can i parallel generators?


Old 10-15-02, 08:55 AM
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can i parallel generators?

ok. so i got a disconnect to keep from frying the poor electrical workers when the power fails and i hook up a 5500 watt generator to the 220 feed coming into the house when the lights go out. now i got a second 5500 watt generator and i'm wondering if i can tie both into the same line without them frying one another? just wondering if anybody out there had tried it to be sure. thanks for any input you folks can give me.
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Old 10-15-02, 09:30 AM
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While it is possible to parallel two generators, I don't think you will be able to do what you want to do here.

In order to parallel generators you have to be sure that they are in phase with each other and they have to be kept in phase with each other on a constant basis. Many industrial users of electricity have taken to producing power from on site generators during times of peak energy usage in a cooperative effort with local utilities to avoid having to build new generating plants. They call this co-generation.

You would need special equipment to measure and regulate each generator in relation to the other. This is cost prohibitive for emergency standby generators for the home.

I have to say that you may get some negative response to your post. It seems by your wording "poor electrical workers" that you are being sarcastic with regard to the safety of the linemen that work day and night to restore power when there is an outage. None of us in the trade take safety as a sarcastic matter.

Keep this in mind!!! Transformers are dumb, all they can do is transform voltage. Under normal circumstances the transformer on the pole takes high voltage and steps it down to a voltage suitable for use in your home. When the power goes out and you run a generator, if you didn't have that transfer switch, your power would go back up the line through the transformer and be "stepped up" to voltage that would normally be present on the line. Not at the same amperage but, it's still high voltage.

Safety for a lineman is what brings him home to his family at night.

Sorry if I took offense at something that was not intended to offend but, I have seen more than one friend severely injured from just what you are talking about.
Old 10-15-02, 09:45 AM
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Many emergency-generator systems will automaticaly start the generator for emergency operation and automaticaly transfer the load from utility power to the emergency generator.If you want to use 2 emergency generators you will have to arrange 2 seperate panels, each connected to it's own transfer-panel and emergency generator.Operating 2 A.C. generators in parrallel is similiar to having 2 gasoline engines each running at exactly 1000 RPM's with the spark-plugs in each engine firing at the exact same instant and the exact same order.It's imperartive that the emergency-generator power be completely isolated from any utility power connections. ---Good Luck!!!
Old 10-15-02, 06:34 PM
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The previous post hit on a possible solution. If you require that much power in an outage you should look for a subpanel or install a subpanel. Install a second transfer switch between the main panel and the subpanel. One generator will run the main panel and the second will run the sub panel.
Old 10-15-02, 08:03 PM
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Wouldnt two seperate power sources(two gens.) feeding 2 seperate panels in the same building contstitute the same code violation that prohibits two seperatly derived services feeding a building, or because it is for temp. only that would not be the issue??
Old 10-16-02, 09:20 AM
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All the connections would be on the Load-side of the Service Dis-connect switch.
Old 10-16-02, 08:38 PM
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Or....sell the two generators and purchase the size you need .Then try not to fry any of US POOR ELECTRICAL WORKERS when you hook it up.You may need to keep us around for more free advice.
Old 10-17-02, 07:25 AM
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Theoretically it's possible, practically, it ain't gonna work.
The generators will fight each other, that is they will oscillate back and forth, not to mention you will have a lot of circulating current. The previous post is the most feasible. Just get a bigger generator. Oh, I'm a poor (retired) electrical worker, too.
Old 10-17-02, 07:23 PM
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Just my 2 cents about "poor electrical workers"

Why don't you get a cabin deep in the woods with no electric or running water, that will solve your problem about the poor electrical workers or remind you just how involved we are in making your simple little life comfortable.
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