This is my main panel cabinet.
My original plan was to put the subpanel in front of main panel inside the cabinet by just letting it stand naturally (because it would be distracting or not good to the look to connect it to the wall outside the cabinet). For those who have tried this. What problems have you encountered? This is why I need to limit the Siemens sub load center to 12 space 18" height so I can still access the main panel.
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This is my main panel with 16 2-pole breakers US style. All use GE (General Electric) plug-in breakers.
The breaker on top is a 125A 2-pole. Are all 125A breakers really that big?
I'm replacing six of the original GE 2-pole breakers with six Siemens GFCI 2-pole breakers. Since I can't directly plug the 6 pcs due to bus nub mismatch. I need to use a subpanel. Now my question:
My 6 pcs of Siemens 2-pole GFCI breakers are rated at 60A 2 pcs, 30A, 4 pcs.
Can I connect them or the 6 branch subpanel to just one of the main breaker output say rated at 70A or even 100A? In a panel, How many ampere can a breaker bus support provided the whole panel is rated at 100A.. is a single breaker bus also 100A? If not, what is the rule of the connections generally?
I can't replace the entire panel because it's difficult to get it out of the concrete wall and put another one fit right for it.
What's the usual way to add subpanel? What did you do?
Best Answer
In the US, part of the panels ratings are the maximum current for a single bus stab. Many panels say on the label not to exceed a certain current level on a single bus stab. Most residential panels are double row so a single bus stab feeds two breakers, one on the left, one on the right. The sum current these breakers supply can't exceed the bus stab rating.
There are other ways to feed a subpanel. If your panel has or can be fitted for feed through lugs, you can feed the subpanel from those lugs.
The NEC has feeder tap rules that allow you to tap the feeders for a subpanel without overcurrent protection - normally a big no-no - within certain limits. The feeder tap rules outline these limits - distance limits, running in conduit, etc.
Another option may be to change out the panel "guts" with a retrofit interior kit. With these kits you remove and replace the bus, lugs, etc. If Siemens makes a retrofit kit with a bus compatible with your breakers, you could replace the guts and use your Siemens breakers. However you'd have to replace all the breakers in the panel with Siemens breakers as well.