MEP System Implementation Guide

Quick Reference

ALWAYS create ports on distribution elements BEFORE attempting to connect them. Elements without ports cannot participate in flow networks.
ALWAYS create at least two ports per segment element (one inlet, one outlet). Segments are flow-through elements.
NEVER connect two ports with the same flow direction. A SOURCE port MUST connect to a SINK port.
NEVER use IfcDistributionSystem in IFC2X3 models. Use ifc_class="IfcSystem" for IFC2X3 compatibility.
ALWAYS use ifcopenshell.api.run("system.add_system", ...) to create systems. NEVER use model.create_entity("IfcDistributionSystem") directly — it skips required relationship setup.
ALWAYS assign elements to a system AFTER creating port connections. The system is a logical grouping; ports define the physical topology.
NEVER assume system.remove_system deletes contained elements. It ONLY removes the system grouping; elements and their ports remain in the model.
ALWAYS use ifcopenshell.api.run("root.create_entity", ...) for MEP elements, not model.create_entity(). The API sets GlobalId, ownership, and validates predefined types.
ALWAYS pass products as a list to system.assign_system (v0.8+ convention).