Starter wiring with in line fuse?

[DeepFrz]

In my opinion, a fuse installed in line(serie) on the load, all the circuit (from end to end!)will immediately affected by a change in amps.Therefore, a fuse placed anywhere in the circuit protect it. Naturally, it is important that the fuse be fast enough to blow before the any damage occur.

Okay, so that's your opinion. Now why don't you challenge yourself to find out the facts? Mainly a fuse placed after a short will not be affected by the short. If you can prove your opinion to be true I'll be happy to change my mind on the matter. I don't know your credentials but I have been in the electronics, radar, computer business for quite a few years now (retired for quite a few as well).

Fact: A fuse should be placed as close to the voltage source as possible. Only the wire after the fuse is protected.

[DeepFrz]

I'm in agreement with many other posts: the 'in rush' current to the starter can be 4-6 times the operating current, amounting to thousands of amps in some cases. Put a 300 - 400amp fuse close to the battery origin. It should be a 'thermal {melting} fuse' which will not have time to build up high temps before the engine starts.

MainSail (Compass Marine) has done some actual testing.

Battery Bank Fusing Photo Gallery by Compass Marine How To at pbase.com

[Frankly]

A fuse is typically used to protect against two different types of electrical problems.

Circuit Overload. To protect a circuit from overheating because of overload it can be located anywhere between the source (battery in this case) and the load.

Circuit Fault (typically to metallic ground on a yacht). Only the circuit downstream of the fuse location will be protected.

This is why we typically locate the fuse as close as possible to the source/ battery. Kill two birds with one stone.

[DeepFrz]

Frankly, you are absolutely right. I had not taken into consideration the cct. overload, only the accidental short in my post above. However we are absolutely right in stating the fuse should be located as close to the source as possible.

[skipmac]

Originally Posted by Stu Jackson

The real issue is to properly fuse the SUPPLY wire to the entire cockpit panel, not just a random wire from it.

Exactly. Fuse the supply to the panel. If there are devices on that circuit that need protection they can be individually fused in line. The fuse to the supply is to prevent any wires in that circuit from overheating and starting a fire. The size of the fuse is based on the size of the wires in the circuit.

[barnakiel]

And the fuse definitely at the power source end of it. Just a little drawing and the picture clears. For starters, it is at the battery best.

BTW some wires (e.g. those on solar panels) have power source at each end. Now what? ;-)


Cheers,
b.

[skipmac]

Originally Posted by barnakiel

BTW some wires (e.g. those on solar panels) have power source at each end. Now what? ;-)


Cheers,
b.

I asked that question a couple of years ago and it was pointed out that solar panels, alternators and such by their nature are current limited IE a 150 Watt solar panel can only put so many amps into the circuit, a 100 amp alternator can put no more than 100 amps into the circuit.

So if you have used the proper size wire to carry the max current from the panel or alternator then you only have to protect against a short that would allow the battery which is not current limited, to discharge into the circuit therefore a fuse on the battery end is all that's required.

My reply was, "Duh. Of course. I should have thought of that."

[barnakiel]

Originally Posted by skipmac

I asked that question a couple of years ago and it was pointed out that solar panels, alternators and such by their nature are current limited IE a 150 Watt solar panel can only put so many amps into the circuit, a 100 amp alternator can put no more than 100 amps into the circuit.

So if you have used the proper size wire to carry the max current from the panel or alternator then you only have to protect against a short that would allow the battery which is not current limited, to discharge into the circuit therefore a fuse on the battery end is all that's required.

My reply was, "Duh. Of course. I should have thought of that."

Yep. This sounds like the best option.

+1!
b.

[Stu Jackson]

Originally Posted by mitiempo

I regularly fuse starter circuits on diesel engines up to about 50 or 60 hp without any issues. I also fused a 6 cylinder diesel and there have not been any nuisance blows in the year since.

Not to you, mitiempo, but the discussion from the OP was about ignition wiring to starter solenoid, NOT the heavy wire to the starter. That's where I think some of the confusion has crept in. Happens...

[smac999]

Originally Posted by Elie

In my opinion, a fuse installed in line(serie) on the load, all the circuit (from end to end!)will immediately affected by a change in amps.Therefore, a fuse placed anywhere in the circuit protect it. Naturally, it is important that the fuse be fast enough to blow before the any damage occur.

watch video at 1:30.... (not my video)

https://www.youtube.com/watch?v=VwK6rCaEVL8

[boatnerd]

Originally Posted by Stu Jackson

Not to you, mitiempo, but the discussion from the OP was about ignition wiring to starter solenoid, NOT the heavy wire to the starter. That's where I think some of the confusion has crept in. Happens...

Universal wiring diagram shows a 20A fuse on the solenoid/ ignition wire and a 30A fuse on + bat wire going to the amp meter which I'm assuming is over current protection for the instrument panel. A better location might be closer to the battery, possibly an ANL fuse on the starter battery cable as mentioned? It's actually before the + terminal on the starter. . I personally would fuse the alternator output too with an appropriate size ANL fuse. It's also shown going to the amp meter. .Although it may be current limited, the alternator is the main electrical conductor which should be protected (abyc). . I believe solar panels call for inline fuses too. Especially if you've using electronic mppt charge controllers. . sorry I'm drifting

[mitiempo]

Every wire connected to a battery should be fused close to the battery as it is the source. Alternators, solar controllers, chargers or any other items connected to a battery are self limiting in output.

[boatnerd]

I didn't realize it but you're correct, according to ABYC E-11.1 an alternator output isn't required to be protected if,
-it's self limiting w/internal reg.
-output wire is <40"
-connected to source other than battery. ie starter +stud
-is sheathed or enclosed entire length.

Looking at the wiring diagram again, the red 30A fuse going from Starter +stud to amp meter is probably all that's needed to be ABYC compliant provided the starter battery cable is covered.

Still i think it's a good idea to fuse alternator output. Especially if you have a high output alternator w/ external reg. What happens if you ground fault this circuit.?
Probably good to fuse solar panels too. I recently installed a couple Bluesky mppt controllers. Manual shows inline fuses close to each panel. .

[mitiempo]

Originally Posted by boatnerd

Probably good to fuse solar panels too. I recently installed a couple Bluesky mppt controllers. Manual shows inline fuses close to each panel. .

Solar panels do not need fuses between the panel and the controller. They do need fuses after the controller and as close to the batteries as possible.

[boatnerd]

Here is a example where they are needed when multiple panels are in parallel. This is from a major solar distributor. In a small setup(1 or 2 panels) a fuse close to battery may be all that's needed..best to keep it simple. . I find biggest challenge when fusing on a boat is waterproofing fuse holder and dealing w/ voltage drop.