When the demand is lower than the minimum part load, I believe EnergyPlus will operate the boiler at 20% capacity because it can't modulate to operate at lower loads. The boiler does not cycle to meet the lower loads, it just outputs its minimum. The result is hotter than normal outlet temperatures.

When the demand is lower than the minimum part load, I believe EnergyPlus will operate the boiler at 20% capacity because it can't operate at lower loads. The boiler does not cycle to meet the lower loads, it just outputs its it's minimum. The result is hotter than normal outlet temperatures.