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Axpert MKS 3000 24V Overload Bypass Enabled/Disabled


AJM

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9 hours ago, Coulomb said:

Ok, changed branding, weird.

I would not personally use this on a 48 V nominal system though, which could see 56 or more volts.

The "100A" i am currently using is rated for 12v. Seems to work to about 82A, i think i will try the 120A or how about this one

http://www.bidorbuy.co.za/item/277468238/Mersen_2_pole_fused_battery_disconnect.html

?

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4 hours ago, PurePower said:

The "100A" i am currently using is rated for 12v. Seems to work to about 82A, i think i will try the 120A

So it's totally unsuitable. It "worked" in the sense of not attempting to disconnect at up to 82 A, but its primary purpose is to safely and completely disconnect in an emergency situation, where the fault current will easily be in the kiloamps, perhaps more than 10 kA. Something rated for 12 V could just explode or contribute to a fire, not prevent one. Using the 120 A version of the same thing (if I understand you correctly) just minimises the nuisance tripping (or attempted tripping), and doesn't make it fit for purpose. 

> or how about this one

http://www.bidorbuy.co.za/item/277468238/Mersen_2_pole_fused_battery_disconnect.html

Much better, though the safety depends largely on the fuses chosen (sold separately). You will need DC rated High Rupture Current (HRC) fuses, capable of clearing the short circuit current of your battery. 

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8 hours ago, Coulomb said:

So it's totally unsuitable. It "worked" in the sense of not attempting to disconnect at up to 82 A, but its primary purpose is to safely and completely disconnect in an emergency situation, where the fault current will easily be in the kiloamps, perhaps more than 10 kA. Something rated for 12 V could just explode or contribute to a fire, not prevent one. Using the 120 A version of the same thing (if I understand you correctly) just minimises the nuisance tripping (or attempted tripping), and doesn't make it fit for purpose. 

> or how about this one

http://www.bidorbuy.co.za/item/277468238/Mersen_2_pole_fused_battery_disconnect.html

Much better, though the safety depends largely on the fuses chosen (sold separately). You will need DC rated High Rupture Current (HRC) fuses, capable of clearing the short circuit current of your battery. 

Excellent, i agree with you that the first option is not fit for purpose and i am pursuing the Mersen breaker.

These are the fuses that would fit this breaker. http://www.bidorbuy.co.za/item/277468410/Bussmann_NH1_type_fuse.html

I'm just awaiting confirmation that the seller has stock of the 125A fuses.

Now considering this is a 2 pole breaker, it also gives me an opportunity to have a breaker on the +ve and -ve side of the battery. I'm seen some installations like this but i'm not entirely sure of its benefits. Could someone elaborate?

Secondly, i have the BMV shunt on the -ve side, should the breaker be installed before or after the shunt?

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3 minutes ago, PurePower said:

These are the fuses that would fit this breaker. http://www.bidorbuy.co.za/item/277468410/Bussmann_NH1_type_fuse.html

Those are the right sort of fuse. A name brand, and "IR 50 kA" written on them (interrupt rating 50 kilo-amps). 

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I'm just awaiting confirmation that the seller has stock of the 125A fuses.

I would be inclined to go for 100 A fuses. These large fuses blow slower on mild overloads than breakers trip. 100 A would likely be more readily available.

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Now considering this is a 2 pole breaker, it also gives me an opportunity to have a breaker on the +ve and -ve side of the battery. I'm seen some installations like this but i'm not entirely sure of its benefits. Could someone elaborate?

 

It's sometimes a requirement that the inverter can be completely isolated from the battery. Completely isolated means both poles. I have a two pole fuse holder like this; I believe the relevant Australian Standard requires it. I have a friend who knows the standards very well, and he designed that part of my installation.

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Secondly, i have the BMV shunt on the -ve side, should the breaker be installed before or after the shunt?

You need some way of isolating the shunt from the battery. If you have nothing else, then yes, these fuses need to be before the shunt. I have the fuses only connected to the Axpert (a separate pair of fuses for a separate charge controller). But I have a pair of battery contactors (EVC500s) connected to a battery management computer that can isolate the shunt and everything else in an emergency. All the contactors drop out if the Estop (big red) button (just to the left of this cabinet) is pressed. It's designed for one or two Axperts; I'm being cheap and using an old charge controller in place of the right hand Axpert. This system runs all the lights and power in my house, except for the stove, oven, and ducted air conditioner. You can count seven (7) EVC500 contactors (one is just for pre-charge; it could be a smaller unit, but they don't seem to cost any less).

moinolith internals sm.jpg

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1 hour ago, PurePower said:

Secondly, i have the BMV shunt on the -ve side, should the breaker be installed before or after the shunt?

I don't think there is any danger in having the shunt upstream from the fuses. If a short happens downstream, the fuse still goes. The only reason to put the fuse before the shunt would be because you are worried that the shunt itself might go faulty and cause a high current draw, but I think this is quite unlikely if not impossible. Let me explain: There are usually two thin red wires connected to the shunt (battery positive and midpoint), both fused with really small fuses. Those are the only two paths that exist by which a fault shunt could possibly go bad. If you discount those two power lines, the shunt is just a (slightly higher resistance) part of the negative cable.

I prefer separate fuses/breakers for the charge-controllers and the inverter. So inverter has its own big Mersen disconnect. Each charge controller has its own breaker. Each PV line has its own fused disconnect.

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