Parker, I consulted with one of my borthers and we agreed that teh old 5x16 took approximately 150 gallons. However, we ran it deeper than most people to avoid any possibility of scorching. We also had a smaller system, but never had runs small enough to worry about only firing up only one or the other. Good luck; hope this helps.
Russell Berg
Mount View Sugar Bush - Since 1989
2004 5.5' x 18' Custom-built Stainless Evaporator w/ 7' Piggyback + Preheater
4,000 - 5,000 taps vacuum/gravity/bags
24' x 32' Sugar Shack