Leybold D16B vacuum pumps can often have a hard time starting up and/or trip a circuit breaker breaker on startup. This occurs typically when turned off overnight or longer and/or in labs that are held at fairly cool temperature. Even if the circuit breaker is not tripping you might hear it struggling to start and there are a couple potential solutions for this.
We generally recommend this large vacuum pump to be on a dedicated 20A "industial rated" breaker. However, we still sometimes see them still struggle on startup even with this and have found if you switch the oil to Leybold's LVO 310 (part L 310 L) this solves this issue in almost all cases. They previously called it Arctic Oil as it was for pumps used is cold environments but we have had no issues using it in warm environments also. It is surprising how much of a difference this makes on almost all pumps that have this issue. Simply drain current oil and fill with the new LVO 310. Below is their website as we do not off this oil. Have found it best to call or chat with them to get quote, etc. https://www.leyboldproducts.us/?countryswitch=US
Another option to consider is some customers have re-wired it for 220V connection if you have this available. Leybolds user manual discusses this and it seems to prevent this issue in general as starts up MUCH easier with this higher voltage.