Generator or Mechanical Interlock Kit

Generator (or Mechanical) Interlock
A generator (or mechanical) interlock kit is a device that prevents both the main breaker and the generator breaker from being turned ON at the same time. It is designed to prevent the generator's power from feeding back into the electrical grid and potentially harming utility workers or damaging electrical equipment.

The kit usually includes a mechanical interlock device that mounts on the face of the loadcenter (or panel) cover and a retaining bracket that mounts on the back fed generator breaker.

Depending upon the type of loadcenter (Type CH or Type BR) and the installed main breaker, Eaton offers the following variety of interlock kits.

For type CH loadcenters

Loadcenter Type	Amperage	Main Breaker	Interlock catalog
CH PON (Plug on Neutral)	≥ 150	CSR	CHPMIKCSR
CH PON (Plug on Neutral)	≤ 125	CH	CHPMIKCH

For type BR loadcenters

Loadcenter Type	Amperage	Main Breaker	Interlock catalog
BR Legacy	≥ 150	CSR	BRMIKCSR
BR Legacy	≤ 125	BR	BRMIKBR
BR PON (Plug on Neutral)	≥ 150	CSR	BRPMIKCSR
BR PON (Plug on Neutral)	≤ 125	BR	BRPMIKBR

Back feeding or reverse feeding

Back feeding or reverse feeding, as name suggests, is using a branch breaker to feed the loadcenter (or panel) by powering it from the “load side” as opposed to “line side”.

When a branch breaker is used to energize the bussing, a retaining bracket is used to hold the breaker in place, so that no one can accidentally remove the back fed breaker. As the back fed breaker is energized from the “load side”, it can electrocute when removed.

Can all breakers be back fed?

No, only certain breakers can be back fed. Breakers that DO NOT have “Line” and “Load” side marked are the ones that can usually be back fed.

How to identify back fed breakers?

The breakers that can be back fed usually do NOT have “Line” and “Load” side marked. Most of Eaton’s residential line (type BR and CH) of breakers are designed to be back fed.

Retaining bracket, what it is and why it is important?

Retaining bracket (also known as hold down kit) holds the back fed breaker in place so as to avoid accidental removal of breaker while it is energized. Contrary to the normally fed breaker (energized from the line side by the bussing), the back fed breaker is energized from the line side so even when it is removed from the buss, it is still energized and can cause electrocution.

How is interlock installed?

The interlock kit is installed in the home's main electrical panel and consists of a series of metal plates that are mounted on the face of the loadcenter or panel cover. The plates are connected to the main circuit breaker and to a breaker for the generator. The interlock prevents both the main breaker and the generator breaker from being turned ON at the same time, ensuring that only one source of power is active at any given time.

To use the generator, the main circuit breaker is turned OFF and this allows metal plates to move positions so that the generator breaker can be turned ON. This isolates the home from the electrical grid and allows the generator to power the home's circuits. Once the utility power is restored, the generator is turned off and the generator breaker is switched to OFF position, then only the main breaker can be turned ON.

Overall, a generator interlock kit is a simple and effective way to safely connect a generator to a home's electrical system, providing backup power during an outage. It ensures that the homeowner can use their generator without putting themselves, their families, or utility workers at risk.