Minor new year emergency. Help please.

[basssears]

Originally Posted by _andi_

• fuse on wooden panel.

I didn't know this was a problem... what is the recommended material to mount a fuse holder to? Or should it be in a junction box of some sort or ???

[a64pilot]

Originally Posted by basssears

I didn't know this was a problem... what is the recommended material to mount a fuse holder to? Or should it be in a junction box of some sort or ???

Something that doesn’t burn so easily, or put a metal heat shield under the component. It’s simply keeping flammable things away from things that get hot.

[Montanan]

Originally Posted by GrowleyMonster

Well, you are sort of over fused. 500a x 12v is 6kw, nominal. 750a would be 9kw.



I bet your connection at the fuse had a high resistance. Otherwise you would not have a concentration of heat there. Make sure there is plenty of ventilation behind that fuse cover, too.

"The inverter didn’t trip at any point."
"The 2x positive cables are 95mm2 and were red hot to touch hence the melting fuse."

Are the cables on the left and the right side of the fuse box of similar dimension? It appears that they are equivalent, albeit with one on the left [presumably connecting to the inverter] and two on the right [presumably connecting to the battery bank].

Was the two parallel positive cables only red hot near the fuse bolt coupling or were they really hot all along the parallel positive cable lengths? Clearly the fuse bar coupling got the hottest as it blacken. Of issue is to identify where the resistance was highest, which appears to be the bolt connection on the battery side, not the inverter side of the fuse block.

Was the single cable to the left also "red hot"? That side of the fuse block does not seem to have heated nearly as much.

First impression: The 750 ampere fuse does seem to be overrated given your inverter is specified to 5000 watts.

I expanded the photo [copied below] and it appears that there are washers behind the bus bar of the fuse, positioned between the bus bar of the fuse block, which washers would restrict the current flow compared to the larger contact surface area of the cable terminal. Not sure what kind of washer was installed, if common steel and not tinned copper then that would become an even much greater resistance current pathway, i.e., a red hot. It appears that the rectangular surface of the fuse bus bar could be directly connected to the fuse block without the need for a lesser current rated round spacing washer. A locking tinned copper washer on the outerside is useful for providing a wider clamping pressure surface than just from the surface of the nut and to assure the nut will not loosen.

What is the current rating of the specific ANL fuse block? They come in many varieties of ratings. Besure that it's replacement is adequately rated; stepping up to a higher than required amperage fuse block is advisable, but DO NOT utilize a fuse that is rated higher than the fuse block and of course larger than the rating of the smallest cabling.

The Quattro inverter is rated at maximum 5,000 watts which provides for 2 X 100 ampere, 230V AC outputs. Note: The inverter's output is rated at considerably less in ambient warm conditions, reference data sheet pictured below. You were pushing the limits of the inverter with the 4,400 + watts. Next time I suggest you temporarily drop one of the oil heaters before making hot water for tea.

What voltage supply from the battery bank that is being provided to this fuse block? E.g., 12 Volt, 24 Volt or 48 Volt? It appears the Quattro 5000 inverter can provide for either 12 volt, 24 volt or 48 volt supply / charging. If anyone sees or knows differently than that multi-voltage capabilities please advise. Reference data sheet below.

I am uncertain of the connections of this fused cable connection. There is a single cable on the left side and two parallel, similar sized cables on the right side and the right side is the side that appears to have overheated. You state that the fuse block is between the battery bank and the inverter on the positive side. In which case the fuse rating should not exceed the inverters maximum output capacity or perhaps just a bit more than the inverter's output capacity, assuming the inverter has internal protection circuitry from overload. The inverter's conversion is rated at 94 - 95 percent efficient so you don't need much supply head room to derive the output rating.


If the voltage supply to the inverter is 12 volts, [worst case for amperage requirement] then the protective fuse should be rated at say 450 amperes; if the DC supply voltage is 24 volts then the fuse could be rated at 225- 250 amperes and if at 48 volts then the fuse could be rated at 125 amperes. All far less than the 750 ampere fuse which was installed and which apparently did not burn open.

The fuse block seems to have considerable heat damage, I strongly recommend replacing such with an adequately high amperage ANL fuse block and going with a lower amperage fuse. Ditto as to replacing the insulative cover for the fuse block.

