Generator wire size

[seige101]

Use 10/3 for up to 30 amps and forget you ever heard about this continuous derating jive, it does not apply to this situation. It is much easier to work with 10/3 than 8/3 as well.

And how does that not apply in this situation?

 

[Highbeam]

Use 10/3 for up to 30 amps and forget you ever heard about this continuous derating jive, it does not apply to this situation. It is much easier to work with 10/3 than 8/3 as well.

And how does that not apply in this situation?

First of all and most importantly, 5000 watts from the chosen genset is not 30 amps. Second, it is not a continuous load. This is not a load but a supply for an intermittent load, by nature not applicable to a continuous loading rule.

The derating rule, I always used 75% but 80% is fine too, applies perfectly to things like baseboard heaters where you actually in practice only put a 16 amp heater on a dedicated 20 amp circuit. Since the 16 amp heater will always be 16 amps when on and is designed for continuous operation at 100%.

So how many 20 amp outlets do you install and only allow 16 amp appliances to be used? How do you prevent someone from plugging in a 20 amp device? Do you use 15 amp breakers on 12 guage wire circuits just to make you feel better about the continuous loading rule? Do your inspectors require this? Mine sure don't.

 

[oldspark]

Thats the thing I could never figure out, the wire has a saftey margin but they want you to derate it. I would not be afraid to put a continuous 30 amps on #10 wire.

 

[livefreeordie]

Lots of great info here and i thanks you for that.

 

[Highbeam]

I just discovered that Seige is an electrician. That's good. I'm not, and am willing to be told I am wrong.

Here's the thing about derating. You still build the ciruit properly meaning a 10 gauge wire on a 30 amp circuit. The derating applies to the load so you would only hardwire a 24 amp load to it. You don't oversize the wire and still put the same 30 amp breaker on it. In other words, if you have a continuous 30 amp load you would bump up to a 40 amp circuit with corresponding wire size.

 

[oldspark]

I just discovered that Seige is an electrician. That's good. I'm not, and am willing to be told I am wrong.

Here's the thing about derating. You still build the ciruit properly meaning a 10 gauge wire on a 30 amp circuit. The derating applies to the load so you would only hardwire a 24 amp load to it. You don't oversize the wire and still put the same 30 amp breaker on it. In other words, if you have a continuous 30 amp load you would bump up to a 40 amp circuit with corresponding wire size.

I am too (electrician is past life) and if the load is a solid 30 amps all the time yea good to bump up, still 30 amps on #10 wire is not going to make it hot, I how ever was an electrician in a plant so the house codes and stuff I did not have to deal with.

 

[seige101]

I just discovered that Seige is an electrician. That's good. I'm not, and am willing to be told I am wrong.

Here's the thing about derating. You still build the ciruit properly meaning a 10 gauge wire on a 30 amp circuit. The derating applies to the load so you would only hardwire a 24 amp load to it. You don't oversize the wire and still put the same 30 amp breaker on it. In other words, if you have a continuous 30 amp load you would bump up to a 40 amp circuit with corresponding wire size.

Yep electrician is my day job to pay the bills. No offence taken. When i do give advice here i give it according to minimum code requirements. I do see lets of shody work on a daily basis and see lots of stuff on a daily basis that shows me that minimum code is not always adequate. I am always a big fan on going over kill no matter that the task on hand is. For a small bit extra the peace of mind and longevity is well worth it in the long run for me.

Just a little something learned from my father and 10+ years in the trade.

 

[oldspark]

In all the wiring I ever did in our plant we just went by the rating of the wire, motor starters and breakers, never had to over size any thing and no problems to be found.