Solar installation

[Steve DAntonio]

Another divergence but an important question in my mind. Steve D said:

"5. Overcurrent protection is not required at an alternator if the ampacity of the conductor is equal to or greater than the rated output of the alternator."

My alternator feed is fused at the battery. The alternators are rated at 100 amps. How large should the fuse be? Can the fuse be eliminated if the ampacity of the wire is large enough. I am interpreting this provsion as so.

There is more to that...

"Overcurrent protection is not required in conductors from self-limiting alternators with integral regulators if the conductor is less than 40 in (102 cm), is connected to a source of power other than the battery, and is contained throughout its entire distance in a sheath or enclosure."

So, in your case, you need a fuse at the alternator because the conductor is, I assume, over 40". Remember, the fuse protects the wire, not the device, so you can make it as large as the wire's maximum ampacity, or at least safely above the alternator's output to prevent it from tripping inadvertently, which would likely damage the alternator. Note: many alternators will briefly put out more than their max rating when cold.

I helped to amend the standard to include this provision, essentially it says that stock alternators wired to the starter post don't need OCP (some manufacturers like CAT still include it) because the output is part of a factory harness which is chafe protected and relatively short. Once you add external regulation, and a longer output wire, that all changes.

 

[diver dave]

Solar panels are current limited eliminating the need over current protection. Now as to ‘’7 inches’’ from battery to an overload protection device, nonsense! .,,.

Rather a philosophical argument. Should roadside speed limit signs say “do not drive too fast?”

Yes, it speaks of a continuum of risk, but places a hard limit. 8” is less safe than 6. 85 mph is less safe than 60. We are dealing with human factors and the very broad ability, or not, to manage risk.
I’m ok with the 7” rule.
Not OK with the bizarre ABYC notion of “self limiting”.

 

[catalinajack]

There is more to that...



"Overcurrent protection is not required in conductors from self-limiting alternators with integral regulators if the conductor is less than 40 in (102 cm), is connected to a source of power other than the battery, and is contained throughout its entire distance in a sheath or enclosure."



So, in your case, you need a fuse at the alternator because the conductor is, I assume, over 40". Remember, the fuse protects the wire, not the device, so you can make it as large as the wire's maximum ampacity, or at least safely above the alternator's output to prevent it from tripping inadvertently, which would likely damage the alternator. Note: many alternators will briefly put out more than their max rating when cold.



I helped to amend the standard to include this provision, essentially it says that stock alternators wired to the starter post don't need OCP (some manufacturers like CAT still include it) because the output is part of a factory harness which is chafe protected and relatively short. Once you add external regulation, and a longer output wire, that all changes.

Ah, external regulation, an important distinction. My alternators are externally regulated 100-amp Balmars. The run from them to the batteries is about 15-feet, round-trip using 6-gauge wire. Although I remember that the standard is to the rated output, I know that the max I have ever seen (start-up bulk charging, FLA batteries at 50% SOC) is 60 amps each). Do I need to fuse the wire at the alternator and, if so, what size fuse? I suspect that if a fuse at the alternator is still required, many folks are not in compliance. Yes, guys, I know ABYC gets the blood of some here boiling but I am one who tries hard at meeting all ABYC standards. Besides, I am getting ready to sell my boat and I absolutely do not want any "fixes" absolutely required at survey and it seems this may be one. Damn, these provisions are difficult for laymen to understand. They are worse than the Internal Revenue Code.

 

[foggysail]

Yeah——yeah—-7’’ or the world will go up in smoke! Not 8’’ or 10’’ or…..geez, is there even a fuse in the circuit? In past years I only met one person who insisted on 7’’ minimum and that had nothing to do with a boat. GET REAL!!!

 

[SteveK]

Xantrex Installation manual clears up the matter for an inverter.

As per ABYC E-11, DC fuses are required 7 inches from the positive terminal of the
battery and another from the positive terminal of the charger. A DC Switch is
recommended on the battery side as well.

 

[Steve DAntonio]

For those of you who are anti-ABYC, I get it, on the face of it it may appear arbitrary or unreasonable, especially if you are unfamiliar with them (and don't have ready access, another issue worthy of debate). By no means is it perfect, but trust me when I tell you, after over three decades in this industry I will tell you it is invaluable. The very discussion about 7" is a perfect example. If I inspect a vessel and point out the absence of OCP or OCP in the right location, without a standard this and virtually every other critique I level at a vessel or builder will be met with, "well, that's your opinion, we've been building boats for 40 years and not having OCP has never been a problem". I hear this often even with the Standards.

