Electricians...Generator House Hookup. Transfer switch vs. interlock kit.

I know you didn't mean anything by it (you said it doesn't make it right )
But as a power utility worker that kind of didn't sit right.
Yes safety rules and PPE should be followed. Guys always should work between a set of grounds. But accidents can still happen.
Test have been conducted that although working between a set of grounds a worker can still get hurt . That is conventional grounding methods.
There is a new method of grounding that is safer and protects worker on a pole . But doesn't protect someone on the ground.
Also if you are back feeding onto the powers system load from your neighbors wont necessarily trip out your genny.
I have seen it several times.

Also when a Generator is hooked up wrong and back feeding the power lines you stand a chance of damage to your generator from grounds put on by a utility worker and stand damage if Generator is on when power lines are reenergized to your house.

Use a transfer switch.....

 

I am a journeyman lineman and would defiantly prefer the transfer switch. I am not familiar with the interlock system , but it must be some kind of automatic disconnect switch. The main reason electric utilities prefer and sometimes make mandatory is because of the visible air gap. I have personally been working on dead lines .. Line unhooked, OCR handle down, source and load side grounded down. The line had 4-5 poles down and the wire was in many pieces. We spliced the wire on the ground in just leather gloves, set new poles, re-hung the phase and neutral. The crew on the south end had started to sag the wire. I went up to tie my pole in.. I put my own ground on neutral first, when it got maybe 3/4" from the phase, I drew a pretty good arc. I warned the other crew members immediately.
We did everything right .. De- energized the line , grounded the line and checked for voltage.. Luckily I used my own personal ground to be extra safe, and thru that realized the line was hot . I have nothing against generator use.. When installed properly. Just shutting off the main or this interlock is still a mechanical device, and they fail. Visible air gap is the safest for everybody. If you breaker fails .. You heat us up. If your breaker fails when we get the line back hot .. We heat your generator up. Pull the meter if nothing else.. Visible air gap
The old saying that electricity takes the shortest path to ground is not true .. It takes ALL paths




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I apologize if I offended you, really. I know things can happen but if you are working in between grounds with no sources of potential in that section of line, how CAN anything happen? I'm not questioning your experiences but in theory that should work, right?

I called my local building department yesterday to check on the interlock. He said he would have to get back to me and I was left a voicemail this morning. The manual interlock is approved for use in residential applications. Now my question, why would this be acceptable if it posed any danger?

 

I realize a flaw in my previous statement. More times than not, you guys won't be so lucky to work a section of line where no transformers exist. Guess it's also not feasible to isolate each cutout.

 

The way it's worded in the NEC code makes it sound as if it's only meant to be temporary and not a true standby system. It also sounds as if it's "assumed" safe if the interlock is installed by a professional. I don't have any other answers for you, Finch. All I know is I would rather be safe than sorry. IF, big IF, something were to fail down the line and someone gets hurt, I don't think you will like your chances in court.

 

Matt, which site are you using to read the NEC or do you have the book? The building department referenced 702.5 in the voicemail and I haven't been able to find it.

 

I'm using the 2011 version you can find it here -> NFPA NEC (2011): National Electrical Code : National Fire Protection Association : Free Download & Streaming : Internet Archive

This is the section they're referring you to. Read the italicized part.

 

I don't think the italicized portion applies to what we are talking about. I believe the interlock IS considered 'transfer equipment' because it's "prevents inadvertent interconnection of normal and alternate sources...."

I'm not sure which scenario the exception would be referring to? What do you think?

 

I read that as transfer equipment being a transfer switch device. The object between the circuits and the new temporary power source (i.e. the generator). The scenario, in my opinion, is referring to a safety interlock like I was inquiring about in the first post. An interlock does in fact "physically isolate" the "normal supply."

I'm not an electrician, I just know that backfeeding a panel with no interlock or safety device is against NEC by my interpretation of that section. Is it done by people often without incident? Probably. I'm not trying to tell anyone how to do things as I'm not in a qualified position to do so.

 

No problem an no offense taken.

As polecatsman aid electricity doesn't take easiest path to ground it takes ALL paths to ground. A worker could be one of those paths.
As I sais tests have been done and yes a person although working between grounds can get enough current to kill him.
Also one misconception on grounding is it is a fail safe protection for workers...it is but only to a point. Another reason for grounds
is to be sure the line trips out in the event of becoming energized.
If the line become energized from the utilities source it enables the OCR (breaker ) to see a fault ( the grounds ) and trip out the ocr (basically a breaker ). But still since electricity takes all paths to ground the worker could still see some current. You could ask then are the grounds really protective......yes they are. The grounds will create enough fault current to trip the breaker. there is a chance a person may not create enough fault current to trip the breaker.
Probably hard to understand and I am not the best at explaining things .

And yeah it is kind of not feasible to isolate each transformer. We will isolate a section of line that is the cause of the fault if possible. This allows us to get people back on up to the isolated spot so they are not off during repair.

 

Got my dangerous Federal Pacific panel replaced last week (known for not tripping to a fault -I have personal experience with this). I went back with a Siemens panel with a copper bus. I also upgraded from 4/0 AL to 2/0 CU. One reason I went with the siemens is because they make their own generator interlock which is $100 cheaper than interlock.com. I did half the work and the electrician only charged me $250 which ain't bad. I like having the option of essentially turning on whichever circuit I choose (within the load limitations of my genny of course).

Got it inspected Tuesday with no issues. The inspector and I talked more about hunting and drinking beer than anything else. She even offered to let me hunt her land.

Old panel












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Hi guys
I am a IBEW trained inside wireman and the interlock will work however you have to turn off other breakers or run the risk of burning up the generator the breaker may trip but probably will not unless you have a short or a large over current IMHO I would go to Lowes and get a emergency panel 6 or 8 circuits they are a three position breaker normal off and emergency no main back feed and no mor work than you would have with the interlock also easy for others to operate the only other option I would use would be the auto transfer switch it is at a much higher cost hope this helps

 

I don't like being limited to 6 circuits. Granted, I'll probably use the same circuits over and over during an outage but there's always that one instance when you may need something else that you wouldn't have wired to one of those emergency panels.