LV D.O.L Starter Thermal Overload Position

It doesn't matter. No matter where in the circuit it is located, the overload relay causes the current to shut off through all components of the circuit.

Moreover, there are MCPs (motor circuit protectors), including overload protection, that are installed "upstream" of contactors.

Being a standard DOL starter I take these to be your industry-standard contactor and thermal relay combinations.

Because that is how all the combination contactor and thermal relays are constructed.

The thermal relay is a control element only. It switches the contactor coil which in turn opens the contactor and electrically isolates the thermal relay. The thermal relay has no high current switching capability or electrical isolation capability itself, hence it is always down stream (after) the contactor.

In my 40+ years of experience I seen Thermal relay only before Magnetic contactor. First time I am hearing this. But it don't matter if it is fulfilling the intended function.

This is the normal Arrangement. Can you send a picture of what you have seen for 40 years.

Mounting it ahead of the contactor offers no more protection for the contacts than mounting it behind. Current in a circuit is the same in all parts of the circuit. Since the way a TOL relay functions is to act upon the coil of the contactor, where the sensing elements are is irrelevant.

As to why they are traditionally below the contactor, that is because of the earliest designs and the fact that in many of those early systems, the OL heater elements were replaceable, so if the TOL was ahead of the contactor and the heaters needed replacing, the terminals were live, whereas if down stream if the contactor, they were not. That predates more modern sensibilities about not working on live equipment at all, but the tradition continues. Now however, that would not be an issue.

SHOULD not be an issue. Mistakes happen. Having the heaters down stream adds a layer of protection if, because of sloppy workmanship, bravado, laziness or defective disconnect the circuit is still live. Should never happen, but can. OP does not seem to understand that current is current no mater where in the circuit it is measured. - JHF

There are some obscure faults where the overload relay could detect a contactor fault if it was mounted ahead of the contactor, a low level fault not detectable by the upstream fuse, (magnetic) circuit protector or (thermal-magnetic) circuit breaker.

Those obscure faults will eventually escalate so they are indirectly detected by downstream overload sensors, such as high resistance or open circuit on one or two phases. The reaction of the motor will cause the overload relay to trip. A fairly common incident is a loose connection between the contactor load side and the overload relay line side, which creates heat that conducts down to electro-mechanical overload relays, tripping them off, and confusing the techs who always look to the motor first.

Line side contactor loose connections escalate to a much higher level before clearing.

Of perhaps more interest is... the N/C contact of the overload block should be in the feed to the coil and not after the coil connecting the coil to the neutral (return) conductor.

Why? If a coil burned out and managed to short to ground with just the right impedance, it could conceivably allow the coil to stay energized even if the N/C contact were to open. I have seen this happen twice in my career.

I agree. However, in reversing and two-speed starters, it has been usual to place the NC contacts after the pair of coils, with red wire between.

Yup... seen this arrangement many times.

I think that practice arose to make it difficult for someone to inadvertently hot wire out the protection.

To get a motor going, a jumper wire from Hot to the Coil is the midnight fix to keep the process going (in the olden days), so having the O/L relay on the neutral side may have been deemed less risky than a grounded coil. I haven't been doing this long enough I guess to see a grounded coil bypass an overload relay, but certainly possible & plausible. On the other hand, I have seen lots of midnight hot wired motor starters (Who me?), especially when no one thought to publish the interlock list, or the button on the control panel is buried in a sea of 120V open terminals (old US style).

Because the motor overload isn't there to protect the contactor; it is there to protect the motor. It is the FUSES that are there to protect the other components in the circuit.

...principally the cables...