detached garage grounding,bonding

[kwired]

The garage-light branch circuit is only switched at the house. It does not serve the house (i.e. no loads of the house are powered by this circuit). Hence, 225.30 does not apply.

OK but you have branch circuit conductors installed in the house that do not originate in the house. I would think this would be considered a supply of some type although there is no load in the house and it requires a way to disconnect it. That method of disconnection should be grouped with the disconnect that serves the structure (the service disconnect in this case)

The general idea of any building being served by one service or feeder or grouping multiple disconnects where allowed together is so that you can shut off all power to the building by going to one place to do so.

In cases where other disconnects are allowed there needs to be signs posted to indicate where all disconnects are located as well as what they control.

Why should the mentioned branch circuit be any different?

I still favor using a low voltage control for this application it solves all of these issues

 

[Dennis Alwon]

I have always felt that 225.30(D) was being meant for situations where the branch circuit originated from the other structure not the building that housed the service.

The reason I say this is that if there were a fire the building could easily disconnect all power to the building. If the branch circuit originated at the main service building then the disconnects at that structure could not deenergize all the power.

Article 225.30 in the 2011 clarifies this for me. This of course does not follow thru for services but how could you de-energize all the power to the building if it were fed from another building. I would have to go with Kwire on this.

225.30 Number of Supplies. A building or other structure that is served by a branch circuit or feeder on the load side of a service disconnecting means shall be supplied by only one feeder or branch circuit unless permitted in 225.30(A) through (E). For the purpose of this section, a multiwire branch circuit shall be considered a single circuit.
Where a branch circuit or feeder originates in these additional buildings or other structures, only one feeder or branch circuit shall be permitted to supply power back to the original building or structure, unless permitted in 225.30(A) through (E).
For the purpose of this section, a multiwire branch circuit shall be considered a single circuit.

 

[mivey]

...Two seperate meters. ...I guess this would be like two seperate services at two seperate houses,,,,,but with a common light shared between the two homes?

Is the garage on the same transformer as the house?

a utility might say something because of the ability of combining the same phase from each service which could cause meter error readings,

How so? It may be that one meter serves some load that would normally go through the other meter but the energy will be billed either way. No different than the customer physically moving loads from the house to the garage or vice versa. The utility will still meter the total usage.

The issue with single-phase residential meters not following Blondel's Theorem is a separate issue that is considered an acceptable error and has no relevance to separate meters. These meters cheat by using the line-line voltage instead of the the two line-neutral voltages. This cheat can cause high or low readings depending on the imbalance between the line-neutral voltages (usually considered a minimal value and yields result within acceptable error ranges).

 

[hurk27]

I have always felt that 225.30(D) was being meant for situations where the branch circuit originated from the other structure not the building that housed the service.

The reason I say this is that if there were a fire the building could easily disconnect all power to the building. If the branch circuit originated at the main service building then the disconnects at that structure could not deenergize all the power.

Article 225.30 in the 2011 clarifies this for me. This of course does not follow thru for services but how could you de-energize all the power to the building if it were fed from another building. I would have to go with Kwire on this.

So explain the requirements in 225.37?

Is the garage on the same transformer as the house?

How so? It may be that one meter serves some load that would normally go through the other meter but the energy will be billed either way. No different than the customer physically moving loads from the house to the garage or vice versa. The utility will still meter the total usage.

The issue with single-phase residential meters not following Blondel's Theorem is a separate issue that is considered an acceptable error and has no relevance to separate meters. These meters cheat by using the line-line voltage instead of the the two line-neutral voltages. This cheat can cause high or low readings depending on the imbalance between the line-neutral voltages (usually considered a minimal value and yields result within acceptable error ranges).

I might be thinking of an install where two buildings was fed from different transformers, it was 3-phase, and was accidentally combined through a transfer switch by an in-house electrician, but it was causing meter errors some how, at times one meter would even run backward?

 

[Dennis Alwon]

So explain the requirements in 225.37?

Hurk, you may be absolutely correct in this, I don't know. 225.37 I am sure was written for 225.30 (A-E) but then they changed 225.30 so it is , to say the least, unclear.

So why the changed in 2011 if it isn't necessary and cover by the other articles? Something is amiss.

 

[hurk27]

Hurk, you may be absolutely correct in this, I don't know. 225.37 I am sure was written for 225.30 (A-E) but then they changed 225.30 so it is , to say the least, unclear.

So why the changed in 2011 if it isn't necessary and cover by the other articles? Something is amiss.

Originally Posted by NEC2011
225.30 Number of Supplies. A building or other structure that is served by a branch circuit or feeder on the load side of a service disconnecting means shall be supplied by only one feeder or branch circuit unless permitted in 225.30(A) through (E). For the purpose of this section, a multiwire branch circuit shall be considered a single circuit.
Where a branch circuit or feeder originates in these additional buildings or other structures, only one feeder or branch circuit shall be permitted to supply power back to the original building or structure, unless permitted in 225.30(A) through (E).
For the purpose of this section, a multiwire branch circuit shall be considered a single circuit.

