Monday, August 4, 2014

Fixing Branch Panel Load Issues in Revit

Now that I've actually had some time to stop, here's a couple of tips on making sure you panel loads are correct. This came up when we were trying to connect a 120/240v single phase panel to a 277/480 3 phase panel.

The correct steps are to add the panels first, and make sure their distribution system is set to the correct type.

Next, create the circuit between the lower voltage panels to the transformer.

The secondary distribution setting for the transformer must match the distribution system of the lower voltage panel. 120/208 3 phase panels should match, and the transformer needs to include 3 single pole breakers.

For the 120/240 to work correctly, set the max number of single pole breakers to 2, so only two slots are used to define the circuit. When creating a single phase panel, the Panel Schedule template tools don't correctly display the example as a true A/B circuit, so don't get hung up on how it looks in the template - the panel schedule will skip showing the 3rd phase (c) when it's added to the project.

Once the circuit between the lower voltage panel is defined to the transformer, create the circuit between the transformer and the 3 phase panel.  The loads between common three phase panels will show up correctly on the same A/B/C phase as in the panel, but totaled.

Here's where we ran in to a problem - the A/B loads didn't appear on the three phase panel, but instead only 0's showed up.

If this happens, try this:

1. Add some wiring to devices on a few circuits for the low voltage panel. This helps you check to make sure the circuits are correctly defined. I used the tab selection to pick a circuit, and then use the grip to add wiring, so it does it all at once.
2. Check the connection between the 120/240 panel and the transformer. Sometimes, you need to edit the electrical circuit, and reselect the panel. Not sure why, but this worked better after I added wires.
3. Check the connection between the transformer and the three phase panel - make sure the distribution systems are both set to 480/277.

Sometimes just re-establishing the connections works, and you can always go back and delete the wire.

And if it still fails after that, then just go back to using spreadsheets for your schedules - now that's definitely not the right thing to do...audit the project, and make sure you don't have any errors, and make sure you're on the latest updates for your Revit release.

When all else fails, punt...

thanks - David B.