grsthegreat
Super Star Member
you answered your own question. if the transfer switch is actually rated 7500 watts, you better not feed it 15,000 watts. something can burn down. tell them...nope.
15Kw generator on 7.5Kw transfer switch
- Thread starter Coyote machine
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George2615
Super Member
I wouldn't think you need to change anything. Your 7500 watt transfer switch is feeding the house. By supplying it from a 15,000 watt generator the generator won't have to work hard at all to maintain your load. The transfer switch load is maximum of 7500 watt and should have protection built in to prevent any greater load than that. Is there any reason to think the house load would be more than that?
Our generator at work is a 250KW 300A. It feeds a 200A transfer switch and has done so for 25 years.
Our generator at work is a 250KW 300A. It feeds a 200A transfer switch and has done so for 25 years.
grsthegreat
Super Star Member
well..not legally true. the wiring for the transfer switch is rated 30 amps...being fed by a device that can supply 62 amps. so there IS a problem. then again, im an electrician so i HAVE to follow the code. An owner doesnt. I have no idea what the actual connected load to the transfer switch is. so im just guessing
Travelover
Elite Member
Exactly - you must make sure that no wiring gets more current than it can handle. Thus the fuse / circuit breaker just behind the power inlet box.
George2615
Super Member
I'm not an electrician so I guess the OP should follow your advice. I just figured the transfer switch would limit the house load to 7500W and not allow the load to exceed that.
Travelover
Elite Member
The transfer switch is just that a switch - it is not a current limiting device.
GMIslander
Silver Member
I have to agree with psdx. The instillation is set up to handle a load of 7.5 kw and if nothing new is added why would the size of the genset be a concern?
Tractor Seabee
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We are going around in circles. It sounds like Coyote's rental has a 30A 220V generator input twist lock cord receptacle and a 30A 2 pole breaker where it feeds to the panel bus. As long as his tenant uses a 30A cord the output potential is limited by the cord and the breaker plus the generator will have a 30A breaker. No problems as long as the generator output is from a 30A outlet. The generator will be loafing.
Ron
Ron
Gary Fowler
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I have to agree with this and other posters. It makes no difference what size genset you have feeding the transfer switch as long as you don't start adding circuits to the switch. It cant possible feed more than what circuits you have installed. The idea that you need to match the transfer switch to the potential input load is idiotic, you match it to output load. If you had to match to input load, you would need to match the potential of the power company supply to your house with all your switch gear equipment. The power company installs a transformer capable of putting out much more power than your 200 or 400 amp house service, but you only need to supply power cables large enough to handle your house load (200 amp in most cases). It has no relation to what power is capable of coming into your breaker, only the amount that you are capable of taking out of the breaker box (200 amps).
The only issue with using a larger genset is that it would cost a bit more in fuel cost to run it but the load would be low thus making the generator work less so it should last longer.
If you were running something like a gas turbine genset for industrial power, they need to be loaded to near capacity to run efficiently. Anything below about 60% load factor and the turbine blades would carbon up and need to be cleaned frequently. This isn't as much of a problem with a gasoline or diesel genset.
OP
Coyote machine
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Interesting info from all contributors. I really appreciate the time you have taken to post the various thoughts. It makes sense to me that the breaker on the generator, assuming it is 30 amps, for this discussion, will handle 30 amps and no more thus protecting the downstream feed to the house.
Though I don't technically, IN VERMONT, have to follow any codes, electrical or otherwise, and in my town there is only wastewater permits for subdivided lots, NOTHING else, no permits to pull, etc. Wohoo!:dance1: BUT to protect my investment property I do stick to all work being done by a licensed master electrician, and I do follow NEC, and fire codes for smoke/CO, etc. to protect my peace of mind, my tenants, and my property.
So I will verify with the transfer switch manufacturer, to hear what they say about the issue. I don't want to put anyone or anything at risk, the tenants are friends of mine too.
I will post back what Gentran has to say.
Thanks again to all who have contributed to this discussion- it has been a valuable learning experience.:thumbsup:
CM out
Though I don't technically, IN VERMONT, have to follow any codes, electrical or otherwise, and in my town there is only wastewater permits for subdivided lots, NOTHING else, no permits to pull, etc. Wohoo!:dance1: BUT to protect my investment property I do stick to all work being done by a licensed master electrician, and I do follow NEC, and fire codes for smoke/CO, etc. to protect my peace of mind, my tenants, and my property.
So I will verify with the transfer switch manufacturer, to hear what they say about the issue. I don't want to put anyone or anything at risk, the tenants are friends of mine too.
I will post back what Gentran has to say.
Thanks again to all who have contributed to this discussion- it has been a valuable learning experience.:thumbsup:
CM out