So if anyone out there is running a Honeywell C-300 with experion. We recently had to replace a bleach pump that runs with a permissive from the DCS (DO). For some reason we are throwing an initialization error and are not able to give the permissive on a set of contacts. Typically this would mean that somewhere along the lines we have an open circuit as the DCS is not seeing a good loop/ feedback or there is not enough resistance through the loop. We have megged the wires and all are good, we can source the signal from a fluke and the pump will start running as it should.
When we installed the first pump we had to add a 2.2K ohm resistor into the circuit and that fixed the issue then. However, this time we are not having success. Whatever is going on I am not getting my 24 VDC out of the DCS point at all and we also tried moving channels with to no avail. Kind of out of ideas on what the issue could be so any ideas or spitballs at all would be greatly appreciated. TIA
Check whether the respective DO channel is turning ON and OFF as per the logic or not.
If it turns ON and OFF as per the requirement, then there is no issue with the system side.
The issue may be with the field or cables. If you have spare cables then try them.
or, for testing, just use pump DCS start or stop or trip cables in place of this permissive, (as they are already working). You can replace either at one end or at both ends i.e. DCS & substation (pump), then check. (different tests & do simulation)
In this way, you can identify the exact issue location, and then you can further investigate.
From what we were able to ascertain we are not the DO channel is not turning on/ off as we are never seeing the 24VDC signal. Odd development, one of the other techs said he put a solenoid coil into the loop and the issue resolved. This would typically make me think it is a resistance issue in the loop. The only issue with that is a 2.2K ohm resistor should be more than enough to alleviate that within the loop.
Sorry for the delayed response we had an unplanned event and have not looked at this issue since. However, I am sure we will be coming back around to it at some point in the near future.
what do you mean by putting the solenoid coil in a loop? please elaborate.
why do you suddenly need an extra resistor in your DO channel? is it the same for other similar DO channels in your system? or are you only facing issues with one channel?
You can also replace the solenoid coil in the field and test it again, it may also cause the issue.
or is the DO channel turning ON and OFF when you disconnect the solenoid coil? if so then it may be load issue from the field.
We think is is a load issue from the field side. We are using an AV4 pump that has some dry contacts. We are using the DO as HS permissive from the board on the dry contacts.