Another “High Limit” Thread Jandy LXi

[umpalumpajay]

Hey guys, I don’t post much but have learned SO much on this site. It’s allowed me to take care of and repair my pool since it was new 8 years ago.

Ok, Jandy LXi heater fires up and then shuts off to cool down after reading a High Limit error. There are other threads on this but I can’t seem to find the answer other than a faulty sensor. I took out the 135 and left the 155 in and it was fine - stayed on. Did the opposite and the 135 tripped and it shut down. So this leads me to believe there’s some fault with that sensor? It’s a closed circuit as I tested it with a meter. They both LOOK good - no corrosion. I cleaned out some small leaves and stuff in the heater and that didn’t help. I’m pretty sure I have adequate flow. Could it be anything else?? (That’s the question that never seems to get answers). Thanks
Jay

 

[1poolman1]

Hey guys, I don’t post much but have learned SO much on this site. It’s allowed me to take care of and repair my pool since it was new 8 years ago.

Ok, Jandy LXi heater fires up and then shuts off to cool down after reading a High Limit error. There are other threads on this but I can’t seem to find the answer other than a faulty sensor. I took out the 135 and left the 155 in and it was fine - stayed on. Did the opposite and the 135 tripped and it shut down. So this leads me to believe there’s some fault with that sensor? It’s a closed circuit as I tested it with a meter. They both LOOK good - no corrosion. I cleaned out some small leaves and stuff in the heater and that didn’t help. I’m pretty sure I have adequate flow. Could it be anything else?? (That’s the question that never seems to get answers). Thanks
Jay

If a 135 is tripping don't look to the switch to be bad first, but why is it doing its job?

It could be bad, but the usual cause is low waterflow somewhere in the system allowing water coming out of the heat exchanger to be over the limit. An internal bypass (all heaters have them), an external bypass (some people have them), a dirty filter that allows just enough water to close the pressure switch but not quite enough to keep from overheating.

A VSP that needs to have its RPM increased because it was set at the bare minimum to get the heater to fire but didn't take into account that a dirty filter, or even a slightly clogged basket, may reduce the flow just enough to cause the issue you are seeing.

 

[umpalumpajay]

Good advice. My VSP is pretty high up with the spa on and any more would make it not fun to be in the spa. I’ll try cleaning my filter. Maybe that’s choking off some pressure.

Essentially, you answered the question, what ELSE could it be other than a bad sensor. What’s an internal and external bypass? That’s one I haven’t read about. Thanks for the response.

 

[1poolman1]

Good advice. My VSP is pretty high up with the spa on and any more would make it not fun to be in the spa. I’ll try cleaning my filter. Maybe that’s choking off some pressure.

Essentially, you answered the question, what ELSE could it be other than a bad sensor. What’s an internal and external bypass? That’s one I haven’t read about. Thanks for the response.

Not all the water going into the heater is going through the heat exchanger. There is a spring-loaded valve between the inlet and outlet plumbing. They go bad on occasion.

 

[umpalumpajay]

Not all the water going into the heater is going through the heat exchanger. There is a spring-loaded valve between the inlet and outlet plumbing. They go bad on occasion.

I've just started reading about that. First im going to straight up REMOVE my cartridges from the filter to see if that fixes it (as a test). Im probably due for new cartridges so they might just be gumming up the system. Then i'll go from there and check that valve. I'll post a followup. Thanks for your help.

 

[1poolman1]

I've just started reading about that. First im going to straight up REMOVE my cartridges from the filter to see if that fixes it (as a test). Im probably due for new cartridges so they might just be gumming up the system. Then i'll go from there and check that valve. I'll post a followup. Thanks for your help.

The heater bypass is internal to the inlet/outlet header. Lower right corner of this diagram: