Generator Interlock - Square "D" QO Load Center

thingiverse

This is an interlock I designed after seeing a similar layout for a GE load center but couldn't find one to match my specific load center. This design prevents the generator from being on at the same time as the main circuit breaker, thus stopping back feeding the main lines to the power company and putting lineman in danger. Note - this is for panels with a 4-inch gap between the main breaker and other cluster of breakers. I did eventually find one pre-made available for purchase on Amazon for over $70. It indicates it can work with gaps ranging from 3 1/4 to 4 inches. If your panel has a 3 1/4-inch gap, you put the breaker on the left side of the box, which moves the switch lower and allows the 4-inch design gap to function properly. If you replicate my design, it's likely to work for you as well (unconfirmed). I printed the pictured version in PLA but plan to reprint it in PETG for increased longevity. I used specific hardware to allow the interlock to slide back and forth. A spacer: #6 ID X 1/4 inch OD X 1/4 inch L, aluminum was used. The product can be found at https://www.amazon.com/dp/B07DS92CBH/ref=cm_sw_em_r_mt_dp_U_fNJ5EbXHTXWBZ. A bolt: M6x32 was also utilized. It can be purchased at https://www.amazon.com/dp/B07Q3MHL9Q/ref=cm_sw_em_r_mt_dp_U_DOJ5EbQ8P1KZX. Additionally, a locking nut: 6-32 304 stainless steel nylon inserted lock nut, 18-8 Nylock was used. It can be found at https://www.amazon.com/dp/B07Z8PDX6S/ref=cm_sw_em_r_mt_dp_U_7PJ5EbB5WEK40. I made use of some existing washers I had on hand already. I needed space between the interlock and panel so it would fit over the breaker edges. The designs I see for sale have a second plate behind this purpose, but I decided to space out the bolt instead. I went in the following order: Bolt + washer + spacer + interlock + washer + nylon nut + panel + Nylon nut. It worked perfectly with no play and using the nylon nuts should keep it that way.