Dtyjlui

Here is pic of the 3 panels. The third right most is a 2nd disconnect (150A going to the 125A main breaker at main panel at middle with 38mm^2 wire). I will need to downgrade the 150A breaker in 3rd stand alone panel as during overload, the 38mm^2 would melt first before the breaker trips. We have these mismatches because in the Philippines, all contractors apply at city hall using simple fake electrical plans (in the plan it's only 22mm^2 main feeder used and no aircons), then after permit released, the contractors change all details and since there is no inspection, they always get away with it).

This is permanent as I won't put any raceway so no problem about S bends, etc. isn't it? We never have inspection.

This is all covered in normal usage:

consider the following connections:

The above subpanel is connected to the right main panel only 3 inches away:

Do you consider it as 6 circuits inside a Raceway? Is it not a Raceway is when there is a PVC tube (with wires inside it). But when they just converge into an opening and diverse again. Then it is not technically called a Raceway right?

The NEC doesn't impose a derate until you get to 24"

NEC 310.15(B)(3)(a) (essentially replicated for you in PEC 3.10.1.15(b)(2)) does not impose any derating factors for raceways (nipples, really) shorter than 600mm (24"), such as yours:

(a) More than Three Current-Carrying Conductors. Where the
number of current-carrying conductors in a raceway or cable
exceeds three, or where single conductors or multiconductor
cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed
in raceways, the allowable ampacity of each conductor shall be
reduced as shown in Table 310.15(B)(3)(a). Each current-carrying conductor of a paralleled set of conductors shall be
counted as a current-carrying conductor.

So, you do not need to worry about this derate for your application, since the raceway routing would need to be quite convoluted to exceed 24".

However, you have two problems here

First off, the normal sequence of events is that the raceway is installed first and wires then pulled through it -- this avoids causing inordinate damage to wire insulation by gouging it with the ends of raceway sections or the edges of boxes. You'll need to very carefully pull the wires back inside the subpanel box for now until you have the raceway installed.

Furthermore, and more importantly, you have a problem here -- surface mounting the subpanel put you in a situation where the raceway needs to make an offset bend ("dog leg" or "S-bend") to get from a knockout in one panel to a knockout in the other. This is especially troublesome for you for two reasons:

1. Conduit bends have a quite wide radius, especially for fat conduit like the 3" you are using


2. Conduit bodies (including L bodies and pull elbows) must be openable without removing finish materials, just like you cannot drywall over a junction box

Furthermore, that giant 3" nipple is going to cause issues if you flush-mount the subpanel (due to the fact that it will split any stud in the way clean in half). The idea of bringing it in via the front of the main panel doesn't work either, because that'd cause merry heck if the main panel's deadfront had to be removed later for servicing (in fact, I'd call it a violation of NEC 314.22's Exception).

Another problem is that there is not legal work area around the panels, particularly the original panel. Placing them inside cabinets does not work unless the cabinets are quite shallow.

I would say a whopper, however, is the lack of ability to put a lid on the main panel! Particularly it is impossible to reset any breaker without direct contact with hot components and the chance of tearing out a wire. This would get inspectors very, very excited in the U.S. and they would most likely revoke your building's occupancy permit on the spot. Any sort of arc flash that occurs in the panel could easily escape the panel and set the cabinets or their contents on fire. Have a bunch of rolls of paper towel, fwoof.

Now the way I would tackle that is with the smaller knockouts on the side of the subpanel. Use those for five of your circuits (now I realize they are smaller wires in loom, not fat wires). Except I would use flexible metal conduit. Route them wherever feasible so you can access a proper entry point on the main panel. Or better, remove those circuits altogether from the main panel and have them join the armored cable in a junction box just below the main panel.

For the feeder, I would plug the 3" hole with a conduit reducing washer designed for a much smaller conduit, say 1", and again use flexible metal conduit to a proper point of entry on the main panel.

And a minor detail, the extra wires tapping the main lugs are not correct. Since these are your lugs, you can simply stack on another lug, such as crimp lugs, which for such small wires are quite thin.