Does anybody use an AFCI (Arc Fault Circuit Interruper) in the PV system?

[Dirk01]

Hi fellow sailors,
I'm not an active cruiser right now but I'm gonna to be in about 5 years. To explain myself a bit: My sail experience is about 20 ksm in my wash (holiday sailing with my spose and friends but 2/3 ship transfers over distances between 500 sm and 1.500 sm at a time). I was trained for machine fitting followed by mechanical engineer studies with a strong electrical background (main topic Energy Technology).

So my planning is going more and more focused, I learned that PV is the method of choice to have a convenient life abroad. And electricity is also a major safety factor.
But a medal has always two sides!
Even electricity is a major safety factor in life, the production (and storing, forming and distribution) might be dangerous. Branking cables or bad connections might cause an electric arc. Not only in a PV system, but in a first approach let's focus on that point. Later on we can expand that topic for the rest of a boats electrical system (including storage, converters, external supply and so on).
In (mostly industrial) PV systems an AFCI (Arc Fault Circuit Interrupter) is built in. This is an automatic acting monitoring system which can detect the harmonics caused i.e. by an Marc.

Does anybody use such an item on a boat? Which brand fits best? What are the important features to consider? Does it interfere the rest of the boats system or the other way round is it interferred i.e. by inverters, radio, radar, etc.? Or are my concerns exaggerated?



I wonder what I can learn from you...


Always a hand-span water under the keel


Cheers

Dirk

[CassidyNZ]

Another thing to add to my paranoia. I’ve never heard of an Arc Fault Circuit Interrupter. Please don’t let marine insurers hear about this - they’ll be insisting on them next.

[stormalong]

Originally Posted by CassidyNZ

Another thing to add to my paranoia. I’ve never heard of an Arc Fault Circuit Interrupter. Please don’t let marine insurers hear about this - they’ll be insisting on them next.

AFCIs are now required in new homes in the USA. They detect if power is flowing in an arc, such as a broken or loose wire where the two ends are close enough together for the voltage to jump the gap. AFAIK these are for mains power only - 110 or 240 Volts AC. I think that arcing would be unusual in a 12 of 24 volt DC system. I would like to know if the solar panels the OP is referring to have built in inverters. Inverter solar panels have no place on a boat.

[Dirk01]

Originally Posted by CassidyNZ

Another thing to add to my paranoia. I’ve never heard of an Arc Fault Circuit Interrupter. Please don’t let marine insurers hear about this - they’ll be insisting on them next.

Well, to close eyes doesn't eliminates issues. IMO it's a thing to think about. If there's no necessity, let's close the thread.
But as far as I know, maritime environment is VERY corrosive and cables on a boat are under constant micro movement. Both could lead to failure. But maybe the solution is a special coating for the connections and a regularly special measurement (which sort of could/should it be?)?
What I would like to avoid is an underestimation of a possible risk which probably could be wiped out easily. Or to come back on board seeing it burning. Not to say being on board and a nasty fire disturbs my nap ...
Under this perspective I welcome different meanings about that issue.
Am I alone? Are my thoughts really alien?

[Dirk01]

Originally Posted by stormalong

AFCIs are now required in new homes in the USA. They detect if power is flowing in an arc, such as a broken or loose wire where the two ends are close enough together for the voltage to jump the gap. AFAIK these are for mains power only - 110 or 240 Volts AC. I think that arcing would be unusual in a 12 of 24 volt DC system. I would like to know if the solar panels the OP is referring to have built in inverters. Inverter solar panels have no place on a boat.

@ stormalong
I'm planning a hybrid system. Due to the high current for the electric motors it will be a 48VDC system. BTW, 48VDC to get the CE certification without special requirements (LVD Low Voltage Directive).
Long story short, to load the LFPs sufficient the MPPT should serve 60VDC (or a bit more at least).
Here in Germany an AFCI is not mandatory yet. Neither on DC side (the solar panels) nor the AC side (after the inverter). But it is only a matter of time when it will be.
Due to rising fire events on the roof and the high voltage of up to 460VDC (and don't forget, DC above 60V is MUCH more dangerous than AC!) the fire fighters have a BIG problem to stay safe.
To cut the AC side does NOT solve the problem, because the solar panels are still producing power (as a equation of Voltage times Current).
To come back to your question: No built in inverters. Classic wiring with Victron inverter/charger.

Take a look at https://www.smainverted.com/industry...afci-solution/

@ CassidyNZ
The AFCI is according to the NEC Code for systems above 80VDC. So no requirements for low voltage systems on boats so far.

But a 60 or 70 VDC system at a peak load of ca. 1 kWp has enough power to cause severe incidents.

