Transfer equipment?

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e57

Senior Member
Does transfer equipment require listing?

Trying to think of a way to power just a few circuits, and a portion of a Homeworks circuit from a generator. Need a way to isolate it from the rest of the circuit and was thinking of using a SPDT relay powered by the generator in a remote enclosure. Trying to think of how was easy, now trying to think of why I can't?
 

MadeInUSA2007

Member
Location
San Jose, CA
Transfer switch, made easy

Transfer switch, made easy

A few years back we bought a simple 6-circuit (20 amps each) transfer switch from Home Depot for under $1200. It measured 8" x 8" x 4". You wire up the pre-fab 6-foot 3/4" flex to the panel you want, run a wire to your generator, and you're done. There are 6 switches, each with three positions, "Generator - Off - Power-Company." The 6 circuits can be just the basics, you can pick and choose which circuits in the panel are most important. Easy peasie. Well easy-ish.
 

Volta

Senior Member
Location
Columbus, Ohio
What I'm trying to figure out is if I can just use a plain jane relay in a box?????

Probably.
For Emergency Systems and Legally Required Standby Systems the transfer equipment shall be "automatic and identified for emergency service/standby use, and approved" . . .
For an Optional Standby System the switch shall be "suitable for the use and designed and installed so as to prevent the inadvertent interconnection of normal and alternate sources" . . .
I assume that your system is optional.
 
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Volta

Senior Member
Location
Columbus, Ohio
I'd say so - so much so that I would not mind forgetting about it en toto....

So where was it that you found that????

Oh I missed my references, sorry.

700.6(A) for emergency systems in general (such as health care facilities)
701.7(A) for legally required,
702.6 for optional.
 

e57

Senior Member
702.6 for optional.
Ah - I am blind....

702.6 Transfer Equipment.
Transfer equipment shall be suitable for the intended use and designed and installed so as to prevent the inadvertent interconnection of normal and alternate sources of supply in any operation of the transfer equipment. Transfer equipment and electric power production systems installed to permit operation in parallel with the normal source shall meet the requirements of Article 705.
Transfer equipment, located on the load side of branch circuit protection, shall be permitted to contain supplementary overcurrent protection having an interrupting rating sufficient for the available fault current that the generator can deliver. The supplementary overcurrent protection devices shall be part of a listed transfer equipment.
My read here is that it is 'permited' to have OCP on the branch it is not neccesarilly required - but if it is there (In the transfer equipment) it would need to be listed. I'm thinking of a breaker on the branch OCP as normal, and an additional breaker for the generator branch both switched by a 2PDT relay. Normal power - the coil would be dead. And with generator power - the coil would energize and switch the source. Anyone else see anything I'm not seeing?
 
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steve66

Senior Member
Location
Illinois
Occupation
Engineer
I personally don't see anything wrong with using the relay. But I think your AHJ has the final say.

I also think the part that says:

"Transfer equipment shall be suitable for the intended use and designed and installed so as to prevent the inadvertent interconnection of normal and alternate sources of supply in any operation of the transfer equipment."

is worth a little thought. Is there any way a relay failure could connnect the generator and utlity? If so, will the breaker just trip disconnecting the two? Or will something worse happen?

Steve
 

e57

Senior Member
is worth a little thought. Is there any way a relay failure could connnect the generator and utlity? If so, will the breaker just trip disconnecting the two? Or will something worse happen?

Steve
A relay would break before make, and if in an odd event that it did not, one or both breakers would trip, if not the ones before them.
 
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