Also the cable insulation seems to have been cut back too far from the terminal end and is unnecessarily and dangerously exposing the bare conductor. Utilize appropriate shrink wrap to cover the exposed cable up to nearer the portion of the cable terminal where it begins to bends to the through bolt hole such that the NEW fuse blocks insulative cover will completely cover the remaining exposed portion of the cable terminals. You don't want any bare conductors that could be exposed to inadvertent coupling.

It sounds like you might also be pushing the shore power towards its extreme. "I’ve been running 3 oil filled heaters, 4000w total from the 16a shore power and also the boats electrics but if I want to boil the kettle for example I’ll turn off the 2000w heater." If the shore power is rated for 16 amperes and at 240 volts that is a supply rating of 3,840 watts, [if the shore power is 220 volts then at 16 amperes the supply is rated at 3,540 watts], powering your stated 4,000 watt draw. You might incur difficulties or dangers from drawing steeply from the limited shore power installation and / or your plug in connection to shore power. That's a lot of heat. Can you dial down the draw, many electric oil heaters have lower power draw step switching.

Glad you were able to smell the burnt insulation and resolve the problem without any major damage or harm.

Best wishes for the New Year.

[Reefmagnet]

I don't 100% agree that mounting a megafuse block directly to wood is a bad idea because wood actually needs a flame or glowing red metal to ignite and, unless only the cheapest of the cheap fuses, fuse holders and wire insulation have been used that are not UL approved, these are unlikely to burst into flame or start glowing red. The biggest danger is hot bits dropping out of melting plastic and landing on something that is going to catch fire or otherwise punch a hole in something that will cause the situation to end badly.

The crimps might look dodgy (what the heck is that pink heatshrink supposed to be doing?) but they haven't been overheating; that melted insulation is caused by heat from the stud.

As a rule of thumb, each mm2 of conductor area will carry 10 amps for runs up to 10 metres or so. Conductor insulation is normally rated with a maximum working temperature. That stuff in the photo looks like it's at the lower end of the scale. The biggest danger for that circuit is that the conductors might heat up enough to drop the wire out of the insulation, and the resistance of the circuit will remain high enough to prevent the fuse from blowing. This definitely would not end well.

Even though the issue just seems to be a bad connection rather than an inherent fault with the circuit, I reckon reducing the load rating of the circuit as has been previously suggested might be a wise move. On my boat, I have a separate inverter and associated circuit specific for high load devices. This lets me isolate it from all other systems and includes a DC supply contactor to allow remote disconnection of the inverter similar in principle to a gas solenoid when not in use or if something goes wrong.

[Montanan]

Indeed, the cabling may be inadequate for the high amperage draw capacity of the Quattro 5000 watt inverter.

There are two parallel cables on the right side of the fuse block and only one cable on the left side; unsure if they are all 95mm2; if so, then the single cable on the left side will be the current limit for the cabling.

If the voltage supply to the inverter is 12 volts, [worst case for amperage requirement] then the protective fuse and supply cabling should be rated at say 450 amperes; if the DC supply voltage is 24 volts then the fuse / cabling should be rated at 225- 250 amperes and if at 48 volts then the fuse / cabling should be rated at 125 amperes. All far less than the 750 ampere fuse which was installed and which apparently did not burn open.

If the cable is 95mm2 servicing this inverter's capacity, the battery bank should be a 48 volt system at least as per avoiding the limits of the cable ampacity specification data sheet copied below.

If any of the cable crimps or connections were compromised then the ampacity would be significantly less than the copied ampacity ratings below.

Suggest ditching the heavy electric draw appliances, e.g., the electric oil heaters, the electric tea pot and perhaps the electric water heater, and / or be sure to configure to a high DC battery voltage supply to the inverter so as to minimize amperage draw requirements.

I would be inclined to install a different current protection device then these comparatively slow acting ANL fuses. I always want to have a fuse or breaker open before anything else gets stressed.

[Uncle Bob]

Certainly been some interesting observations here, no heatshrink, cables stripped too far back, only one cable to left hand side of fuse, crimps not good enough among others.
My observations from looking at the same pics, red heatshrink that has shrunk and split, insulation that has started to melt and pulled back from the crimp, two cables to both sides of the fuse block each with damaged heatshrink, crimps that have obviously done their job, the heat apparently having been generated by the incorrect addition of a washer between fuse and holder.
But then I am not a "marine professional", so what would I know or even what I am looking at?

