The boiler type (condensing/non-condensing) and the boiler sizing (in order of priority of operation) are required for this step. Note that most identical boilers in a system are likely to rotate in terms of which one is the lead boiler, and that is okay. A smaller or larger boiler, compared to the rest of the boilers in a system, is likely to be a dedicated lead or lag boiler and should be specified in the priority order accordingly. Boiler efficiency is an optional input. The default is 80% for non-condensing boilers and 91% for condensing boilers. Boiler stage-up part-load ratios are also optional as input. The default is 100% loading to sequence the next boiler. There is no benefit to under 100% for non-condensing boilers.