The drafters would make a copy of piping isometric line work, scale them to fit the EHT isometric title block, and then manually add the EHT layout/Power connection/RTD location. The EHT isometric may span across multiple piping isometrics and line numbers. The EHT drawing number is usually based on the EHT controller. We have recently started performing model reviews on EHT as it’s easier to see where the piping low points are and see where the temperature reading is coming from (RTD location). These model reviews help ensure that we have appropriately located RTD and heat trace. In an ideal situation, I would have an addition attribute (maybe more than one as there could be more than one EHT run on an item) for all components (piping/equipment/instrument) such that we could populate the EHT isometric/controller number. It would also be good to be able to generate the EHT isometric based on that populated EHT drawing number (like the isosheet attribute).