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PTO Generators Observations
Several safety points from a utility engineer on generators.
A properly installed transfer switch is a must on your service entrance. The transfer switch is a double throw switch whose common point is the house distribution panel. In the normal position the power company provides electric to your distribution panel. In the alternate position the generator provides the electric to your house panel.
Utility lineman have been killed from improper generator connections. If the power company source is not isolated from the generator you will back feed voltage to the service transformer. The transformer will step the 120/240 VAC from the generator up to a primary voltage, which is typically, 7200vac. This can be much higher depending on your utility. This voltage can kill. Additionally, if the utility company re-energizes the service with your generator connected an over-voltage occurs which can cause serious damage to your equipment.
Generators are excellent tools when used properly and by knowledgeable people. If you don't know what you are doing get someone who does. Because, someone's life maybe at risk. Dave
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PTO Generators Observations
Murf, we like to be advised when homeowners have generators so we can be on the lookout for potential problems. Fortunately, no one at our utility has been injured due to improper generator connections.
A few years ago in the electric utility industry the buzz word was "distributive generation". This is were a industry or commercial establishment has an agreement with the utility company to use their emergency generators for load shedding. The utility will allow the power from the generator to back feed into its system, thereby reducing the utility's demand. In turn the utility will exercise and maintain the customer's generator.
We considered this but didn't purse due to the low cost of electric in our part of the country, approximately $0.05/KWH, and the adverse effects it would have on our contract with our transmission supplier.
Every winter we will issue a public notice about the proper way to connect a generator, trying to educate the public. However, there are those out there to don't listen or think they know more than they do.
Take care, Dave
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PTO Generators Observations
Denwood, I agree with Ibrown, this is not safe, and you said it yourself "almost safe". There is no middle ground when it comes to safety, its either safe or its not safe. Any installation that fails to meet code, NEC and/or NESC, is considered a dangerous situation.
I would suggest on an existing house panel that is not connected to the utility source that you do the following: remove the main service conductors to the main breaker (typically 200amp) from the panel then connect your generator to the main breaker lugs. This way you will have a visual open connection to the utility and the distribution panel breakers will protect you and the circuit. However, you can overload the generator. A typical house(1500-2500sqft) in our area will use 9 - 13kw. Be sure the connecting conductors between the generator and panel are rated to carry the load. Better still, get advice from your electrical inspectors. Dave
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PTO Generators Observations
For those of us in the USA the NEC (national electic code) is the governing publication for installation of electric facilities.
By definition, Art. 100, Switch, Transfer is "An automatic or nonautomatic device for transferring one or more load conductor connections from one power source to another". As someone has already stated, this means you break one source before make of the other source.
Additional information on generators, standby power systems, etc can be found in Art 230, 445, 700, 702, & 705 in the NEC. You should be able to acquire a copy at your local library.
This is the only way to connect a generator and be safe for all parties involved. Dave
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PTO Generators Observations
Murf, excellent reply, which I agree with.
A couple of additional points, some areas permit PVC water supply lines from the house to the main, thereby reducing or in effect eliminating the benefit of the ground to the water line connection.
The terms stray voltage and ground potential rise both refer to current flow in the neutral/earth ground system. The purpose of the bonding is to prevent a difference of potential, which can also be called step potential (touch potential). This is defined as the potential difference between two points on the earth. If this voltage (potential difference) is large enough it can kill.
If anyone is interested there is an excellent book called "Ground Currents and Stray voltage" written by O.C. Seevers. Published by the Fairmount Press in 1989. Mr Seevers was a long time engineer with Kentucky Utilities in Lexington, Kentucky.
An additional reference source is the IEEE green book.
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Denwood, pulling an electric meter is considered tampering and is against the law. If you notice there is a colored wire seal attached to the meter base that you must cut to remove the meter. the purpose of this seal is to indicate to the utility that an un-authorized person had access to the meter base. This is the utilities source of revenue and they are very protective. We prosecute for tampering with the service.
Additionally, it is very dangerous if you don't use the proper equipment. Not only can the meter glass break but a lug could break and cause a short circuit resulting in a flash burn. People have been seriously hurt, you can have 5000 to 10,000 amps of available fault current at the meter base. Saving the cost of a service call could end up costing alot more in the long run. Dave
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Ncruch32, your engineer friend needs to read the Engineer's Code of Ethics, and review the oath he took when he accepted his license. His attitude is a disgrace to the profession.
With my company, you can schedule a disconnect for first thing in the morning with a reconnect prior to quiting time. That is provided your electrician (and passes inspection) can complete the job within the time frame. We take pride in being responsive to the needs of the customer and do our best to work with them.
Depending on the location and accessibility of the distribution panel a main service disconnect maybe required, ref NEC art. 230.70, between the meter and distribution panel. Dave
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