Fusing and busbars

dixonge

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Time to finalize some things, and I keep banging my head against the wall in an attempt to make one final parts order. This is in an RV w/ lead acid batteries. Diagram (incomplete) attached. So, a few questions I've been unable to find answers for:
  1. Way too many things attached to the most-positive battery terminal. Time for busbars.
    1. On the positive side I have a 150A ANL fuse between battery and inverter. I think the busbar should go in between the fuse and the inverter, right?
    2. Devices connected to the positive busbar would be include two SCC's - one is 4 100w panels in 2s2p configuration. One is 2 100w panels in serial. Would an MRBF fuse at the busbar work for these?
    3. Also connected to the busbar are an Iota DLS-55 charger, the power cable for the shunt bluetooth circuit, and an exhaust fan thermostat. It has two 30A fuses but I think those are for reverse polarity. Does the charger need a fuse at the busbar? If so, would an MRBF fuse work there as well?
  2. On the negative side:
    1. I think the busbar would need to be off of the shunt opposite of the end connected to the battery, right?
    2. Need to move the Iota charger negative and vent fan negative to busbar.
    3. Both SCC negatives would go to the busbar as well, correct?
  3. The two new solar panels are portable, but probably too big to hinge together. I will be connecting them in series w/ Anderson Powerpole connector. This will be just one red and one black wire, and I can't find any sort of weatherproof boot for just one wire. Any ideas? I'll be connecting black to red, which seems to not be something these connectors are made for.
  4. Each time I set them up, I'll need to take the other two wires and connect them to my PV extension cable w/ an SB50 connector. Can't figure out how to do that and keep the connection weatherproof... any ideas there?
RVSolar.png
 

FilterGuy

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an attempt to make one final parts order
There is no such thing as "One final parts order"!! It is a universal law of all DIY projects! :ROFLMAO:

On the positive side I have a 150A ANL fuse between battery and inverter. I think the busbar should go in between the fuse and the inverter, right?
I would put the 150A fuse between the Battery and the bus bar. Just be sure all the battery and inverter wires can handle 150A.
The rest of the wires off of the positive bus bar should also be fused.

1633578066230.png

However, rather than have a bus bar and independent fuses, I like to do a fuse box for the smaller fuses.
1633578121986.png
 

dixonge

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Fuse box = fuse block??? And is that replacing the positive busbar?
 

dixonge

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However, rather than have a bus bar and independent fuses, I like to do a fuse box for the smaller fuses.
View attachment 67830
A few notes:
  1. The small power line for the shunt is already fused (1A inline) - guess maybe I could find a fuse block w/ a busbar built-in?
  2. Charger is 55amp so 60A ANL fuse.
  3. What kind of connections were you thinking of where the ANL fuses go into both the fuse block but the battery connection still goes directly to the inverter? Seems like a 2-post busbar would work? (or maybe an internal busbar in the fuse block?)
 

Zwy

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Fuse box = fuse block??? And is that replacing the positive busbar?
Use the busbar to connect large cables. Then run a fused/breaker circuit to a fuse panel. Take a look at this photo, note the ANL fuse after the busbar which is the circuit to feed the fuse panel. That fuse panel also has terminals for the negative/grounds, those are located on the bottom of the fuse panel.

Power comes into the right side of the positive busbar from above, then 3 seperate cables for each larger load. 2nd from right is inverter circuit, 3rd from right is the fuse panel, 4th from right or left terminal is to a breaker that provides power to my buck converter as this is a 24v system.


24V fuse panel and busbars.jpg
 

dixonge

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Use the busbar to connect large cables. Then run a fused/breaker circuit to a fuse panel. Take a look at this photo, note the ANL fuse after the busbar which is the circuit to feed the fuse panel. That fuse panel also has terminals for the negative/grounds, those are located on the bottom of the fuse panel.

Power comes into the right side of the positive busbar from above, then 3 seperate cables for each larger load. 2nd from right is inverter circuit, 3rd from right is the fuse panel, 4th from right or left terminal is to a breaker that provides power to my buck converter as this is a 24v system.


View attachment 67871
so in my case:
batteries > busbar
FROM the busbar:
* 150A ANL Fuse > Inverter
* 60A ANL Fuse > Charger
* ? Fuse > Fuse block ???
* ? Fuse > MPPT SCC ???
* ? Fuse > PWM SCC ???
 

Hedges

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  1. Charger is 55amp so 60A ANL fuse.

Can charger deliver 55A?

Recommendation (and NEC where applicable) would be to size OCP 25% larger than continuous load. 70A fuse for 55A circuit, to avoid nuisance blowing.
Thermal protection devices are pushed closer to tripping/blowing by ambient temperature, and resistive connections.

I think Midnight says their magnetic/hydraulic breakers can be operated at 100% of rating, rather than derated to 80%.
But for (thermal) fuses and thermal/magnetic breakers, best to leave some headroom.

Of course, wire ampacity comes first, should be large enough for the fuse used.
 

eXodus

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Recommendation (and NEC where applicable) would be to size OCP 25% larger than continuous load. 70A fuse for 55A circuit, to avoid nuisance blowing.
Thermal protection devices are pushed closer to tripping/blowing by ambient temperature, and resistive connections.
NEC is another weird imperial standard. But also a 2x4 piece of wood is 1.5x3.5 inches and 2 inch pipe is 2.3 inches. so no surprise that in North America you don't use what it printed on the label for power.

