Siemens spring loaded breaker 

Close...you CAN close this breaker with load, but it is not a good practice and is ultra hazardous. (Speaking of main breakers here, some plants use this style breaker to feed downstream panels and equipment, which would make them more like a hi tech Pringle switch or feeder breaker in that application.) It is still always best and safest practice *especially on first commissioning or after ANY fault that trips a main* to open ALL downstream breakers/switches, reset the main, then gradually bring the other breakers/switches on line, one at a time. This also helps determine where a fault may have occurred or is still present. Breakers over 1,000 amps you should always wear appropriate arc flash PPE with the minimum cal ratings as per any warning labels. In older systems with no labels or ANY older style main breaker, regardless of amperage, the best practice is a minimum 20 cal rated suit, and face protection. It only takes one time to seriously burn or unalive yourself with this stuff.

@@mxslick50 sorry but you arw wrong , breaker are design to handle load that is there fonction especially closing closing on load is no more that closing no load, opening with load will create small arc and a fault.... lots of it lol but they can handle it... breaker are self contain vs bold and pringle switch and for closing section by section that is the old day .. now a day you want to do the minimum operation live to prevent arc flash risk if there is a fault if coordination is correct fault will be limited to the faulted area... except in case of short circuit where multiple breaker can open ps amp rating si irrelevant wear ppe if needed ... i hace seen 200 amp panel with 40 calories....

@@moreause Your comment was a hard read with all the misspellings and grammatical errors...but you are wrong on many points, right on a few. I have been dealing with that gear for over 35 years and have seen too many incidents trying to close into a full load, especially one on a large plant with many 480 - 120/208 stepdown transformers. The inrush current can easily go well beyond what the breaker can safely handle, or at best it will trip from the inrush requiring multiple attempts to close in, which magnifies the risks considerably. Closing in to a load is ALWAYS MORE than no load. It is not nor ever has been "no more that closing no load". Minimum operations is in theory a good principle but in cases of large plants (I did a wastewater treatment plant with a 4000 amp service) it was impossible to close the main without first isolating the 8 other feeders, the inrush was horrendous. It had to be done in stages, and in a specific order. Try to just close the main, or in the wrong sequence, and you'd be resetting that main multiple times if not causing it to fail, violently. (Which had happened TWICE in the past, the cabinet still had the burn marks.) System coordination is tricky and works about 75% of the time, but as you said, short circuits usually defeat coordination and trip multiple breakers. Available fault currents have risen dramatically over the years, and many places with older switchgear are serious hazards because the older gear was not designed to handle the increased available fault currents, which BTW makes the staged sequence of closing in SAFER overall. I will agree with the last thing you said, and yes 40cal PPE can be required on most any size of service, regardless of amperage. Thus my warning to use at least 20 cal even if no PPE requirements are called out.

​@@mxslick50 you are mixing bad design vs breaker operation if you have to split load because of transformer inrush or overload triping that is bad design .... yeah 35 year ... i could say the same on my side ... as a service tech that do maintenance specificcaly on these type of breaker i say it again closing on a full load is no worse that no load, it's doesn't create any wear on contact or mechanical part ..... breaker can easely handle inrush current... breaker are design to handle short-circuit current. Just so we are clear a breaker can TRIP because of overload, bad setting ect .... that is part of breaker protection design and is no issue to the breaker itself you can have a 1000 amp breaker triping on inrush ..... but that breaker is physicaly design to be able to withstand 22,55,65 and even 100 KA depending on the breaker type if the breaker trip on inrush it is not a breaker issue it's a system design and setting issue Available fault current have not change over here thru the year ..mostly the opposite .... mostly because arc flash changed the way they design stuff ... but yes you can end up with a BAD design ... old stuff hooked to a new section that result in incorrect short circuit capacity ps 20 calories in in between standard ...ok they are suppose to be gone ...old standard was level 8,25 and 40 calorie 20 for some reason is starting to appear ...my new arc flash helmet is 20 calories ps in what part of the world are you ? ps when i started a while back we had customer with similare triping issue on start up, now a day with arc flash, electronic relay, ect you are not suppose to see that anymore