Which switch to use SPST or SPDT?

[moecarama]

I just installed a GPS antenna via a NMEA2000 network. I installed the mandatory network power off switch (spst). It is suggested that the unit be connected with a switch also to prevent electrolysis in the power cable plug. I don't want to drill more holes in the dash. My question to those familiar with this method of wiring; is will a single pole double throw switch be better to shut off power to both systems; as opposed to (2) separate single pole single throw switches.

[Cane Pole]

I turn everything electronic on/off with one switch. SPST. No power, no electrolysis, except in different metal contact situations.

[moecarama]

That's simple and straight forward ; I will put them both on the same switch and mount a switch on the main positive cable near the battery.

[Cane Pole]

I would put a fuse before the switch to protect the wire (per wire gauge rating), then inline fuse individual pieces of equipment at the recommended fuse rate and near the equipment to be protected for convenience.

[moecarama]

I didn't think about fusing near the battery and switch; all items are fused per manufacture recommendations. Now should I fuse based on the sum of amperage from all items or use a 50 amp breaker....got one of those on hand from a TM.

[thill]

Using a DPDT switch would work fine, if you want to separate them for some reason, but I can't think of any real benefit to doing it that way, rather than just connecting both to the same SPST switch. Maybe easier to connect the spades to, instead of using a piggyback?

No, no big 50A for electronics. The inline fuses rated for the unit and antenna are just fine.

What Cane pole was suggesting, is that you put a heavier, say 15A or 20A fuse in line before the switch, just in case a wire gets cut or grounded before it gets to the switch, for EXTRA protection. That is certainly not necessary, and it could cause problem spots later, if corrosion were to get into the extra fuses, but it is not the worst idea, either. Up to you.

But sometimes, overkill causes more problems than it prevents.

-TH

[moecarama]

I like the way ya'll think, one switch has been installed.

[Cane Pole]

BoatUS

Overcurrent Protection

Overcurrent protection is a frequently misunderstood subject. Its need arises from the fact that if a short circuit develops in onboard wiring, high current flows occur, generating heat and causing cables to melt down. If the short is a serious one (a "dead short"), cables can burst into flames, setting fire to the boat and its surroundings. Electrical fires are among the most common fires onboard.
Fuses and circuit breakers, which collectively are known as overcurrent protection devices, are the primary defense against electrical fires. To be effective, they must meet two conditions: they must be properly sized for their circuit, and they must be placed as close as possible to the electrical source for the circuit.

[Barnacle Bill]

What Tom is saying. Fuses protect people not electronics.

[Tracker123]

What Tom is saying. Fuses protect people not electronics.

Ditto on that.