My in-ground spa is run with Pentair equipment. The water temperature is set to 98F. I noticed today that when the temperature reached 96F, the heater shuts off. After about 30 seconds, it fires back up for about 20 seconds & then shuts off again. This cycle repeats itself without the water temperature reaching the set limit of 98F. The temperature reading on the EasyTouch control panel remains at 96F. I would appreciate any thoughts that you might have as to what the problem might be. Thank you kindly for your help.
Heater Cycling Before Reaching Set Temperature
- Thread starter Kit
- Start date
- Jul 21, 2013
- 53,238
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
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 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.
There doesn't appear to be any air in the pump basket. The temperature of the water flow seems normal (i.e. not excessively hot). Also, no unusual noises from the heater while it is cycling on & off.
I am not familiar with the location of the water temperature sensor, but is it possible that it needs to be cleaned of any scale?
I am not familiar with the location of the water temperature sensor, but is it possible that it needs to be cleaned of any scale?
- Jul 21, 2013
- 53,238
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Manual is here —> https://translate.pentairpool.com/~...ater_installation_and_users_guide_english.pdf
See section 5 - Troubleshooting. You need to look at the LED Diagnostics and see which of the safety switches is causing the cycling.
See section 5 - Troubleshooting. You need to look at the LED Diagnostics and see which of the safety switches is causing the cycling.
Thank you. In fact I have the manual. I will follow the diagnostic tree the best that I can. By the way, where are the "LED diagnostics" you are referring to? On the heater readout panel or on the EasyTouch control box?
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I removed the thermal regulator & noted that there was an accumulation of rust on the unit. I removed the regulator & ran hot water over it. The unit opened up about 1/8". Is that normal or should it open more? I ran it under hot water after I cleaned the rust off as best as I could. There was no change in how much it opened.
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I would replace it.
The LEDs are on the back of the control board.
The following are the LEDs:
1.....PS (Pressure Switch)
2.....HLS (High Limit Switch)
3.....SFS (Stack Flue Sensor)
4.....AFS (Air Flow Switch)
5.....AGS (Automatic Gas Shutoff).
6.....Service System
7.....Thermistor
8.....Heating
9.....Pool On
10...Spa On
11...Service Heater
Most likely, the high limit is tripping due to low flow through the heat exchanger.
Once the heater cools, the heater will restart.
The purpose of the thermal regulator is to keep cold water from flowing through the heat exchanger because cold water creates condensation which can damage the heater over time.
The thermal regulator opens when the heater fires and the water gets hot.
If the thermal regulator does not open enough the water in the heat exchanger will overheat and trip the high limit switch.
When the thermal regulator is closed, the water flow goes through the internal bypass.
A broken internal bypass can cause the high limit to trip if it allows too much water to bypass the heat exchanger.
You can check the internal bypass by looking into the inlet to see the spring part or looking in the hole where the thermal regulator goes to see if the round disc is in place.
Low total flow from low rpm or a dirty filter can cause overheating as well.
Make sure that the rpm is sufficient for heating and that the filter is clean.
The LEDs are on the back of the control board.
The following are the LEDs:
1.....PS (Pressure Switch)
2.....HLS (High Limit Switch)
3.....SFS (Stack Flue Sensor)
4.....AFS (Air Flow Switch)
5.....AGS (Automatic Gas Shutoff).
6.....Service System
7.....Thermistor
8.....Heating
9.....Pool On
10...Spa On
11...Service Heater
Most likely, the high limit is tripping due to low flow through the heat exchanger.
Once the heater cools, the heater will restart.
The purpose of the thermal regulator is to keep cold water from flowing through the heat exchanger because cold water creates condensation which can damage the heater over time.
The thermal regulator opens when the heater fires and the water gets hot.
If the thermal regulator does not open enough the water in the heat exchanger will overheat and trip the high limit switch.
When the thermal regulator is closed, the water flow goes through the internal bypass.
A broken internal bypass can cause the high limit to trip if it allows too much water to bypass the heat exchanger.
You can check the internal bypass by looking into the inlet to see the spring part or looking in the hole where the thermal regulator goes to see if the round disc is in place.
Low total flow from low rpm or a dirty filter can cause overheating as well.
Make sure that the rpm is sufficient for heating and that the filter is clean.
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JamesW: Just wanted to follow up on your last reply. I noted that the High Limit Switch LED was illuminated. Based on your explanation, I can see where the rusty thermal regulator could be the culprit. To eliminate other possible causes, I cleaned the filters & verified that the rpms were 1,800. So I think I'm good there. I will check the internal bypass today. Assuming that the bypass is not the issue, it sounds like the thermal regulator and/or the HLS might be the culprit(s). However, in the meantime, I have a call into Pentair to see if I can submit a warranty claim. If so, I'll just provide the technician with the information I have gathered thus far. Thank you for your help. I'll report back when I have more information.
Ok, hopefully, Pentair will fix it under warranty. If not, replacing the thermal regulator is pretty easy and inexpensive.
Well, seems like the heater is out of warranty. So I replaced the thermal regulator & all seems well. Thank you so much for your guidance. Truly appreciated!
