LO CODE on my Hayward Heater

[manzov22]

I have Hayward H150FDN Universal H-Series, Low NOx, 150,000 BTU, Natural Gas, Pool and Spa Heater and I am getting a LO code with is a flow problem. I have my intermatic timer set for 755am to turn on and give my equipment power, then at 8am the Hayward pump turn on. Can the heater be on without flow for 5 min? Will this cause a LO error code? Another thing is that I have my Hayward variable speedpump at 1900 rpms, is this flow to low?

 

[Starplex]

Was it working before at the pump speed of 1900 rpms? Shouldn't be a problem there I wouldn't think. What type of filter do you have? If the filter has a high DP, (cartridges that haven't been cleaned in a long time), it can reduce the flow to where the heater won't fire. I had a very similar issue on my Hayward. I changed the cartridge filters thinking that was the problem, but it turned out that the pressure switch was stuck. I took the plastic end off (end where the water piping enters the heater) about 6 screws and that exposes the pressure switch on the piping. Gave it a tap with the handle of a screwdriver and the code went away and started working like normal again. The heater will not come on without flow, it can be enabled, but will not fire until a flow is registered.

 

[manzov22]

Its speratic. I wake up in the morning and its ok. Working good. Then a few hours later its back to LO code. Im very confused