Constant issues with Hayward H250FDN Heater for 2500 gallon Spa...now LO code

[bobby2175]

Hi Everyone,

Have been having one issue after another with my spa heater.

A couple of months ago, I got some great advice from everyone here and finally got my spa heater running (found someone to clean the heat exchanger and replaced the temp limit switch, adjust the gas pressure). Everything worked great after that for one use and now I have a constant LO code and the heater will not fire up at all. As I cycle through the options on the heater panel (power, spa, pool), it changes to bO, but after 5 seconds or so, it goes back to LO.

In my area, finding anyone to work on your pool is impossible. First, there seems to be an unwritten rule that companies won't work on another company's pool and everyone is so busy, there's no time to get to it. Even the pool builder who built our pool never finished the job 3 years ago and won't come back to do the work because they are busy building new pools - there was a $20K holdback in the contract until it gets done that they seem to not even care about). So, my wife and I are starting to learn how to fix things and slowly getting things cleaned up. We're prioritizing what we do and I'll likely have several posts to help us get through it all because there's a lot.

Can anyone help me to diagnose the issue? I don't really know heaters, but I'm willing to learn. I've read over multiple posts here with similar issues, but it always seems like the person has some knowledge and is able to skip a few steps to get to the end when finding and testing the various sensors that could be the issue. I've verified pump is working properly, filters have been cleaned and now need to take the next step. I may need a little light hand holding to get to the right place.

Thanks in advance for your help.

Picture attached to show the equipment. Spa stuff is on the left.

Bobby

 

[ajw22]

Bobby, you have a multimeter and know how to check for continuity?

First, remove the cartridge from the filter and see if your heater runs.

 

[bobby2175]

I have a multi-meter...somewhere. Haven't seen it since we moved here a few years ago. Will see if I can find it. Definitely not an expert on them - used it in the past for some very basic issues with electrical outlets but I think I can learn it.

I'll remove the cartridge and give it a shot and report back.

 

[ajw22]

If removing the filter does not fix the LO code then you need to test each of the sensors to see if they are open or closed…

Hayward Heater LO Code [5 Easy Fixes] - HeaterFixLab

The Hayward heater LO code is one of the most common Hayward heater error codes. The possible causes behind this error message are- a dirty pool filter, water pressure switch fault, vent pressure switch fault, temperature limit switch fault, and exhaust gas temperature limit fault. Read our...

heaterfixlab.com

Hayward H-Series Heaters - Further Reading

www.troublefreepool.com

A Hayward LO code is a limit string open error that occurs when any of the safety circuits on your Hayward pool heater opens. This forces the heater to shut down to protect your heater from damage.

Usual reason for the LO code is lack of sufficient flow not closing the Water Pressure Switch. Low water pressure can be due to a filter that needs to be cleaned, low pump RPM if a VS pump, open heater bypass valve, low skimmer water level, or even a stuck weir door.

Also on the Limit String is the Temperature Limit Switch, exhaust gas temperature limit, and Vent Pressure Switch.

See pages 40-43 in the Universal H-Series Diagnostics Guide.

 

[bobby2175]

Ok, I removed the filters and no change.

Started working the inside and would like some advice on whether this is right or not. Please see that the water pressure switch is just kind of hanging and not attached to anything. The bottom piece just falls out (there's nothing holding it together other than the strength of the magnet holding the two pieces together, but it doesn't take much to pull them apart. Seems like there is something missing. . Any thoughts?

Thanks.

Bobby

 

[bobby2175]

Ok, confirmed that it's the pressure switch. I can close the switch and the LO goes to bo, but as you can see in the picture, the diaphragm from the pressure switch is bubbled up good when the pump is running. Is this a normal failure of the switch - with the two half's separating or do I need to investigate further?

 

[ajw22]

Replace the Water Pressure Switch.

 

[bobby2175]

Thank you so much for the help! Got everything running. This is the second issue you guys have helped me fix and I can't thank you enough. I have several more coming as I have to fix the many issues the pool builder left us with.

I also went to a gold supporter to help the community! Thanks so much for all of the help!