I am currently installing a back up generator for a residence that has a 100 amp service with 120/240V 1ph power. The owner has a 5KW portable generator which is really insufficient for back up power, but as stated in article702-5 " The user of the optional stand by system shall be permitted to select the load connected to the system" I am using a 100 amp manual double throw three pole safety switch to transfer the loads with because of the inadequate generator and an automatic transfer system would overload the generator without managing the emergency loads. I am using the 3 pole switch because I believe that the neutral conducter must also be kept seperate and independent from each source of power. Am I correct, or is a 2 pole switch ok? This is unclear to me in the NEC book.
Residential Emergency Generator
- Thread starter lu302dan
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wayne123
Senior Member
- Location
- North Carolina
Re: Residential Emergency Generator
I think a two pole switch will be fine.The neutral should be common to the house neutral. Generac makes a great 5kw transfer switch that I like to use for small loads in houses. The hots are the only thing switched in them and the neutral is common to the existing house panel out to the generator plug in.
I think a two pole switch will be fine.The neutral should be common to the house neutral. Generac makes a great 5kw transfer switch that I like to use for small loads in houses. The hots are the only thing switched in them and the neutral is common to the existing house panel out to the generator plug in.
Re: Residential Emergency Generator
This portable generator probably has an internal bond connection of frame to neutral. This being the case, you would actualy need the three pole switch and additional grounding to the GEC. The generator may have an external lug you can use to accomplish the additional grounding. If you disconnect the internal factory connection you might have warranty issues. If for some reason the manufacturer has instructions for this, you could disconnect the internal connection and go to a two pole switch.
Roger
This portable generator probably has an internal bond connection of frame to neutral. This being the case, you would actualy need the three pole switch and additional grounding to the GEC. The generator may have an external lug you can use to accomplish the additional grounding. If you disconnect the internal factory connection you might have warranty issues. If for some reason the manufacturer has instructions for this, you could disconnect the internal connection and go to a two pole switch.
Roger
Re: Residential Emergency Generator
Anyhow, you cant go wrong using a 3 pole switch i take it. The portable generator is on wheels and will be grounded to the grounding electrode system of the homes main service panel with an alligator clip and #8 wire attached to the generator frame
Anyhow, you cant go wrong using a 3 pole switch i take it. The portable generator is on wheels and will be grounded to the grounding electrode system of the homes main service panel with an alligator clip and #8 wire attached to the generator frame
michael nye
Member
- Location
- California
Re: Residential Emergency Generator
This would make an exellent diagram for the cover page.
This would make an exellent diagram for the cover page.
abode electric
Member
- Location
- New jersey
Re: Residential Emergency Generator
I have used a Seimens panel and a Cutler Hammer panel that has opposing main breakers that don't allow both breakers to be on at the same time. This is a UL approved system and they do not disconnect the grounded conductor (neutral).
I have used a Seimens panel and a Cutler Hammer panel that has opposing main breakers that don't allow both breakers to be on at the same time. This is a UL approved system and they do not disconnect the grounded conductor (neutral).
pierre
Senior Member
- Location
- Westchester County, New York
Re: Residential Emergency Generator
Hello Abode Electric,
702.6 Transfer Equipment... Transfer equipment shall be required for all standby systems subject to the provisions of this article and for which an electric-utility supply is either the normal or standby source. (2002 NEC)
Is this equipment UL listed as transfer equipment?
Pierre
Hello Abode Electric,
702.6 Transfer Equipment... Transfer equipment shall be required for all standby systems subject to the provisions of this article and for which an electric-utility supply is either the normal or standby source. (2002 NEC)
Is this equipment UL listed as transfer equipment?
Pierre
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
Re: Residential Emergency Generator
Seimans, Cutler-Hammer and Generac all make a packaged transfer switch with 8 to 10 circuit breakers. That way you can select which loads you want to have active in an emergency. Why transfer the whole 100 amp panel ? The homeowner will be fooled into thinking he/she can use any or all appliances they wish during a power failure.
Also, I would check with the generator manufacturer as to whether the generator neutral should be bonded to ground or float. I believe Roger's response cited this.
