Solar controller question

Hi cardude01,

This is where David and I disagree.

He is correct that the panels are current limited and can't fry the wiring. This is why I have consistently referred to it as a "disconnect" not "circuit protection" on the panel side.

And, unless you are dealing with a high voltage system, which is unlikely, it is no threat to a human.

As far as I know, there is no ABYC requirement for either a disconnect or circuit protection, and,,just for reference, to my knowledge, NEC only requires it when multiple strings are wired in parallel such that the current from 2 or mote can overpower the wiring of 1. Think about 3 strings joining a common bus. The protection would be requires on each of the 3 strings, not the common bus.

But, I still very strongly advocate for a disconnect. I don't like poking at live things when it is avoidable.

Earlier I said I wanted the disconnect when adjusting voltage. I was misremembering. I did that live to see the voltage output.

When I wanted the disconnect is when I was changing wiring to and had to slide wires through an energized controller to get them out and put pliers in to tight spots to trim the exposed wire first, and dropped some of that wire as I did.

Now...just because the two supply wires are rated for the maximum current suppliable by the panels most certainly doesnt mean any two points in that controller box are. Screwing up poking live can potentially damage things.

So, what you need in this case is no more that what you'd like.

I used breakers because, at the time, I'd just bought the boat and didn't know the panel rating to know the wiring was safe. Enough else was wrong, that I just figured it couldn't hurt. It was still only half protection, because, if that'd been a problem, the short could have been before the breaker. So, it was a good disconnect but not adaquate as circuit protection. Regardless, I eventually got the spec sheet and the wiring was fine.

A cheap way is just to use a plug disconnect as it goes into the controller or, if reachable, at the too. This way you are only adding one crimp connection, not two.

gkesden said:

I guess it is worth a few words to explain the location of the circuit protection thing further...

Placing it close to the bus or battery provides the most protection...

Click to expand...

This is true, but this is not 'optional' -- ABYC E-11 (and every other regulation world-wide) requires overcurrent protection to be placed very close to the source of the current. The ABYC spec for batteries requires the overcurrent device to be located within seven inches of the battery terminal. The only exception to this is for conductors that feed engine cranking motors.

re: "Placing it close to the bus or battery provides the most protection, because it protects both the wires and device."

The primary overcurrent device (at the battery) is generally sized to protect the conductor only. Downstream, every subsequent termination point (such as a bus) must then also have overcurrent protection, also within seven inches and also sized to protect the branch conductors -- not the end devices. When the current source is not a battery, there are exceptions up to 40 inches for wiring in enclosed panels or protected sheathing.

This is important, because (check your insurance policy...), any wiring you do on your boat that does not follow these rules exactly could give your insurance company every good reason to deny any claims found to be the result of your wiring.

Here's an example of how easy it is to mess this up. I can't tell you how many times I have found owners who needed a source of DC somewhere below decks -- and so they attached a wire to the starter motor main conductor -- with no fuse at all. Often it is the starter motor for the generator. Remember that the cranking motor wire is exempt from the overcurrent device rule, so if that wire shorts, there is nothing to prevent it from starting a fire (almost instantly).

When one of these boats burns to the waterline, among the first things the ajduster/surveyor is going to do is look at the starter motors to see if there are extra ring terminals under the positive cable lug -- as you can see in the photo below.

That adjuster/surveyor will have earned his money because he just saved his employer the cost of paying the claim.

When it comes to electrical matters, please don't rely on anything you read in an online forum. Go buy a book, or join ABYC and download the standards...

Every wire on every boat...

gkesden said:

Hi cardude01,

As far as I know, there is no ABYC requirement for either a disconnect or circuit protection...

Click to expand...

There absolutely are. ABYC, the C.F.R. (and every other organization worldwide) requires overcurrent protection at the source of the current for every ungrounded wire on every boat, except for cranking motor conductors.

