Is Double-Throw Safety Switch the Service Disconnect?

[delectric123]

i am adding a 300 amp panel to an existing 208/120 600 amp system for a hog facility. the hog facility is about 1000 ft. off a gravel road. on the side of the road is the utility meter. the HV step-down tranny is 50 ft. away from the facility. right next to the tranny is a double-throw 600 amp fused safety switch. the tranny is on one pole and a generator on the other. from the safety switch, 3 triplexed cables,one overhead and two underground, feed 1 Ph 240/120 breaker panels in various locations of the building. 2 ungrounded conductors, and one grounded. the neutral\ground bond takes place at each breaker panel. is that code compliant? now the 300 amp 3 ph breaker panel i'm adding in yet another location of the facility, will be fed by an underground conduit from the safety switch. do i need to pull in a seperate EGC or can i just make a neutral/ground bond at the 300 amp breaker panel?

 

[Smart $]

Answer to title question is yes.

Not certain what code cycle made the change, but it used to be permitted to not run an EGC with outside feeders, and make a neutral to ground bond in the subpanels (main of the fed structure). It is still compliant for existing systems. No longer permitted for new systems, so you will have to run an EGC with your new feeder, and the neutral will remain isolated from ground at the subpanel. Also, you will have to make the service grounding electrode system compliant and install a main bonding jumper at the disconnect.

 

[ptonsparky]

Taking an EG to a new panel isn't going to change a thing. You have a genuine ...

You would have to look back to when the building was built to see if the installation was correct at the time, then at each addition. That is most likely when things started going awry.

Thankfully, hog confinements have all but disappeared from our area so we do not have the chance to check for ground loops and the effects on hogs. Again, thankfully.

It sure would be interesting to measure the neutral currents at the distribution point as loads are cycled. What are the chances of there being almost no L-N loads? Possible if the buildings were designed that way.

 

[delectric123]

what if i would have decided to go overhead to the new breaker panel, would that have required 5 wires? i think my situation is an exception, since its an existing installation.doubt it that neutral currents were taken into consideration. facility is farrowing, so there are hundreds of 120v 250W heat lamps.

 

[kwired]

i am adding a 300 amp panel to an existing 208/120 600 amp system for a hog facility. the hog facility is about 1000 ft. off a gravel road. on the side of the road is the utility meter. the HV step-down tranny is 50 ft. away from the facility. right next to the tranny is a double-throw 600 amp fused safety switch. the tranny is on one pole and a generator on the other. from the safety switch, 3 triplexed cables,one overhead and two underground, feed 1 Ph 240/120 breaker panels in various locations of the building. 2 ungrounded conductors, and one grounded. the neutral\ground bond takes place at each breaker panel. is that code compliant? now the 300 amp 3 ph breaker panel i'm adding in yet another location of the facility, will be fed by an underground conduit from the safety switch. do i need to pull in a seperate EGC or can i just make a neutral/ground bond at the 300 amp breaker panel?

Reading your description, it was probably compliant to run feeders with no EGC at time of install, but sounds like you still have a situation where a building was fed with multiple feeders. 225.30 in 2011 NEC requires one feeder to a building with some exceptions. Most of what you would typically run into with a swine facility doesn't meet any of the exceptions.

If each panel is feeding a separate building then it was code compliant, but I understand what you wrote to mean there were feeders to various locations in same building, which would not be code compliant.

 

[Smart $]

i am adding a 300 amp panel to an existing 208/120 600 amp system for a hog facility. the hog facility is about 1000 ft. off a gravel road. on the side of the road is the utility meter. the HV step-down tranny is 50 ft. away from the facility. right next to the tranny is a double-throw 600 amp fused safety switch. the tranny is on one pole and a generator on the other. from the safety switch, 3 triplexed cables,one overhead and two underground, feed 1 Ph 240/120 breaker panels in various locations of the building. 2 ungrounded conductors, and one grounded. the neutral\ground bond takes place at each breaker panel. is that code compliant? now the 300 amp 3 ph breaker panel i'm adding in yet another location of the facility, will be fed by an underground conduit from the safety switch. do i need to pull in a seperate EGC or can i just make a neutral/ground bond at the 300 amp breaker panel?

... but I understand what you wrote to mean there were feeders to various locations in same building, which would not be code compliant.

Correct*. I missed that in my first reply... :rant:

*Though it is possible under 225.30(B)(2) to have multiple feeders and be compliant.

 

[Smart $]

what if i would have decided to go overhead to the new breaker panel, would that have required 5 wires? i think my situation is an exception, since its an existing installation.doubt it that neutral currents were taken into consideration. facility is farrowing, so there are hundreds of 120v 250W heat lamps.

Underground, overhead makes no difference.

 

[kwired]

Correct*. I missed that in my first reply... :rant:

*Though it is possible under 225.30(B)(2) to have multiple feeders and be compliant.

Just how large does it have to be? NEC leaves that determination to installer and AHJ.

I don't know how much you know about swine farrowing facilities, but it doesn't take a lot of size with all the heat lamps they use in those places to load a 600 amp 120/208 supply. It will be a big facility in comparison to what used to be on your grandfathers farm, but certainly not something that will not need more than 5-10 acres of land to build it on.

 

[delectric123]

first part of building was made in late 70s with additions created about every 5 years. quite an outfit. could leave an AHJ scratching his head.

 

[Smart $]

Just how large does it have to be? NEC leaves that determination to installer and AHJ.

I don't know how much you know about swine farrowing facilities, but it doesn't take a lot of size with all the heat lamps they use in those places to load a 600 amp 120/208 supply. It will be a big facility in comparison to what used to be on your grandfathers farm, but certainly not something that will not need more than 5-10 acres of land to build it on.

Your first statement is exactly correct.

And I'd say a facilty requiring 5-10 acres of land would be sizable enough for an amenable AHJ to allow multiple feeders.

 

[kwired]

Your first statement is exactly correct.

And I'd say a facilty requiring 5-10 acres of land would be sizable enough for an amenable AHJ to allow multiple feeders.

5-10 acres is not large for a livestock facility these days, although not much 547 applications are inspected here, the ones that are would AHJ would not call a facility that small large enough to justify additional services - unless there were a need for high capacity like multiple 2000 amp entrances. You want large 547 applications, I can show you cattle operation structures that are right about 1/2 mile long. They are each served by 277/480 at opposite ends with a 1/4 mile feeder from each way, and taps every so often to supply 480 x 120 transformers to supply heaters in drinking water tanks and a HID luminaire near vicinity of each tank.

Farrowing facility has a lot of load in farrowing rooms, where heat lamps are in heavy use. But that is probably only about 1/4 to 1/3 of the facility. The rest of the facility has relatively little load in comparison because they don't use heat lamps in the rest of the facility. Just somewhat minimal lighting, ventilation, feed and water systems. The rest of the facility is breeding and gestation areas, mechanical room, and a small office, break room, shower room, and that is about all there is to most of them. One I do work in is probably on only about 10 acres of land, the building is not 10 acres it sits on 10 acres. It has "wings" with open spaces between "wings" for air flow, fire separation, and other reasons. It is supplied by 600 amp 120/208 volt. Not sure just what total load for the entire facility is. There is an identical facility just a few hundred feet away, but it is served by an additional 600 amp 120/208 supplied by a different POCO transformer.

They are in a way a little like a small industrial plant as far as wiring goes, just not so pleasant smelling as some plants.

Still better than the receiving area of a dead livestock rendering plant. I have not worked one of those, but have known people that did work in such places, they have electric powered machines and automation and need electricians too.:happyyes: