SQ D 400 amp panel

Note the small red test buttons on each 200 amp breaker.

It was a vacant home so I pushed them and the breakers tripped.

With the breaker labeled “A” tripped, I found the “B” panel in the garage unpowered and the “A” panel still powered. The labeling was just magic marker installer type labeling so I made it clear that no wiring changes were needed just corrections to the labeling.

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That little red button (sometimes a little yellow button) is called a “trip exerciser”. It’s on the annual PM check for breakers of this sort. It is intended to trip the breaker, as you found. I’m not 100% sure I could advise any home inspector (more likely commercial property inspectors) to press the trip exerciser, because Mruphy’s law says you’ll unleash the clockworks gremlins and the breaker won’t reset. That’s not really out of the realm of possibility, because it happened to me on an annual check of some Square D PAF breakers, and they’re 10 grand each, rebuild of existing 2 grand. Those PowerPact breakers in your picture retail for between 600 and 900 dollars each for a 200 amp.


I guess I don’t get out much…did not realize they cost so much…makes me think hard before tripping.

Just make sure you have finished the inspection before tripping them. Also only do it on new, vacant property to discover an expensive problem for your client.

What are the two black plastic devices on the right? Also, aren’t there bend radius restrictions for those wires? Do the 10 tight bends appear to meet the guidelines?

Those 2 black devices on the right are Polaris connectors. They are just pre-insulated giant wirenuts.

Thanks Jim, that’s what I suspected but wanted to make sure. Were they simply used to extend those two wires?

Thats what it looks like Mike.

Note to self -

Don’t touch the little red button,

or the little yellow button

Thanks for the info Mark!

I will add to Marc Shunk’s comment along the way with the exercizer tripping system.,

if you have to exersiczing them make sure the system is not loaded or turn off all branch breaker before you trip the main breaker.

some of the larger main breaker don’t like to open up under load and it can do pretty instering event this is true with larger commercal breaker where the cost of each very large breaker run in thousands of bucks if they screw up.]

just a simple way when you run the exersizer trip them and reset once but if refuse to reset do not attempt to do it twice because something can be jammed or malfuncted.

just pass the word to be safe on large main breaker if you see that set up as you see on the photo if dont have the exersizer you should be ok.
but i treat them as they are " hot "

Merci, Marc

You already got ironed out that they’re Polaris connectors, so I’ll add that there is no minimum bend radius for conductors. There are minimum bend radiuses for cables, but not for conductors. You can bend them to a hard 90 if you’re man enough, as long as the insulation is not damaged. Very high voltage cables and conductors do have a minimum bend radius, but you’re likely to never put your eyes on such an installation. The idea there is that the current flow can literally blast out of the side of too tight of a bend, sorta like a race car going too fast and running off the track on a bend.

Thanks Marc…maybe I was remembering that from my commercial/industrial facilities days, heck I don’t know.

so how is this a 400 amp panel?

How do you mean? The rating of the panel, in this case 400 amp, more relates to the “heavy duty-ness” of the bus and doesn’t necessarily have anything to do with the breakers in it. In this case, we have two, 200-amp breakers installed, which probably comes close to fully utilizing the rating of the panel it is installed in.

Yep, its a 400 amp main panel, with two seperate disconnects.
The garage has two, 200 amp sub panels.

The meter on this 5800 sf house was 320 amp. I noted this as a simple comment in the report.

I was told by my local power company that they do not have any 400 amp meters about a year ago. I think they know that a 320 amp meter will not meltdown with 400 amp load for a rare few minutes if ever.

If anyone has a closeup picture of a 400 amp 240V meter, please post it.

You’re likely to never see one, but here’s a few pics of a 400 amp across the line meter, just the same. Greater than 320 is almost always CT metered, so this is a very rare bird:

I totally agree. A “real” 400A service in a home is a very rare thing. Everyone I have seen or done has been a 320/400.
Over that would be 600A (and up) in most situations and either CT or primary metered.

Best I can do. Saw this today actually. Sub was in garage.



Yeah, that’s a 320, which for some reason is what we all call a 400 amp service.


The buyer had the plans with him, which called for 400 amp service and a 100 amp sub. I was a little confused by this. The sub I found was in the garage, and was fed from the second disconnect, which if not mistaken is 200 amps as well right? I looked everywhere for another sub but no luck. New home too. Ideas?