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Old 05-09-2013, 15:40   #1
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Fuses

Hello folks, I have a single battery hooked up to solar panels, no engine. My question is do I need a fuse between the battery isolator switch and the fused distribution panel?

thnx.
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Old 05-09-2013, 16:32   #2
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Re: Fuses

According to ABYC E-11 (11.12.2.9.1.2.2) there must be a fuse within 7 inches of the power source, or within 40 inches of the power source if the conductor is enclosed in a panel or box.

IMO, that means a fuse or circuit breaker must be near the solar panel, in addition to the battery, but no to between the fuse panel and the disconnect.
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Old 05-09-2013, 16:48   #3
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Re: Fuses

You should have a large fuse as close to the battery as possible - i.e. the fuse protects the cable to the switch/panel. Ask yourself what happens if that cable shorts out. Then protect for that.

IIRC ABYC says within 7" of the battery.
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Old 05-09-2013, 17:47   #4
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Re: Fuses

Righto fellas, I shall add a fuse in both positions.
thank you.
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Old 06-09-2013, 10:32   #5
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Re: Fuses

Although the solar panel is a "Power Source" depending on its size it seems to me it would not need a fuse since it can't produce enough current to do any damage.
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Old 06-09-2013, 10:42   #6
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Re: Fuses

Yeah mate, I was wondering about that, the panels are two 40 watts.
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Old 06-09-2013, 12:54   #7
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Re: Fuses

The 40W solar panel will provide ~12V at ~3A.

A fault like a short will have lots of heat dissipated somewhere w/o a fuse.

IMO, ABYC should be followed w/ having a fuse to protect the wiring.
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Old 06-09-2013, 22:52   #8
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Re: Fuses

Thanks mate, i will do as you suggest.
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Old 07-09-2013, 07:05   #9
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Re: Fuses

A fuse is not required if the wire size is capable of handling the full current that the power source can produce.

If the maximum current produced by the solar panels is say 3 amps and your wire can safely carry say 5 amps, then there is no point is having the source fused.

Presumably the wiring from the solar panel will be rated for much more than 5 amps.
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Old 07-09-2013, 07:17   #10
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Re: Fuses

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Originally Posted by Wotname View Post
A fuse is not required if the wire size is capable of handling the full current that the power source can produce.
Does that appear anywhere in ABYC?
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Old 07-09-2013, 07:57   #11
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Re: Fuses

Quote:
Originally Posted by wingless View Post
Does that appear anywhere in ABYC?
Don't know!
But I do know how to analyse an electrical circuit and to calculate resistance, volts, amps, watts, power dissipation and so forth.

Think about it....

FWIW, the 40W solar panel will probably not deliver its rated output into a short circuit anyway.

An ancillary question would be - what size fuse does one put in the lead from the alternator?

The correct answer, it depends; some arrangements don't need one and others do. What is the maximum output of the alternator and what gauge wire is being used etc etc etc.
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Old 07-09-2013, 08:40   #12
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Re: Fuses

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Don't know!
But I do know how to analyse an electrical circuit and to calculate resistance, volts, amps, watts, power dissipation and so forth.
It sounds like SOMEBODY stayed at a Holiday Inn Express last night...

It would be better if the OP provided the model number of the solar panel.

Here is the GANZ 40W Solar Panel Installation Manual.

The manufacturer shows a fuse or a controller on the panel output.
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Old 07-09-2013, 08:59   #13
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Re: Fuses

Firstly, its your boat.

ABYC E-11 requires over current protection device (OCPD, fuse or circuit breaker) to protect the conductor.

Quote:
11.10.1.1.1 Overcurrent Protection Device Location - Ungrounded conductors shall be provided with overcurrent protection within a distance of seven inches (178mm) of the point at which the conductor is connected to the source of power measured along the conductor.
There are caveats that allow > 7" of unprotected conductor. An OCPD is not required at the output of a current limited device (alternator, solar panel) but is required at the other end of the conductor where it is connected to the DC system B+.

Lastly, it is your boat.
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Old 07-09-2013, 09:10   #14
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Re: Fuses

I installed a fuse between my solar panels and the battery. Sure, solar cannot provide enough energy to do harm but that is only half of the story. If somehow a short occurs in the panel wiring or the panels themselves, then my battery bank will see it.

And yes, I have my batteries fused but the fuses are in the 250-300 amp sizes! So if a panel or wiring shorted, it is chancy that the high current would be enough to blow the battery's fuse because of wire resistance. Without over current protection, the damage risks just become greater.
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Old 07-09-2013, 09:15   #15
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Re: Fuses

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Originally Posted by wingless View Post
The 40W solar panel will provide ~12V at ~3A.

A fault like a short will have lots of heat dissipated somewhere w/o a fuse.

IMO, ABYC should be followed w/ having a fuse to protect the wiring.

NO! Solar panels are current sources not voltage sources so there will be little to no heat from a shorted panel....you may get 3 amperes but the voltage will be near zero.

NOw if that panel is connected to a battery and it shorts, it will be the battery that does the damage.
So yes, fuses by all means.
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