I just put in a new pool with a Laars LT 400,000 BTU natural gas heater. The pipe from the gas meter to the heater is 1 1/2" and is reduced to 3/4" at the meter and at the heater. The length of the 3/4" pipe is about 4" at the meter end and about 18" at the heater end.
When I turn the heater on, the blower comes on at high speed for about 15 seconds then goes to a low speed. About 15 later the heater fires up and I can hear a jet engine like sound. There is warm air coming from the vent and it appears like it's working fine. About 15 seconds later, the fan goes back to high speed and the burners go out. This cycle goes for 2-3 times and then it stops trying all together. The AGS (auto gas shutdown) light will flash red.
1 - Do I need a high-flow gas meter to keep up with the heater demand?
2 - Is the 18" length of 3/4" pipe at the heater too restricting? If so should I plumb the 1 1/2" pipe as close as I can get?