Main Panel Amp Limit?

[Cmy]

Looking at breaker change for 120% rule. With 200a feed, what determines a panel's amps - manufacture label, main breaker, volume for larger wires? Is code OK with changing a 200a panel's 200a main to 225a main breaker, or do I need a 225a panel? I assume you can change a 200a panel to a 175a, or lower, main breaker without code issues other than total breaker amps.

Currently have a 100a line to a 100a shop panel that I want to replace - old, ugly, and no breaker slots left. Trenching a new URD 200a line to a new 225a panel that takes inverter's grid tied AC out. Replace the 100a panel with a 150a panel, use old 100a main breaker, and save the 150a panel's 150 main for the new 225a panel.

The existing 100a panel works but I could tap the new 225a to the 100a replacement panel. That would surplus 300+ ft of 4awg cable (1987 code?) and its 1.5in buried conduit. Conduit is too small for 200a cable and 4awg probably too large for for panel connections. Run a string line in case a hybrid shows up some day and I need distant CTs.

Would a 4awg ALU serve as ground for a 200a feed, some charts show 2awg? One less URD wire to run. Shop panel was first on site and has its own ground with a copper wire going into the ground under the slab. New buildings added new panels and the shop 100amps changed from grid to a new panel, but ground was never moved. So the home has its ground and the shop its own ground and that needs to change.

 

[Hedges]

There should be a sticker giving the busbar rating. It might be 200A, might be 225A.

There are several rules to choose from: 120%, 100%, Sum of Breakers.

Probably 120% rule works best here; 200A busbar with 200A main breaker allows 40A backfed PV breaker. Change to 175A main breaker and you can have 65A backfeed breaker, etc. If 225A busbar, that lets PV breaker be even bigger.

To go higher without involving panel upgrade and your utility, you could move all branch breakers to new sub-panel and install a 200A breaker or tap in existing panel.

Whether your pull-out 150A breaker works in new 225A panel depends on form-factor. I use QO, and they have two sizes.

Wire and trenching gets expensive. If you can stick with 100A breaker (80A continuous) and just upgrade panel, that saves money and work.

 

[Cmy]

Been awhile so I pulled the 100 amp panel's breaker cover and found the incoming mains are 4awg copper and not aluminum. Old panel label says 100a but a 125 main was installed before I got here. 12 breaker slots, some filled with 1/2 breakers, other with double wires - this panel is going, maybe used later near the inverter.
Paired 100a breakers feed the existing 4awg Cu wire, wish I could change them to 150a but charts say no. I trenched a 130 ft propane line and this would be ~95 ft. But if Growatt's 48 AC amps is happy with a 100 amp breakers and line then it save time and money.

House has GE panels, 2019 addition got a Homeline, so new Homeline to get some breaker commonality.

 

[Cmy]

I see what you mean about breaker size. Encouraged by lower prices then found the Square D chart with QOM 1 and 2 frame sizes with the breakers for each. 2s seem almost $100 more than the 1s with the big box stores out of stock. Electrical sites are closer to Square D's list price.

 

[Hedges]

Schneider msrp and Grainger prices are ridiculous.

I've bought some on eBay, often new.
One I bought for close to $100 including shipping had a faded $39 price tag from Home Depot.
Just Googling for part number and "price", I often find reasonable distributors.

Outdoor 3R panels come with cover. Indoor, often you have to buy either flush or surface mount cover separately, sometimes comes in a bundle. Some bundles even come with a few breakers.

Most of what I see is $50 to $400, depending on size and main breaker included.
The 200A main breaker only box was about $185 at Home Depot. The ring-type meter socket was another $150, I think (ringless I bought first had been $95)

I have a bunch in "stock" (mostly allocated to future plans in my mind), but I need to buy a 200A or 225A main lug only panel for PV combiner.

 

[Cmy]

Just went through Ebay and QOM2s, 125-225 amps, can be had for ~$80 and up. Prices overlap.

Getting the hom3060L225PGCVP panel for the 100 amp line as it will take 200a if I need a line upgrade. Can't decide between QOM2s 125, 150, or 225. 225 for future needs and never need to change, 150 works well with 120%, but 125 is all I need now.