Pool Heat Pump in SoCal?

[michaelbuday]

I’m wondering how many of you have experience with heat pumps to heat a 18,000 gallon in-ground pool and 8 person spa. My current 11 year old Raypak 407 heater is nearing end of life, and - last year we installed 12KW solar system that’s generating almost double the amount of power we need - hence why I’m considering switching from gas to electric.

Our gas heater we use only on demand given the high cost to run it - hence we swim and use the spa less often than we’d like to. It’s fast to heat, but our moderately warm SoCal summers near the beach cool the pool down at night pretty quickly (our pool isn’t well suited for a pool cover given it’s very non linear shape and multiple coping heights, making placing and removing a cover tricky).

Yes, I know heat pumps are MUCH slower to heat than gas fired heaters, but - my hope - given our electricity is now virtually free - is that I can set the temperature on the heat pump to maintain the pool at 87 degrees from May thru Oct. yes it might be slow to get to the desired temp, but once there - we leave it running almost all day.

Heat pumps are almost non existent in SoCal, and all the installers I’ve e contacted speak negatively about them even though they have no experience with them. Given our ambient temps during swimming season range from 60 to 90 - it seems like a heat pump would be a great option.

Many thanks in advance!

 

[flynwill]

I think a heat pump would be able to keep the pool warm May-Oct but without a cover you will probably use up all of that "free" electricity and then some. You could probably get a pretty good estimate as to how much by turning on your gas heater now for a week (while we have May gray weather), and monitor your gas usage. (Take a picture of the meter daily). Subtract off your normal household gas use (which is likely pretty small by comparison). Once you have data on how much natural gas it takes to keep the pool warm in May it is straightforward to estimate how much electricity a heat pump will need for the same task.

Heating the spa is a different can of worms, most heat pumps rapidly loose their efficiency as the water temperature rises relative to the air temperature. You may want to keep a gas heater in the mix for just the spa (assuming you like typical 95-100F SPA temps).

 

[michaelbuday]

Thanks for the detailed reply. I dipped my toe into the heat pump world when our 16 year old household gas water heater died last Oct. With so much solar on the roof and the huge rebate incentives, we decided to switch to electric water heating via a hybrid hot water tank (electric + heat pump). So far, so good. We’ve noticed no appreciable increase in our electric bill despite the fact the heat pump does run for very long periods to get the water up to 135 degrees (it only uses the electric heating element if demand outpaces the ability of the heat pump to get to the desired temp - but we’ve never had that happen).

So we know, on a much smaller scale - that the heat pump can achieve the desired water temp when our ambient garage temp (where it’s located) hovers around 60 degrees.

If I maintain the pool at 87, then the heat pump must raise it another 13 degrees for the spa - so the question is, how long does it take to get there? My Raypak, under those conditions takes about 30 min.

As to a pool cover, I would LOVE to use one, so if anyone knows of a cover that’s easy enough to use with a pool like mine, please direct me there!

 

[ajw22]

My Raypak, under those conditions takes about 30 min.

How many BTUs in your gas Raypak?

How many BTUs in the pool HP you would get?

How many gallons in your spa?

 

[flynwill]

So we know, on a much smaller scale - that the heat pump can achieve the desired water temp when our ambient garage temp (where it’s located) hovers around 60 degrees.

Indeed, and likely your water heater is a modern variable speed inverter driven unit that can work efficiently with a large temperature difference. Most swimming pool heat pumps don't fall into that category (but there are a few makers out there, a web search turned up this Canadian company: Arctic Heat Pumps who's products look promising on paper (but I have no direct knowledge of them).

If I maintain the pool at 87, then the heat pump must raise it another 13 degrees for the spa - so the question is, how long does it take to get there? My Raypak, under those conditions takes about 30 min.

That's going to depend on the heat pump and the ambient temperature, but probably 2-3 hours for your typical 10-ton nominal capacity pool unit.

As to a pool cover, I would LOVE to use one, so if anyone knows of a cover that’s easy enough to use with a pool like mine, please direct me there!

Yea I'll agree that's a tough one. You could deploy a floating "bubble wrap" cover but I'll be the first to admit those are significant work to put on and take off.

