How accurate are spa's built in thermometers?

[gores95]

I went out and bought an outdoor thermometer sensor for my hot tub on the advice of one of the forum members.



Works great but the sensor is about a degree lower than the hot tub display.  We like the tub hot so we set the temp to 103, the tub thermometer says 103, but my sensor will say 101.7 or 102.3 at the most.  If we have the tub set to 101 for the kids temps show 99.9 on my sensor.  I know its only a degree or so difference but is this typical?

Also if we are soaking for a while (espcially now with 40/50 degree outdoor temps) the water temp will not be able to be maintained.  Even on the spas thermometer the temp will drop from 103 to 102 or even 101.  Have others noticed this?

I know I am being nit picky here but I was just curious how other's temps fluctuate.  I don't want to call the dealer when there is no real problem.

Thanks,

Marc

EDIT...one other note after being covered all night and set to 103 I lifted the cover this morning and the spa's thermometer read 102.  The sensor I bought showed 101.7.  Do you think there is an issue with my spa's heater?  I am concerned that the spa's heater did not reach and maintain the 103.

[gores95]

One thing I had not been doing and that may have affected the spas temps when not in use.  I had not been closing the four air injector valves when the spa is not in use.  Just closed them this morning and I will report back if this helps retain heat better.

Marc

[Chas]

I generally am glad that the spas I sell do not have a temp readout - at least one of the brands do not.

The other one does, and I get calls from time to time that sound a lot like your post.

Don't worry too much about it - most companies will have an allowable tollerance for the readout. In other words, if you call and tell them it might be part of one degree off, or even if it is off by one full degree, they will most likely not send out a technician. They may not even do anything for two degrees.

The important thing is that the tub get to the temp you like and stay there, regardless of what the readout says.

I have customers who set the tub for 104 knowing that it is really 103. The tub is always at that temperature, so they are fine. Before, it was reading 102 when it was really 103 and I came out and replaced a temp sensor for them - it just changed the readout to 104 for an actual temp of 103... and we all just decided to live with it that way rather than trying to fix something that really wasn't broken.

 8-)

[gores95]

Thanks for the reassurance Chas!  I am not going to worry about it.  

Regrading the four air injectors do you remommend to your clients to turn them to the off position when the spa is not in use?  Does it make a difference?

Thanks.

[George]

One thing I had not been doing and that may have affected the spas temps when not in use.  I had not been closing the four air injector valves when the spa is not in use.  Just closed them this morning and I will report back if this helps retain heat better.

Marc

I would think 1 or even 2 degree difference in two different devices is normal.  If you want a more accurate temp, test with a medical certified device.  But like others have said it really doesn't make that much difference as long as it heats and maintains temp.  

On your air injectors question, leaving them on can cool the water during the cleaning cycle and cause the heater to have to run longer to bring the heat back up.  If your clean cycle ran just before you checked it this morning that could explain the lower than set temp.    On some models the heater does not run with the pumps on, so those models don't maintain the temp as well during use or cleaning cycles.

[gores95]

One thing I had not been doing and that may have affected the spas temps when not in use.  I had not been closing the four air injector valves when the spa is not in use.  Just closed them this morning and I will report back if this helps retain heat better.

Marc

I would think 1 or even 2 degree difference in two different devices is normal.  If you want a more accurate temp, test with a medical certified device.  But like others have said it really doesn't make that much difference as long as it heats and maintains temp.  

On your air injectors question, leaving them on can cool the water during the cleaning cycle and cause the heater to have to run longer to bring the heat back up.  If your clean cycle ran just before you checked it this morning that could explain the lower than set temp.    On some models the heater does not run with the pumps on, so those models don't maintain the temp as well during use or cleaning cycles.

Calderas run the heater with both pumps running so that should not be the issue.  When we are in the tub with both pumps running I can feel the 24 hour circ jet and it is coming out hot.

[lskarp]

I would also think that the location of the temperature reading should be taken into consideration.  I know that the bottom of the spa will be warmer (at least in sunny South Florida) than the top where the heat is escaping to.

This could account for a 1 degree or so difference in temp.  I like the wet test method for temperature as well.  If it feels good, then the temp is good.  If it is too cool, turn it up, too hot, you get it...

