harryting
Lifetime Supporting Member
I’m thinking seriously about replacing all or part of a BMS with PLC based system. Any tips and insights would be appreciated. Sorry about the long post but I think some background is necessary.
Background:
Our factory got hundreds of AB PLCs and also a BMS (Building Management System) that’s based on Siemens Apogee system with an Insight Interface (a type of HMI and programming tool). The BMS controls the lights in the factory and the HVAC for both the plant and the office areas.
Due to missteps in the past, the BMS network wiring is quite screwed up. The BMS network consists of two levels, the BLN (Building Level Network) and the FLN (Floor Level Network). The BLN is on the Ethernet physical network (not sure about the protocol) but the FLN is some type of serial network. The FLN is what link all the devices together.
To get this system functioning correctly, we have to go through the entire network to find dead-points, clean up the programming, fix mis-wired FLN points, etc.. No matter how I look at this, it will be a lot of work. We also pay a yearly support agreement to Siemens similar to the Rockwell deal that includes a few hours of support (and you think Rockwell is bad) and software updates.
My thinking:
It’s easy to change the lighting controls, etc to PLC control. It can be Micrologix 1100, Flexlogic, or Compact Logic with digital I/O. Due to already heavy presence of AB equipment I don’t see a lot of benefits to go with other PLC.
The single biggest problem with going with PLC is the office HVAC control. Office air duct are controlled with VAVs (Variable Air Volume device), http://en.wikipedia.org/wiki/Variable_air_volume which is basically a damper. VAV got a specialized controller called TEC, that measures pressure drop (air volume), temperature of the duct, temperature of the room, and actuate the damper. Some VAV also includes heating coils.
This TEC unit only cost about $1k. Yup, that’s right. To replicate the same funcationality with a PLC would be costly; PLC, DI, DO, AI, AO, pressure sensor,… ouch.
Solution?
- I am thinking of keeping these TEC units but someone controlling them with a standard HMI. I have no idea what can convert the FLN to standard protocol, any idea? I doubt Siemens will lend me much help swapping out their system.
- Alternative is to swap out the TEC with another VAV controller that talks standard industrial protocol, suggestions?
- Do this with a cheaper PLC than AB but I will need analog IO.
Some past topics:
http://www.plctalk.net/qanda/showthread.php?t=28389&highlight=bms
http://www.plctalk.net/qanda/showthread.php?t=14882&highlight=bms
Background:
Our factory got hundreds of AB PLCs and also a BMS (Building Management System) that’s based on Siemens Apogee system with an Insight Interface (a type of HMI and programming tool). The BMS controls the lights in the factory and the HVAC for both the plant and the office areas.
Due to missteps in the past, the BMS network wiring is quite screwed up. The BMS network consists of two levels, the BLN (Building Level Network) and the FLN (Floor Level Network). The BLN is on the Ethernet physical network (not sure about the protocol) but the FLN is some type of serial network. The FLN is what link all the devices together.
To get this system functioning correctly, we have to go through the entire network to find dead-points, clean up the programming, fix mis-wired FLN points, etc.. No matter how I look at this, it will be a lot of work. We also pay a yearly support agreement to Siemens similar to the Rockwell deal that includes a few hours of support (and you think Rockwell is bad) and software updates.
My thinking:
It’s easy to change the lighting controls, etc to PLC control. It can be Micrologix 1100, Flexlogic, or Compact Logic with digital I/O. Due to already heavy presence of AB equipment I don’t see a lot of benefits to go with other PLC.
The single biggest problem with going with PLC is the office HVAC control. Office air duct are controlled with VAVs (Variable Air Volume device), http://en.wikipedia.org/wiki/Variable_air_volume which is basically a damper. VAV got a specialized controller called TEC, that measures pressure drop (air volume), temperature of the duct, temperature of the room, and actuate the damper. Some VAV also includes heating coils.
This TEC unit only cost about $1k. Yup, that’s right. To replicate the same funcationality with a PLC would be costly; PLC, DI, DO, AI, AO, pressure sensor,… ouch.
Solution?
- I am thinking of keeping these TEC units but someone controlling them with a standard HMI. I have no idea what can convert the FLN to standard protocol, any idea? I doubt Siemens will lend me much help swapping out their system.
- Alternative is to swap out the TEC with another VAV controller that talks standard industrial protocol, suggestions?
- Do this with a cheaper PLC than AB but I will need analog IO.
Some past topics:
http://www.plctalk.net/qanda/showthread.php?t=28389&highlight=bms
http://www.plctalk.net/qanda/showthread.php?t=14882&highlight=bms