[Jim Cate]

Just a comment: those cables surely were not "red hot". At well less than red hot the vinyl insulation on the cables would have been charred and black... and they ain't! Possibly a bit of melting just at the end of the jacket, but really not much to look at. The only part that appears to have gotten seriously hot is the end connection at the fuse itself.

And do note that the fuse is only overheated on one end, yet both ends have passed the same current. This suggests that the connection on the "hot" end was more resistive than the other, which in turn suggests that it was different in some way, like hidden corrosion or lack of tightness... different some way for sure.

So, while the crimps may not be the best and it is possible that the cabling is smaller than ideal, the actual problem seems isolated at the single end of the fuse itself.

In Dave's place I'd clean up those fuse connections, replace (if possible) the fuse, best with a smaller value, and avoid those huge loads... and carry on with the cruise.

Jim

[Grattaway]

Welcome to 2019

Others have pointed out the repairs that you need to the fuse block but at 750a it sounds way to big to me - even 500 sounds excessive. If it is not going to fail when something goes wrong its not doing its job

and as I understand oil fin heaters they draw around 10 amps each - and heating hot water or boiling a kettle is also a major user - so 16a shore power is also over loaded?? - or the inverter is consistently under significant demand pressure which is not ideal

[GordMay]

Originally Posted by smac999

5000w inverter will have a peak surge power around 10,000. Likly fused fine. Fuse value and cable sizes would be in manual.

Indeed.
Manual specifies 750 AF.
DC Supply: Parallel 90 mm2 Cu Conductors - Hence Nominal AWG : 2 x 3/0 Cu each Pos + Neg (4 Total) or 1 x 350 MCM Ea.
Pg 14 ➥ https://www.victronenergy.com/upload...2%20-%20EN.pdf

[jbd3dmd]

Consider some lithium grease sparingly on the terminals to eliminate inadvertent high resistance terminal connections.

Sent from my SM-N920R6 using Cruisers Sailing Forum mobile app

[davedindubai]

Thank you for all the input.

I’ve now spoken to my dealer, Victron U.K. and my electrical installer and all are happy with the parts used, the method of install, fuse size and the cabling.

I’ve taken all apart (see pic) and cleaned up. I’ll re heat shrink and put it all back together and wait to see what the feedback is from my electrician while awaiting delivery of a new 750a mega fuse. Will also be more careful of our electrical draw.

I’ve attached a pic of the battery compartment for those interested too.

[_andi_]

Originally Posted by davedindubai

Thank you for all the input.

I’ve now spoken to my dealer, Victron U.K. and my electrical installer and all are happy with the parts used, the method of install, fuse size and the cabling.

In case there are no fuses hidden in the battery terminals:



Maybe you should consider getting another installer or at least get a printout of lloyds complete catalogue (it is a british vessel?) and hit your current installer with it a couple of times.

4.6
Non-fused cables, e.g. battery cables, are to
be laid safe from short circuits, i.e. they must be laid
in such a way that the possibility of a short circuit can
be excluded even if the insulation should fail.

... and then there's the main positive line zip tied to the negative. ouch.

http://rules.dnvgl.com/docs/pdf/gl/m...gl_i-3-3_e.pdf
(from german lloyd but the concept is probably the same.)

[CharlieJ]

I wasn't going to jump in because all salient deficiencies had been covered by others but this:

I’ve now spoken to my dealer, Victron U.K. and my electrical installer and all are happy with the parts used, the method of install, fuse size and the cabling.

set my hair on fire!!! What did they attribute the failure to, bad karma???

In the USA, this would be called BS.

As several posters have pointed out, this incident was caused by a high resistance connection at the connection of the two conductors to the fuse holder on the right hand side of the photo provided. The fuse size is adequate and the conductor size is adequate IAW the Victron manual, assuming that this is a 12VDC inverter/charger.

Here are the defects that I would put in a forensics report if I was called in to investigate this "installation":

1. First off, this is not a "MegaFuse". It is a standard ANL fuse.
2. The photo shows that the washers that are supplied with the ANL fuse holder were installed under the ANL fuse tabs.
3. The visible crimps on the conductors appear to be inadeauate as there is no indication of upset metal.