I don't know either, but the above in red was put into the 2011 for a reason?
To me this more or less is saying that this other building has its own supply/service?
But the words "to supply power back to the original building or structure" to me would indicate that the service originated in the other building?

 

[Rockyd]

Let me see if I can muddy the water a bit. 225.37 Where a building or structure...See the definition of Structure.

I'd say talk to the local AHJ. Bet the fire marshall would not want the power from onebuilding on that of ofthe other. I do like the remote concept however. Just like the button at the house when driving up to the house and hitting the garage door opener.

 

[hurk27]

Let me see if I can muddy the water a bit. 225.37 Where a building or structure...See the definition of Structure.

I'd say talk to the local AHJ. Bet the fire marshall would not want the power from onebuilding on that of ofthe other. I do like the remote concept however. Just like the button at the house when driving up to the house and hitting the garage door opener.

A stand alone garage fits both definitions of "building and structure"

As far as the X-10 goes, add a plug in wireless transceiver and they have key-chain remotes that you can turn on the light sitting in your car.
I did this for my Brother in-laws truck garage, from one key-chain he can turn on all outside lights, open his garage doors, and turn on the inside lights and turn up the heat as he is pulling into the drive, right from the cab of his semi.

I remember discussing this on here, a long time ago, and if I remember right there was a proposal that made a change or didn't because the current code allowed it, guess later I'll dig through the ROP's from eairler code cycles.

 

[boyle78]

thanks for all the indepth thoughts....hard wiring the switch doesn't seem a horrible idea...but the more I think about it, the wireless 3way seems less potential for trouble......I haven't totally decided yet.

 

[mivey]

I might be thinking of an install where two buildings was fed from different transformers, it was 3-phase, and was accidentally combined through a transfer switch by an in-house electrician, but it was causing meter errors some how, at times one meter would even run backward?

Even with two different transformers it should meter the load correctly but that would be the least of the problems. The biggest concern would be tying two sources together through the relatively small load! One of the sources was obviously acting like a load to the other and made the meter run backwards. Bad juju.

 

[mivey]

Suppose there were two transformers. Will a plug-in X-10 signal travel through these to another building?

 

[hurk27]

Suppose there were two transformers. Will a plug-in X-10 signal travel through these to another building?

Most likely not, even sometimes bridging between phase when even on the same transformer has to be done, which they make a module for this, for different transformers you would have to use the RF repeater modules

 

[boyle78]

Is the garage on the same transformer as the house?

Yes it is.....the utility tapped off the overheads to a 100a meter that was on the garage......I'm upgrading to a 200a this spring

 

[mivey]

That's good. It gets riskier when there are two different supply sources in the same building. Two feeders is bad enough.

 

[pct_elect]

Alternative solution?

Alternative solution?

http://www.youtube.com/watch?feature=player_embedded&v=XKZUFu97vus

I guess some folks just want to burn it down and start over, eh?

 

[boyle78]

update to my situation..........the H.O. wants to have a warning system, that if there is a fire in the garage, they will know in the house....and visa-versa. Thinking interconnected heat in the garage tied to smoke dets in the house. The outside light being switched from both locals was question enough. Now what?
Like I said, one overhead feeder to the house and garage, from the same transformer, just two different meters but with water lines running from the house to the garage.

 

[hurk27]

update to my situation..........the H.O. wants to have a warning system, that if there is a fire in the garage, they will know in the house....and visa-versa. Thinking interconnected heat in the garage tied to smoke dets in the house. The outside light being switched from both locals was question enough. Now what?
Like I said, one overhead feeder to the house and garage, from the same transformer, just two different meters but with water lines running from the house to the garage.

Depending upon the brand installed in the house, a pair of these might work if the distance is not too far:

http://www.brkelectronics.com/product/SA520B

 

[boyle78]

thanks! I will contact them monday and ask them about heat detectors with this system.

 

[Rockyd]

Making you earn the money on this one!

 

[renosteinke]

Congratulations! You've found a code deficiency.

Different buildings, separate lightning targets ... both need ground rods.

Detached building, same service ... exception lets you run the light without needing the ground rod. Two or more circuits, and you do.

Also, two or more, you need a disco on the building. Separate service, you need a main disco on the building.

BUT ... as I read it, if you have any sort of 'panel' in the garage, you're not allowed to have power from the second service. Even if you allow it, you need to have the 'main disconnect' kill that power as well as the power to the panel in the garage.

Soulution? Power the light from within the garage, control it with radio, or low voltage relay, from elsewhere.

Or, propose the code address this situation. (I'm in favor!)