Jump to content
JACKVJR

Caldera Kauai does then doesn't hold temperature

Recommended Posts

We have a ten-year-old Caldera Kauai with a fluctuating temperature problem.  It will usually heat up to 104 degrees, sometimes hold that for days.  Then, randomly, it won't heat.  Rebooting via shutting off power will usually get it heating again, sometimes not.  Sometimes, it takes several reboots to get it to kick in.  Now that the temperatures are below freezing, this behavior means we can't leave the place for any length of time without worrying it will freeze.  All suggestions appreciated.

1. Plenty of continuous flow out of heater outlet in the bottom center and when the heater is on, output is definitely hot.

2. Timer for clean cycle works on schedule.

3. Never any error codes displayed.

4. Jets all have excellent flow.

5. New filter.

As an experiment, I set it at UT1 and it reaches 105 and is at present staying there.  How would varying the set temperature affect the sensor which cuts off at high/cuts in at low?

jack vines

Share this post


Link to post
Share on other sites

Get a Free Hot Tub Quote

Save time and money by receiving multiple, independent quotes for a hot tub.

The heater is either not turning on because it can't or because it isn't being told to.  Since you can get to 104 by apparently random powering on and off cycles, my guess is that the heater itself is OK.  That means either a sensor isn't telling the circuit board to turn on the heat, or the circuit board can't turn on the heat due to a logic or relay problem.

Check the water temperature with an independent thermometer.  How does it compare to the tub's display?  A degree or so variance isn't significant, but if the control panel thinks it's 104 and your thermometer says it's 90, than the temp sensor is probably due for replacement.  It's a good idea to replace the hi limit sensor as well.

If the sensor's appear to be accurate, the next suspect is the pressure switch.

When the tub SHOULD be heating, but isn't,  I would check the element to see if it's getting the proper voltage.  Then, check the pressure switch to see if it's closed.  If it's open when the spa should be heating but isn't heating, I would jumper the wires to see if that turns the heater on.  If it does, you probably need a new pressure switch.

If the sensor's are all good, the element is good and you're still not getting heat, my guess is that the circuit board can't turn on the heating element.  Get out your wallet,  a Watkins circuit board isn't cheap.

Dave

 

Share this post


Link to post
Share on other sites
On 1/6/2018 at 8:46 AM, Jersey Hot Tub Repair said:

Hi, Dave, thanks for the suggestions:

The heater is either not turning on because it can't or because it isn't being told to.  Since you can get to 104 by apparently random powering on and off cycles, my guess is that the heater itself is OK.  That means either a sensor isn't telling the circuit board to turn on the heat, or the circuit board can't turn on the heat due to a logic or relay problem.  Agree, the heater is obviously OK, as it heats when it gets told to work.

Check the water temperature with an independent thermometer.  How does it compare to the tub's display?  A degree or so variance isn't significant, but if the control panel thinks it's 104 and your thermometer says it's 90, than the temp sensor is probably due for replacement. Temperature display is accurate.

It's a good idea to replace the hi limit sensor as well.  How does the high limit sensor function?  Does it just temporarily shut off the heater at 105?  Is it possible the temperature is running past 104 and being then the heating system is being totally shut off by the high limit sensor? 

If the sensor's appear to be accurate, the next suspect is the pressure switch.  When the tub SHOULD be heating, but isn't,  I would check the element to see if it's getting the proper voltage.  Then, check the pressure switch to see if it's closed.  If it's open when the spa should be heating but isn't heating, I would jumper the wires to see if that turns the heater on.  If it does, you probably need a new pressure switch.  l'll try jumpering the pressure switch.

If the sensor's are all good, the element is good and you're still not getting heat, my guess is that the circuit board can't turn on the heating element.  Get out your wallet,  a Watkins circuit board isn't cheap.  Could turn out to be the circuit board, but solid state stuff is usually good/not good.  It is to be hoped since rebooting gets heat, the problem is a pressure switch.

Thanks for the suggestions.

Jack Vines.

