Thread: No Transfer Switch Main Disconnect

This transfer switch is designed to turn on the generator and power the house if grid power goes out OR the homes main power disconnect is turned off. How is someone supposed to turn the power off to the whole house in one location without the generator powering it back on? There is no main disconnect on the transfer switch. It looks as though you would have to turn off each individual breaker. Is this the case? And if so, how do you get around the rule of the N.E.C. which states you can not have more than 6 throws to turn off all the power to the house?

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Originally Posted by Matthew Barnicle

This transfer switch is designed to turn on the generator and power the house if grid power goes out OR the homes main power disconnect is turned off. How is someone supposed to turn the power off to the whole house in one location without the generator powering it back on? There is no main disconnect on the transfer switch. It looks as though you would have to turn off each individual breaker. Is this the case? And if so, how do you get around the rule of the N.E.C. which states you can not have more than 6 throws to turn off all the power to the house?

Matthew,

You probably already know this, but just to make sure.

Normally, when I see a generator, it is connected to, or a part of, a panel that has a limited number of circuit breakers. The idea is that a large backup generator is expensive to purchase and operate and is only intended to function for a limited period of time to provide power for lights, refrigerator, maybe a well, maybe the microwave oven. Just basic necessities.

In order to turn off the power, the main has to be turned off and the generator has to be turned off as well. I have never seen a generator panel with a main disconnect. I had never even thought about a main disconnect before.

The generator itself has a main service disconnect.

The generator also has a switch which selects 'Off', 'Manual', or 'On'. Switch to 'Off' and then shut the power main house power down, the generator will not start up.

If the generator starts up when you shut the house power down, turn off the main disconnect on the generator 'Off' to shut the power off to the house from the generator, then shut the generator switch down by switching to 'Off'.

Yes, but this requires occupants to turn the power off to the home in two different locations, one at the generator and one at the main disconnect. So, is this not a violation of the NEC rule that says you can have no more than 6 throws and that they need to be in the same location? The generator is 100 feet away in the back yard, the main disconnect is in the garage. What I envision is an electrical emergency where an occupant needs to turn the electric off to the entire house. They finally turn it off, thwarting whatever disaster was imminent... only to have it kick on again when the generator turns on automatically.

Jerry's Comments below:

"The generator itself has a main service disconnect.

The generator also has a switch which selects 'Off', 'Manual', or 'On'. Switch to 'Off' and then shut the power main house power down, the generator will not start up.

If the generator starts up when you shut the house power down, turn off the main disconnect on the generator 'Off' to shut the power off to the house from the generator, then shut the generator switch down by switching to 'Off'."
__________________

Originally Posted by Matthew Barnicle

Yes, but this requires occupants to turn the power off to the home in two different locations, one at the generator and one at the main disconnect. So, is this not a violation of the NEC rule that says you can have no more than 6 throws and that they need to be in the same location? The generator is 100 feet away in the back yard, the main disconnect is in the garage.

Well .... ... it is not a violation unless ...

But first ... effectively, there still is only one disconnect location.

There is a single disconnect for the utility power supply at the service equipment. The generator is not supplying power, so there is no need for a disconnect for the generator at that same location.

There is a single disconnect for the generator supply at the generator, which is also the service equipment when under optional standby generator power, and, because it is under generator power and the utility service power is off, there is no need for a disconnect for the utility power at that same location.

In effect you only have one source of power at a time, and each source has its own disconnect.

Okay, here is the "unless" part: (underlining and bold are mine)
- ARTICLE 702 Optional Standby Systems
- - IV. Sources of Power
- - - 702.11 Outdoor Generator Sets.
- - - - Where an outdoor housed generator set is equipped with a readily accessible disconnecting means located within sight of the building or structure supplied, an additional disconnecting means shall not be required where ungrounded conductors serve or pass through the building or structure. The disconnecting means shall meet the requirements of 225.36.

(from the definitions)
In Sight From (Within Sight From, Within Sight). Where this Code specifies that one equipment shall be “in sight from,” “within sight from,” or “within sight of,” and so forth, another equipment, the specified equipment is to be visible and not more than 15 m (50 ft) distant from the other.

You stated that generator is 100 feet away, therefore an additional disconnect is required at the structure.

Also note that, where the code DOES NOT ALLOW conductors to use the panel enclosure as a raceway without (i.e., without landing on a terminal in the enclosure), there is a section in the optional standby power sections which specifically does all for this condition.

- ARTICLE 702 Optional Standby Systems
- - II. Circuit Wiring
- - - 702.9 Wiring Optional Standby Systems.
- - - - The optional standby system wiring shall be permitted to occupy the same raceways, cables, boxes, and cabinets with other general wiring.

Excellent references Jerry, thanks. The generator is directly adjacent to the building/structure but 100 ft. away from the main disconnect. So, it appears it meets the standards. For practical purposes, I think the manufacturer should include a main disconnect/override on that transfer switch.