Pool heat pump - How many BTUs?

[harry]

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 req uire less time on, thus use, in theory, less electricity - but it's about $

500 more expensive than the small

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

ewed?  Is it worth the extra cost?

Most houses here have electricity here is at 230volts/single phase/

100A. There is no 120 volts except on construction sites when step down transformers are used.

However if you have more than say 15Kw continuous heating, you will be expected to get three phase (depending on location).

Electric heating of swimming pools is virtually unheard of due to cost, there is a gas supply to 99% of places.

Outdoor pools are uncommon here, there's probably only ten days/year warm enough to use one.

[harry]

the correct unit for my needs (an Aquacal TropiCal) puts out 112,000 BTUs (40 amps/5.8 KW). I'm thinking that a larger unit that puts out 141,000 BTU s (50 amps/6.4KW), would heat the pool quicker and require less time on, th us use, in theory, less electricity - but it's about $500 more expensive th an the small unit. We'll probably only use the pool on the weekends. Not su re how long it will take to break even on this with running it for only a c ouple days per week. Anybody have any thoughts or opinions about this? Is m y thinking skewed? Is it worth the extra cost? Thanks!

I think you'd better go back to school

1 btu raises 1 pound of water 1 degree F

[harry]

A lot of it would be down to the Coefficient of Performance of the heat pump. X4 is typical but they have improved a lot lately. I would have thought one that size would need three phase supply, But whatever you do, you need to minimise losses (pool covers etc) first so that the smallest possible plant is needed.

[gfretwell]

You are there and we are here. Different all the way around.

Nobody gets 3 phase in a dwelling unless you are Al Gore. They don't even have a 3 phase primaries on most residential streets We also have one transformer per every 2 or 3 houses. UK does that differently. I know a few UK electricians and inspectors. On our contractor BB we have separate forums because very little actually translates. The topology of the wiring is different (no rings here), the overcurrent protection scheme is different (no fused plugs), the voltage and frequency is different, ground fault protection is different (GFCIs on each circuit, not a RCD on the feeders) and the color codes are different.

Electric heaters are heat pumps and compared to propane, they are usually cheaper. Natural gas is probably cheaper than either, depending on where you are.

We both agree solar is the way to go. I have a gas heater, I think we have used it 2 or 3 times in 4 years. I have even migrated my spa to solar ... an excellent deal.

[gfretwell]

We just use bigger wire and single phase units unless it is a commercial installation.

[trader4]

I agree that is one of the obvious problems. Dumping that home AC heat into the pool could help, but when you look at the whole situation, it doesn't make much sense to me. Among the problems:

As you point out, heat is not available when you need it most. And when the most heat is available you need it least, or not at all. The OP is in FL, which would be one of the worst climates with regard to that.

Typical home AC is maybe 4 tons, or 48K BTUs. And that is when it's actually runnning. On days that are just modestly hot, when you'd typically want to heat the pool, what percent of the time is it actually running? 20%? So, now you're down to

10K btus. Typical pool heater is 100K to 400K btu

To try to roll your own is not a trivial task. And the one system available, that was shown on This Old House, requires cutting refrigerant lines to install the additional water based heat exchanger, modifying the existing system, recharging it, etc. All that isn't cheap and I'll bet you can kiss your warranty good bye. For the same amount of money, you could buy a solar system, which, if you have the space for it, IMO, is a much better option.

[trader4]

ts out 112,000 BTUs (40 amps/5.8 KW).  I'm thinking that a larger unit th at puts out 141,000 BTUs (50 amps/6.4KW), would heat the pool quicker and r equire 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 coup le days per week.

skewed?  Is it worth the extra cost?

I'm sorry for you harry. If true, just another sign of the inadequacy of the Britts.

 There is no 120 volts except on construction sites when step

Who cares? The pool heat pumps all run on 240V.

That's just 62 amps. What exactly is the problem with having a 150A service that makes 3 phase necessary?

150A services are very common here, the min pretty much that's put in today for a house. 200A are very common too. A friend has 300A. All those are done using single phase, nothing unusual at all.

