Hello! & Hoping for Feedback on my Planned System?

[John Frum]

Understood on your concepts on devices being hosed for sure. I guess my question is if your devices (Inverter/SRR) were not protected internally and just fired, I assume this will create a short as well then blow the fuse even though its rated for way higher?

I thought I already said this.
In a BMS protected system on a dead short the BMS usually disconnects first.
Then either the device fuse, branch fuse or battery fuse depending on the wire size and selective coordination.
Typically it can take a fuse up to 5 minutes to blow at 150% of their rating.
On a dead short the same fuse will blow in milli-seconds before the wire or the appliance will get noticably warm.

This is why nothing has ever been extremely problematic?

That is my story and I'm sticking to it.

So in a way:
sizing a breaker based on allowable wire load = protection for wire and less prone to unwanted trips while
sizing a breaker based on circuit load = Protection for the device but more prone to unwanted trips.

For me its not about un-wanted trips.
Higher rated fuses typically have lower resistance.
Its about not turning your very expensive DIY electricity into waste heat.

So somewhere in the middle is best for devices not protected internally?

See above, my patience is wearing thin.

Anyway to not continue beating a dead horse you would recommend running fuses based on max wire capacity? which is 250A & 100A.

Yes, won't say it again.

 

[keef2]

Thanks for clearing this up for me. I was stuck on what if a device doesn't have internal protection. But in that case it sounds like it will short and trip the overrated fuse no matter what. I definitely appreciate your thorough responses and time. Cheers!

 

[John Frum]

Thanks for clearing this up for me. I was stuck on what if a device doesn't have internal protection. But in that case it sounds like it will short and trip the overrated fuse no matter what. I definitely appreciate your thorough responses and time. Cheers!

I don't recommend the use of loads or sources that don't have basic internal protections.

 

[keef2]

In a system with LFP batteries the BMS usually trips in micro seconds on a dead short.

Hey John - One last question. Do I need to add a BMS to my system? Or is this the same as the Smart Shunt you provided above?

 

[John Frum]

Hey John - One last question. Do I need to add a BMS to my system? Or is this the same as the Smart Shunt you provided above?

If you have a lead acid battery, no.
If its any flavour of lithium, yes.
BMS = battery management system.
It keeps the cells within a safe voltage envelope and many of them also try to protect from over-current.
Just about none of use trust them to do over-current protection by themselves though.
The BMS typically also try to maintain the battery top-balance.