Incorporate adjustable trip breakers
Add the ability to specify breakers with electronic trip units (ETUs), aka adjustable trip breakers, in Design Master projects.
The intent of adding this capability would be to allow the user to flag where an ETU is used and display the required/desired settings.
It would NOT be the intent to make DM have the functionality to do the coordination studies necessary to develop the settings.
1) Electronic trip breakers, when used, are usually MCBs or feeder breakers with the following characteristics:
Breaker Frame (AF)
Breaker trip (AT)
Breaker plug size (AP)*
Long-time pickup (LTPU)
Long-time delay (LTD)
Short-time pickup (STPU)
Short-time delay (STD)
Instantaneous Pickup (IPU)
Ground-fault delay (GFD)
Some breakers for the European market have these settings in lue of GFPU and GFD:
Earth-leakage trip delay
2) These results could be presented on the drawings by:
a. A settings table/schedule listing the circuit and the characteristics listed above.
b. A modified panel schedule header incorporating the items above when the main has an ETU.
c. A modified switchboard schedule listing the above characteristics as columns on each feeder and the header section modified to incorporate the ETU attributes on the main.
3) DM would probably need to create a new SubType 4 for ETUs in the panel and circuit tables. tblCircuit would need to have fields added for the characteristics above.
4) To enter the settings there would need to be a user selection on:
a. The panel definition screen - for panels where the main is adjustable.
b. The switchboard definition screen - for switchboards where the main is adjustable.
c. On the circuiting screen - for switchboard feeders with ETUs.
All three of these would call the same screen to enter and store the characteristics above.
5) Some additional rules:
a. Default wire selection should remain as it is now “Size Automatically. If a user wants to change the wire ampacity to match a LTPU setting they should have to manually add a wire size for that amperage and change the wire selection.
b. ETUs are usually not available in frame sizes smaller than 250A.
c. It would be helpful to capture the basis-of-design for each ETU, by that I mean the manufacturer and breaker catalog number/description used.
- Some manufacturers allow the selection of plug sizes different from the trip and frame setting. For example GE offers a 1175 amp plug for its 1200AF with a 1200AT as an alternate means to meet NEC 240.87 (energy reducing active arc flash mitigation).
** Some manufacturers, e.g. Schneider, offer built-in amp or energy metering on their Micrologic trip units.