How hot is normal for my wires?

[almostalx]

Hi,

I just finished my electrical setup of 300ah lithium + 2000w inverter. I just tested my system with a 1800w toaster oven plugged into my inverter and everything was running smoothly?. The thing is some of the wires that goes from my inverter gets very hot, especially the shorter ones between my switch and my fuse (cable is around 5-6 inches). It’s not so hot that I can’t touch it, but I wouldn’t want to keep my hand on it for too long. The wires are 2/0 gauge and from my calculation are overkill for the current that it delivers (Around 170 amp for 3 feets)

So I guess my question is how hot is normal and how hot should have me worried that there’s something wrong with my wiring.

 

[gnubie]

Check where the heating is actually happening. 2/0 at 170 amps shouldn't be getting so hot that you can't hold onto it for extended periods. From your description of shorter wires being particularly noticably hot I wonder if your terminations - the lugs - are correctly sized and correctly fitted and properly secured, ie nuts / bolts done up correctly with right torque etc.

 

[almostalx]

Yeah I’ll triple check this, but everything looked in order. I’m using 2/0 lugs that were crimped with a crimping tool and everything is nice and tight. I really don’t see what I’m doing wrong here. But I’ll check again to make sure thanks

 

[Brewman]

Do you have a schematic of your system

 

[almostalx]

It looks something like this

 

[Brewman]

Does the wire feel hotter in any one spot?

 

[almostalx]

I’d say the short one between the switch and the fuse feels a little bit hotter than the rest. This cable is so short though, there’s basically only 1 inch between the 2 lungs if that changes anything.

 

[RCinFLA]

Wire gauge is not just voltage drop. Nat Elect Code house wiring gauge to max current is based on roughly 2-3 watts of heat per foot with some other criteria about conduit size, insulation thickness, and number of current carrying wires, all of which relate to how much possible heat build up in a confined space. For example, SOOW wire commonly used for portable generators has a lower current rating for its wire gauge because it is wrapped with thick insulation blanket that inhibits heat dissipation to the air.

Having said all that, 170 amps is not too bad for 2/0 wire. It would be about 1.2 watts of heat per foot. For short pieces, a common issue is connectors, crimps, and terminals bolted to, which may be where the heat is coming from and just conducting into the wire.

It's alway nice to get a narrow field IR heat sensor gun to check for hot spots.

 

[somewhereinusa]

I would replace the wire or crimp new lugs on the one getting hot. I've seen wires that looked fine have bad crimps.

 

[John Frum]

The fuse should be as close to the battery positive terminal as possible.
At the very least swap the fuse and the disconnect switch.

 

[almostalx]

Yeah I think I’ll get a terminal fuse instead and remove this cable altogether

 

[Zil]

You can do a voltage drop test. Use a multi-meter set to dc volt and poke the leads on each side of the connection and each end of the cable while the inverter is running the toaster. I run my microwave at 150 amp dc for 6 minutes with no heat, no noticeable warmth in my 2/0 cables or connections.