 

 

 

 

Share this post


Link to post
Share on other sites

Hi Jack,

The hi limit sensor shuts off the tub if the temperature gets above 115 - 118.  I've never seen a hi limit sensor work intermittently, it usually works or it doesn't.  However, if the heater relay is not shutting off the heater when the PCB tells it to, the tub would continue to heat until the hi limit sensor trips.  In that case, rebooting the hot tub after it cools enough would resolve the problem, at least until the next time it overheats.  I doubt if the hi limit is your problem, my only point is that Watkins recommends replacing the hi limit and temp sensors together.  I usually don't, although about 20% of the time, when one goes the other isn't far behind.

If the problem is the circuit board, it may be a relay that's not opening or closing properly.  It could be due to a defect in the mechanical mechanism itself, or the PCB may not be sending the proper voltages to open and close the relay.   You can send the circuit board out for evaluation and repair.  I don't recommend it because if one component on the circuit board goes bad, chances are the rest of the board isn't far behind.  I've also had less than reliable results on circuit board repairs.

Dave

Share this post


Link to post
Share on other sites

Thanks for the suggestions.  I've been watching the temperature display several times a day.  It seems accurate and it has never shown a temperature above the set point; this indicates the high limit isn't the problem.

Yesterday, just to experiment, I tried the UT1 and sure enough saw 105 for an hour or so; then it stopped heating began to coast downward.  After the football game, when we went in, the temp was down to 101.  Manually pressing the "Set" button got the heater working again and a strong flow of hot water raised the temperature one degree while we were in it.

If a function were completely failed, it would be easy to find.  That everything works part of the time makes it more difficult.

jack vines

Share this post


Link to post
Share on other sites

Did you every try jumpering the pressure switch?  I've seen older pressure switches stick open or closed.  If your pressure switch is right at the edge of being properly set, vibrations could be causing it to open.  For example, if your particular spa requires 3.4PSI to close the pressure switch and the switch is set for exactly 3.4PSI, the slightest amount of turbulence or vibration could prevent it from closing.  Reduce the sensitivity of the pressure switch by an eight of a turn and see if that helps.

If you reduce the sensitivity of the pressure switch, make sure that disconnecting the circ pump causes the pressure switch to open and the heater to turn off, otherwise you'll be defeating a major element in your overheat protection which can create massive damage if the heater overheats and starts burning things up.

Dave

Share this post


Link to post
Share on other sites
Quote

 Reduce the sensitivity of the pressure switch by an eight of a turn and see if that helps.

Aha!  So the pressure switch is adjustable?  Thanks for that valuable info which I've not read anywhere in two weeks of searches and researches.  The 1/8-turn should be in or out to reduce the sensitivity?

jack vines

Share this post


Link to post
Share on other sites

When the problem comes and goes makes diagnosis difficult.  We were gone for a week, lowered the setting and it held 80 degrees.  We're back and now it's holding 105 (1UT) for a week.

jack vines

Share this post


Link to post
Share on other sites

As mentioned, an intermittent malfunction is frustrating.  After holding near 105 for a couple of weeks, the temp drifted down to 98.  A reboot brought it back to 105, but still no diagnosis.

jack vines

Share this post


Link to post
Share on other sites

Always a mistake to assume because two things happen at the same time that they are related.  For a couple of weeks we had mild temps in the 40s and the spa would hold between 103-105 degrees.  However, since the outside temperature has dropped into the single digits, the spa will no hold temperature at all.   It loses a degree an hour until it is rebooted; then it immediately heats up to 105 within an hour or two.  When the temperature reaches 105, the heater shuts off and will not restart without a reboot.

What about colder outside temperature would prevent the heater from holding temperature?

jack vines

Share this post


Link to post
Share on other sites

When the heater shuts off and will not restart without a reboot, I usually look to the hi limit sensor as being the problem.  It could be that when your temp is 106, the hi limit thinks it's 118.

Given the cheap cost of a hi limit sensor, I'd buy one and put it in.

Dave

 

Share this post


Link to post
Share on other sites
Quote

When the heater shuts off and will not restart without a reboot, I usually look to the hi limit sensor as being the problem.  It could be that when your temp is 106, the hi limit thinks it's 118.

Given the cheap cost of a hi limit sensor, I'd buy one and put it in.