The industry standard for over current protection devices (OCPD) for inverter/chargers is a Class T fuse and matching fuse holder. ANL fuses are cheaper but at the very least, a ceramic ANL fuse should have been used. BTW, bow and stern thrusters are usually supplied with these ceramic ANL fuses and associated fuse holders as part of the installation kit.

If copper is assigned a value of 100 for conductivity, stainless steel will be about 15. The placement of the SS washer under the ANL fuse wings was probably the primary cause of this failure.

I personally install hundreds of ring terminals on 1/0, 2/0 and 4/0 conductors every year. I use a $1200 USD, 12 ton hydraulic crimper to perform these crimps. So believe me, those crimps are inadequate and certainly aided in promulgating the failure.

My recommendations:

1. Replace the ANL fuse system with a Class T fuse holder and fuse.
2. If you do not use a Class T fuse, at least procure a ceramic ANL fuse and appropriate ANL fuse holder.
3. Re-terminate the conductors using a box crimper that will adequately deform the barrel of the ring terminal. The crimp must withstand a significant force. ISO 10133 requires that the crimp on 95mm^2 conductor should witstand an axial force of 550 N (124 pounds) without movement between the barrel and the conductor.

As was stated by others, this installation has all the telltales of being performed by somebody who was not adequately trained (amateurish). That the Victron dealer and the installer are literally giving you the brush off is un-professional and they should be taken to task.

Your characterization of this incident as a "minor new year emergency" is just a bit naive. Under the conditions stated and with the two photos provided, the fuse would probably never open and the heat would continue to be generated until molten metal was produced or the fuse holder failed and the wooden substrate was brought to ignition temperature. Where the molten metal would land is certainly unknown but certainly could have started a major fire.

In short, this is a shoddy installation, and the consequences of the installation could have been catastrophic. You were lucky.

[CatNewBee]

Originally Posted by davedindubai

Thank you for all the input.

I’ve now spoken to my dealer, Victron U.K. and my electrical installer and all are happy with the parts used, the method of install, fuse size and the cabling.

I’ve taken all apart (see pic) and cleaned up. I’ll re heat shrink and put it all back together and wait to see what the feedback is from my electrician while awaiting delivery of a new 750a mega fuse. Will also be more careful of our electrical draw.

I’ve attached a pic of the battery compartment for those interested too.

Attachment 183050Attachment 183051

Hi Dave,

the cause is bad contact on the fuse terminals.

I have, as you know, a 1000Ah LFP bank connected to the Victron Quattro 12-5000/120 100-100, and the spec is indeed 750A, but I have done the wiring and the fuses differently to prevent this from happening.

I have 2 ANL fuses with holders on one side both connected directly to the massive copper bus bar on the battery pole and on the other side connected single 95mm2 wires to each fuse back to the inverter, I use 400A fuses, so slightly more than the recommended 750A. Another option would be 350A fuses, totalling of 700A. The advantage is, you double the connection area. I also use copper washersabove the fuse and spring washer on top than the screw all copper plated. Before assembly, clean the surface of all the parts from any oxidation and tighten the screws. You can use noalox or similarconductive paste to prevent oxidation and improve contact. Also every wire is separately protected, what means if one crimp or wire fails, the other wire is protected by half the fuse size (400A), what will blow instead of putting 750A over a single 95mm2 wire.

After putting it together put the highest load on the inverter can handle and check the temperature on the wire, connectors etc., also check the negative side and all battery connections for unusual heat. If there are hot spots, tighten the screws further or improve the contacts by cleaning the surfacec or increasing the connection surface.

When everything is to your satisfaction, take some liquid rubber paint andpaint over the bars and all exposed metal on the connection. It peels easy off if you need to disassemble, but protects the connection efficiently from moisture and corrosion to prevent degradation of connectivity.

If the wire ends get warm around the cable schoes, you may need to apply some more force on the crimping too. You really need to check every single connection along the way of the high current path twice, little things cal lead to big problems when dealing with high currents!

[KTP]

See, this is my excuse to get a thermal imaging camera. I have always wanted one and now I can say it is a safety device for quickly inspecting wiring and connections.