But for DC stuff - imperial weirdness doesn't apply since it's made in metric, so you better go with what is on the box. Don't oversize to far!

When you buy a Breaker for 20A in Europe - you can use up to 20 amp continuous no math involved.
 

dixonge

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Can charger deliver 55A?
Good question. I guess it adjusts itself? Max volts would be 15.1 for equalization.
Recommendation (and NEC where applicable) would be to size OCP 25% larger than continuous load. 70A fuse for 55A circuit, to avoid nuisance blowing.
Continuous is rarely over 10-15 amps. Occasionally we fire up a 900W blender. Not sure how to protect for that...
Of course, wire ampacity comes first, should be large enough for the fuse used.
Batteries and inverter are all 2AWG. Charger and SCC are all connected to battery via 6AWG. Everything else is 10AWG or smaller.
 

Zwy

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so in my case:
batteries > busbar
FROM the busbar:
* 150A ANL Fuse > Inverter
* 60A ANL Fuse > Charger
* ? Fuse > Fuse block ???
* ? Fuse > MPPT SCC ???
* ? Fuse > PWM SCC ???
I'd install ANL between battery and busbar. The reason is total load and complete system protection Size is based upon max amps/cable size the cable will carry from battery to busbar. That would be with multiple higher loads powered.

I used a breaker to inverter, this way I have a switch, same with 40a to buck converter. Fuse block I used ANL for under the max amps the Blue Sea fuse panel was rated for, in this case 100a and panel is rated for 135a.

From my PV array, I used a combiner box on the roof. https://www.amazon.com/gp/product/B07F5HDP2W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 I removed the MC4 connectors and installed waterproof glands and simply ran the PV cable into the terminals. The combiner comes with a breaker. I did install a switch that can be reached at ground level shown on the right side of the photo. It was overkill for what I needed but I knew this switch was waterproof and would be switched often. https://www.amazon.com/gp/product/B011EYWMDS/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

Every circuit that drops to a smaller wire will require a fuse or breaker. This is important to remember.
 

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Hedges

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Good question. I guess it adjusts itself? Max volts would be 15.1 for equalization.

Continuous is rarely over 10-15 amps. Occasionally we fire up a 900W blender. Not sure how to protect for that...

Batteries and inverter are all 2AWG. Charger and SCC are all connected to battery via 6AWG. Everything else is 10AWG or smaller.

If batteries were low and you plugged in the 55A charger, it could deliver 55A for a while.
So this was just charge current and 60A fuse I was thinking of.
I guess if you ran an AC load at the same time, it would pull current too, so more likely charger drives 55A.
With 6 awg, 70A is fine.

With fuses, you don't want them to blow due to loads. That should only happen if there is a fault.
 
Last edited:

dixonge

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If batteries were low and you plugged in the 55A charger, I could deliver 55A for a while.
So this was just charge current and 60A fuse I was thinking of.
I guess if you ran an AC load at the same time, it would pull current too, so more likely charger drives 55A.
With 6 awg, 70A is fine.

With fuses, you don't want them to blow due to loads. That should only happen if there is a fault.
Yeah, while I might have a small load (5 amps or so) when charging, most likely I'd have the inverter off.
 

Hedges

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55A / 460 Ah = 0.12C
Isn't that exactly what these FLA want to be charged with?
 

dixonge

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55A / 460 Ah = 0.12C
Isn't that exactly what these FLA want to be charged with?
Yes, which is why I bought this unit. Unfortunately I wired it direct to the battery, bypassing the shunt and therefore any way to monitor the current. I'll re-route it after I get my busbars installed.
 

dixonge

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Can charger deliver 55A?

Recommendation (and NEC where applicable) would be to size OCP 25% larger than continuous load. 70A fuse for 55A circuit, to avoid nuisance blowing.
Thermal protection devices are pushed closer to tripping/blowing by ambient temperature, and resistive connections.

I think Midnight says their magnetic/hydraulic breakers can be operated at 100% of rating, rather than derated to 80%.
But for (thermal) fuses and thermal/magnetic breakers, best to leave some headroom.

Of course, wire ampacity comes first, should be large enough for the fuse used.
My SCC's are both 30amp w/ 6AWG to the busbar/battery. So, 30amp fuses? (or Tocas surface-mount breakers like Will recommends?)

I like 70amp for the charger, as you recommended (same 6Awg sire)
 

Hedges

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Thermal fuses and thermal-magnetic breakers should be sized 25% above continuous operating current.
Magnetic-hydraulic may be ok without oversize.
If SCC delivers 30A I would want 40A fuse.

6 AWG ampacity, assuming 90 degree C insulation and 30 degree C ambient, is 75A in cable up to 3 conductors or 105A for individual conductors in free air.
I would be inclined to use 40A for both SCC even if they share one 6 awg run of individual wires.

 

dixonge

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I don't feel like I have enough low-amp devices to justify an entire fuse block. And I need more disconnects, sooooooo...

Surface-mount breakers it is! A 30-amp on each SCC and a 70-amp on the charger. Additional plain battery disconnect switches on the battery (between fuse and busbar) and the rooftop solar panel line coming in to the MPPT SCC.

That leaves the fan/thermostat and I have a feeling an inline 1-5amp mini-fuse or glass fuse should be plenty.

Moved my diagram over to diagrams.net, desktop version. Here's my current more complete drawing:

RV Solar.drawio.png
 
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