blackandredwarrior
Member
Firstly I don't have a lot of experience with PLCs.
We have a customer that we are putting together a project for and one part of that project is updating the controls for part of their cooling system. We'll be controlling 2 condensers (total of 3 pumps and 3 fans), 6 evaporators (one contactor, 1 RTD and 4 SOVs per evaporator) and 2 recirculator pumps (one recirc pump will be primary and if it fails/trips the other pump will take over.)
We'll have a 4-20 pressure transducer on the condenser as well as an outside air temp (RTD). All of the emergency controls are outside of our scope and are existing. Though we will try to get an output from that system in case we need to do anything.
The customer is worried about using a PLC and having it fail and being stuck with about $5M worth of produce in the cooler. They've had an HMI die on them on a vacuum tube and it took months to get a replacement (from Australia with a price of about $15,000.)
We are looking to use an AB ML1400 1766-L32AWA with (1) 1762-IF4 (2) 1762-OW16 (2) 1762-IR4. We may also be adding the 4-20 output module if the customer approves VFDs on the condensers. This is subject to revision as we get further along. Our A-B supplier recommended to use Modbus RTU to control the VFDs but when looking up information to get ideas it seemed to be that is a Bad Idea^TM. If we go VFD I'm planning on hard wired start/stop from the PLC with 4-20 speed control.
How do you handle a situation like this? I suppose we could provide them with a complete backup PLC setup programmed and ready to go ($2000-3000 extra) if they need to swap it out. What kind of failures usually happen if any? It will be in a hot climate (AZ/MX/CA border area with summer temps in the low 100s-120) on the south side of a building but they are not usually in production the summer. The enclosure will be cooled by an A/C unit. I'm also going to suggest a canopy over the panel.
It seems that designing a backup hard wired system would defeat the purpose of using a PLC in the first place. The idea of splitting half the controls to one PLC and the other half to another was also brought up.
What kind of UPS protection would you recommend? The customer states that the utility voltage is really high (+/- 500VAC is the summer normal) and can swing. We'd want something that would be an online type I believe.
My boss has seen some output terminal boards that have small switches for H-O-A on them. I can't seem to find any. These are usually in custom panels (Frick Quantum LX I believe).
If more information is needed I'll be happy to provide what I know. I'm looking forward to hearing everyone's experiences and helpful hints. Hope everyone has/had a great holiday (if it applies.)
We have a customer that we are putting together a project for and one part of that project is updating the controls for part of their cooling system. We'll be controlling 2 condensers (total of 3 pumps and 3 fans), 6 evaporators (one contactor, 1 RTD and 4 SOVs per evaporator) and 2 recirculator pumps (one recirc pump will be primary and if it fails/trips the other pump will take over.)
We'll have a 4-20 pressure transducer on the condenser as well as an outside air temp (RTD). All of the emergency controls are outside of our scope and are existing. Though we will try to get an output from that system in case we need to do anything.
The customer is worried about using a PLC and having it fail and being stuck with about $5M worth of produce in the cooler. They've had an HMI die on them on a vacuum tube and it took months to get a replacement (from Australia with a price of about $15,000.)
We are looking to use an AB ML1400 1766-L32AWA with (1) 1762-IF4 (2) 1762-OW16 (2) 1762-IR4. We may also be adding the 4-20 output module if the customer approves VFDs on the condensers. This is subject to revision as we get further along. Our A-B supplier recommended to use Modbus RTU to control the VFDs but when looking up information to get ideas it seemed to be that is a Bad Idea^TM. If we go VFD I'm planning on hard wired start/stop from the PLC with 4-20 speed control.
How do you handle a situation like this? I suppose we could provide them with a complete backup PLC setup programmed and ready to go ($2000-3000 extra) if they need to swap it out. What kind of failures usually happen if any? It will be in a hot climate (AZ/MX/CA border area with summer temps in the low 100s-120) on the south side of a building but they are not usually in production the summer. The enclosure will be cooled by an A/C unit. I'm also going to suggest a canopy over the panel.
It seems that designing a backup hard wired system would defeat the purpose of using a PLC in the first place. The idea of splitting half the controls to one PLC and the other half to another was also brought up.
What kind of UPS protection would you recommend? The customer states that the utility voltage is really high (+/- 500VAC is the summer normal) and can swing. We'd want something that would be an online type I believe.
My boss has seen some output terminal boards that have small switches for H-O-A on them. I can't seem to find any. These are usually in custom panels (Frick Quantum LX I believe).
If more information is needed I'll be happy to provide what I know. I'm looking forward to hearing everyone's experiences and helpful hints. Hope everyone has/had a great holiday (if it applies.)