Orion -TR Smart Isolated DC-DC Charger 12/12V-30A

[mikefitz]

fusing is to protect the wire, not the appliance

Fusing protects both the wire and the appliance. Victron suggest a 50 amp fuse.

Mike

 

[jbird526]

Fusing protects both the wire and the appliance.

Correct. Guess I look at it that protecting the wire, and sizing correctly, ultimately protects the appliance and is the first step in the chain. I had to learn that just because you have a fuse on the appliance does not mean that should not protect the wire from ninja smoke.

 

[John Frum]

Correct. Guess I look at it that protecting the wire, and sizing correctly, ultimately protects the appliance and is the first step in the chain. I had to learn that just because you have a fuse on the appliance does not mean that should not protect the wire from ninja smoke.

In which scenarios would a circuit fuse protect the appliance?

 

[jbird526]

In which scenarios would a circuit fuse protect the appliance?

So correct me if wrong in this scenario @smoothJoey .

• An appliance is rated at 50 amps max.
• You ridiculously oversize the wire to 2/0 gauge.
• Before the wire you have a 50 amp fuse.
• You push 80 amps through the fuse, which would blow that fuse.
• The wire can more than handle 80 amps.
• Would that fuse then be considered to protect the appliance instead of the wire?

I get that this is an unrealistic scenario, or it should be unless you want to waste money.

 

[John Frum]

So correct me if wrong in this scenario @smoothJoey .

• An appliance is rated at 50 amps max.
• You ridiculously oversize the wire to 2/0 gauge.
• Before the wire you have a 50 amp fuse.
• You push 80 amps through the fuse, which would blow that fuse.
• The wire can more than handle 80 amps.
• Would that fuse then be considered to protect the appliance instead of the wire?

If by appliance one refers to either a load or a charge source and not a battery or other in-line components of the circuit.
Those appliances regulate current.
If there is a short upstream then the appliance is out of harms way.
If there is a short downstream then the appliance regulates the current.

If the appliance has an internal short then the fuse will protect the wire.
Its too late for the appliance.

The scenario I can see where a fuse may protect an "appliance" is if there are inline "appliances" that don't regulate current.
Like a BMS, battery protect or shunt etc...
I'm thinking that those should be treated as part of the wire and the fuse should be sized to protect the wire(including these "appliances").
I guess it also depends on one's definition of "appliance".

Thanks for making me think.

 

[mikefitz]

Perhaps the statement should be ,
" also the fuse protects against any fault within the appliance", thus reducing or eliminating fire or component damage. Wiring/components internal in the Orion connected to the feed cable will have a fault current limit.

Mike

 

[MisterSandals]

• An appliance is rated at 50 amps max.
• You ridiculously oversize the wire to 2/0 gauge.
• Before the wire you have a 50 amp fuse.
• You push 80 amps through the fuse, which would blow that fuse.

The appliance pulls amps. I would not expect a “50 amp appliance” to pull more than 50A except as mikefitz points out, there is a fault within the appliance.

Imagine if the grid pushed amps, all hell would be breaking loose in the house at every level: 200A service breaker, 20A circuit, .5A DC adapter plugged into wall.

Not trying to play with semantics, it’s an important concept to understand.

 

[John Frum]

Most decent appliances include at least some of these protections.
Reverse polarity protection is also common but not called out here.

"Extensive electronic protection
Over-temperature protection and power derating when temperature is high.
• Overload protected.
• Short circuit protected.
• Connector over-temperature protection." -- https://www.victronenergy.com/uploa..._Isolated/Orion-Tr_Smart_DC-DC_Charger-en.pdf

 

[jbird526]

Imagine if the grid pushed amps, all hell would be breaking loose in the house at every level: 200A service breaker, 20A circuit, .5A DC adapter plugged into wall.

That is an important point and about the fact that appliance PULL amperage.

What about something akin to a lightning strike at the point before the fuse, wire and appliance scenario? That is a case where amperage is not being pulled but rather sent toward an appliance, through the fuse that is supposed to pop, to prevent being sent down the wire to the appliance.

I am not trying to play with words, rather learn as to not look as stupid later. Maybe I am also saying amperage where I should be saying current at times?

 

[jbird526]

And to think this thread started with question about connecting a DC to DC converter on an aux battery. I find the fringe and corner case conversations intriguing though. That is where I tend to have the light bulb moments, pun intended.