Two countdown timers connected to one inline fan — Does it work?

This is the classic "DC electronics guy thinking schematic. Here, you need to think wiring diagram due to NEC 300.3(B) and the eddy currents induced by AC EMF. So wiring routes must be a "tree" topology; no loops or bubbles.

All wiring throws EMFs. For steady-state DC power, it's like a refrigerator magnet. Not for AC power; its constant changing causes powerful EMF effects.

As long as all related conductors are tight-packed in the same cable, these EMF effects cancel each other out. Say there's 6A on hot1 and 4A on hot2 both returning 10A on neutral. That's 10A of EMF that are equal and opposite, and cancel each other out, and that is fine.

Anytime AC power goes out one path and back another, that encircled area becomes the core of a transformer. So if hot2 took a different path, now you have 4 ampere-turns being induced into the encirclement, which will cause vibration (leading to wire cracking leading to overheat), eddy current heating in anything ferrous or nonferrous, etc. That's why we don't do that thing.

However, what happens inside a junction box is something we are resigned to. And it helps for EMFs to use a metal box. I don't know why people are so in love with plastic boxes, SMH.

So here's the plan

Wire it with a /2 cable from supply to timer1, then /3 to timer2, then /2 to the fan. This is "tree" topology and complies with 300.3(B).

Supply to time1 carries always-hot (black), neutral (white) and of course safety earthing.

Timer1 to time2 contains always-hot (black), switched-hot (red), neutral (white), and earth.

Timer2 to fan contains switched-hot (black remarked red), neutral (white) and earth.

The remarking of black to red is not a Code requirement but it makes the circuit easier to understand by making colors match wire function.

At timer1, the timer connects to always-hot (black) and switched-hot (red).

At timer2, ditto.

Wow, that was easy.