Dave

Hi, Dave,

Thanks for the suggestion and I'll order the part to have on hand as soon as the outside temps get conducive to lying on the ground.

jack

Share this post


Link to post
Share on other sites

These rolling, random problems are not fun to diagnose.  For  two days, it held at 105 degrees and then POOF,; it drifted down and for the first time ever, rebooting wouldn't get it heating again.  I spent a day doing all the testing and troubleshooting without finding any definitely failed parts.  Reassembled everything and POOF, the three days so far, it's holding 106 degrees.

Dave, I'm going to ask for a favor to help me understand the control logic and what does/affects what.  Please correct any misunderstandings I've gotten:

1. Turn on the spa.  Temp is below set point.  A low limit switch checks the pump pressure and if the pressure switch says OK, it starts the heater.

2. When the water temp gets to the set point, an upper limit switch turns off the heater.

3. Should the upper limit switch fail, there's a 115(?) degree over temp/safety switch.  If this is triggered, does it always shut down the system and wait for a repair or reboot?

4. Since my temp never goes beyond 106, why does the control system sometimes shut down and require a reboot, but function as it should other times? 

5. Even more confusing, once, when we were gone, I set the temp at 80 degrees, where there should have been no possibility of triggering the over-temp switch, and it failed to hold 80 degrees.

6. Now, rebooting doesn't trigger a normal sequence.  New filter, heater circulating pump feels strong.  Pressure switch is working.  Am not getting 220v across the two heater terminals.  Does this indicate a failed heater relay circuit board?  If I jump 220v to the two heater terminals, would it begin to heat?  Does the exterior of the stainless pipe begin to feel warm?

7. Should I just replace the pressure switch and the high limit switch as normal wear parts?  Anything else while I'm in there?  From whom would you recommend ordering Caldera/Hot Springs/Watkins parts?

Thanks in advance.

jack vines

Share this post


Link to post
Share on other sites

I guess it's possible to learn to live with a spa which doesn't reliably hold temperature, but it would be 

On 3/5/2018 at 9:27 AM, JACKVJR said:

These rolling, random problems are not fun to diagnose.  For  two days, it held at 105 degrees and then POOF,; it drifted down and for the first time ever, rebooting wouldn't get it heating again.  I spent a day doing all the testing and troubleshooting without finding any definitely failed parts.  Reassembled everything and POOF, the three days so far, it's holding 106 degrees.

Dave, I'm going to ask for a favor to help me understand the control logic and what does/affects what.  Please correct any misunderstandings I've gotten:

1. Turn on the spa.  Temp is below set point.  A low limit switch checks the pump pressure and if the pressure switch says OK, it starts the heater.

2. When the water temp gets to the set point, an upper limit switch turns off the heater.

3. Should the upper limit switch fail, there's a 115(?) degree over temp/safety switch.  If this is triggered, does it always shut down the system and wait for a repair or reboot?

4. Since my temp never goes beyond 106, why does the control system sometimes shut down and require a reboot, but function as it should other times? 

5. Even more confusing, once, when we were gone, I set the temp at 80 degrees, where there should have been no possibility of triggering the over-temp switch, and it failed to hold 80 degrees.

6. . Should I just replace the pressure switch and the high limit switch as normal wear parts?  Anything else while I'm in there?  From whom would you recommend ordering Caldera/Hot Springs/Watkins parts?

Thanks in advance.

jack vines

We're living with the problem, but it's work.  I've tested everything recommended to me and none of them seem to be in failure mode.

Share this post


Link to post
Share on other sites

Just an update; for the past six months, it's decided to hold a steady 106 degrees.  Not only that, the leak has slowed and we no longer have to add water very often.  A possible explanation is it just took a few months of continuous use and a couple of filter changes,to get all the crud out and the system accustomed to working again.  No guarantees on a ten-year-old system.

FWIW, our son and DIL had to have control boards replaced on a two-year-old spa.  The tech said, "Set it and leave it alone.  Whatever you think you're saving by turning the temp up/down/on/off, you'll end up paying in repairs.

jack vines

Share this post


Link to post
Share on other sites

Well, I jinxed myself by reporting the problem had gone away.  As soon as the outside temperature dropped below freezing, the spa temperature no longer holds steady.

What is this telling us?  Yes, the heater has to work longer and more often when the outside temperature is lower, but it was reaching 106 and holding steady for months, until yesterday.  Nothing changed other than the temperature dropping to 29 degrees over night and not going above 32 during the day.

jack vines

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×