Automatic Switch for generator and shore power ( one more time)

[luvrbus]

Ok guys I bought the auto change over but in the fine print it says 50 amps and to be used with no larger than a 12.5 kw generator.My generator is 80 amps is this going to blow up the change over  .  Do I need to bite the bullet and buy the high dollar change over to handle the 80 amps.
I can not see this generator ever producing 80 amps for my needs but then I am no electrical genius either so help me out here,if need be I will spend the 600 bucks for a 80 amp change over just to be on the safe side 

thanks   

[scanzel]

Call the manufacturer or their tech support.

[LuckyChow]

If there is a 50 amp breaker between the automatic change over device (source) and your electrical panel (load), you are good.  The breaker will limit the current the change over device will experience. 

On my panel, I have the electrical panel feed coming in through a 50 amp breaker.  These are nominal values of course, but the breaker will not let a load greater than it's rating occur to the wiring or devices that precede it. 

[buswarrior]

Two issues: breaking and making connections under load, which may arc the contacts, and the device's ability to pass current through, which melts the weakest link inside.

Neither will be good at higher than rated amps.

The manufacturer has already indicated 50amps, they won't recommend anything beyond that, unless they are fools spoiling for a lawsuit after it goes wrong....

As noted, protect the device with a 50 amp breaker, then you are safely designed for it's limits, if you calculate you'll not broach that amperage.

happy coaching!
buswarrior

[bobofthenorth]

Is your gennie wound for 220 or 110? I assume it's 220 and if so 220 @ 50 amps is all it can put out anyway.

Sent from my SM-G900W8 using Tapatalk

[luvrbus]

Is your gennie wound for 220 or 110? I assume it's 220 and if so 220 @ 50 amps is all it can put out anyway.

Sent from my SM-G900W8 using Tapatalk

Bob,it's both there is a tag that says 160/80 amps and there is a 80 amp breaker on the housing of the generator

[bobofthenorth]

Could it actually be a 16.5 kw?

Sent from my SM-G900W8 using Tapatalk

[luvrbus]

No it is 20KW EPS generator in a quite box I forgot to mention that a great generator just to big for our needs (I think)

[bobofthenorth]

If all you're going to have in the bus is a 50 amp panel then your cheapest and easiest solution would be to swap out the gennie breakers for 50/100 amp versions.

And I apologize for my earlier stupid comment about sizing. I thought you had said it was 12.5 kw but I see now that you were referring to the x-fer switch.

Sent from my SM-G900W8 using Tapatalk

[bevans6]

Current from a generator is two things - maximum capacity and maximum load.  If you never pull more than 50 amps load, no problem at all.  As noted, you can put a 50 amp breaker on it and hey presto, it's a 50 amp maximum generator.  You can pull 30 amps per leg from it, and it's a 30 amp generator.  I would use the 50 amp transfer switch, replace the 80 amp breaker with 50 amp might be the easiest or front-end the transfer switch with such a breaker, size my cables for the anticipated max load, and load it to less than capacity of the weakest link.

It's like at my house - I have a dedicated mains transformer on the pole that is rated at probably 1,000 amps, and I have 100 amp cables to the house protected by 100 amp breakers.   The fact that the transformer could supply 1,000 amps is irrelevant - I only use about 25 amps max anyway.

Brian

[Seangie]

Current from a generator is two things - maximum capacity and maximum load.  If you never pull more than 50 amps load, no problem at all.  As noted, you can put a 50 amp breaker on it and hey presto, it's a 50 amp maximum generator.  You can pull 30 amps per leg from it, and it's a 30 amp generator.  I would use the 50 amp transfer switch, replace the 80 amp breaker with 50 amp might be the easiest or front-end the transfer switch with such a breaker, size my cables for the anticipated max load, and load it to less than capacity of the weakest link.

It's like at my house - I have a dedicated mains transformer on the pole that is rated at probably 1,000 amps, and I have 100 amp cables to the house protected by 100 amp breakers.   The fact that the transformer could supply 1,000 amps is irrelevant - I only use about 25 amps max anyway.

Brian

Cliff - I agree with Brian, swap out the breaker on the Genny. Unless your wife brings all her sewing machines you'll never hit 80amps.

-Sean

[luvrbus]

Ok,it was 109 degrees here to day I started the generator,turned on all 5 roof tops fans on high,fridge, the inverter  chargers and lights I am pulling 119 amp on 110v.We never run 5 Ac units but I wanted to know I am going to change the generator breaker and try it  thanks   

[blue_goose]

Relays are just like circuit breakers they should never be run at there max load.  You need to be using at least a 150 amp relay.
Jack

[Seangie]

Ok,it was 109 degrees here to day I started the generator,turned on all 5 roof tops fans on high,fridge, the inverter  chargers and lights I am pulling 119 amp on 110v.We never run 5 Ac units but I wanted to know I am going to change the generator breaker and try it  thanks 

Cliff -

Im assuming the 119 amps is total, 60 on each leg?

I know it gets confusing when you start talking about 50 amp service and its 50 on each leg, not 50 total.  Im assuming the genny breaker is per leg, 80 per with 160amps total  (160 x 110 = 17,600 watts)

Also, legs are not always perfectly balanced so you could have 70 on one leg and 50 on the other.

Maybe you should just go to the 100amp switch.  Call it a day and then you wont have to worry about your wires browning out.

-Sean

Sent from my SM-N920P using Tapatalk

[luvrbus]

I think you right Sean or just leave the manual switch in place and forget about it,the manual switch works good it's just a pain to open the bay door and flip the handle every time