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?