Fuse and AWG choice for immersion heater circuit

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I am planning to operate a 1500 W resistance immersion heater with an SSR and I'm trying to determine which fuse and AWG wire to use. The 1500 W heater on 115 VAC should operate at a current of around 13 A. The SSR is rated for 25 A. The chart from Grainger's website says that 14 AWG should be good for up to 15 A, so I'm planning on going with that size. I searched on McMasterCarr for a fuse for 13 A and the closest thing that I found was 15 A, so that is what I'm planning on using. Is the 15 A rating too high above the expected 13 A operating current?

Part of the reason for the fuse is to protect the circuit from power spikes/surges, but how much higher can those surges make the current go, compared to the normal current of the circuit? Should I be using 12 AWG wire (rated for 20 A) to account for power surges that might bring the current above the 15 A that the 14 AWG wire is rated for?

I have also seen some diagrams where it looks like the fuse is installed on the return line (shown black below) instead of on the hot wire (shown red below) before the SSR like in my diagram below. Should the AC fuse be placed before the SSR or on the return line and why would I install it on the return line if that is the right way? These questions are related to the AC loop in the diagram below:

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Best Answer

In the US and Canada most 120 volt outlets will be protected by a 15 amp circuit breaker and wired with #14 wire, although 20 Amp circuits with #12 wire may also be used. There should be no need for your Fuse 2, but there is no harm in having it. The fuse should be at least 15 Amp - if the fuse rating is too close to the normal load, then it may blow for no real reason.

All fusing and switching must be in the "hot" wire to ensure that the circuit following the switch or fuse is dead when the switch is off or the fuse is blown.