Again, while the Standards may be imperfect, I nitpick them all day long, they are invaluable to those building and repairing boats (and buying), without them it truly would be the wild west.

And for the skeptics, ABYC's definition of self-limiting...

"11.4.30 Self Limiting Device - a device whose maximum output is restricted to a specified value by its magnetic or electrical characteristics.
NOTES:
1. The output remains at a value or will automatically decrease to a value such that it will not damage the battery charger or inverter/charger after application of a short circuit at the output terminals.
2. The output current will not exceed the ampacity of the conductor that is specified for connection to the battery charger or inverter/charger by the manufacturer."

 

[SteveK]

Steve D, to me you are the messenger. I welcome your input. ABYC secret society not so much.
When I get a surveyor who picked up something from ABYC tell me that what existed without problems for 50 years is now flagged for so my insurance can say fix that or else, I get real pissed.
As others have said the 7 inch rule is arbitrary and still does not make sense. An OCP makes sense, but why precisely at 7 inches not 7 1/2". why not at the terminal, why not a foot away on the bulkhead? So a fuse sitting on the battery with a 7 inch wire is the correct way seems silly.

Back to this thread about "solar installation".
You quoted ABYC which says 7 inches from charging source (MPPT) and without any other ABYC quote then state 7 inch from the battery. WHY? No quoted ABYC says 7 inch from battery for solar installation, so is that your opinion?

 

[Steve DAntonio]

SDA: My responses below.

Steve D, to me you are the messenger. I welcome your input. ABYC secret society not so much.
When I get a surveyor who picked up something from ABYC tell me that what existed without problems for 50 years is now flagged for so my insurance can say fix that or else, I get real pissed.
As others have said the 7 inch rule is arbitrary and still does not make sense. An OCP makes sense, but why precisely at 7 inches not 7 1/2". why not at the terminal, why not a foot away on the bulkhead? So a fuse sitting on the battery with a 7 inch wire is the correct way seems silly.

SDA: I truly understand the frustration. Look at it this way, if you bought a car from 1950 and took it to your mechanic to check it out and he said, "will you drive this car with your loved ones?", and you say, "Yes, sure, my wife and maybe kids from time to time, why?" He says, "It has no seat belts, no air bags, no ABS, I could go on, I just want you to be aware of this, it not as safe as a car built in 1990, much less 2022" Would you be angry at him? A wire on a 40 year old boat that has no OCP doesn't keep track of time, it can short circuit tomorrow, next year or never. It should, must be identified as a fire potential. Lots of old houses don't have GFCIs in bathrooms, do they lead to electrocutions? Yes. What is a surveyor supposed to do, say, "the law of averages dictates this won't be a problem, but I can't guarantee it"?

Back to this thread about "solar installation".
You quoted ABYC which says 7 inches from charging source (MPPT) and without any other ABYC quote then state 7 inch from the battery. WHY? No quoted ABYC says 7 inch from battery for solar installation, so is that your opinion?

SDA: Arbitrary? Here's the definition, "Determined by chance, whim, or impulse, and not by necessity, reason, or principle." I don't believe the 7" rule is arbitrary, it is based on the experience of those who are on the ABYC Project Technical Committee, again hundreds of years of collective experience. As a certified marine electrician I find it very reasonable, I want the OCP as reasonably close to the battery as possible, with enough room to mount it and make connections. And, there are exceptions, 40" or 72" if sheathed, giving installers options. If 7" seems arbitrary to you, what would you suggest?

SDA: The MPPT is not a charge source, it is a regulator/controller, the solar panel is a charge source. I believe the Standard I quoted is amply clear, you need OCP at the battery, period, solar or not it doesn't matter. You need it at a charge source, the solar panel in this case, unless it meets one of the exceptions.

 

[DavidM]

SDA:
SDA: The MPPT is not a charge source, it is a regulator/controller, the solar panel is a charge source. I believe the Standard I quoted is amply clear, you need OCP at the battery, period, solar or not it doesn't matter. You need it at a charge source, the solar panel in this case, unless it meets one of the exceptions.

And if anything meets the rule's exception as a self-limiting device, solar panels sure do. Solar panels absolutely, positively cannot put out more than their Isc spec without getting millions of miles closer to the sun .

David

 

[SteveK]

You say
You must have OCP within 7” of the battery (72” if sheathed), period, no exceptions. So the question is, do you need it in both locations?

Re. the solar panel and regulator, ABYC’s language applies… You then quote ABYC which says within 7 inches of the charging source

Where does it say within 7 inches of the battery?
I question why the battery is considered a charging source.
BTW I agree with an OCP near the charging source to protect from downstream short. I do not agree with a fuse 7 inches from the battery on the wire from the charging source.

