I purchased and installed this unit in my QO load center. I had to move two single pole breakers to lower slots such that this unit is in the slots closest to the service entrance lugs. From the instructions it indicates you should have good ground paths ( I have two separate paths) and it does not replace surge protection for electronic devices. Rather it augments the surge strips for those devices. I bought it primarily to protect my appliances and AC unit. Time will tell if it is effective.If you have no experience with working in a load center, hire an electrician.