The maximum distance from the source to the OCP is seven inches for conductors connected to batteries, and no more than 40 inches for conductors connected to bus bars in protected enclosures. If a wire is protected inside a conduit, the overcurrent device can be up to 72" away.

When I installed my solar panels, the supplier insisted on breakers between the panels and the controller, and as near as possible to the panels. That is code for home solar installations. I followed that for the boat as well. The wiring exceeds requirements for the loads from the panels. So...there is a breaker on both sides of the controller.

FYI, the electrician connected the wiring after the controller breaker to a bus bars between the batteries and the house loads.

Jim

Riverguy said:

There absolutely are. ABYC, the C.F.R. (and every other organization worldwide) requires overcurrent protection at the source of the current for every ungrounded wire on every boat, except for cranking motor conductors.

The maximum distance from the source to the OCP is seven inches for conductors connected to batteries, and no more than 40 inches for conductors connected to bus bars in protected enclosures. If a wire is protected inside a conduit, the overcurrent device can be up to 72" away.

Click to expand...

Riverguy,

Thanks! That ABYC recommendation is pretty clear. (I had misremembered the alternator exception to be broader). My next trip trip my boat, "need" them or not, I'm climbing the top and adding fuses all the way at the top if they aren't already there. I dont want to second guess the collective wisdom of those who have been standing on each others' shoulders for decades.

(Btw, I dont think NEC has this requirement, except as I mentioned, see attached).

Thanks again,

-Greg

JDCAVE said:

When I installed my solar panels, the supplier insisted on breakers between the panels and the controller, and as near as possible to the panels. That is code for home solar installations. I followed that for the boat as well. The wiring exceeds requirements for the loads from the panels. So...there is a breaker on both sides of the controller.

FYI, the electrician connected the wiring after the controller breaker to a bus bars between the batteries and the house loads.

Jim

Click to expand...

Re: "supplier insisted on breakers between the panels and the controller, and as near as possible to the panels. That is code for home solar installations."


Yes...the key concept here is that we need to protect the conductors from turning into flameing red-hot firestarters in case of a short circuit downstream, and the only way to do that is to limit the current that can flow into them. That means putting the overcurrent device as close to the source of the current as possible. Solar panels, battery chargers, inverters etc.

It's a universal concept (residential or marine), but very frequently misunderstood or ignored. I don't know why, but I see it way more in boats than in residential situations.


Kudos for hiring an electrician...

Sorry Riverguy, but not true. Solar panels are one of the few marine devices that have a fixed, unalterable maximum current that they can produce, usually the Isc value. You would have to somehow increase the sun's energy to produce more than Isc current.

So as long as the wire connected to the panel can take the Isc (and for any installation it should be able to do so) then there is no need for an over current protection device because there is no way to produce an over current situation.

Batteries, yes. Solar panels, no.

David

djmarchand said:

Sorry Riverguy, but not true. Solar panels are one of the few marine devices that have a fixed, unalterable maximum current that they can produce...

David

Click to expand...

Unless, of course they get hit by lightning. Anyways they are code for home installs. At least that was what I was told. Maybe it’s a belts and suspenders kind of thing.

Jim

djmarchand said:

Solar panels are one of the few marine devices that have a fixed, unalterable maximum current that they can produce, usually the Isc value. You would have to somehow increase the sun's energy to produce more than Isc current.

So as long as the wire connected to the panel can take the Isc (and for any installation it should be able to do so) then there is no need for an over current protection device because there is no way to produce an over current situation.

Batteries, yes. Solar panels, no.

David

Click to expand...

I get what you are saying (in theory), but ABYC makes no exception for solar panels. I think you are referring to the "self-limiting devices" exclusion.


The problem is that when the wiring is installed, you might know which (and how many) panels are feeding it, but there's no knowing when the solar panels might be upgraded or more panels added to the same circuit.


re: "You would have to somehow increase the sun's energy to produce more than Isc current..."


Either that, or install new solar panels a few years now when the efficiency triples. All of a sudden, you CAN fry those wires.