LK

[anne]

I generally am glad that the spas I sell do not have a temp readout - at least one of the brands do not.

Why wouldn't a person want to know the difference between set temp and real temp? Assuming there is relative accuarcy to both, of course.

[George]

I generally am glad that the spas I sell do not have a temp readout - at least one of the brands do not.

Why wouldn't a person want to know the difference between set temp and real temp? Assuming there is relative accuarcy to both, of course.

You only think it is not important if the brand you sell doesn't offer a display.  Hot Springs doesn't tell the temp of the water they just have a LED that comes on when it is within range of the set temp. Since they are number one, it must not be that big a deal to most consumers.

[Dr. Spa™ Ret.]

Here's one reason. This is a true story, and not the only time it's happened.

Someone goes out to the spa and checks the thermometer. It says 104. Unbeknown to them, it's broken and not reading correctly. They just jump in the spa............ It's actually 160+

This is the reason I advise against using thermometers or relying on any kind of temperature display. Stick your finger in the water. Does it feel right? If your finger will not penetrate the surface of the water due to it being frozen, do not get in. If you pull back a bloody bony stump, do not get in.

[kervis]

Here's one reason. This is a true story, and not the only time it's happened.

Someone goes out to the spa and checks the thermometer. It says 104. Unbeknown to them, it's broken and not reading correctly. They just jump in the spa............ It's actually 160+

This is the reason I advise against using thermometers or relying on any kind of temperature display. Stick your finger in the water. Does it feel right? If your finger will not penetrate the surface of the water due to it being frozen, do not get in. If you pull back a bloody bony stump, do not get in.

 
Use common sense?!  Puleeeeeeeezzzzz!!  We'd be putting attorneys and lawyers out of work!  

[anne]

Here's one reason. This is a true story, and not the only time it's happened.

Someone goes out to the spa and checks the thermometer. It says 104. Unbeknown to them, it's broken and not reading correctly. They just jump in the spa............ It's actually 160+

This is the reason I advise against using thermometers or relying on any kind of temperature display. Stick your finger in the water. Does it feel right? If your finger will not penetrate the surface of the water due to it being frozen, do not get in. If you pull back a bloody bony stump, do not get in.

Hmm...with that logic, I should disengage my car's spedometer. But somehow that does not seem like a very good idea to me. I can see where you are coming from, but common sense is gonna have to kick in whether there is a temp read out or not. I'd rather have the info in front of me, and have to rely on common sense to decide if there might be an error, than to simply have no info with the assumption that there would be error.

[Gary]

The real reason Hot Springs does not display current temp is so people will not call and say my tub is cooling down while they use it.

Most tubs will cool some depending on ambient temperature and the users also get used to the water (meaning that is the water is 102 five minutes later is does not feel 102). With a spa that display current temperature people will look at the panel and see if is down 1 degree and say it is cooling down and then they call and complain. With no current temp display they will chalk it up to them getting use to the water (no call to the dealer).

[Dr. Spa™ Ret.]

Well................ over the years I've worked on one lawsuit, and turned down 2 others that are pretty much my exact description. Two of the cases the plaintiffs "said" they checked the thermometer and it looked fine. I know in at least one of these there was a 7 figure settlement. The third, there was no thermometer and the person was getting in slowly. He only made it a little past the ankle. I should also point out, that in EVERY case, alcohol was involved (no, I'm not talking about the alcohol in the thermometer). ?And yes, I do still sell thermometers, I just recommend against them.

[gturn]

Here's one reason. This is a true story, and not the only time it's happened.

Someone goes out to the spa and checks the thermometer. It says 104. Unbeknown to them, it's broken and not reading correctly. They just jump in the spa............ It's actually 160+

This is the reason I advise against using thermometers or relying on any kind of temperature display. Stick your finger in the water. Does it feel right? If your finger will not penetrate the surface of the water due to it being frozen, do not get in. If you pull back a bloody bony stump, do not get in.

 
Use common sense?!  Puleeeeeeeezzzzz!!  We'd be putting attorneys and lawyers out of work!  

If all the tubs had thermometers who would buy those little ducky thermometers.