double fuses?

[mainjet]

I am putting in a switch panel like this one
https://www.amazon.com/gp/product/B003E24MKA/ref=ox_sc_act_title_4?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

And a fuse block like this one.
https://www.amazon.com/gp/product/B000THQ0CQ/ref=ox_sc_act_title_8?ie=UTF8&psc=1&smid=A1UNWS4MSNTF2A

Both of these items appearently fused. My question is - is it okay to have fuses at the switch and then again at the fuse block or should I be doing something else?

I have been doing a lot of reading on here concerning all this and it seems to be the same items that people in the know are recommending. It just got me thinking when I saw that they were both fused.

Also, should there be a fuse on the main positive line running between the battery and the fuse block?

 

[kofkorn]

No problems running double fuses. Just need to remember both sets if something starts going wrong. It'll probably be easier to have smaller fuses in the fuse block so that if they blow, the small ones will blow first, and you know where to look.

Definitely should have a fuse between the battery and the fuse block. It should be sized based on the main trunk wire that you are going to run from the batter to the fuse block. Make sure your fuse melts before your wire does!

Good luck!

 

[BigTerp]

Not to hijack, but I'm also planning on using the same switch panel as mainjet. Been doing alot of reading on wiring and seem to getting a decent grasp on the subject. If one were to use the fuse block that mainjet has linked would you only have to run positive wires from the fuse block to your accessory? I see it has a ground within the fuse block. Just thinking it would make things cleaner in the boat to not have to run 2 wires to each accessory. I'm thinking battery > fuse block > switch panel (positive only) > accessories (positive only). But maybe I'm way off base here??

 

[mainjet]

The negative side has to go back to the battery somehow to complete the circuit. So you could use the neg bus on the fuse panel or you can use a separate neg bus bar. Either way the neg side from the component need to come from the component back to the battery to complet it. So using the neg bus on the fuse panel seems the easiest and least expensive to me since you already have it there.

 

[MNHunter505]

I am using the same switch panel and IMO, the fuse block is not necessary. Why spend that $40 if you don't need to. Just go to Lowes and buy two $4.50 bus bars. One for ground, one for positive. Save you some money and look clean. And yes, the wire going from the battery to the bus bar should be a big gauge wire with an inline fuse.

 

[twds]

Not to intrude with another question, but I am just finishing my build. I also use a fuse block for some of the accesories and the switch panel for the other accesories. I have 4AWG running from the battery to the fuse box and swith panel. How big of fuse would you recomend? On fuse box running, steroe, 2 Cig lighter plug, depth finder and electric anchor. On swith panel running, two lights, cig lighter plug and bilge pump. Also how do I know what fuse to place in each spot of the Fuse panel and switch panel?

 

[mainjet]

This is what I believe to be true but others will chime in with the real truth. LOL

for the fuse for the fuse box should be one sized to cover the total amperage of the accessories hooked to it. Add up the amp draw from each accessory and be sure to use the amps that the cig lighter is rated for in case you plug in a high draw item.

If the fuse panel has fuses and the switch panel has fuses then match the same fuse for each circuit. example - if the bilge is on a switch and it draws 5 amps then put a 5 amp fuse in the switch panel and a 5 amp fuse in the fuse box.

for which fuse to use in each spot - look at the rated amperage for each accessory and fuse for that amperage. It it says it draws 5 amps, use a 5 amp fuse.

I decided to do what MNHunter505 said and use busbars. Not exactly because it's cleaner because I thing that the fuse panel would have been very neat. But I decided to do it because I don't want the double fuses. if something blows on the 5 amp circuit, I don't want to need two 5 amp fuses just to get it going again.

 

[mainjet]

Can someone please check the wiring layout here for obvious omissions or things I have missed?

This is a 14 ft boat. I may move the battery back to between the 2nd seat forward and the 3rd seat and put it to the left side of the boat in an enclosure I build. I want it forward to balance out the boat but I sit on the right side of the rear seat as I steer the boat. If someone is in front of the boat then they would normally be centered on the bench seat. So even if they weigh as much as me, the fact that I am sitting to one side and they are in the middle, seems to me that the battery on the left side should hemp balance the boat.

Right now I will be running one 12V deep cycle battery and running everything on that. I don't have a fish finder and I will rarely use the Anchor light or running light. Mostly I will be running the trolling motor and maybe using the 12V power outlet to keep a phone charged. Later, I may add a small second battery and then hook all the accessories to that and run the trolling motor only on the deep cycle.

