Heater shutting off after refill (air lock?)

[Phffbbt]

Hello all!

I have a Caldera Aventine hot tub. 5 years old, regularly maintained, no issues, water changed frequently.

After a water change recently the heater kept shutting off. Air lock, right? Here's what I did:

1. Ran water hose through filter hole to break lock. Done several times, no success.

2. Cracked every pipe seal to bleed out air - no luck.

3. Drained tub entirely and refilled slowly through filter hole - no luck.

4. Forced air through pipes to try and force out air lock - no luck.

5. Forced water through pipes to break lock - no luck.

6. Blood offering to the spa gods - didn't help either.

I can't imagine at this point that it's an air lock. Runs OK on high speed with no shutoff. At low speeds it heats the water, but shuts off anywhere from 10 seconds to 10 minutes of operation. At that point there is a click from the circuit board; a half-second later the GFCI clicks and everything shuts off.

Failing heater? Faulty circuit board? Or failing GFCI?

Any and all help is greatly appreciated.

 

[C5Mike]

My guess would be a failing heater. It seems reasonable to rule out the GFCI breaker in your spa's sub-panel since it appears to be responding to something that is happening in your spa. The control panel seems like it could be ok since it appears to still be operational. The heater may be leaking current to ground causing the GFCI to trip. It could be tested with a megohmmeter.

The click you are hearing from the circuit board in the control panel could be a relay that controls the heater. Without a schematic diagram of the control panel it is difficult to tell exactly what is happening with that.

https://magneticbackup.s3.amazonaws.com/media/medialibrary/2012/10/caldera_vacanza_manual10.pdf

http://www.nema.org/Products/Documents/NEMA-GFCI-2012-Field-Representative-Presentation.pdf

 

[Phffbbt]

Many thanks. I have suspected it may be the heater, so will have a technician come check it out.

 

[Splash99]

One other thing to check... clogged filters! When it cuts off, is it by chance indicating an "Heater High Temp Limit" error?

My hot tub started shutting off after a water change, first every couple of weeks, then the period got shorter and shorter, until it would not stay on for two minutes before tripping. (This took months.) I just assumed that I screwed something up by not properly purging the lines at the initial startup, possibly damaging the heaters. I knew it was going to cost me so I put it off as long as possible.

I finally started troubleshooting, it was flashing an "Over-Temp" alarm, so I thought it might be the Safety Circuit Board. Seemed to work, so I immediately suspected the thermistors, as it clearly wasn't over heating, and the heaters would get hot for the few minutes I could get it to run. Determined that the thermistors were good, then noticed that the ozone was not bubbling up, and noticed air in the recirc lines which go through the heater. So now I was suspecting a weak recirculation pump. Then I learned that one of my five filters is dedicated to the recirc pump and heater. Since we had not been using the hot tub much, I never suspected clogged filters. After all, I thoroughly "cleaned" them at the water change, right? But the one filter for the recirc pump is used 24/7, and apparently got more clogged as time went on. Once I pulled that filter, the hot tub worked flawlessly! I figure that when I did the filter cleaning, I swapped them around, and one of the "dirtier" ones got put in the position for the recirc pump. So that filter got more and more clogged as time went on, tripp more and more frequenctly. With low circulation, the safety circuit trips out because it compares the water temp at the inlet and outlet of the heater, and if the delta is too great, it assumes that it is overheating.

So, in my case, what could have been a costly repair turned out to be dirty filters! For what it's worth, the manual has a troubleshooting tip for "Heater high limit thermostat tripped: Disconnect power for at least thirty seconds to reset heater high limit. If it will not reset, check for clogged filters. If tripping continues, call for service." I read that, but was sure my filters weren't clogged. What an idiot!

Hopefully your problem will turn out to be something simple like that!

 

[Phffbbt]

Heater element. Tech said it only takes a moment in an airlock condition to burn it out. It has been replaced and the tub is working fine now. In the future, will fill up the tub slowly via a hose in the filter hole.

 

[C5Mike]

Thanks for reporting the resolution to the problem.