[GordMay]

Originally Posted by Dirk01

... The AFCI is according to the NEC Code for systems above 80VDC. So no requirements for low voltage systems on boats so far.
But a 60 or 70 VDC system at a peak load of ca. 1 kWp has enough power to cause severe incidents.

2011 NEC Section 690.11 requires that PV systems installed on buildings with a maximum system voltage of 80 volts or more be equipped with a listed means of detecting and interrupting series arc-faults in PV source and output circuits. Following detection of an arc-fault, operation of the PV system must be disabled. The system must provide a visual indication that an arc-fault has been detected, and the system must be manually restarted to reset the error and resume operation.
This requirement may be enforced as listed PV AFCI devices become available where state and local Authorities Having Jurisdiction (AHJ’s) have adopted 2011 NEC.
➥ https://www.sma-america.com/fileadmi..._130811_2_.pdf
➥ https://standardscatalog.ul.com/stan...standard_1699B

Excepting the potential for nuisance tripping (due to RF etc), I cannot see where installing AFCI's would hurt. Seems a good idea to me, even for lower voltages, on boats.

[Dirk01]

Originally Posted by GordMay

2011 NEC Section 690.11 requires that PV systems installed on buildings with a maximum system voltage of 80 volts or more be equipped with a listed means of detecting and interrupting series arc-faults in PV source and output circuits. Following detection of an arc-fault, operation of the PV system must be disabled. The system must provide a visual indication that an arc-fault has been detected, and the system must be manually restarted to reset the error and resume operation.
This requirement may be enforced as listed PV AFCI devices become available where state and local Authorities Having Jurisdiction (AHJ’s) have adopted 2011 NEC.
➥ https://www.sma-america.com/fileadmi..._130811_2_.pdf
➥ https://standardscatalog.ul.com/stan...standard_1699B

Excepting the potential for nuisance tripping (due to RF etc), I cannot see where installing AFCI's would hurt. Seems a good idea to me, even for lower voltages, on boats.

@ GordMay
Radio uses HF carrier waves. AFCI units detect harmonics. That is my understanding (up to now, pls correct me, if I'm wrong).
Radar also works with HF in a much higher frequency band.
In buildings there're normally neither a radio nor a radar or other typical equipment like generators, strobe lights and so on.
If there is (even a slight) feedback, might that (probably) interfere on a boat? That's my concern. I'm just uncertain and want to sound out rough edges.
Is there anybody out there who knows and (sorry GordMay, it's not against you, it's my evil German engineer gene, I apologize) doesn't "cannot see where installing AFCI's would hurt".

[donradcliffe]

I'm not going to rush out and replace all my $5 breakers with $50 arc breakers. Not to mention the arc breakers have a history of false trips. I'll be using the $5 ones until they stop selling them. They are worse than putting GFCI outlets in dry locations.


Hopefully someone in your country will do a cost benefit analysis before they saddle you with this major step backwards.

[dougweibel]

I would need some convincing that this is useful on a boat's (relatively low voltage, DC) solar system. What fault mode does this protect against that is not adequately protected by a regular circuit breaker or fuse?

[GordMay]

Ground-Fault Circuit Interrupters (GFCI) and Arc-Fault Circuit Interrupters (AFCI) circuit breakers are occasionally reported to “trip” (open the circuit) when a strong RF signal is present, usually a ham’s HF transmissions. GFCI circuit-breakers operate by sensing unbalanced currents in the hot and neutral conductors of an ac circuit. In the absence of RF interference such an imbalance indicates the presence of a fault somewhere in the circuit, creating a shock hazard. The breaker then trips (opens) to remove the shock hazard.
An Arc Fault Circuit Interrupter (AFCI) circuit breaker is similar in that it monitors current to watch for a fault condition. Instead of current imbalances, the AFCI detects patterns of current that indicate an arc – one of the leading causes of home fires. The AFCI is not supposed to trip because of “normal” arcs that occur when a switch is opened or a plug is removed. However, a known problem exists with one model of Eaton breaker, particularly with the 20, 17, 15, and 12 meter bands. See ARRL Helps Manufacturer to Resolve Arc Fault Circuit Interrupter RFI Problems in the November 19, 2013 ARRL News for additional details, including Eaton contact information for problem resolution.
➥ GFCI and AFCI Devices

Another common cause of nuisance tripping, of AFCI’s, will be that the neutral of the circuit is mixed somewhere with the neutral of another circuit (‘split’ ccts).

