Heater Cycling Before Reaching Set point temp

[wwtennant]

Moved from here... Heater Cycling Before Reaching Set Temperature

I had that problem recently after opening my pool and using my spa for the first time. What I noticed was the pump basket had lots of air in it when the spa was on and no air when the pool was on. And air bubbles were coming out of the spa returns. I could hear rattling as the water flowed through the heater from the air in it.

I spent a bunch of time purging air through my DE filter which got most of the air out of the pump basket in spa mode. It seems there was lots of air in the spa suction line that needed to be purged. Once I got the air out the heater worked fine.

With the air in the lines the heater did not have sufficient water flow and was overheating and shutting down and cycling. I also felt the water coming out of the spa return was hotter than normal for the short time the heater would be on.

You have to observe and listen at the equipment pad when the heater is cycling and it will give you clues to the problem.

I believe that I am having a similar problem with the air in my line causing my heater to cycle. This only happens in spa mode, not in pool mode for the equipment set-up. I can see the air coming out of the jets in my spa when it shouldn't be. I have an "air blower" that sends tons of air to the spa/hot tub when it is on and "leaks" a little air into the line all the time. However, this "air blower" should only put air into the line after it goes through the heater.

So, where can the air be entering my line before it gets into the heater?? Any ideas would be appreciated. Thank you!!

 

[ajw22]

Look at the pump basket through the clear top. Run in POOL MODE, do you see an air bubble? Run in SPA MODE, do you see a bubble or a larger bubble? In my case I did not have an air bubble in POOL mode and one appeared when in SPA mode. Air was in my spa suction line that needed to be purged.

Do you have an air relief valve on the top of your filter? I kept on burping the air relief valve on my filter that released air. Over time the air bubble in the pool basket got smaller. If you can’t reduce the air in your line then we need to look for a suction leak on the spa suction line.

Your air problem is in your spa suction line.

 

[JamesW]

The spa jets can pull in air due to the venturi effect.

I would suspect that the problem is the thermal regulator.

If it's the thermal regulator, the High Limit LED should be illuminated when the heater begins to turn off.

I would replace the thermal regulator.