Thanks. I have some work to do to get it where I want, but I have learned a lot and I am making progress.
I also had a problem finding a relay and in truth, have not found the right one quite yet. I wanted an enclosed DIN rail mount relay and did not find one easily. You need a power relay that is DT (dual throw), can handle 30A, and has a 120VAC coil voltage. Relays like this: http://www.digikey.com/product-detail/en/T92P11A22-120/PB492-ND/365926 have a 30A NO rating and a 3A NC rating. I wasn't initially sure why there was such a NO/NC difference (if it was real or just a rating thing), but I didn't want to be a tester.
So I selected this relay: http://www.alliedelec.com/schneider-electric-magnecraft-300xbxc4-120a/70184975/
As it turned out this relay wasn't perfect either. I learned this the hard way, because despite the 30A rating, it probably should have a lower NC rating like the relays above because it will not successfully disconnect the load when it is running in sparge mode. So, if I release the relay when applying 240V (sparge mode) and the SSR is on, it will trip the breaker supplying it. I believe an arc is forming in the air gap between the NO, common, and NC contacts. Since the NC contact is tied to neutral, there is an electrical pathway there. So, my work around has been to always make sure the output to the SSR is off before turning the output for the relay off. This is easy enough to do in programming, so it has not been an issue.
I may look for a decent replacement relay someday (not a priority right now), or I may wire the other pole in parallel to reduce the current in half through each pole, as this may resolve the problem.
BTW I have been intermittently successful using PID on the BCS for sparge water heating on the fly. Sometimes it dials in and other times it is unstable. I am going to test a new tuning method but will likely just go to a duty cycle, since the flow is very consistent, and the output temp is not super critical. It sucks that the BCS doesn't have autotuning, and I am convinced it is also not calculating or applying output periods correctly.
I also had a problem finding a relay and in truth, have not found the right one quite yet. I wanted an enclosed DIN rail mount relay and did not find one easily. You need a power relay that is DT (dual throw), can handle 30A, and has a 120VAC coil voltage. Relays like this: http://www.digikey.com/product-detail/en/T92P11A22-120/PB492-ND/365926 have a 30A NO rating and a 3A NC rating. I wasn't initially sure why there was such a NO/NC difference (if it was real or just a rating thing), but I didn't want to be a tester.
So I selected this relay: http://www.alliedelec.com/schneider-electric-magnecraft-300xbxc4-120a/70184975/
As it turned out this relay wasn't perfect either. I learned this the hard way, because despite the 30A rating, it probably should have a lower NC rating like the relays above because it will not successfully disconnect the load when it is running in sparge mode. So, if I release the relay when applying 240V (sparge mode) and the SSR is on, it will trip the breaker supplying it. I believe an arc is forming in the air gap between the NO, common, and NC contacts. Since the NC contact is tied to neutral, there is an electrical pathway there. So, my work around has been to always make sure the output to the SSR is off before turning the output for the relay off. This is easy enough to do in programming, so it has not been an issue.
I may look for a decent replacement relay someday (not a priority right now), or I may wire the other pole in parallel to reduce the current in half through each pole, as this may resolve the problem.
BTW I have been intermittently successful using PID on the BCS for sparge water heating on the fly. Sometimes it dials in and other times it is unstable. I am going to test a new tuning method but will likely just go to a duty cycle, since the flow is very consistent, and the output temp is not super critical. It sucks that the BCS doesn't have autotuning, and I am convinced it is also not calculating or applying output periods correctly.