Question about minimum heat pump specs

[tenguzero]

So we purchased our home this past August, and are opening the pool this year (it wasn't opened last year by the prior owners.) Although it had become a frog pond, thankfully everything works and there are no leaks, so we've been shocking and running the pool to get it back in shape. There is currently a propane heater (Jandy lite2) installed, however the plumbing has been cut, so we're not sure if the prior owner did this because the heater is broken, or just because they wanted to simplify the system for the sake of maintenance (they had been renting the place out for several years before we purchased.) At any rate, the neighbors have been able to fill us in on a lot of details, and the last they knew, when the owners lived there they kept the pool at like 90 degrees all season (cost them something like $900 a month to do so) so we know that it was definitely working up to a few years ago. The neighbors have a heat pump and they swear by it, so we've been looking at this as an option, as we plan to use the pool regularly throughout the swimming season here in New England (as opposed to heating it up periodically for guests or a party.) We're trying to determine what the minimum BTU electric heat pump is that we can get away with, as the darn things are expensive and we're already staring down the barrel of a huge bill to put down a cement pool deck (currently pavers in awful shape.)

All my calculations online would seem to indicate a recommendation of anywhere from 120k-150k BTU, which is a hefty price for a pump. Whereas reading the experiences of others would seem to indicate that we can get away with quite a bit less (one heat pump we were looking at on Craigslist comes in and 90k BTU, and the owner says they've had no problem heating an inground pool larger than ours.) We will be utilizing a solar cover to help retain the heat, and the specs on my pool are in my sig.

Can anyone provide me with some recommendations? Thanks for the help, and as a new pool owner I look forward to reading these forums regularly!

 

[jhalpinjr]

I would personally reccomend atleast 125K heat pump. The cost from 90 to 125K is not much. If I may ask where are you getting quotes?
Remember your btu output on a smaller unit will mean it will have to run longer. We have several experts here on tempertaure rise that will help you a bit more on the technical aspects of heat gain vs loss and efficiency.

If it matters at all my pool is 18000 gallons and I have a 125K btu heat/cool unit.

Apart from the size of the pump, from personal experience I reccomend:
1. use a solar cover- it will save you considerable energy and minimize the heat pump run time.
2. Look for a heat pump with a titanium heat exchanger- they are becoming more and more common.
3. If you going to do the installation DIY- its relatively easy - just be sure to read the installation manual and be sure about your local codes and such (electrical etc...most require atleast a 50Amp service)

 

[tenguzero]

Thanks. We've been obtaining price quotes from a combination of sources (local pool shops and online sellers) and it would appear that we would likely be into it (after the cost of the pump and wiring work) for at least $4k. The confusion on our part comes from the mixed input we're getting: prices to purchase online appear to be better, but I'm told one needs to be wary of online purchases from places like Amazon, as the heaters are frequently reconditioned, and furthermore if it breaks you're up a creek, as many local pool stores won't touch someone else's heater, meaning it could get very pricey if you have to send the thing off somewhere. On the flipside several of the pool stores we've talked to either don't sell heating devices, or only sell things like propane heaters (I understand traditional heaters have historically been more popular here in New England, but heat pumps are starting to replace them -- though it would appear there are pool stores that haven't caught onto this trend yet.)

Interestingly enough, one employee suggested maybe we consider a compromise -- install a lower BTU (ie. less expensive) heat pump for heat maintenance, but keep the propane heater to get the pool up to temp initially. Might this be a consideration?

 

[JasonLion]

One big question is what times of year you will want to heat the pool. In the middle of the summer, with warm air temperatures, almost any size heater will keep up as long as your leave it running continuously. But if you are trying to heat the pool in the spring/fall, with colder air temperatures, the efficiency of the heat pump falls dramatically just when the pool needs much more heat than it would use in the summer. At that point having a larger heater can make a big difference in how much you can extend the pool season.

 

[tenguzero]

Good question. We'd be looking for standard New England usage -- open in mid-May (ready to go by Memorial Day) close sometime mid-September after Labor Day. The calculators I've utilized all suggested a heat pump upwards of 150k BTU (using 648 sq. ft. surface area x 20 degree rise x 11), but we're being told by people in our area that they're keeping their pools comfortable with under 100k BTU and a solar cover.

So if I understand the general consensus, it's that a larger pump might cost us more up front, but it won't have to work as hard or as often, potentially prolonging lifespan and costing less in utilities, whereas a smaller pump might cost less up front, but it'll be running harder and more often.

 

[jhalpinjr]

Good question. We'd be looking for standard New England usage -- open in mid-May (ready to go by Memorial Day) close sometime mid-September after Labor Day. The calculators I've utilized all suggested a heat pump upwards of 150k BTU (using 648 sq. ft. surface area x 20 degree rise x 11), but we're being told by people in our area that they're keeping their pools comfortable with under 100k BTU and a solar cover.

So if I understand the general consensus, it's that a larger pump might cost us more up front, but it won't have to work as hard or as often, potentially prolonging lifespan and costing less in utilities, whereas a smaller pump might cost less up front, but it'll be running harder and more often.

 

[ps0303]

If this is your primary residence then why purchase something off of craigslist unless it's brand new in a box. You also have to consider the cost of running a dedicated 240V line out to the equipment pad for the heat pump. So don't forget to add that into your initial costs if you haven't already.

Have a gas heater to initially heat the pool and then use electric to maintain is a great combo.

 

[harleysilo]

Do you know at what temperature you enjoy swimming? What i mean is when it's cold out, how warm does the pool have to be for you to consider it comfortable? When it is 70 degrees out i'll swim at 88, but really would prefer 90 or 91. Kids don't care. When it's 90 + i prefer mid 80's.

I think mine is 140K BTU, i have ~19,000 gallons and when overnight temps are in the 50's it can maintain pool temp, possibly even increase 1 degree. Took 2.5 days to put 30 degrees into the water from 58 to 88.

 

[tenguzero]

We're figuring about a 20 degree temperature rise (figure average temp in two coldest months, May and September, likely 60) and we'd be looking for an 80 degree pool.

It sounds like many of you have heat pumps that are more than adequate for your pool size (at least, using the online calculators) so I guess that's our best bet. My brother in law is a plumber and my wife's cousin is an electrician, so we can get a reasonable deal on the hookups. If we end up going for a comfortably sized heat pump, we'll probably sell the propane heater to try and make a few $$. I kinda like the idea of the hybrid heater/heat pump combo myself, but in the end it's probably just more stuff to worry about maintaining!