 

[1poolman1]

Thanks for the detailed reply. I dipped my toe into the heat pump world when our 16 year old household gas water heater died last Oct. With so much solar on the roof and the huge rebate incentives, we decided to switch to electric water heating via a hybrid hot water tank (electric + heat pump). So far, so good. We’ve noticed no appreciable increase in our electric bill despite the fact the heat pump does run for very long periods to get the water up to 135 degrees (it only uses the electric heating element if demand outpaces the ability of the heat pump to get to the desired temp - but we’ve never had that happen).

So we know, on a much smaller scale - that the heat pump can achieve the desired water temp when our ambient garage temp (where it’s located) hovers around 60 degrees.

If I maintain the pool at 87, then the heat pump must raise it another 13 degrees for the spa - so the question is, how long does it take to get there? My Raypak, under those conditions takes about 30 min.

As to a pool cover, I would LOVE to use one, so if anyone knows of a cover that’s easy enough to use with a pool like mine, please direct me there!

With a pool of that complex shape, many who have one will first install a solar cover, get it cut to shape, then cut it into sections that are easier to handle. If you do that, never just remove a section and allow people to swim (drowning hazard) and never store the sections on that lawn. Also, an opening to allow the spa overflow to NOT fall on the cover is needed (the water feature as well). Solar covers are hard enough to handle without a bunch of water on them and the efficiency would be little affected.

 

[redturboeclipse]

delete

 

[michaelbuday]

How many BTUs in your gas Raypak?

How many BTUs in the pool HP you would get?

How many gallons in your spa?

My pool is about 18,000 gallons. Can’t say about my spa other than it seats six adults comfortably.

Current gas heater is 400,000 BTU.
Heat pump would be 140,000 BTU

 

[ajw22]

My pool is about 18,000 gallons. Can’t say about my spa other than it seats six adults comfortably.

Current gas heater is 400,000 BTU.
Heat pump would be 140,000 BTU

If I maintain the pool at 87, then the heat pump must raise it another 13 degrees for the spa - so the question is, how long does it take to get there? My Raypak, under those conditions takes about 30 min.

Your HP will take about twice as long to heat your pool or spa as your Raypak heater would on an 80/80/80 day. On colder times your HP will take 2.5 to 3X longer.

 

[michaelbuday]

With a pool of that complex shape, many who have one will first install a solar cover, get it cut to shape, then cut it into sections that are easier to handle. If you do that, never just remove a section and allow people to swim (drowning hazard) and never store the sections on that lawn. Also, an opening to allow the spa overflow to NOT fall on the cover is needed (the water feature as well). Solar covers are hard enough to handle without a bunch of water on them and the efficiency would be little affected.

Great advice - thank you. I may try a solar cover even without the heat pump.

 

[treyrich]

We JUST opened our new pool build right down the road (San Clemente). We had both a heat pump and a gas heater installed. Chose the heat pump due to excessive PV solar as well.

It’s not going to be apples to apples because we do have an auto cover, and the only data I have on the heat pump is from the last 3 weeks (very cold and miserable). But the heat pump has been able to keep up and maintain the temperature at 85° no problem, so 87° shouldn’t make much difference. However, I’d expect at least 1-half day for it to heat the spa to temperature (never tried it), maybe I’m over estimating it, but it is SLOW compare to the gas.

The other thing I’ll add is that it uses a lot of electricity, which is fine because you prepaid for the electricity when you put on your PV system. However, I think you’ll likely end up with over-use, especially if you’re regularly heating the spa and if you have AC for the house for the few weeks it’s hot enough for it. Not a big deal, but something worth considering if you were hoping to have $0 electric bill when you true up.

I’m happy to experiment, or provide any data you’d like as I’m so close it should be a good approximation of how the heat pump would work for you.

 

[Aquagenarian]

@michaelbuday how is the heat pump working out? I also live in socal and given the HUGE increase in natural gas costs I am also considering adding a heat pump to my equipment pad to heat the pool to around low to mid 80’s.

 

[sanheatpump]

Bumping and adding some experiences from North SD County 3 miles inland...

• Stratos 100k BTU heat pump
• Pentair 400k BTU gas heater
• Around 25-35,000 gallon pool
• 2 person spa
• No cover - use liquid cover 2 cap fulls each week
• Some solar excess to use for the pool

Same stories of installers saying 'heat pumps don't work' etc, so went and bought one myself, had the pool guy pipe it, hook it up to the computouch, and hired an electrician to run the wiring.

