I’m building a new house so I’m hard wiring as much as possible. For my alarm sirens and irrigation valves I’m using an ESP32 WiFi board connected to a relay. I’m using the appropriate wire gauge between the relay and siren/valves. But, I’m wondering if I should still put an in-line fuse between the relay board and the siren/valve. Does anyone have an opinion on this?
More than anything else, the fuse would be there to protect the wire leading to the load and possibly the relay contacts. Is there current limiting at the power source? What’s the voltage, expected current, and wire gauge for the loads? What scenarios can you imagine about the probability of shorts along the wire or at the load? Would there be a fire hazard? If there’s a short due damage to a wire along it’s length, realize you’d still need to fix or replace it.
So firstly, im assuming that you’re in the US and i need to say that i dont know absolutely anything about domestic electrical regularions in the US. Check your wiring regulations first and read them whole
But common sense says that since fuses are there to protect the installation, not the device, if you’re using the right conduit diameter in whole circuit already protected by a fuse/MCB, you shouldnt need to use an additional fuses (unless you want to protect the device and it doesnt have a built in fuse).
Yep, I’m in the US. In my area there aren’t regulations for low voltage wiring.
My main concern is protecting from fire. I’ll run 16/2 wire from the relay to the siren (it’s overkill but I have a bunch of 16/2 wire). My longest run will be about 100 feet. I’m also pre-wiring irrigation valves (18 gauge wire, 24V 500ma load) and motorized roller shades (16 gauge wire, 24V 1.5amp load). I’m wondering if I should put a fuse on those too.
The 16-ga wire works out well for everything powered by the same supply. Assuming the supply current capacity is above the rating of the overcurrent protection device, a single 3A or 5A fuse or circuit breaker between the supply and the load could provide protection for the wire as long as there’s no appreciable startup current on the motors. With some measurements, you might even be able to pick a device so it trips (or fuses) when there’s a stalled motor. I would suggest you design the automation such that only one load is being powered at a time.