This is why the conductors must be protected at the source of the (planned or future) current.



At the end of the day, every conductor on every boat MUST have overcurrent protection located at the source of the current, and MUST be sized based on the capacity of the conductor....not just for the devices that are supplying current today, but for any future devices using that conductor in the future.



ABYC E-11 is quite clear on this.


If there is a fire on your boat, and you didn't put overcurrent protection at the current source, do you think you will win that argument with the insurance company? No...you won't.



Not worth the risk, even if your logic is sound.


Once again (for the record), no one should be taking advice on electrical issues from an online forum. Buy a book or join ABYC and read the standards.

"Once again (for the record), no one should be taking advice on electrical issues from an online forum. Buy a book or join ABYC and read the standards. __________________
~~RiverGuy~~"


That is something we can both agree on.


David

Sorry another question:

I have to leave the boat for a few weeks and go back to Texas. Should I turn off the AC powered battery charger and just let the solar charge the batteries? I have very little draw when away. Basically everything DC is turned off except for the bilge pump.

I’m still trying to decipher this Victron app, but this is what the panels did today. Doesn’t appear to be much and it was super sunny. I did notice that unless I turned on lots of DC drawing appliances the panel output dropped way down to basically nothing. I only had one fridge running and some LED lights all day and the batteries stayed at 100% . When I turned on the freezer the panel watts kicked way up.


Each 300w panel has its own Victron SmartSolar 100/30 controller.

IF you are in a slip with shore power leaving the AC battery charger on is a good idea as it can power a couple of bilge pumps "forever".

Yeah I’m in a slip right now. Couldn’t remember if the AC battery charger would “fight” with the solar panels and controllers in some strange way.

Most charging devices rely on the voltage they see, so which ever has a higher voltage will be doing the work , the other just watching it happen. No problem.

Thanks.

Riverguy said:

At the end of the day, every conductor on every boat MUST have overcurrent protection located at the source of the current, and MUST be sized based on the capacity of the conductor....not just for the devices that are supplying current today, but for any future devices using that conductor in the future.

Click to expand...

This is not a requirement, as it would be quite impossible to satisfy. If I put in 4/0 conductors for my 100 watt panel, I can still add a gigawatt of solar later and overload it. Any installer that adds capacity to a charging system and does not check that the existing wires are large enough to handle it is incompetent and liable for the result.

To another comment: fuses to protect against lightening are a fools errand.

cardude01 said:

Sorry another question:

I have to leave the boat for a few weeks and go back to Texas. Should I turn off the AC powered battery charger and just let the solar charge the batteries? I have very little draw when away. Basically everything DC is turned off except for the bilge pump.

I’m still trying to decipher this Victron app, but this is what the panels did today. Doesn’t appear to be much and it was super sunny. I did notice that unless I turned on lots of DC drawing appliances the panel output dropped way down to basically nothing. I only had one fridge running and some LED lights all day and the batteries stayed at 100% . When I turned on the freezer the panel watts kicked way up.


Each 300w panel has its own Victron SmartSolar 100/30 controller.

Click to expand...

Yes to your first question. Turn off everything except the solar and let the very good controllers do their job of keeping the batteries topped up for free.



If your batteries are mostly or fully charged then the panels won't be delivering much power to them. In fact I use panel output as a simple way to know if my batteries are charged. If I get on the boat and its full sun and the power output from the panels is very low I know the batteries are fully charged.


Ken

Ok cool. That’s what I did— turned off the AC battery charger. I wanted a good idea of what the panels were doing while I was gone and didn’t want the battery charger complicating things.

" let the very good controllers do their job of keeping the batteries topped up for free. "

A battset in good condition will self discharge 1/2 percent per day.

On a 1000 amp house battset or about 5 amps at 12v DC per day .

Creating 10A of 12v to charge the battery for an hour pr day would be 120watts .

The savings of not paying for dock power at even 25c a KW, a dollar a month, might easily be overlooked as cheap insurance should the boat need her bilge pumps.