System operating on arrival, noted a couple issues with the duct work but assumed system worked before with the current duct design. Found gas pressure too high possibly causing unit to cycle on high limit switch, adjusted gas pressure down to 3.5 inches of water column on high and down to 2.7 on the low. Cycled system to check operation tested both low and high fires, system should be able to maintain and keep up to desired set point of 67-68°F