[ June 13, 2003, 06:13 AM: Message edited by: goldstar ]
Seimans, Cutler-Hammer and Generac all make a packaged transfer switch with 8 to 10 circuit breakers. That way you can select which loads you want to have active in an emergency. Why transfer the whole 100 amp panel ? The homeowner will be fooled into thinking he/she can use any or all appliances they wish during a power failure.
Also, I would check with the generator manufacturer as to whether the generator neutral should be bonded to ground or float. I believe Roger's response cited this.
[ June 13, 2003, 06:13 AM: Message edited by: goldstar ]
- Location
- Massachusetts
Re: Residential Emergency Generator
But if you use these panels the generator neutral must not be bonded to generator frame.
[ June 13, 2003, 06:23 AM: Message edited by: iwire ]
UL approved if installed per NEC, I like the panels you describe.
But if you use these panels the generator neutral must not be bonded to generator frame.
[ June 13, 2003, 06:23 AM: Message edited by: iwire ]
Re: Residential Emergency Generator
Thanks for all of your responses! I will try to adress them all in this message. First off, I tried to sell the customer an automatic system with all loads that he wanted on to be routed to an emergency panel. I wanted to use a 15KW natural gas generator/auto transfer switch package with this emergency panel. but it was too costly for him. This person is an engineer on fluid flow metering and has a good mechanical mind that knows how to manage the loads. Doesnt do much for resale value of the home though does it! I should have posted exactly what I am doing in the post instead of adressing only the neutral problem.
This is what is going on here. The customer has a pretty large home. It has a 400 amp 120/240 volt single phase main service panel. The metering side of course is using ct's to meter the load and has a buss on the meter side. From this buss there are two feeds. One feed goes directly to a 100 amp main breaker on the customer side of the service panel and feeds a 100 amp subpanel located in the garage. The other feed also goes to a 200 amp breaker that protects distribution at the main service panel. This panel feeds the larger loads, AC, pool, etc and another 100 amp panel located in the house.
I am actually using 2 double throw 100 amp manual transfer switches that will tie each of the two subpanels into the emergency generator. Like I said, the customer is going to manage the loads at these subpanels. These subpanels only have single pole 15 and 20 amp breakers feeding plugs,lighting, furnace blower, circ pump, and such. The generator is overload protected.
I will be grounding the generator with a #8 wire from the generator frame to the grounding electrode system for the main service panel at the UFER ground.
Thyis turns out to be a $5000.00 job rather than a $15,000.00 job done this way. Even though the owner has the money, he wont do it the way I recommended! So I am doing it in this fashion, making sure it is 100% installed to the NEC is my focus now....
Thanks again...
Dan
Thanks for all of your responses! I will try to adress them all in this message. First off, I tried to sell the customer an automatic system with all loads that he wanted on to be routed to an emergency panel. I wanted to use a 15KW natural gas generator/auto transfer switch package with this emergency panel. but it was too costly for him. This person is an engineer on fluid flow metering and has a good mechanical mind that knows how to manage the loads. Doesnt do much for resale value of the home though does it! I should have posted exactly what I am doing in the post instead of adressing only the neutral problem.
This is what is going on here. The customer has a pretty large home. It has a 400 amp 120/240 volt single phase main service panel. The metering side of course is using ct's to meter the load and has a buss on the meter side. From this buss there are two feeds. One feed goes directly to a 100 amp main breaker on the customer side of the service panel and feeds a 100 amp subpanel located in the garage. The other feed also goes to a 200 amp breaker that protects distribution at the main service panel. This panel feeds the larger loads, AC, pool, etc and another 100 amp panel located in the house.
I am actually using 2 double throw 100 amp manual transfer switches that will tie each of the two subpanels into the emergency generator. Like I said, the customer is going to manage the loads at these subpanels. These subpanels only have single pole 15 and 20 amp breakers feeding plugs,lighting, furnace blower, circ pump, and such. The generator is overload protected.
I will be grounding the generator with a #8 wire from the generator frame to the grounding electrode system for the main service panel at the UFER ground.
Thyis turns out to be a $5000.00 job rather than a $15,000.00 job done this way. Even though the owner has the money, he wont do it the way I recommended! So I am doing it in this fashion, making sure it is 100% installed to the NEC is my focus now....
Thanks again...
Dan
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