Why so undersized on the heat pump?

Don't have floor space in the equipment area for the larger square footprint heat pumps without removing the existing gas heater, so went with the largest rectangular I could find. Figured if I needed more, could stack a 2nd on top.

How is it performing?

This summer, once we got out of the unusually long gloom period, I run the heat pump about 7 hours a day set to 87 from 9-4.

Pool water drops to about 82 overnight, gets to about 86 in the afternoon on the days when it's mid to low 60s at night and mid to high 70s during the day.


Tried heating the spa alone a few times. Seems to go from 60 degreeish water to 100 degrees in a few hours.

We started our full pool season by 'boosting' it for a day with the gas heater, then ran the heat pump during the following days That got us up to 87/88 for a few days and didn't have to run the heat pump as much those days.

What am I trying to figure out?

Is running a gas heater 'boost' once a week more efficient than just relying on the heat pump mid summer? - assume we are maxed out on solar with our 'base' heat pump usage

Would i get the same results using the heat pump for 7 hours Midnight to 7am instead of 9am - 4pm to take advantage of 'super off peak' rates?

What's the most efficient for extending the pool season (getting 87 degree water in Nov and Mar/Apr) - a second heat pump or using the gas/heat pump combo?

 

[ajw22]

Figured if I needed more, could stack a 2nd on top.

Does your HP Installation Manual give a minimum clearance on top for the HP?

In general stacking top discharge HPs are not recommended. You need to keep them out of each other's airflow so that one unit doesn't suck in exhaust air from the other.

Vertical stacking of heat pump outdoor units - GreenBuildingAdvisor

I’m in the process of finalizing the outdoor placement of a heat pump. This may end up being the only one, but there’s also a possibility we’ll add one for […]

www.greenbuildingadvisor.com

 

[Ahultin]

This summer, once we got out of the unusually long gloom period, I run the heat pump about 7 hours a day set to 87 from 9-4.

How did the heat pump do during the gloomy period? What kind of electric usage are you seeing?

 

[sanheatpump]

How did the heat pump do during the gloomy period? What kind of electric usage are you seeing?

During the gloomy period didn't play with it as actively as I should have since we weren't in the mood for swimming in the gloom. The occasional spot spa heating was during the gloom though.

It uses about 5kw per hour. Not an 'inverter' type though the sales lead of the manufacturer (works at HQ) insisted those weren't useful.

This was the TTI response to whether an inverter style would be more efficient than theirs:

"We tested it 2 years ago and there are no economy for a swimming pool heater"

"For houses it is different we are making heat pumps for houses And pools since 1986 so we have experience"

I'd take that statement with heavy salt, am curious about some of the newer inverter based models with higher BTU, but also could believe they tried inverter models for pool heating and ended up with the results being about the same.

Does your HP Installation Manual give a minimum clearance on top for the HP?

In general stacking top discharge HPs are not recommended. You need to keep them out of each other's airflow so that one unit doesn't suck in exhaust air from the other.

Vertical stacking of heat pump outdoor units - GreenBuildingAdvisor

I’m in the process of finalizing the outdoor placement of a heat pump. This may end up being the only one, but there’s also a possibility we’ll add one for […]

www.greenbuildingadvisor.com

Thanks it's a side inlet/discharge, not top discharge. Maybe something along the lines of this.

Amazon.com

Though if I find I can comfortably ditch the gas, then there's room to put a full sized top discharge in there as the 2nd heat pump with no stacking.

 

[redturboeclipse]

I have an Aquacal T115 112,000 on a 9500 gal pool in norcal
On gloomy days even with some slight sprinkling with temps only in the low 70s high 60s, I was able to get the pool temp to mid 80s with solar blanket within 2 days when starting water temp was also in the low 70s. Only running once sun is out to about when sun set, not running over night.

Everyone in the neighborhood with solar roof heating were lucky to even hit mid 70s during this period, out of about 20 solar roof heating owners, they all said their temps were high 60s low 70s at most as there was barely if any sun at all during this gloomy period where I knew heat pump was still > solar roof heating in CA