If the combination of the three loads requires an S260, then that is what I would go with. It seems the conversation has left out the fact that, according to the TS, he needs a 260 to actually meet his need, but is worried about the times when the demand drops. In that case, the 130 would be find for Steamup's low load, which is actually not low for the S130. However, when heat was needed in all three areas, the S130 wouldn't be sufficient. Considering all these factors, with the information given, the 260 seems to be the logical choice.