If you are using a mechanical relay, you should to use bang-bang, not PID. With PID, there is a good chance of it welding closed.
If you want to use PID, use a SSR. If your using a DC supplied bed, then get one that's listed at the bottom here: [duet3d.com]
If you want to use PID, use a SSR. If your using a DC supplied bed, then get one that's listed at the bottom here: [duet3d.com]