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Author Topic: Diagnosing a high-limit error that shouldn't be happening on Sundance Palermo  (Read 3647 times)

desl

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TL:DR Questions
  • Why is my tub showing the high limit error if my high-limit sensor is giving the same reading as the tub temp sensor (94F)?
  • What position should the tube that holds the high-limit sensor supposed to be in?

The tub is a Sundance Palermo (780 series) from around 2006. It's showing the "- - -" error code. In the manual this is suggested to be the high limit sensor. I can confirm that the water is not too hot. (Family members were in the tub when it switched). The tub's thermometer suggested it was around 93F (it generally reads a bit cold and we have small kids so is normal).

On this tub the high limit sensor is stuffed into the end of a tube. I'm not certain where this tube is supposed to be or what it's requirements are (this is not covered in the user manual). The lead coming out of the control box is not very long (24"). The tube is long enough that needs to coil or snake around to be within that distance of the control box.

My first thought was to buy a new sensor, but I"m not sure that's necessary. I put a meter on the sensor and got a reading that was essentially the same as the hot tub's temperature sensor (both were in the ballpark of 23.41 on the meter, which is auto-ranging and I forgot to look at the scale. The water was around 84F and I assume this maps to ~23000 ohms).

For fun, I unplugged the sensors which are on the same connector and the error codes changed to SN1, SN2 (I assume this means sensor1, sensor2 for both the temp and high-limit), which seems reasonable. That would be a reason to replace the sensors.

A bit of background that seems irrelevant but for completeness: my darling children last week managed to get "water bomb" (think water balloon but thicker and reusable) past the filter and caused flow to be reduced and trigger a pump error. Removed the pump, cleared the blockage and re-installed and now everything was fine. This "- - -" error is happening 48 hours later.


 

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desl

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Update

The high-temp/watchdog error seems to to have cleared for "no reason".


I also found a service manual that looks to be for an LX-15 spa controller which seems to be what is inside the Sundance Palermo. The manual is published by Jacuzzi and contains info for many brands including amazon.com sold spas. For reference the control box in my spa is branded Sweetwater.

The diagnostic process for the high-temp/watchdog shows the first step to be what I have already done (compare resistance between the temp sensor and the high-limit sensor. Based on the chart a resistance of 23,280 ohms maps to a temperature of 87.8F. Seems about right based on sticking my hand into the water. There goes the dream of a quick parts swap and being done. :)

The second step in the diagnostic is to use the spare control panel you have (I don't have one) and see if that clears the error. My control panel appears to work fine: all the lights light up and display reads the things it's supposed to. Since the tub was going into the high-temp/watchdog mode after a short startup sequence (maybe 30 seconds) where am able to change the temp on the tub, I figured I'd try setting the tub back to temp and unplug the display. Not a perfect test, but might indicated if the display was causing problems and warrant purchase of another one. I reset the power to the tub and changed the desired temp to 95F... and the pump stayed on. It stayed on long enough to get back to temp, but was back in high-limit/watchdog in a few hours.

If you have experience with a transient watchdog error being cured by replacing the display/control panel I'd love to hear about.




CanadianSpaTech

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Are the filters in or out? Dirty filters slow the flow of water, Water in heater tube gets to hot sends error

desl

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The filter was in place... but I'll give it a go right now with the filter removed.

desl

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Removing the filter did not fix the issue.

The next step in the manual is to "replace the control panel". I don't suspect the control panel (The behavior persists when the control panel is unplugged. The control panel is working in every other observable way and is digitally connected to the circuit board.... I don't know what the behavior of the tub would be without the control panel... it may try to detect the control panel and do nothing.

I moved forward with the next step of debugging which is to check the voltages from the transformer. 246VAC and 14.6VAC. I don't have enough context to know if the extra .6 volts could be causing a problem (the test suggests that it should output 12-14 volts a/c.. I also know that when loaded transformers output voltage drops. However.. since I don't believe this transformer does anything other than the circuit board and tub lights it seems like it's voltage should be relatively unaffected.

SerjicalStrike

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A few things to check:

The capacitor on the board.  it is the big silo looking thing sticking out in the middle of the board.  Does it have a flat top, or is the top rounded over?

The flow switch.  Make sure it is reading fairly close to 0 ohms when closed, and that there is no reading when open.  If the ohms are in the hundreds/thousands/millions, your flow switch is bad.  If you mix that with an intermittently bad circ pump or a circ pump that isn't pushing enough water, the heater will run too hot. 

Heater relays.  You can either ohm them out with the power off or check for voltage when the power is on.  240v to the heater before the red light kicks on indicates a stuck relay. 

If those check out fine, in my experience, you are 99% looking at a bad temp sensor.


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