I bought the subject burner about a month ago with the NG conversion kit. I did my first brew with propane and it was awesome. I even ran an experiment with 5 gal of water and got 12 min. from 60 degF to 160 and and less than 25 min from 60 degF to boil. I just put together the fittings and hose to run it on NG. I’m getting terrible results. From 60 degF to 168 it took 32 minutes. I know there is 15% less energy but this is ridiculous. The conversion kit says it has a 1/8" orifice and I verified it with a measurement. It also says you need 5" WC for the gas. I measured it at the source and at the burner and I get about 7". I’m using a 32’ stainless 3/8" hose with 3/8" flare on the ends. I contacted Blichmann before I purchased it and they said it should be fine.
Here is a pic of the flame with NG - I’m sure the flames were much taller with propane:
These are plots of temperature versus time for the LP and NG (note: LP is more than 2x as fast):
Any suggestions? Do I need a bigger orifice? (this burner is rated at 75,000 btu/hr LP and 60,000 NG)