Pentair Ultratemp question

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J

JRennie834

Member
Jan 22, 2019
21
Prosper, Texas
Hello, first time posting, so forgive me.

Starting the build process on a 20,000 gallon pool with a standard sized hot tub. Depths will be 3.5-5.5, and pool will be in full sun from 10a - 5p in the summer.

Question I have is, can you use the Pentair UltraTemp to heat your hot tub, or do I need a separate NG heater to handle that job?

Reason I ask, I live north of Dallas, Texas and like the cooling option on the Ultratemp, but not sure if the heating function is adequate for the hot tub? Seems redundant to buy two heating units?

Thanks in advance.
 
Welcome to TFP.

While the Ultratemp is designed to heat spas, it may help to know which model you're getting?
Since you mention heat and cool I'm guessing that it's either the 127 or the 140, hopefully the 140.

It would also help to know what size the spa is going to be?
 
Wow! Thanks for the prompt replies. Yes, it is the 140 I was referring to. The spa will be 6 x 8. I have also considered going the Glacier Pool Cooler route but have been warned about the ambient temp issue as it is not uncommon to have night time temps here in north Texas close to 90 degrees. Will the 140 have the same issue?

Re: the UltraTemp ETi Hybrid, does it have a cooling option as well?

Thanks again!
 
Welcome yo TFP.

How many gallons will your hot tub be?

What BTU Ultratemp are you thinking of?
 
Based upon my calculations, the hot tub will be 700 gallons (6 x 8 x 3)

Not sure on the BTU? Back to my first post, seems completely redundant to buy a Pentair NG heater for the hot tub and then a heat pump/chiller to cool the pool.

Just trying to educate myself, prior to my meeting with the PB on Friday, on what my options are.

Thanks a million.
 
Jandy has a spa heating calculator at https://www.jandy.com/en/calculators/spa-heater-sizing

Key with a spa is how long it takes to get the desired temp rise. If the pool water temp is 80 and you want to heat the spa to 104 hw long will it take? That is all about BTUs your heater can put out.
 
Thanks again for all of the assistance. The PB (prior to me bringing up the cooler idea) suggested I get the Pentair 400K NG heater for the hot tub. So the 400K stand alone heater versus the 140K heat pump/chiller, how much slower should I expect the hot tub to get to temp assuming the water is (let's use winter pool temps for instance) 70 degrees.
 

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JRennie834 said:
Thanks again for all of the assistance. The PB (prior to me bringing up the cooler idea) suggested I get the Pentair 400K NG heater for the hot tub. So the 400K stand alone heater versus the 140K heat pump/chiller, how much slower should I expect the hot tub to get to temp assuming the water is (let's use winter pool temps for instance) 70 degrees.
Click to expand...

Depends what the OAT and is. Using round numbers if your heat pump is putting out 100K BTU and the NG heater is doing 400K BTUs then the NG heater will get the spa to desired temp 4X as quickly.
 
I have the Pentair 140 that you are looking at. No hot tub though, just pool. It does have a "spa" mode on it though -- but I wonder how well that works. The people I know with spas have NG heaters, and use them to warm up the spa when they want to use it, and they heat up reasonably quickly. But the heat pump heats slower, and works best at maintaining a temp, not raising it on demand. On the pool, it can increase about 1 degree per hour on my 15k pool, no idea on the hot tub. I've noticed the water coming out the return tends to be about 5 degrees hotter than the pool water temp.

With regard to the cooling option -- how hot are your summers? This past summer we were over 100 for a month straight, and the only time I used the cooling option was to see how well it worked, we never really needed it. Our pool got up to about 86, but never higher than that, though we do have some shade on it. This was our first summer with the pool. Some summers we can get weeklong stretches of 110+, and then maybe it would be necessary, but that hasn't happened yet for us. So you might consider whether you really need the cooling option -- enough to outweigh the benefit of the NG heater for your spa.
 
scdaren said:
On the pool, it can increase about 1 degree per hour on my 15k pool, no idea on the hot tub. I've noticed the water coming out the return tends to be about 5 degrees hotter than the pool water temp.
Click to expand...

Heat rise should be proportional to water volume. Based on your experience it should raise a 700 gallon spa by around 20 degrees an hour. Note though that heat pump performance will be less on colder nights when you want to hear the spa. So you may only get 10-15 degree an hour temp rise in the spa on colder nights.
 
Man, you guys are great!

Just seems like (if I went the heat pump route in lieu of the 400K NG) I'd just have to plan further ahead if I wanted to heat up the hot tub, versus having it ready to go in 15 minutes with the 400K.

Point well taken on the cooling option. May just have to get through one season, see how it is, then reevaluate. Can always have a little extra pad poured for the equipment just in case I want to add it later I suppose.
 
ajw22 said:
Heat rise should be proportional to water volume. Based on your experience it should raise a 700 gallon spa by around 20 degrees an hour. Note though that heat pump performance will be less on colder nights when you want to hear the spa. So you may only get 10-15 degree an hour temp rise in the spa on colder nights.
Click to expand...

It would also depend on the starting temperature of the hot tub water. Also keep in mind the heat pump will not work at all once it gets down to about 55 degrees ambient temp, so if your winters are below that, you won't be heating your hot tub during those months.
 
JRennie834 said:
Man, you guys are great!

Just seems like (if I went the heat pump route in lieu of the 400K NG) I'd just have to plan further ahead if I wanted to heat up the hot tub, versus having it ready to go in 15 minutes with the 400K.
Click to expand...

That is the basic issue. As stated before, heat pumps are good at maintaining a water temp. They don’t heat water quickly.

NG heater has over 4X the BTUs to heat cold water up to desired temperature.

I can get my 60 degree spa to 104 in around 30 minutes with my Pentair Mastertemp 400K NG heater.
 
Yeah, that heating power is hard to pass up.

The heating (Pentair 400K NG and Pentair Ultratemp 140 heat pump with chiller) redundancy is killing me if I want a cooling option, other than the swamp cooler route, e.g. Glacier.

Oh well, first world problems! Thanks again for all of the replies.
 
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