Raypak heater High Limit 2 Fault

[hillyjd]

For the past two months, our Raypak 406a heater throws a High Limit 2 fault as the spa heats up. Usually when the water temp is about 93F. We found if we wait about two minutes, the fault clears and from then on the heater works perfectly. It's a feature; it happens every time. Any suggestions would be appreciated.

 

[ajw22]

Add a heat shield around the HLS sensors as described in RayPak Heaters - Further Reading

It is a design flaw in the heater.

New Raypak LP heater issue. high limit fault

Just installed my new heater. It keeps tripping the high limit 2 switch. I think it’s a 135 degree trip. I put a thermocouple on that switch and noticed that if the side cover is off, it runs 120 - 128 degrees. If I put the cover back on it runs 127 - 137 degrees and trips. Why would it run...

www.troublefreepool.com

 

[hillyjd]

Since I'm considering replacing the sensors, I looked at the parts breakdown in the manual and it's a bit confusing. For my model (polymer headers after 2019), the drawing (left side in the attachment) shows the sensors (red arrows) but does not list a part number. For models prior to 2019, it says both sensors are number 1-C (P/N 006725F which are 135 deg limits). The drawing for bronze header models after 2019 show two different limit sensors, one at 135 deg and one at 150 deg. I'm assuming mine are both 135 deg sensors, but I hate to assume.

 

[hillyjd]

Thank you. I saw that information but I wasn't sure it fit my problem, since the fault clears so quickly as the water temp rises. But I will try that first.

 

[ajw22]

All models should have a 135 and 150F sensor.

I believe they come in a 2-pack with both.