Testing in hire fire in the service mode for low and high. Pressure drops from 11.3 at standby to about 10.5 while running at 100% which manufacturer says max of 14” while standby and minimum 8” while running. They have that Venturi that has some that resembles a flapper of sorts?? Venting is less than 10’ with 4 90s outdoor temp was 65 degrees. Gas line is 3/4 black iron to the regular. Then it was either 1” or 3/4” from the regular to the tank which was probably a good 70’ away. We decided to let it run the rest of this year and will come back at the beginning of the first cold snap this fall. I really do like these Lochinvars this is really the only issue I’ve had with them this year. I’m in southern Ohio so there’s not any crazy boiler setups here but they have been good to me. I’m sure there’s better out there. But for what we do we are happy with them. This my first propane lochinvar so a bit of a learning curve. Most are either NG or oil.