Interlock vs. throwing the main circuit breaker for generator powering a house

   / Interlock vs. throwing the main circuit breaker for generator powering a house #1  

JFoy

Silver Member
Joined
Dec 23, 2015
Messages
234
Location
Clemmons/Lexington, NC
Tractor
Kubota BX25D
Is there a difference in safety if I just turn off the main 200amp circuit breaker versus having a generator interlock installed? My understanding is the danger of backfeeding power to the outside power pole and transformer.

Thanks,
JFoy
 
   / Interlock vs. throwing the main circuit breaker for generator powering a house #2  

Oldoak

Veteran Member
Joined
Feb 20, 2013
Messages
1,810
Tractor
Kubota L5060GST, J D X758 GT, J D 855D XUV
They both will accomplish the same thing. However, an interlock is your safest bet. An interlock eliminates the chance of human error by forgetting to turn off the main breaker.
 
   / Interlock vs. throwing the main circuit breaker for generator powering a house #3  

RNeumann

Elite Member
Joined
Aug 29, 2016
Messages
4,136
Location
North Idaho
Tractor
Mahindra 1538
Yes major difference- “just throwing the breaker” requires a manual sequence of events to prevent damage or injury. While the interlock is designed to be in either/or position with one move.

IMHO it’s short sided to setup something that your spouse, neighbor or child couldn’t easily do.
 
   / Interlock vs. throwing the main circuit breaker for generator powering a house #4  

aczlan

Super Star Member
Joined
Mar 7, 2008
Messages
17,816
Location
Northern Fingerlakes region of NY, USA
Tractor
Case 480F LL, Kubota L3830GST, B7500HST, BX2660
Is there a difference in safety if I just turn off the main 200amp circuit breaker versus having a generator interlock installed? My understanding is the danger of backfeeding power to the outside power pole and transformer.

Thanks,
JFoy
If you don't want to buy an interlock switch, there are companies who make an interlock plate that goes on your existing breaker panel and makes it so that one of the top Breakers cannot be turned on at the same time as the main breaker is on.

Aaron Z
 
   / Interlock vs. throwing the main circuit breaker for generator powering a house #5  

marchanna

Gold Member
Joined
May 5, 2017
Messages
483
Location
Pictou County, NS, Canada
Tractor
Kioti DS4110, Kubota GR2120
I don’t have an interlock, I wish I did. But because of my particular electrical layout, it was not practical. My wife knows that she should not even attempt to switch it over, and it would be very difficult for someone to figure out if he power we’re to go out, layered safe guards , which I have done intentionally.
 
   / Interlock vs. throwing the main circuit breaker for generator powering a house #6  

RickB

Super Star Member
Joined
Sep 18, 2000
Messages
15,206
Location
Up the road from Dollar General WNC
Tractor
Just a Scag
A legitamate transfer switch interrupts the neutral bond to the electrical grid. Opening a circuit breaker does not. That is a huge safety concern for utility personnel and a major reason that most codes require a transfer switch.
 
Last edited:
   / Interlock vs. throwing the main circuit breaker for generator powering a house #7  

aczlan

Super Star Member
Joined
Mar 7, 2008
Messages
17,816
Location
Northern Fingerlakes region of NY, USA
Tractor
Case 480F LL, Kubota L3830GST, B7500HST, BX2660
I don稚 have an interlock, I wish I did. But because of my particular electrical layout, it was not practical. My wife knows that she should not even attempt to switch it over, and it would be very difficult for someone to figure out if he power we?*e to go out, layered safe guards , which I have done intentionally.
Look at a trapped key interlock. Something like this: KIRK KEY INTERLOCK QTY 2 (228) "NEW" | eBay
587926d1547998215-interlock-vs-throwing-main-circuit-s-l500-jpg

One goes on the main breaker, the other goes on your generator breaker. One key gets locked up as a spare, the other is locked into one lock (that is installed so that it keeps the main breaker off when the key is removed). The other lock is installed so that it keeps the generator breaker off when the key is removed.
To turn on the generator, you turn off the main breaker, lock the interlock to keep it off, remove the key, unlock the generator interlock with that key and turn on the generator breaker.

Aaron Z
 

Attachments

  • s-l500.jpg
    s-l500.jpg
    30.2 KB · Views: 633
   / Interlock vs. throwing the main circuit breaker for generator powering a house #8  

marchanna

Gold Member
Joined
May 5, 2017
Messages
483
Location
Pictou County, NS, Canada
Tractor
Kioti DS4110, Kubota GR2120
That’s a brilliant idea.
 
   / Interlock vs. throwing the main circuit breaker for generator powering a house #9  

dieselcrawler

Elite Member
Joined
Jan 2, 2008
Messages
2,898
Location
New Martinsville WV
Tractor
2013 JD 3005 2001 Kubota BX1800
My power system is also layed out such that in interlock won't fit the bill. Main breaker is at the house, generator feed is at the barn, which is fed from the house. Things are clearly marked, wife and oldest son understand the process and order of events clearly. We likely have a better understanding of the safety risks than most, as I have 20+ years of electrical background, and have installed many very nice back-up generator systems with auto-transfer switches, and hope to have my own someday.

The point I state clearly, every time we have a power issue, is turn off the main breaker FIRST, and save the life of the guy out in the cold/rain/snow trying to fix the power outage, then go to the barn and hook up the generator, start it, and very last turn on the breaker for generator feed to the barn panel.
 
   / Interlock vs. throwing the main circuit breaker for generator powering a house #10  

Jstpssng

Super Star Member
Joined
Aug 7, 2005
Messages
18,582
Location
Maine
Tractor
Kubota L3301
If you don't want to buy an interlock switch, there are companies who make an interlock plate that goes on your existing breaker panel and makes it so that one of the top Breakers cannot be turned on at the same time as the main breaker is on.

Aaron Z
It looks like this...
Mine was installed when I bought the building, but I have never used it. If my power ever does go out for a long period of time I will have to build a cord before using it.
Until reading RickB's comment below I never really thought about how mine worked; but I have heard that this can still allow power to feed back into the utility line.
 

Attachments

  • 0120.JPG
    0120.JPG
    75.8 KB · Views: 239
 
Top