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
Call the manufacturer or their tech support.
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.
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
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.
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Quote from: bobofthenorth on June 09, 2016, 11:48:15 AM
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.
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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
Could it actually be a 16.5 kw?
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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)
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.
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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
Quote from: bevans6 on June 09, 2016, 03:59:33 PM
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
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
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
Quote from: luvrbus on June 09, 2016, 05:14:04 PM
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
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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
Quote from: luvrbus on June 10, 2016, 07:19:02 AM
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
Yes, use the KISS principle, less chance for malfunction, and cheaper.
Quote from: luvrbus on June 10, 2016, 07:19:02 AM
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
Cliff - when I was still designing my bus layout I was excited about an auto transfer switch and looked into how I was going to set it up and how it was going to work.
I put it off because of cost but now 3 years later I think I just saved a bunch of money.
Ive gotta pull out all the cable and hoses and set it it up when I park anyways how much more effort is it throwing a manual switch when you are standing right there.
Some of the guys say its nice because if its raining and you lose power you can just start the generator but in my 3 years thats never happened. If it happened once in the next 3 that would be once in 6 years Id have to get wet walking outside in the rain to switch it over.
Eh. Manual works fine for me.
-Sean
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The breaker should be sized for 125% of the measured maximum load, so I would be looking at sticking with the 80 amps per leg and getting a bigger transfer switch. Or lose a couple of AC's or whatever other load shedding you are comfortable with. You have you a lot of load, there...
Brian
You will need no less than 150 amp relays. You can use the time delay that you have now and just buy the two relays. Be sure to get the extra contact on the side so both relays can't pull in together.
Jack
Clifford...Was just reading up on your inverter and I think best way is to keep manual switching...Your inverter doesn't like auto switching of the AC source unless it does it itself, or there is a minimum 30 sec time delay. HTH...Tim
I blew an inverter when the ATS switched to it with the AC on. Blew all the output mosfets.
Brian
Hello, I built a transfer switch with an Allen Bradley motor reverser. This reverser is made with two 90 amp contactors tied together a with mechanical interlock. All of the RV transfer switches I looked at have Chinese contactors. One brand of 50 amp transfer switch has 40 amp contactors in the box. I was able to find the Allen Bradley reverser at a motor surplus place in Portland. Even the surplus price was hard to swallow. I have a 20KW generator with an 80 amp main breaker.
Thanks, Bandsaw
Clifford are you going to run a separate switch panel and breakers and auto Kill switch for the sewing machines individually or as a whole. Got to agree with Sean on that one.
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