How much heat does your tub lose in cold weather?

[gores95]

Hi all.  We have had our tub for almost two weeks now and love it.  We use it every night for 20 minutes up to an hour.  The hotter the better...102-104!  Here in NW NJ temps have been around freezing at night.  One thing we have felt is a noticeable drop in water temp after soaking for a while.  The water actually starts to feel lukewarm and I know after soaking a while one's body gets used to the hot water but the tub thermometer reflects that temp drop as well.

We soak without jets, then with jets...sometimes with air diverters on full and then off.  We also use the air blower on occasion.  I know that adding air to the tub whether through the jets or the blower can and will decrease temp.  We have noticed temps in the tub go down to 100-101 in the time we are soaking...usually after 15 minutes or so.  Tonight was EXTREMELY windy and 40 degrees and the tub temp actually went down to 98 although I think my daughter may have accidentally lowered the spa set temp to 101 so that could explain this dramatic drop.  Wind I would think would lower spa temps quicker, correct?  

We own a Caldera that has two jet pumps (one is two speed), an air blower and a 24 hour circ pump.  The electrical on the Caldera allows the heater to operate with all jets and air blower on as well.  I read this fact on this forum and can feel the 24 hour circ water is still hot when everything is on.  I have not looked under the "hood" to verify the heater remaining on however.

I was just curious if our temp lowering was in the normal range or is it something I should call the dealer about?  He's 45 miles away and I hate to bother him for nothing.  BTW the temp is now back to 103.7 on my indoor thermometer but of course the cover has been back on for hours.  

Those in colder climates, do you refrain from letting excess air enter the tub by not using the blower and turning the air diverters to low or off?  Does having just the jets on without air also work to RAISE temps?  

How fast do you lose your heat???

Lots of questions....thanks or being patient!  

Marc

[lagator43]

Marc,

I was in my tub for around 30 min tonight and the temp outside was about freezing.  I did not have the blower on but the temp went down one degree while I was in it.  I had it set at 102 and it dropped to 101.  

I enjoyed the pics you provided.  

[Tman122]

It comes down to heater size and gallons. My 400 gallon tub with a 5.5KW heater can keep up and actualy heat, down to below freezing, around 10-20 any colder and it struggles to maintain depending on how much air you introduce and how long the jets are on high.

[Repeat_Offender]

Surface area has a lot ot do with it. The larger the area the faster the temp drop and evaporative rate. Does the wind make it drop faster? When you blow on your bowl of hot soup does it cool quicker? YES! Running the jets also quickens the cool down rate as it exposes more heat to the water surface. Now the question is is your heater allowed to operate while the pums are on, and what is the heaters capacity or KW  rating. In short, how fast can it recover the inevitable heat loss?

[gores95]

Thanks guys.  Yes my heater should be able to operate with everything on and it is a 475 gallon tub, 89" x 89".  How can you check if the heater is indeed on?  Is feeling the hot water out of the circ pump enough of a test?

[Vinny]

My tub seems to drop about 1 degree in 20 to 50 min. My soaks tend to be longer than a jet cycle (20 min) but most of the time I lose track of time, I come in and it's later than I thought it would be.

What I noticed is the temp is usually 1 degree higher than the set temp when I open the cover. It drops almost immediately (10 minutes max) to set temp and by the time I'm done with the soaking it will be 1 degree lower than set temp. The heater is kicking on and if the jets aren't on, heating the footwell first.
Last winter I was impressed that in whatever winter weather we had here in central NJ (never did get a chance to tub in the snow, kids did though) my tub didn't lose too much heat.

As far as the tub feeling lukewarm - your body is probably used to it. I'm sure your tub can keep up with the demands of a 20 minute soak or even a 2 hour soak. BTW, my heater is a 4 KW heater ... it seems on a 220 volt tub this is rather small, most tubs have a 5 or 5.5 KW heater.

[Repeat_Offender]

I get about the same results as you Vinny. My tub has a 5.5KW heater and I rarely lose more than a degree from setpoint. I only run the jets for 10-15 minutes and I'm sure that has an effect on heat loss.

[In Canada eh]

Gores95

         This is probably an unfair comparison because your tub is alot bigger then ours.   Our tub a Bullfrog 451 with a 5.5 kW heater and about 300 us gallons, only drops about one degree before the heater kicks in.  Due to the fact that its a small tub with a large heater the heater keeps ups just fine.  Temperatures around here have not been to bad yet,  around the high 30's at night.  Southwestern Ontario is considered the Canadian Banana belt

[hot tub Frank]

that is perfectly normal
if you inject air you see a lot of evaporation from you tub.
also we have to consider where where the actual temperatur feeler is. mine is close to the bottom. even with the lid on as soon as i start the pumps my tub jumps up a deg do the fact that the cooler water is on the bottom and the jets will mix it up.  

[pg_rider]

During our blizzard the other day it was around 32 degrees with ~20mph winds.  My Optima started at 102, dropped to 101 within a few minutes, then stayed at 101 with the heater on.  If there's no wind it will hold whatever temperature I want.  Needless to say we plan on putting some kind of windbreak around our tub!

[tony]

Now my Optima will hold temp within a degree or two constantly even in the coldest of temps.  The way the system works is when the water temp drops two degrees from the set temp, the heater will kick on until it reaches the set temp.  Most of the time this will result in the temp guage reading one degree lower than the set temp.  For instance, if you set the temp at 102, the heater won't start until the temp drops to 100...then stays on to 102 and turns off.  Much of this time, the readout will be 101.  You may never see 100 because as soon as it drops out of 101, the heater is on.  You will see 102, but when its cold it will start to drop soon.  If you want to soak at a true 102, you would have to set it at 103.

[Chas]

My spa holds temperature. I don't have what some here would call 'cold weather' though,

a cold evening for us is in the fifties.

 8-)

[Brookenstein]

You beat me to it Chas, I was just gonna post the same thing.  

[bosco0633]

If you like "the hotter the better" then here are two tricks that I have learned over the past year.  This will help when the weather is so cold that the temps in the tub drop a couple of degrees.

First.

I read a post right before delivery last year.  It was about tripping switches to raise the temps in the tub.  I asked my service guy about it and he did it without any questions.  Now my tub  can heat to 107 from 104.

Second.

If you cant get someone to do this to you, sometimes if the tub is at 104, I go outside and turn the pumps on high for 20 min. to 30 min. before I soak.  I shut the lid as well.  Now when I go out for my soak the tub is warmer around 105 to 106.  That way when the temp drops because of the weather, it is still really hot for me.

I agree the hotter the better, especially when it is -26 and snowing.  

Thats just my two cents.

[gturn]

I was in my tub last night for about 25 minutes.  My water temp is set at 103, the temp was at 103 when I got in, after a few minutes it went down to 102 and the heater came on.  When I got out it had come back up to 103.  I was running both pumps on high with air to the jets the whole time (I did not run my blower).  The outside temp was 34 degrees with no wind.  My heater has a LED light that comes on when ever the heater is on, and my 4k heater works when the pumps are on. My tub has TP insulation and the inside cabinet temp got up to 112 while I was using it last night. (I have a remote sensor inside and track all my temps and power usage) When the wind is blowing and it is that cold the temp does drop 1 degree and does not come back up before I get out.