It's not really electric heating. That terms is typically used to refer to resistance heating. The pools use heat pumps, which are referred to as heat pumps. If gas is the only viable option in the UK, how do you explain this:

Like I said, if they let you out of the nuthouse at least once in a while, maybe you'd see some stuff.

[harry]

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 abo ut $500 more expensive than the small

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

g skewed?  Is it worth the extra cost?

A 15Kw three phase system here is just 22 A/phase as the voltage is

410v. Putting loads like this on a single phase system causes voltages to appear on the neutral which can upset RCD devices.

[harry]

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 abo ut $500 more expensive than the small

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

g skewed?  Is it worth the extra cost?

Virtually never used. Most homes here have wet heating systems. This boiler can easily be used to heat the pool via a heat exchanger.

Where there is no gas, either oil or propane is used. Heat pumps are being offered in the last ten years or so but there are icing problems on the evaporators in our climate.

There are big differences too between the UK and USA in energy costs and how the tariff is structured.

[chaniarts]

Is it worth the extra cost?

everyone in one post.

the nights are normally just as hot as the days.

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

yet, strangely, none of them use a cover.

that cold down here for that kind of thing, I would think.

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.

[chaniarts]

it is nearly impossible to get 3 phase power at a house in the US. utility companies don't run this in residential areas, only in commercial areas. if it was even somewhere in the neighborhood, it would cost 10's of thousands of dollars to have it run even a few blocks.

[trader4]

) puts out 112,000 BTUs (40 amps/5.8 KW).  I'm thinking that a larger uni t that puts out 141,000 BTUs (50 amps/6.4KW), would heat the pool quicker a nd require less time on, thus use, in theory, less electricity - but it's a bout $500 more expensive than the small

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

ing skewed?  Is it worth the extra cost?

Sure, who should we believe? You who doesn't even have any experience with a pool or all the companies obviously selling heat pump based heaters?

What most do doesn't mean there isn't a viable market for heat pump systems. Most pools here in the US don't have heat pump systems either. Matters not a wit. If the application is right, they can be the right choice.

Icing on a pool heat pump? Icing indeed!

[trader4]

) puts out 112,000 BTUs (40 amps/5.8 KW).  I'm thinking that a larger uni t that puts out 141,000 BTUs (50 amps/6.4KW), would heat the pool quicker a nd require less time on, thus use, in theory, less electricity - but it's a bout $500 more expensive than the small

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

ing skewed?  Is it worth the extra cost?

Only if the single phase system is half-assed. Apparently that must be the case. And all this time I thought you Britts were so superior. Most houses only have a 100A service and if you need more you have to go to 3 phase. Must be a grand place. Or, more likely, your're just BSing as usual.

[trader4]

kewed?  Is it worth the extra cost?

o everyone in one post.

and the nights are normally just as hot as the days.

ey.  Once the temperature dips down below 75 or so, they don't generate e 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.

[gonjah]

I see. My mistake. Interesting.

[krw]

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.

skewed?  Is it worth the extra cost?

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).

[DD_BobK]

kewed?  Is it worth the extra cost?

o everyone in one post.

and the nights are normally just as hot as the days.

ey.  Once the temperature dips down below 75 or so, they don't generate e nough heat for them.  I also don't like having all that weight on my roof tiles.  Just my preference on that one.

heaters, yet, strangely, none of them use a cover.

't get that cold down here for that kind of thing, I would think.

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

[DD_BobK]

n't get that cold down here for that kind of thing, I would think.

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.

[harry]

al) puts out 112,000 BTUs (40 amps/5.8 KW).  I'm thinking that a larger u 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

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

nking skewed?  Is it worth the extra cost?

Due to the climate, outdoor pools are unusual here, Of the few that exist a tiny percentage are heated. Indoor pools are obviously vastly more expensive and these too are rare. How many outdoor pools are there in Alaska?

Doesn't the evaporator in you freezer ice up you dolt? Why therefore shouldn't the evaporator in any heat pump ice up?

[harry]

al) puts out 112,000 BTUs (40 amps/5.8 KW).  I'm thinking that a larger u 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

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

nking skewed?  Is it worth the extra cost?

A 100A supply is 23Kw. here. Why would you need more than that?