See also ➥ https://structuretech1.com/wp-conten...patibility.pdf

[roland stockham]

PV in industrial or land based systems is generally running at least 110v, often much higher. In small marine applications it is often 12 or 24v. Even 'high voltage systems' with MPPT control are generally only about 48v to the controller then stepped down to 12 or 24v. I don't see a big need for AFCI protection on these voltages and have not heard of PV systems being a significant fire hazard (unlike in domestic mains where 30% of fires are attributed to arcing).

On the A/C side I do definitely see a rational. Vibration is a significant issue and the main reason practices for marine electrics are very different, multi strand wire, bolt or crimp connections etc etc. Also sea water cause corrosion and sea water is a conductor so damp is a bigger issue. Both of these can and do cause arcing. The result is not only a fire hazard but can wreck equipment. I have had one inverter fried on my boat because of arcing. A low mounted receptacle got immersed and salt water invaded the cable sheathing. The cable was arcing internally for some time but was not noticed until it burned through the outer cover. By that time it had pretty much fried the inverter. So while I have not seen AFCI fitted to boats I can see a good reason for it. GFCI's on all outlets are in my opinion essential and must be at the low current personal protection level although again I have seen many boats that do not have them. Code for leisure boats seems to be more a guide to good practice that rigorously enforced as it is on land and you don't need to draw a permit to work on boat electrics. The ideal in my view would be AFCI trips with GFCI outlets same as code for bathrooms and kitchens but assume the whole system is in the shower area!!

[stormalong]

Originally Posted by donradcliffe

I'm not going to rush out and replace all my $5 breakers with $50 arc breakers. Not to mention the arc breakers have a history of false trips. I'll be using the $5 ones until they stop selling them. They are worse than putting GFCI outlets in dry locations.


Hopefully someone in your country will do a cost benefit analysis before they saddle you with this major step backwards.

In residential use one AFCI covers the entire house.

The NEC - national electrical code does not require AFCI retrofit on older homes, only on new construction so I doubt that the pleasure boat marine industry could get away with requiring it. Also, thanks to GordMay's research we know that they are not required on low voltage DC circuits.

[Brewgyver]

While it's possible that the AFCI standard may get expanded to boats, it's unlikely. Not required in any land-based commercial applications, only new residential construction.

However, if it DID get expanded to include boats, it would be relatively simple to cover the AC circuits with addition of a single AFCI main, and not even be very expensive, as boat projects go.

As to DC arc protection, as pointed out above, even where it's currently required, the PV system has to pass the 80 max volt threshold. Personally, I would never consider having PV system that developed that voltage on my boat. That's a genuinely lethal accident waiting to happen.

[Dirk01]

Hi fellow sailors,many thanks to all of you. So much detailed information in such a short time around the world. I'm really impressed!

Time to have a conclusion about what I've learnt:
AFCI is mandatory for new dwellings/homes/buildings in the US (only), not on a boat (even US flagged).

AFCI inline with an HF emitting device is always a problem. To have it inline with radio or radar is not a good idea (irrelevant if it is AC or DC supplied).

AFCI on the AC side is basically a good thing. But some HEP might cause problems. On the other hand it might protect the inverters too.

AFCI on the PV DC side is not necessarily seen as useful (due to voltage <80VDC).



My estimation / consideration:

AFCIs are now in the 3rd+ generation. Nuisance tripping is going to be a more and more seldom thing (the reports are now 8+ years old). I'll consider them on the AC side.
Even AFCIs on the PV side seems to be not useful I'll consider them. Why? Two of the panels will be retracted while sailing and extended while anchoring. Due to the 48VDC LFPs (nominal 51.2VDC) the panel voltage will be ca. 60—70VDC. Due to the electrification of not only the propulsion system but also the cook top (induction), steam oven, dishwasher, washer-dryer, A/C, watermaker, compressor and so on, the summerised PV peak power will be ca. 2kWp (or slightly more if possible). Even devided into 4 strings results in 8+ A continious current. Large enough to heat up a bad / corroded connection or a broken cable. If it doesn't work I have a spare.
Radio, radar, nav lights, windlass, winches, watermaker, fridge, head pumps and so on will be supportet by a 100-150Ah@24VDC housebank which is fed by the propulsion banks and insofar safely seperated from the AFCI.

So I won't have a complete AFCI protection, but on the continious feed and high power consumption side.


(BTW, I'll still have a 10kW Diesel generator as a backup for the long run of the props, 5kts in the Panama canal or clouds for days. I try to minimize my footprint but I'm not stupid ��



What I've also learnt or rather affirmed: 80% are the new 100% ��


Cheers & thanks again

[GordMay]

... Time to have a conclusion about what I've learnt ...

I think you’ve summed it up, pretty well, Dirk.