Electrical plan for shuttle bus conversion

[sovocoolp]

Reaching out for feedback on this plan.

[dzl_]

pressing the printscreen key + windows logo key will take a screenshot and save it to /pictures/screenshots/ if you are using windows 10


This will give you an easier to read schematic. If you are using some other system, there will be some similar key combo to take a screeenshot, it can be googled

[dzl_]

Some potential issues, thoughts and questions (see the attached image to match numbers/colors to what they refer to in your system).

1.Not enough detail of the PV array to know if it is wired or protected properly. Not enough detail on the breaker to know if it is correct

2. What is going on with the two connections between the starting battery and main house busbar? Looks like one runs via the alternator and one via a dc-dc charger. Feels like there may be some unintended consequences here.

3. Switch and breaker are largely redundant here, since the breaker is both a switch and overcurrent protection. There is nothing wrong with the way you have it, if you have reasons for liking this approach. Also, you breaker rating is stated.

4. A 300A breaker is nowhere near capable of protecting a 4AWG wire (also to my knowledge a 300A breaker does not exist at a reasonable price, above 200A you need to either use a fuse or be prepared to pay > $100).

5. There are no grounding wires in your schematic best I can tell (other than the main DC side system grounding point at the negative busbar). Read your inverter manuals advice on grounding. You need to make sure you understand the ground logic, and how to properly install your system (or pay someone who does). Of particular importance is understanding neutral-ground switching/bonding, and giving your inverter a fault path on the DC side (it is likely your inverter has a ground lug, it is likely the manual will tell you this needs to be connected to the negative busbar or designated grounding point).


As a general point, I get the impression you have not properly sized or understood how to size fuses/breakers to the wire. The primary purpose of fuses is to protect the wire. An overcurrent protection device should never be rated higher than the rating of the wire. You use a lot of 4AWG in your design, this can safely carry continuous currents in the ballpark of 95-160 amps depending on variables like insulation temp and ambient temp.

[sovocoolp]

Thank you for taking your time to review this. I did not design this electrical system, I had a third party design it. I wanted to post it to get a feeling on if it was done somewhat correctly.

I am using mostly 8 awg wire to carry the 240v. I do have 200 amp fuses and breakers and I will not use 300 amps.

I have three separate battery areas. One for the engine, one that controlled the lift and a few other items and the 7 lithium battery bank that I installed.

The neutrals and ground for the AC side are not displayed in the drawing.

I have the inverter/charger and battery bank on one side. The other side I have the other components.

[dzl_]

Originally Posted by sovocoolp

I do have 200 amp fuses and breakers and I will not use 300 amps.

A 200A fuse cannot reliably protect a 4AWG wire either. The fuse has to be sized relative to the wire and the load.

The way to size a fuse is to size it (greater than) > 1.25x the max current of the circuit and < (less than) the rating of the wire. 4AWG is rated for between 100 and 160 depending on the wire you use.

A fuse is an intentional weak point, so in order to serve its purpose it has to be weaker than the rest of the system its meant to protect.

So you either need larger wire or smaller fuses. I suggest this short video or this short article (part 1: wire, part 2: fuses/breakers)

Here is an Ampacity chart to see how much a wire can safely carry, it does not consider voltage drop which is not a safety factor but is a factor to be considered

The neutrals and ground for the AC side are not displayed in the drawing.

I mostly ignored the AC side as I dont feel comfortable or qualified giving advice there. However the ground connection I am referring to is on the DC side of the inverter (consult the inverter documentation, or have the person who designed your system do so as this is certainly something they should've considered).