Generator inlet with interlock kit wire and breaker sizing anticipated loads

[Tracs]

I am going to install a generator inlet to connect a portable generator for the frequent power outages we have.

The generator is a gas fuel source only champion 10000 watt running 12500 watt starting. I plan on buying/constructing a permanent enclosed shelter for the generator turning it into a permanently stationary home back up generator.

The inlet and interlock kit are sorted out.

The question is about wire size and breaker size.

6/3 with a 50 amp breaker. These are items I would have to buy.

I have lots of 8/3 wire and 40 amp 2 pole breaker already.

But this isn't so much of a pinching pennies situation. I was just wondering if the 8/3 and 40 amp breaker would be sufficient.

 

[Chuckster in NJ]

Big question: What is the connected load? Without knowing this I cannot answer your question…… A 40 amp breaker may be good.

 

[mike93lx]

Breakers at that size are usually cheap, but the wire will be costly.

I bet 40a is probably just fine (what big loads would you be running in an outage? Multiple a/c zones? Electric dryer? Electric water heater?) but tripping a breaker during an outage would ****.

That generator is going to use A LOT of fuel

 

[PCustoms]

The question is about wire size and breaker size.

6/3 with a 50 amp breaker. These are items I would have to buy.

I have lots of 8/3 wire and 40 amp 2 pole breaker already.

Let's back up several steps.

1) what are you trying to power?
2) where will this inlet be located relative to the panel?
2a) will you be running the wire (whatever you pick) outdoors or underground?
3) what type of wire do you have?

 

[Tracs]

We are creatures of comfort. During an outage I don't want to have to change our routine or make sacrifices. I know the ultimate solution would be a 26kw+ generac home standby generator run on propane, but that is out of the question for a few years.

I would want to run things like the AC/heat pump, having a hot shower, cooking food if need be, watching TV and surfing the net. We are all electric for heat/cooling/hot water.

I did a quick calculation and came up with 19500 demand watts for the house.

I know obviously a 10000 watt running 12500 peak won't run the whole house.

The inlet will be within 10' of the house panel. The plan was then a 50amp extension cord with NEMA 14-50P male plug, NEMA SS2-50R female receptacle to plug the generator into the inlet.

I have 8/3 NMD90 wire which would run from the panel though the exterior wall into the surface mount receptacle box.

And this sucker sure will **** fuel!

I hadn't planned on getting a large generator like this one, but while at the hardware store a couple weeks ago it was a deal no one would ever pass up, so I "had" to buy it. Lol.

 

[PCustoms]

I would want to run things like the AC/heat pump, having a hot shower, cooking food if need be, watching TV and surfing the net. We are all electric for heat/cooling/hot water.

I did a quick calculation and came up with 19500 demand watts for the house.

I know obviously a 10000 watt running 12500 peak won't run the whole house.

You're going to want to do 50A inlet. And manually manage loads...

The inlet will be within 10' of the house panel. The plan was then a 50amp extension cord with NEMA 14-50P male plug, NEMA SS2-50R female receptacle to plug the generator into the inlet.

I have 8/3 NMD90 wire which would run from the panel though the exterior wall into the surface mount receptacle box.

Eek, Canada! Don't know enough about the codes up there.

For that short of a distance the correct wire shouldn't be too expensive

 

[mike93lx]

You are likely going to need a soft start for the a/c

 

[Firebrick43]

There is no reason to worry about the breaker size in the panel as long as the wire size from the generator hookup receptacle and the receptacle itself is rated for the same or higher than the breaker. You could make it even larger if you so desire for larger future generators as long as the wiring/receptacle is sufficiently sized.

The breaker for the interlock protects the wiring, not the generator. The circuit breakers on the generator itself protect the generator

 

[wyliesdiesels]

I would run conduit from inlet to panel which would enable you to use individual #6 conductors for hot and neutral and #10 for ground. this will save you some money on wire

 

[mike93lx]

I think the chances of ever popping a 40a breaker without causing the generator to brown out is very unlikely.

I'd run what you have with a 50a inlet

 

[PCustoms]

I think the chances of ever popping a 40a breaker without causing the generator to brown out is very unlikely.

I'd run what you have with a 50a inlet

Maybe I'm thinking about this wrong, but his generator can put out 12k watts, his house can obviously pull more then that.

His 40A wire could see 50A before the genny breaker trips, right?

 

[mike93lx]

Maybe I'm thinking about this wrong, but his generator can put out 12k watts, his house can obviously pull more then that.

His 40A wire could see 50A before the genny breaker trips, right?

The generator can surge to 12k but only do 10k continuous. 8/3 can handle more than 40a, especially on a short run and in bursts.

I'd breaker it at 40.

Also, if he actually draws anywhere near that for long stretches, the need to refuel every 3ish hours will probably get him to turn some stuff off.

Just saying what I would do.

 

[Chuckster in NJ]

You are likely going to need a soft start for the a/c

DEFINITELY ^

 

[mike93lx]

DEFINITELY ^

I think it's a good idea regardless so it doesn't trip out if something else big is on, but if it's a 2 to maybe 2.5ton, that generator may start it ok

 

[mm08822]

I think it's a good idea regardless so it doesn't trip out if something else big is on, but if it's a 2 to maybe 2.5ton, that generator may start it ok

Depends on what else is already running. Better to add it JIC.