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Pool/spa heater
- Thread starter h2ofun
- Start date
Heat pumps, as with heating homes and hot water for the home, are the most efficient for heating pools and spas.
If you have an in-ground pool/spa combination this will likely work:
UltraTemp High Performance Pool Heat Pump
We have a standalone hot tub with electric resistance heating. To maximize solar PV excess production, we will heat it on sunny days then top up the temperature right before use. The hot tub retains a large percentage of its heat from hours and days before because of good insulation, so time shifting is very doable.
israndy
Supercharger Hunter
I wanna do that with our hot tub, how do you control the heat cycle? How do you know when there is excess solar? What if a cloud rolls by?
I was thinking I might wanna go with a more efficient way to heat the pool and I was looking at Heat Works Ohmic Array demand water heaters. I have an old Model 1 I was gonna play with. I am not sure how it compares in efficiency and complexity and cost to a heat pump. Does anyone even make a heat pump sized for a hot tub?
Of course I could also just put a solar water heater panel in the sun next to the spa and run a tiny aquarium pump to cycle the water when it's hot.
I was thinking I might wanna go with a more efficient way to heat the pool and I was looking at Heat Works Ohmic Array demand water heaters. I have an old Model 1 I was gonna play with. I am not sure how it compares in efficiency and complexity and cost to a heat pump. Does anyone even make a heat pump sized for a hot tub?
Of course I could also just put a solar water heater panel in the sun next to the spa and run a tiny aquarium pump to cycle the water when it's hot.
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As I was thinking more about this, for the heater to work, the pump has to be running. And since they do not heat quickly, have to leave them on a lot.
With my 400k Propane heater, I can heat the water about 1 degree a minute. So I just turn it on like 10 minutes before I am ready to use with the pump.
Interesting trade offs when what I have is paid for.
I don't know much about heat pump units for pool/spa combinations such as if any offer Time of Use control features, but that would be nice. Heat Pump water heater units have them.
Our combination meter shows real time power delivery vs. consumption in kW. As for a few clouds, no need for that granularity - a glimpse at the weather forecast and CAISO will show excellent opportunities where the grid has surplus and solar PV curtailment.
Could be a fun project. Would need to run a recirculation loop.
Not aware of any heat pump units for standalone above ground hot tubs.
For those with room for a jerry rigged solar thermal setup as you suggest, that would probably work. May be a business opportunity.
Currently I also have solar hot water panels and tanks I added. So it of course pre heats the house water. But I also added a circulation pump with heat exchange coils in the solar tank which goes into the spa. Only issue, which I was not told about or may not have spent the big bucks to do, is during the off season, the solar hot water only gets to maybe 75 degrees, so cannot be used for the spa. During the summer, gets to 150, but I tend not to use the spa when it is hot and light outside.
We use our hot tub mostly in the spring and sometimes in the fall. With summer evenings, it’s still too warm for the hot tub to be enjoyable. In winter, it’s too cold to be enjoyable when getting out to dry off.
We do about 90-95% of heating the hot tub when exporting solar PV and/or there is max/curtailed solar PV on the grid.
We do about 90-95% of heating the hot tub when exporting solar PV and/or there is max/curtailed solar PV on the grid.
israndy
Supercharger Hunter
I always wanna turn off the tub around Thanksgiving and not back on until Easter or so, but the wife wants it ready at the drop of a hat. I will probably end up doing as the Hot Tub guy said and putting a tub timer on the 20 amp circuit so the heaters are off overnight.
As I have thought about it more, since I already have a 400K BTU propane heater on my spa, will just leave it. I can turn it on whenever since it heats like a degree a minute, and not have to run the pump for all the time an electric needs.
My wife likes to use just the opposite, when its dark. I already have the hot water panels that heat the spa in the summer.
Those look great, but when I look at how much they cost, since I have something already, ...
Watts_Up
Well-Known Member
Are you connecting the electric heater more or less directly from the solar panels,
or are you converting your solar energy into low voltage batteries and then converting it into the higher voltage?
Did you considered using a solar water heater?
This solution seems more straightforward, however dealing with electrical wires is way more simple than water pipes !!!
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Apparently their smallest 5 kW 015ZA/B unit can be used with stand alone hot tubs. It looks like it would require some experience to retrofit the usual hot tub that already has electronics and plumbing internalized. Still, good to see a product like this out there.
It's a typical hot tub with built in 240v resistance heating elements. No batteries involved. We heat the tub when we are exporting energy and/or the grid is curtailing solar surplus so by all reasonable accounting standards are self consuming and/or using 100% renewable electricity. It's connected to a subpanel in our backyard.
Our hot tub is not right next to the house or a sun exposed structure to make that work. It uses a 50A, 240V electrical conduit already run underground and all pipes are internalized, so much more straight forward in our case. For the hot tub, we just change the water each year (unless high use then more), keep chemicals balanced closely, and refill/top-off with a garden hose when needed.
israndy
Supercharger Hunter
On the day we turned the clocks back I finally got up early enough (3:30 am) to activate the Summer Mode feature on my Hot Springs hot tub to delay the heating until the sun is fully up in the sky. It's supposed to be used in HOT climates to keep the tub from getting TOO hot, but I am using it to delay overnight heating. When you activate it, the tub turns off on a timer for 8 hours, no pumps, no heat. When it turns on again it's mid-morning and the sun is high in the sky. Yesterday I tracked it took 24 minutes to heat the tub instead of the usual 12 and it didn't happen at 4am or 7am or even 10am when the world is still cold, it happened when I had almost enough solar to cover the usage entirely. I still had three other heat cycles after the sun went down that day that lasted the usual time, but I had a hot tub timed so that it gets a bunch of its power from the sun, and this will repeat every day until the tub loses power or I turn it off.
May still get a pool timer to extend when the heaters are off, as one of my heat cycles was a 1:40 am, I am NEVER gonna go in the tub at that time, but this I already own and means I do have a tub ready when I am likely to use it.
May still get a pool timer to extend when the heaters are off, as one of my heat cycles was a 1:40 am, I am NEVER gonna go in the tub at that time, but this I already own and means I do have a tub ready when I am likely to use it.
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