 

[diver dave]

This reads like folks are caught up in the verbiage without a clear understanding of the intent.

Simply: if a fault will exceed the ampacity of a wire, then OCP is required.

Lets work thru some examples to put that in practice.

 

[SteveK]

Dave, I resemble that person.
A fuse near the battery protects the battery. A fuse near the charge source protects the battery AND the wire that goes to the battery. The ABYC quoted near the charging source, yet there is talk of putting near the battery on a charging line.

 

[diver dave]

Dave, I resemble that person.
A fuse near the battery protects the battery. A fuse near the charge source protects the battery AND the wire that goes to the battery. The ABYC quoted near the charging source, yet there is talk of putting near the battery on a charging line.

Nope. We r not protecting batteries.
We r preventing wire from overheating and catching fire.

And, i’m having heartburn with the loose term “charging source”. Hopefully thats well defined in a glossary. And, not sure why it is called out as a special item re: OCP

 

[diver dave]

Ok. Another simple way of looking at this.
Attach a #4 wire, 40 feet long firmly to a NEG battery post. Now, walk or crawl around with a bare end and touch that bare end to various exposed electrical items, that r > 7” from the POS post of the battery. Can I start a fire doing that? If so, then thats an issue.

 

[Steve DAntonio]

Nope. We r not protecting batteries.
We r preventing wire from overheating and catching fire.

And, i’m having heartburn with the loose term “charging source”. Hopefully thats well defined in a glossary. And, not sure why it is called out as a special item re: OCP

Agree, OCP protects conductors with few exceptions, this entire discussion is making the case for the value of the standards.

A charging source is a battery charger, alternator, solar panel, wind generator etc. Relatively self explanatory. It is not a regulator.

Pass the Tums.

 

[firehoser75]

Steve K (SV),
I think where your confusion is coming in is the fact that the battery "receives" charge from the various devices and does not (except for use with an inverter) "give out" a charge (under most circumstances). However, all of these charge sources connect to the batteries' positive terminal. In this case (the OP's solar), if a dead short (eg. caused by wire chafe) connects that charge wire (actually the positive battery terminal) directly to ground, then a large amperage flow from the battery to that ground (short) is possible, greatly exceeding the amperage capacity of the wire and possibly causing a fire (and maybe "other" issues). Hence the need for the OCP close to the battery!
At least that is my understanding, and to be clear, I am not a marine electrician

 

[SteveK]

Steve K (SV),
I think where your confusion is coming in is the fact that the battery "receives" charge from the various devices and does not (except for use with an inverter) "give out" a charge (under most circumstances). However, all of these charge sources connect to the batteries' positive terminal. In this case (the OP's solar), if a dead short (eg. caused by wire chafe) connects that charge wire (actually the positive battery terminal) directly to ground, then a large amperage flow from the battery to that ground (short) is possible, greatly exceeding the amperage capacity of the wire and possibly causing a fire (and maybe "other" issues). Hence the need for the OCP close to the battery!
At least that is my understanding, and to be clear, I am not a marine electrician

No confusion here Tom.
We have a celebrity in our midst quoting ABYC saying within 7 inches of the charging source telling us that means within 7 inches of the battery. I kept asking for the ABYC quote on 7 inches from battery in several ways.
I have no issue with a fuse 7 inches from the battery, but don't quote the ABYC that says otherwise. I even quoted my inverter manual which suggests a fuse at both ends without getting a comment.

 

[Steve DAntonio]

No confusion here Tom.
We have a celebrity in our midst quoting ABYC saying within 7 inches of the charging source telling us that means within 7 inches of the battery. I kept asking for the ABYC quote on 7 inches from battery in several ways.
I have no issue with a fuse 7 inches from the battery, but don't quote the ABYC that says otherwise. I even quoted my inverter manual which suggests a fuse at both ends without getting a comment.

I have shared these previously, but here they are again.

The 7" rule, which has exceptions for 40" and 72", means you must have OCP at one of these maximum distances. You may or may not need OCP at charge sources (including an inverter, but I'd argue it isn't specifically necessary as it is current-limited, but no harm in having it there as well), based on the exceptions shown below. Here it is in plain English https://stevedmarineconsulting.com/over-current-protection/

