did.
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On Thursday, May 23, 2013 5:05:34 AM UTC-4, VinnyB wrote:

Thanks for the replies and thoughts, everyone. Let me try to reply to ever yone in one post.
I live in South Florida, so it's fairly sunny here for most of the year and the nights are normally just as hot as the days.
No propane or natural gas here in my area.
I have neighbors who have solar systems and they told me to save my money. Once the temperature dips down below 75 or so, they don't generate enough heat for them. I also don't like having all that weight on my roof tiles. Just my preference on that one.
No home furnace - electric heat in the house.
A pool cover is definitely an option. I think all my neighbors have heater s, yet, strangely, none of them use a cover.
No, there is no insulation between the pool and the ground. It doesn't get that cold down here for that kind of thing, I would think.
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On May 23, 8:44 am, snipped-for-privacy@gmail.com wrote:

ugh heat for them.  I also don't like having all that weight on my roof t iles.  Just my preference on that one.

d text -

First, the idea that the bigger heat pump is going to be less expensive to use because it will be on for less time isn't right. Yes, it will be on for less time, but it will also be using proportionately more electricity than the smaller unit while it's running. There isn't a free lunch here. The real advantage of the larger one is that it will heat the pool faster, so if it's not at temp and you want to raise it, that will be possible faster. In the case of a pool heater, it's better to be too large than too small, for sure.
Usually nat gas is going to be significantly less expensive than a heat pump, but it depends on the relative cost of the two fuels where you are. As others have said, for FL, I would definitely be looking at solar. You need an array roughly the size of the pool. Plus, if you do solar, you may not need to screw around with a cover. When you're paying for fuel, a cover makes a huge difference in the operating cost. With solar, you have to move the water to filter anyway, so heating it is essentially close to free after the system is paid for. And the additional cost to add it is the cost of the solar array, the additional piping, and a controller. You will probably recover the cost of it versus shelling out $$$$ for electricity or other fuel in just a few years.
Also, the size of the heater you need depends on what you want to do with it. If you're just trying to boost the temp a bit at times and extend the season a bit, you can get away with a smaller unit. If you want to keep the pool open year round and use it in any weather conditions, then you need a bigger one.
I would go talk to some neighbors in your area and see what they are doing, get recommendations, etc.
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On Thu, 23 May 2013 06:25:24 -0700 (PDT), " snipped-for-privacy@optonline.net"

All true. However, based on the OP's posted numbers, the larger unit is slightly more efficient, roughly 6% more efficient. But that doesn't change what you say -- running for less time isn't a savings in and of itself.
Edward
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On 5/23/2013 5:44 AM, snipped-for-privacy@gmail.com wrote:

propane can come in tanks. i had a friend who had a 100gallon propane tank put in for a spa

Once the temperature dips down below 75 or so, they don't generate enough heat for them. I also don't like having all that weight on my roof tiles. Just my preference on that one. solar panels can go on the ground

you'd be wrong. ground temp is always less than air temp, unless you're living on a volcano. so, it's always a heat sink 24x7. insulation around a pool is always a winner, but it's hard to put in after the pool is done.
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nough heat for them.  I also don't like having all that weight on my roof tiles.  Just my preference on that one.

If he wants to rule out solar because it can't go on the roof and also there is no room on the ground or he doesn't want it there. that's fine. But I would not rule it out based on some comments from a couple of neighbors. I would do so more research. The neighbors obviously have some cheap system, which I suspect is not unusual. And that can be fine if you only want to heat it part of the season. But then you can't complain because that system doesn't work well below 75.
The more you need to heat it, the more fuel you're going to be using with any system other than solar. I'd do some math and figure out how much that will cost. And I think it would be quickly seen that the payback time for either a larger or more efficient solar array system is fairly short. If the system isn't heating well below 75, make the array substantially bigger, and you get more heat. Or you can use a smaller array with more expensive, higher tech components that will generate more heat.
I think you have to get a grasp on how enormous the heating requirement for a pool can be. Here in the NYC area, just to extend the season maybe two months, can easily result it nat gas bills in the thousands of dollars. I know FL will be different because it's warmer, but if you're trying to extend the season to all year and think solar isn't good below 75, how much gas or electric do you think you'll be using? IMO, the payback time of a really good solar system would make it a very viable solution. Don't assume the neighbors have a really good one, because there objectives could be very different from yours.
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nough heat for them.  I also don't like having all that weight on my roof tiles.  Just my preference on that one.

chaniarts is correct... the R factor for concrete is terrible about 1.5 for 8" of reinforced concrete. In ground spas & pools lose a LOT of heat to the ground.
I had reasonably sized above ground spa and was it boost the temp on demand and it stayed reasonably warm (but not hot enough for real use) for days. It had spray foam insulation ~R 2 per inch
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the R factor for concrete is terrible about 1.5 for 8" of reinforced concrete. In ground spas & pools lose a LOT of heat to the ground.

if that was true we wouldn't need very large pool heaters...
the heat capacity of concrte is only 1/4 that of water. :(
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On Thu, 23 May 2013 05:44:59 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

The ground temperature in Florida is around 70F. That is the temperature of all those beautiful Florida springs. You want your pool quite a bit warmer than that. Water and concrete conduct heat well -- not like metal but well enough for insulation to make a big difference.
In the long run, the installation cost of solar (with virtually no operating cost) is tiny compared with the operating cost of a heat pump, so it's worth doing even if you do the heat pump also. Every bit of heat added by the sun doesn't have to be added by the heat pump. And you say tile -- if you have a concrete tile roof, then you should not be worrying about the weight of the solar heat system, which does not have much water in it at any given time. Just make sure to use a reputable installer so they don't damage the tile.
The larger unit will run less, but when you buy electricity, you pay for energy used. Energy = power times time. You have a power rating in KW -- that's power input and is what you pay for. You have another power rating in BTUs/hour -- that's power output and is what you get in your pool. Both the power output and the power input are different on the two units, so a difference in run time alone doesn't mean much by itself. The ratio of the power outputs (in kiloBTU/hour) to the power inputs (in KW) is 20.69 for the smaller unit and 22.03 for the larger unit. Thus the larger unit is slightly (about 6%) more efficient. That's the figure you should use for deciding which is better in terms of energy use. It may take a long time for the greater efficiency to compensate for the greater initial outlay.
Other than that, everything everybody else said ...
Edward
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wrote:

Agree with everything you say, except the power output/input ratio. No way you can get 20X the energy out of a heat pump that goes into it. Something like 4X is more like it. If you got anywhere near that amount of heat, everyone would be using one instead of gas, oil, etc.
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On Thu, 30 May 2013 14:52:21 -0700 (PDT), " snipped-for-privacy@optonline.net"

The ratios I gave were BTUs/hour over watts. I didn't bother with the conversion factor to make it a real output/input ratio (for example watts out over watts in) because the only point was to compare the two units.
Thanks for reading carefully!
Edward
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