Hello all, I'm having some trouble interpreting what is required in regards to modulation w/ heating and cooling equipment. I have always trusted the curves in the Trace ASHRAE library members however, I have recently seen some conflicting documentation and model reports that are confusing me. Per Trace curves, all equipment is inherently capable of modulation. At 100% load, a boiler consumes 100% of the power and at 1% load a boiler consumes 1% of the power. It seems like Trace has this wrong. The only thing I have been able to find in ASHRAE refers to cooling part-load efficiencies, and states that minimum efficiency requirements need only be adhered to if the compressors are capable of modulation. However, there is nothing that defines whether or not compressors should be modulating, so it would appear that the baseline is on/off. There are no specifics outlines in regards to boiler/furnace modulation that I have been able to find either. Can you tell me in your experience, what the requirements are for baseline equipment modulation for all equipments types? And does Trace really have this wrong with all their ASHRAE library members or am I missing something? Best, Jason -- *Jason Dietterick, CEM* Associate The Stone House Group ? Suite 400 ?? 301 Broadway Bethlehem ?,? PA 18015 tel. 610 868 9600 | dir. 484 548 4007 fax 610 868 2272