11.10.1 Overcurrent Protection - DC
11.10.1.1 GENERAL REQUIREMENTS
11.10.1.1.1 Overcurrent Protection Device Location - Ungrounded conductors shall be provided with overcurrent protection device(s) within a distance of seven inches (178 mm) of the point at which the conductor is connected to the source of power measured along the conductor (see FIGURE 8).
EXCEPTIONS:
1. Cranking motor conductors.
2. If the conductor is connected directly to the battery terminal and is contained throughout its entire distance in a sheath or enclosure such as a conduit, junction box, control box, or enclosed panel, the overcurrent protection shall be placed as close as practicable to the battery, but not to exceed 72 in (183 cm).
3. If the conductor is connected to a source of power other than a battery terminal and is contained throughout its entire distance in a sheath or enclosure such as a conduit, junction box, control box, or enclosed panel, the overcurrent protection shall be placed as close as practicable to the point of connection to the source of power, but not to exceed 40 in (102 cm).
4. Overcurrent protection is not required in conductors from self-limiting alternators with integral regulators if the conductor is less than 40 in (102 cm), is connected to a source of power other than the battery, and is contained throughout its entire distance in a sheath or enclosure.
5. Overcurrent protection is not required at an alternator if the ampacity of the conductor is equal to or greater than the rated output of the alternator.
6. Pigtails less than seven inches (178 mm) are exempt from overcurrent protection requirements.
NOTES:
1. Multiple main overcurrent protection devices may be connected to a common busbar connected directly to the source of power.
2. If the DC electrical distribution system is not connected as a grounded system per E-11.5.2.3, then both the positive and the negative DC conductors are ungrounded conductors.

 

[SteveK]

Thank you Steve for post 48.

Post #16. You must have OCP within 7” of the battery (72” if sheathed), period, no exceptions. So the question is, do you need it in both locations?

Re. the solar panel and regulator, ABYC’s language applies…

11.10.1.1.2 In addition to the provisions of E.11.10.1.1.1 the ungrounded conductors to a battery charger, alternator, or another charging source shall be provided with overcurrent protection within the charging source, or within seven inches (178 mm) of the charging source, based on the maximum output of the device.
EXCEPTION: Self-limiting devices.

Now post 16 in concert with post 48 seen together explains what I was looking for. The font in red refers to 11.10.1.1.1 (green) and not to 11.10.1.1.2 which wants a 2nd OCP at charging source, and to which you also question the need.

11.10.1.1.1 Overcurrent Protection Device Location - Ungrounded conductors shall be provided with overcurrent protection device(s) within a distance of seven inches (178 mm) of the point at which the conductor is connected to the source of power measured along the conductor

 

[Steve DAntonio]

I should clarify too, I said "7 inches from the battery, period, no exceptions", that's not entirely accurate, there are exceptions, it can be 72 inches from a battery if sheathed"

I apologize for any confusion that may have caused. Ultimately, the closer OCP is to the battery the better.

 

[twistedtree]

There is a lot of arguing over the language in the standard by people who haven’t read it. If you want to read it in it’s entirety, including definitions, notes, and exceptions, then I think we could have a productive discussion.

As for OCP, it’s really not that complicated, and all makes good sense.

1) Always have OCP at the battery because it is effectively an unlimited source of current. Place the OCP within 7” of the terminal, or sheath the wire and the OCP can then be placed up to 72” from the terminal. Note that is doesn’t matter whether the protected wire is used for charging or loads. If it becomes shorted then unlimited current will flow from the battery and it needs to be interrupted. That’s the reason for OCP.

2) for other devices that are power sources, they too should have OCP within 7” to 72” depending on sheathing. This is again to protect a wire shorted to ground from the output current of the power source. The result is that wires between a battery and charging source can be double fused, one at each end of the wire. One protects from current coming from the battery, and the other protects from current coming from the power source.

Now for the exceptions in #2. If the power source is such that it is limited in its power output, and the wiring can handle that full current, then it doesn’t need to be fused at the power source. This is because a shorted wire will not cause a fire because the current is limited and the wire can handle it.

 

[twistedtree]

There is a detail with solar panels and fusing that’s important to understand. If you have multiple solar panels, you might find do DO need fusing for each panel, and you might find that you DO need fusing for the MPPT and can’t just rely on panel current limiting.

First, consider 4 panels wired in parallel. If one panel shorts, you can have 3 panels dumping their full load into the shorted panel which can be a hazard. So you need to look at the max allowed current for each panel, and if other parallel panels’ combined Isc can exceed that max, then each panel needs to be fused.

Similarly, when evaluating OCP for an MPPT output, you need to look at the max possible MPPT output current, not the panel Isc. They are related, but the MPPT can operate at a very different voltage and current vs the panels. So you need to do the match.

And related, you actually need to calculate for Isc plus 15%. Isc is at standard light and temp conditions. Under edge conditions it can jump up by as much as 15%. NEC actually calls for an addition 15% derating to ensure the wires operate at no more than 85% load.