in ground spa - heater question

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missbliss

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Sep 27, 2013
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Hi, I have a combined pool/spa with spill over. The pool and spa have separate plumbing coming in and going out, but they both come together into the common pump/filter.
there is no heater on the system
My primary goal is to heat to the spa to 104 or so degrees (hot tub temperature) in winter months only. Heating the pool is not particularly important to me.

I had a pool guy come over and give me an estimate for installing an electric heater (has to be electric, i don't have gas).
I would have to upgrade the electrical, 136 kbtu top of the line heater - $4400.
For this system, every time i wanted to use the spa, I would have to go over and switch the valves to isolate the spa, then turn on the heater and wait 40 minutes for it to come up to temperature. Then turn it off and switch the valves back to pool when i'm done.

So I thought...for all that expense...why not just permanently isolate the spa, and install a combined spa pack (heater and pump) and keep the spa hot all the time?
I would purchase a high R value cover for the spa. As I said, I don't really care to heat the pool.

When I asked the pool guy about this, he said he's never heard of that and that it was "weird".

I just moved to south florida. People up north keep their hot tubs hot all the time. I would be using this thing several times a week, so to me it doesn't make much sense to reheat it every time I use it. Is there any reason why this would be a bad idea in south florida? would the fact that its in ground make this a bad idea? i.e. excessive heat loss through the concrete? Has anyone out there tried this with an in ground spa and can you tell me anything about your electricity costs?

Thanks for any info you can pass on, much appreciated!

MissBliss
 
:wave: Welcome to TFP!!!

What you are saying can be done ... although usually we see post just the opposite. They have isolated spa/pool and wish they were connected for a few reasons. One being, if you separate them, you will have to maintain the chemicals is 2 separate bodies of water and you will also have to run 2 pumps for circulation/filtration. And running the heater all the time will be very expensive, you will be loosing a lot of heat into the ground even with a good cover.

Unless you are using the spa at least everyday, it will be cheaper to just heat the spa when you want to use it.

You can get some automation that would automatically turn the valves and start the heater. In fact, you likely could set it to automatically switch to spa if you know you are going to use it on a schedule.
 
The chemistry thing doesn't bother me. to me that's less worth than: isolating the spa valves, turning on the heater, waiting an hour, then turn it all off when done. I'm already doing chemistry for the pool.

What about one of these electric "heat pumps"? Supposedly they are much more efficient...?

Anyone have experience?

Oh and thank you for the nice welcome. :) I'm a pool newb...just 2 months.

jblizzle said:
:wave: Welcome to TFP!!!

What you are saying can be done ... although usually we see post just the opposite. They have isolated spa/pool and wish they were connected for a few reasons. One being, if you separate them, you will have to maintain the chemicals is 2 separate bodies of water and you will also have to run 2 pumps for circulation/filtration. And running the heater all the time will be very expensive, you will be loosing a lot of heat into the ground even with a good cover.

Unless you are using the spa at least everyday, it will be cheaper to just heat the spa when you want to use it.

You can get some automation that would automatically turn the valves and start the heater. In fact, you likely could set it to automatically switch to spa if you know you are going to use it on a schedule.
Click to expand...
 
Not sure of your spa size, but size does matter when it comes to heat. Using a cover to retain heat also matters. I think heat pumps do great on heating pools, but are unable to heat spas as it looses it efficiency and ability to heat when heating above 80 degrees.

Here are my calculations which are ball park estimates that do not account for unit efficiency, wind, etc.:

Degree
Gal lbs BTU lbs/BTU Start Stop Dif Hours to Heat
400 3320 136000 0.024411765 85 102 17 0.42 (Estimate Using Cover & retained heat from prior day)
400 3320 136000 0.024411765 70 102 32 0.78
400 3320 136000 0.024411765 50 102 52 1.27

700 5810 136000 0.042720588 85 102 17 0.73 (Estimate Using Cover & retained heat from prior day)
700 5810 136000 0.042720588 70 102 32 1.37
700 5810 136000 0.042720588 50 102 52 2.22
 
My setup with the pool/spa and a valved spillover sounds similar. I have seperate pumps and filters for each function with a heater for the spa only. If I need to refresh the spa water, I just turn on the spillover. My heater is propane and I also looked into an electric heater, but ran into the cost issue with running the electric line (#6 wire about 100 feet long, plus fusible disconnects, a large main breaker and a big labor bill!). Propane is not cheap at $4.50 to $5.00 a gallon in my part of Florida, but the setup is simple if you don't mind having that tank in your yard (I have mine surrounded by privacy fence).

I would recommend not considering a heat pump. They take forever to get warm and when you uncover your spa, you may loose heat faster than the HP can make up for the loss. My heater will warm the spa 1-1/2 to 2 degrees a minute. In the winter that can still be a long time, but this time of the year, I'm usually sitting in the warmed spa by the time the coffee pot finishes at 5:00 AM in the morning. I sit in the spa for 20 minutes, enjoying a cup of coffee, looking at the stars, stretching.... all before I get dressed, shower, and get into the car and go to work. :) It is a nice way to start the day.

You do have to pay very close attention to the chemistry in the spa because things change much faster than the pool. I'll usually close my spa around the first of the year and start using it again in March. During those 3 months, I just leave the spillover on and address the pool chemistry.
 
If you just install a couple valve actuators, you can just have a remote control. One push of a button and the spa is ready to use in about 1/2 hour. One more push and it all switches back. That's how mine is setup and it works well.

Keeping an inground spa hot 24/7 to use a couple time a week using electric heat will be $$$$, and you won't like doubling your testing and balancing tasks. It will be like maintaining both your pool and your neighbor's.
 
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