 

[kofkorn]

You've got a potential hazard in your wiring, as your 14 awg and 12 awg wires are only protected by the 30A fuse. 30A is too big for 14ga, and really borderline for a 12ga wire. If you happen to cut the wiring jacket with an oar or anchor, you could have a short to the hull that could cause a fire with the wiring before the fuse blows.

I would suggest that you move the bus bar as close to the switch panel as possible, using 10 Ga (or bigger) wiring between the 30A fuse and the switch panel. This way your fuse will blow before the wire heats up.

Additionally, you'll want to make sure that you run your ground wires directly back to the grounding bus. Not a good idea to use the aluminum hull as your return. It accelerates any galvanic corrosion conditions that already exist around the hull.

Good luck!

 

[mainjet]

Thank you for the tips.

I should have made it clearer on the grounds - all of them are running back to the ground bus bar not to the hull. I removed the ground lines on the drawing for better clarity but it seems it just confused things. LOL

If I understand you correctly, I could take the ground and positive bus bars and move them by the switch then put the 30 amp fuse there by the switch?

The switch panel that I have there is fused for each circuit. I figured that the 30 amp was just protecting the whole fuse panel itself and the individual fuses on the panel were protecting the circuits but I guess I have it too far away for that? I was under the impression that the fuse needed to be close to the battery.

thanks for your help.

 

[kofkorn]

You're right that the fuse needs to be as close to the battery as possible. Your 30A fuse is in the proper location. However, when you break down to the smaller wires at each of the bus bar locations, you need to have the individual lines protected with a fuse of the proper size. 30A is too big for 14Ga wires. Immediately after the bus bar should be fuses for each individual branch that are of smaller values (based on wires and equipment). The fuses should be as close to the breakout point as possible. the fuse location you have drawn on your Aft Livewell circuit is correct, and this is how the rest of the lines should be fused.

In this case based on your drawing, it seems like it would be easier to move the bus bar close to the switch panel, and then if I remember correctly each of the switches is already fused with a smaller value. If your fuse is 30A, you should use a 10ga wire for each connection between the 30A fuse, the bus bar, and the switch panel. It is unlikely that you'll be drawing 30A on a regular basis, so the 10ga is acceptable for the longer run from the front of the boat to the switch panel.

The key here is that it should always be:

Power supply > Immediate fuse of the proper size > Wire > Equipment

If the wire size changes, you need to consider if the fuse in front of it is of equal or smaller value than the rating of the wire. If the wire cannot handle the rating of the fuse in front of it, a new fuse of the right size needs to be added. No issue with stacking up fuses within the system.

 

[mainjet]

That's good info. Thank you.

So maybe I should just go back to my original plan in my first post in this thread. Just take out the busbars and put back in the fuse panel in the location the busbars are in my drawing now. Then I would go from the battery positive to a fuse then to the main positive on the fuse panel. At that point, each line would then have an individual fuse there and then again on the switch panel.

For the Negative side of the fuse panel I would just come of the neg side of the battery and go to the ground bus ont he fuse panel. Then all the grouds from each circuit would go to the ground bus on the fuse panel.

That sounds about like what you are describing as the proper fusing and routing, correct?

 

[kofkorn]

That would certainly do the job. Although, it looks to me like you could use less wire and save some money by moving the bus bar closer to the switch panel and use one 10ga wire from the battery. Then you would only need to small 10 ga jumpers to the individual switches. This also eliminates the need for the extra fuses.

Take a look:

 

[mainjet]

Oh that is perfect! I like that. Thank you for taking the time to do that for me. I will do it the way you show.

Would it make sense to put the negative bus back by the switch also and run a 10 ga. to that? Or would the neg bus location be more a matter of what is the shortest/easiest location for each run at that point?

 

[kofkorn]

That's up to your preference. It made more sense for the positive, because all of the connections were going to the switch panel. When it comes to the ground, it's less straightforward.

I think that your wiring might be cleaner if you simply duplicate the positive bus system, running pairs of wires for each unit, but that will use more wire than simply running the shortest route back to the battery. I guess in your case you've got an open boat. I would probably just run the wires back to the battery. If it was something like a fully decked boat, it will probably be easier to run the wire pairs together, less wire to chase through tough spots.

Either way shouldn't be a big problem. If you are using the bus system, just duplicate the wire sizes in reverse to be safe.

Good luck!

 

[lckstckn2smknbrls]

You can down size one gauge for the negative.