Does anyone know if a 2 speed 2hp Hayward Tristar pump will typically have enough water flow to operate the Hayward H-Series Universal Lo Nox Heater? This system has 2.5" PVC suction/return with about 50 foot run to pool. On low speed the Hayward Nav actually works. If the heater does not come on in low speed, can we adjust the Pressure Switch in the heater until it comes on? The pool and equipment are level. I understand that Hayward improved the flow through the Heat Exchanger, so I'm wondering then if a greater gpm is now required to create enough back pressure for the Pressure Switch. Any help here?